The causes and effects of cultural eutrophication at Quidenham Mere, Norfolk, UK. 2011

Sophie Studley (200389800)
Sophie Studley
The causes and effects of
cultural eutrophication at
Quidenham Mere.
BSc Geography
Geography Dissertation 2011

Contents Page
List of Figures.......................................................................................................................................... 5
List of Tables........................................................................................................................................... 8
Acknowledgments.................................................................................................................................. 9
Abstract ................................................................................................................................................10
Chapter 1: Introduction........................................................................................................................11
Chapter 2: Aims and Objectives...........................................................................................................13
2.1. Aims............................................................................................................................................13
2.2. Objectives...................................................................................................................................13
2.3. Hypotheses.................................................................................................................................14
Chapter 3: Overview of core themes ..................................................................................................16
3.1. Eutrophication ..........................................................................................................................16
3.2. Lake deposits ............................................................................................................................17
3.3. Geochemistry ...........................................................................................................................17
3.4. Micropaleontology ...................................................................................................................19
3.4.1. Gastropods.....................................................................................................................19
3.4.2. Bivalves .........................................................................................................................20
3.5. Summary ...................................................................................................................................22
Chapter 4: The Study Area ...................................................................................................................23
4.1. Site location and description ....................................................................................................23
4.2. Site Selection ............................................................................................................................24
4.3. Limitations of site chosen .........................................................................................................24
Chapter 5: Methodology .....................................................................................................................25
5.1. Coring procedure ......................................................................................................................25
5.2. Sediment lithology ....................................................................................................................25
5.3. Sediment composition ..............................................................................................................26
5.4. Chronology ................................................................................................................................26

5.5. Geochemistry ............................................................................................................................27
5.6. Magnetic susceptibility .............................................................................................................28
5.7. Mollusc Analysis ........................................................................................................................29
5.8. Statistics ....................................................................................................................................30
5.9. Limitations of methods .............................................................................................................31
5.10. Ethical Issues ...........................................................................................................................32
5.11. Summary..................................................................................................................................32
Chapter 6: Results ................................................................................................................................33
6.1. Sediment Lithology ....................................................................................................................33
6.2. Sediment composition ..............................................................................................................33
6.3. Geochemical analysis.................................................................................................................36
6.4. Non-parametric analysis (1) ......................................................................................................37
6.5. Magnetic susceptibility .............................................................................................................38
6.6. Non-parametric analysis (2).......................................................................................................39
6.7. Mollusc Analysis ........................................................................................................................39
6.8. Quantitative zonation. ...............................................................................................................42
6.9. Non-parametric analysis (3)………...............................................................................................44
6.10. Summary .................................................................................................................................45
Chapter 7: Discussion...........................................................................................................................47
7.1. When did the eutrophication events happen at Quidenham Mere? ........................................47
7.1.1. The onset of the eutrophication process ......................................................................47
7.1.2. The onset of the restoration process.............................................................................47
7.1.3. Summary .......................................................................................................................48
7.2. Possible causes of cultural eutrophication at Quidenham Mere ..............................................49
7.2.1. Possible causes of the medieval/ post-medieval eutrophication event .......................49
7.2.2. Possible causes of the second eutrophication event ....................................................51
7.2.3. Summary………...............................................................................................................52
7.3. The effect of cultural eutrophication at Quidenham Mere upon the Mollusca phylum ..........52
7.3.1. Bithynia tentaculata ......................................................................................................53
7.3.2. Gyraulus.........................................................................................................................53
7.3.3. Lymnaea.........................................................................................................................54

7.3.4. Valvata………...................................................................................................................56
7.3.5. Pisidium .........................................................................................................................57
7.3.6. Summary .......................................................................................................................57
Chapter 8: Conclusion ..........................................................................................................................58
8.1. Summary of main finding ..........................................................................................................59
8.2. Limitations of the study .............................................................................................................60
8.3. Significance of main findings .....................................................................................................60
8.4. Scope for further study..............................................................................................................61
Chapter 9: Bibliography .......................................................................................................................62
Chapter 10: Appendix...........................................................................................................................76
10.1. Methodology ..........................................................................................................................76
10.1.1. Loss-on-ignition ...........................................................................................................76
10.1.2. Geochemical Analysis ..................................................................................................76
10.1.3. Molluscs Analysis ........................................................................................................77
10.2. Results ....................................................................................................................................77
10.2.1. Sediment lithology ......................................................................................................77
10.2.2. Sediment composition ................................................................................................77
10.2.3. Geochemical Analysis ..................................................................................................84
10.2.4. Magnetic Susceptibility ...............................................................................................87
10.2.4.1. Upper Section .............................................................................................87
10.2.4.2. Lower Section ..............................................................................................89
10.2.5. Mollusc Analysis ..........................................................................................................92
10.3. Reflective Log .........................................................................................................................95
10.4. DSG Report Forms ..................................................................................................................96
10.5. Interim Report ......................................................................................................................104
10.5.1. First Interim Report ..................................................................................................104
10.5.2. Second Interim Report .............................................................................................117
10.6. Control of Substances Hazardous to Health (COSHH) ..........................................................134
10.7. Risk Assessment Forms ........................................................................................................137

List of Figures
Figure 1. Diagram identifying the main stages of the eutrophication process (Triplepoint
Water Technologies, 2011) .......................................................................................... 17
Figure 2. Diagram of a generalized gastropod. The operculum is a corneous plate that
molluscs secrete over their shell opening to survive predators and periods of drought
(Ghesquiere, 2011). .................................................................................................................20
Figure 3. Diagram of a generalized bivalve, with the main features labelled. Note that when
the adductor muscles relax the hinge ligaments expands and the shell opens (Little,
2008).......................................................................................................................................20
Figure 4. A geological map of East Anglia, with the location of Quidenham Mere indicated
(Peglar, 1993). .........................................................................................................................23
Figure 5. The local topography of Quidenham Mere and the local landmarks. .....................23
Figure 6. Diagram of the Bartington system designed to measure the magnetic susceptibility
of sediments (Nowaczyk, 2001). The loop sensor should be a similar size to the core in order
to produce accurate results.....................................................................................................28
Figure 7. A mollusc acquisition curve for the QUID1 core. In order to produce an accurate
acquisition curve, 10 samples were taken from the core at each weight, and the average was
recorded. The plots reaches asymptote at 12 individuals per sample weight. It is therefore
clear that a sample of 20 g should be extracted to achieve a full species representation.....29

Figure 8. A comparison between Peglar’s (1993) sediment composition diagram (434 – 1240
cm) and the QUID1 sediment composition diagram (125-830cm). The coloured lines indicate
where the organic and carbonate component correspond. Silica has been recorded first to
allow a clear comparison between the organic and carbonate variables...............................34
Figure 9. A diagram of the sediment lithology and sediment composition, with the
calculated dates identified.......................................................................................................35
Figure 10. The geochemistry of Quidenham Mere from the Medieval Period to the present,
focussing upon the concentration of sodium and potassium. ................................................36
Figure 11. The magnetic susceptible elements in the sediments of Quidenham Mere .........38
Figure 12. Bithynia tentaculata: Belonging to the gastropod class, this is a common
prosobranch found in slow-moving, well-oxygenated lakes (Kerney, 1999). It can survive well
in lakes with high concentrations of potassium and calcium rich waters (Jokinen, 1992).....39
Figure 13. Gyraulus laevis: Belonging to the gastropod class, these pulmonates are
extremely common in clean, quite water (Kerney, 1999).......................................................40
Figure 14. Lymnaea peregra: Belonging to the gastropod class, these pulmonates are found
in a variety of environments, such as rivers, canals and ephemeral ponds (Kerney, 1999)...40
Figure 15. Valvata macrostoma: Belonging to the gastropod class, these prosobranchs are
found in slow moving water, well-vegetated, calcium rich waters (Kerney, 1999). They are,
however, extremely rare in The British Isles. ..........................................................................40

Figure 16. Valvata piscinalis: Belonging to the gastropod class, this is a common
prosobranch found in muddy or silty substrates (Kerney, (1999). Furthermore, this snail is
tolerant to oligotrophic zones and varying carbonate concentrations (Fretter and Graham,
1978; Grigorovich et al., 2005). ...............................................................................................41
Figure 17. Pisidium sp.: Belonging to the bivalve class, this species is found in a variety of
environments (Kerney, 1999). The diagram shows a generalized Pisidium species...............41
Figure 18. The concentrations of the molluscs at Quidenham Mere, divided by quantitative
zonation. The graph shows that the concentrations of the molluscs increase between the
first (800 – 685) and second (455 -325) episode of cultural eutrophication.. ........................44
Figure 19. Peglar’s (1993) pollen stratigraphy of Quidenham Mere. There is a rapid increase
in Cannabaceae, during the medieval period (QM–9b). After a gentle decline of
Cannabaceae, at the end of the subzone QM-9b, Cannabaceae, increases rapidly to a
maximum of 94% during the post-medieval (QM-9c).............................................................49
Figure 20. A proposed explanation of the medieval/post-medieval eutrophication event at
Quidenham Mere. ...................................................................................................................50
Figure 21. A proposed explanation of the most recent eutrophication event at Quidenham
Mere.........................................................................................................................................51
Figure 22. Diagram of a Lymnaea snail with the main features labelled................................55
Figure 23. In order to survive in periods of low DO, the snail hangs suspended from the
upper surface of the water by its foot. The snail subsequently takes in oxygen by opening its
pneumostome (Clifford, 1991) ................................................................................................56

List of Tables
Table 1. A summary of statistical analysis performed to address aim number two. For the
Anderson-darling test, the data is normally distributed if P > 0.05. For the Spearman’s Rho
test, the two variables are statistically correlated if P < 0.05. ...............................................37
Table 2. A summary of the statistical analyses performed on the mollusc data. For the
Anderson-darling test, the data is normally distributed if p > 0.05. For the Spearman’s Rho
test, the two variables are statistically correlated if p < 0.05. ................................................46
Table 3. Sediment lithology using the terminology of Troels-Smith (1955). The work of Birks
and Birks (1980) also provided additional support. ................................................................65
Table 4. Results from the Loss-on-ignition analysis ................................................................71
Table 5. Geochemistry results regarding the concentrations of potassium and sodium in the
sediment of Quidenham Mere. ...............................................................................................73
Table 6. Magnetic susceptibility results from the upper section of the core .........................76
Table 7. Magnetic susceptibility results from the lower section of the core..........................78
Table 8. Results from the mollusc analysis. Concentrations of molluscs are in the following
units: concentration per 20g ...................................................................................................81

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Acknowledgements
Many thanks go to Ian Lawson for his invaluable help and support during this project. I
would also like to thank John Corr for his assistance during the preparation and
identification of numerous mollusc species. I would like to express my gratitude to Martin
Gilpin and Rachel Gasior for their patience whilst teaching me laboratory methods. Thanks
also go to Richard Preece, Stephen Brooks, Rosemary McIntosh and Ian McIntosh for their
interest in this project. Finally, I would like to thank Margaret and David Studley, Matthew
Fine, Nicole Bridgman and my fellow geographers for their admirable support and
encouragement.

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Abstract
The results of a geochemical record from the top 8.3 m of sediment retrieved from
Quidenham Mere, Norfolk, are displayed. This, together with results from sediment
composition analysis and magnetic susceptibility, are used to infer and explain periods of
cultural eutrophication at Quidenham Mere since the medieval period. The effects of
cultural eutrophication upon the abundance of molluscs in the sediment have also been
discussed. Two episodes of cultural eutrophication have been determined at Quidenham
Mere. The first episode occurred during the medieval period due to hemp retting and forest
clearance. The second episode, which is a new finding, occurred within the last 200 years
due to the development of Quidenham Hall Parkland. Both of these episodes of cultural
eutrophication caused a significant rise in the concentration of molluscs, followed by a rapid
decline. The abundance of molluscs at this location, therefore, was significantly affected by
anthropogenic activities.
Keywords: cultural eutrophication; Quidenham Mere; geochemical analysis; magnetic
susceptibility; mollusc analysis
Word Count: 10,517

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Chapter 1: Introduction
“The person who does not worry about the future will shortly have worries about the
present”
Chinese Proverb
Environmental change has been a problem, on a local level, since the beginning of
civilisation. Reasons for this include population growth, agriculture, deforestation and
smelting. There is an increasing concern that anthropogenic activities, especially those
involving a change in land use, are causing a decline in biodiversity (Huggett, 2010).
Although it is extremely difficult to identify the total number of species in the world,
extinctions themselves are normally well documented (Holden, 2008). Understanding
extinctions and loss of biodiversity are therefore important topics in evaluating the effects
of anthropogenic activities.
One of the major causes of loss of biodiversity by anthropogenic activities is cultural
eutrophication. Cultural eutrophication is defined as an excessive input of nutrients and
organic material due to anthropogenic activities. A phylum which is greatly affected by
cultural eutrophication is Mollusca (Russell-Hunter, 1978). Harman and Forney (1970)
showed that eleven species of molluscs were lost from Oneida Lake after fifty years of
increased nutrient input. The molluscan productivity also significantly decreased at this
location. Bovbjerg and Ulmer (1960) and Clampitt, et al., (1960) also recognised this trend
and showed that eleven species of gastropods were lost from Lake Okoboji, Iowa, due to
changes in the trophic level of the lake. Furthermore, Morgan (1970) documented the loss
of six gastropods species from Loch Leven over the last thirty years; a lake noted for
progressive eutrophication. It is therefore clear that anthropogenic activities, which cause
eutrophication, have a deleterious effect upon the ecology of fresh waters.
The interest in cultural eutrophication however declined in the 1980s due to the heightened
interest in acidification, and many paleolimnologists altered their studies to address these
new problems (Smol, 2002). It needs to be acknowledged that cultural eutrophication is still

12
a serious problem, and is a topic that requires further work. This will enable important
questions regarding the management of this phenomenon to be answered. Battarbee, et al.,
(2005) and Cheng, et al., (2007) fully support this idea and argue that more holistic studies
need to be undertaken. Additionally, the study of ecology needs to become more predictive.
Sutherland (2006) argues that subjects such as economics and engineering are looked upon
more highly than ecology as they allow predictions to be made. It is therefore clear that
more paleolimnological work needs to be undertaken regarding cultural eutrophication, in
order to predict the course of present environmental change.
This study therefore investigates the effect of cultural eutrophication upon the abundance
of molluscs at Quidenham Mere, Norfolk. Quidenham Mere is an ideal location for this
investigation as the calcareous marl layers are abundant in molluscs. Furthermore, Cheng, et
al., (2007) documents that this location experienced cultural eutrophication during the
medieval Period. This literature will therefore contribute to the knowledge and
development in this research field.

13
Chapter 2: Aims and objectives
2.1. Aims
1) To identify and date episodes of cultural eutrophication at Quidenham Mere, Norfolk.
2) To produce possible explanations as to why Quidenham Mere experienced episodes of
cultural eutrophication.
3) To record changes in the population of molluscs in the sediment of Quidenham Mere in
response to cultural eutrophication.
2.2. Objectives
1) In order to date the core, a sediment lithology and sediment composition analysis will be
performed.
2) In order to identify and explain the episodes of cultural eutrophication at Quidenham
Mere, the concentrations of potassium (K+
) and sodium (Na+
) in the sediment will be
calculated and analysed.
3) The further explain the episodes of cultural eutrophication at Quidenham Mere, the
magnetically susceptible elements in the sediment will be analysed.
4) A mollusc record will be produced in order to determine the effects of cultural
eutrophication upon this phylum.
5) Appropriate statistical tests will be performed upon all of the data to prove that the
conclusions of this literature are significant.

14
2.3. Hypotheses
Five hypotheses have been investigated in this literature. These have been carefully
designed to fulfil the aims of the literature.
To fulfil the first aim of this literature the hypotheses are as follows:
1) Research Hypothesis (H1): There is a significant statistical correlation between the
potassium variable and the sodium variable.
Null Hypothesis (H0): There is not a significant statistical correlation between the organic
matter variable and the sodium variable.
To fulfil the second aim of this literature the hypotheses are as follows:
2) Research Hypothesis (H1): There a significant statistical correlation between the silica
variable and the magnetic susceptibility variable.
Null Hypothesis (H0): There is not a significant statistical correlation between the silica
variable and the magnetic susceptibility variable.
To fulfil the third aim of this literature the hypotheses are as follows:
3) Research Hypothesis (H1): There is a significant statistical correlation between the mollusc
variable and the organic variable.
Null Hypothesis (H0): There is not a significant statistical correlation between the mollusc
variable and the organic variable.
variable and the potassium variable.
variable and the potassium variable.

15
variable and the sodium variable.
variable and the sodium variable.

16
Chapter 3: Overview of core themes
3.1. Eutrophication
Brandt (1901) first documented the process of natural eutrophication, establishing a
relationship between the concentration of plankton and the concentration of nitrogen in
the freshwater lakes of Germany (Smith, 1998). Naumann (1919) later classified waters in
Sweden depending on their nutrient content and Pearsall (1921) documented that an
oligotrophic lake would ‘evolve’ to become a eutrophic lake. The idea of categorising a lake
by trophic states is shared with Dokulil and Teubner (2011). Nowadays the definition of
eutrophication is a much-discussed topic as highlighted by Jørgensen and Richardson (1996).
The most common use of the term, however, is related to the excessive input of mineral
nutrients and organic matter (Harper, 1992). It must also be acknowledged that when we
speak of eutrophication, it is cultural eutrophication that is of most interest, as natural
eutrophication (ontogeny) occurs with the aging process of a lake (Deevey, 1984; Andersen,
et al., 2005).
Cultural eutrophication was first acknowledged as a phenomenon post World War 2, due to
the increased need of fertilizers and pesticides (Moss, et al., 1997; Cheng, et al,. 2007).
Cultural eutrophication is an active area of scientific research, and is the most widespread
environmental problem affecting freshwaters of developed countries (Carpenter, et al.,
1998; Smith, 2003). This is due to the large number of severe problems that it can cause
(Muir, 2009). For example, the primary effect of nutrient enrichment is a change from slow
growing perennial algae (green algae) to fast growing ephemeral algae (blue-green algae)
(Dokulil and Teubner, 2011). This can lead to an increased risk of flooding and the blockage
of water filters. Furthermore, low oxygen levels can develop due to the bacterial
decomposition of algae and macrophytes (Duarte, 1995; Borum, 1996; Cloern, 2001;
Andersen, et al., 2005). Harper (1992) therefore documents that cultural eutrophication can
have a significant negative effect upon the biodiversity of the ecosystem.

17
Figure 1. Diagram identifying the main stages of the eutrophication process (Triplepoint
Water Technologies, 2011).
3.2. Lake Deposits
Lake deposits have been used extensively for the reconstruction of past environments. In
recent years, however, there have been many advances and developments in the
techniques required to analyse and date lake deposits (Anderson, et al., 2007).
Palaeolimnologists now have the capability to generate high quality time-series data in
order to address important issues regarding cultural eutrophication (Battarbee, et al., 2005).
In comparison to other types of deposits, lake sediments provide continuous stratigraphic
records. This is because the sediments can accumulate over several epochs undisturbed by
erosion and weathering (Jenkin, et al., 1941; West, 1991; Anderson, et al., 2007). Lake
sediments can therefore provide a record of the environmental conditions in which the
sedimentation occurred and a record of the biological history.
3.3. Geochemistry
Geochemistry has been used as a valuable tool in palaeolimnology since the 1960s and plays
a central role in this field (Mackereth, 1966). Boyle (2001) argues that geochemical analysis
is extremely important in palaeolimnolgy in order to make conclusions about the

18
environment. However, the analysis of a geochemical record for phosphorous and nitrogen,
the root cause of eutrophication, is extremely difficult (Smol, 2002). This is because (i) the
preservation of phosphorous in sediments is determined by the sorption onto iron oxides,
and redox reactions can therefore affect this process (ii) anoxic conditions can causes the
post-depositional mobility of phosphorous, and phosphate can therefore be returned to the
lake water (Smol, 2002). Enstorm and Wright (1984), who also discusses the difficulties of
measuring past phosphorous concentrations, support this idea. Furthermore, Smol (2002)
reveals that the calculation of past nitrogen levels is fraught with error. It is for these
reasons that the phosphorus and nitrogen concentrations of the sediments at Quidenham
Mere will not be studied.
The concentration of sodium, however, can prove to be an alternative proxy for
eutrophication. A great body of literature has accumulated regarding this idea, despite
controversy over the mechanisms of this process. Provasoli (1969) documents that the
population of blue-green algae, a consequence of cultural eutrophication, increases with
enhanced sodium concentrations. Sharp (1971), who documented that the Twin City Lakes
(Minnesota) developed an extensive blue-green population following high inputs of sodium,
furthers this idea. Makarewicz and McKellar (1985) also acknowledged this relationship, and
Baybutt and Makarewicz (1981) documented that there was a significant correlation
between the increase in blue-green algae and the increase of the concentration of sodium.
There is therefore reason to believe that blue-green algae were present at Quidenham Mere
as it is one of the most common consequences of cultural eutrophication.
Possible explanations for this relationship include the necessary role of sodium to transform
nitrogen to ammonia in nitrogen fixing blue-green algae (Brownell and Nicholas, 1967). NAS
(1969) provides an additional explanation by documenting a strong relationship between
the release of phosphate from the lakebed and the total ionic content of the water. An
increase in the concentration of sodium in the water would therefore increase the
concentration of phosphate in the water, thus resulting in eutrophication. Furthermore,
Makarewicz and McKellar (1985) document that sodium can stimulate the phosphate
uptake in blue-green algae, and thus increase the growth rate. Therefore, an increased
concentration of sodium will result in an enlargement of the blue-green algae population,
and thus lead to eutrophic conditions.

19
Potassium may also be used as a proxy for eutrophication. Leentvaar (1980) documents the
possible role of potassium in the eutrophication process and argues that it is much more
complex than excessive phosphate and nitrogen inputs. This is supported by Wist et al.,
(2009) which argue that an increased concentration of potassium could cause a decline in
the population of blue–green algae (a direct cause of eutrophication). Furthermore,
Emerson and Lewis (1942), Allen (1952) and Kratz and Myers (1955) recorded the
intolerance of blue-green algae to increased potassium concentrations. It is therefore logical
that potassium can act as a recovery mechanism for eutrophication and that an increase in
the concentration of potassium can indicate the final stages of eutrophication.
3.4. Micropaleontology
Micropaleontology is a branch of science concerned with the study of microfossils in order
to reconstruct paleoenvironments (Martin, 2000). A particular fossil commonly used in
micropaleontology are the freshwater molluscs. Freshwater molluscs have an extraordinary
fossil record dating back to the Cambrian Period, and include two classes: Gastropod and
Bivalvia (Sturm, 2006; Dillon Jr., 2000).
3.4.1 Gastropods.
The Gastropoda class is the largest of the molluscan classes containing approximately 150,
000 species (Aktipis, et al., 2008). Gastropods are classified by having a dextral, helically
coiled aragonite shell (Ponder and Lindberg, 2008). They are unique among the classes of
molluscs as they display torsion of the body (Figure 2). (Karleskint, et al., 2009).
Furthermore, the class of gastropoda can be divided into two taxa: Pulmonata and
Prosobrachia (Boss, 1978). Snails of the subclass Prosobranchia are gill breathing, while
snails of the subclass Pulmonata are non-gill breathing. Snails of the latter carry an air
bubble nderneath their shell in order to respire (Sturm, 2006).

20
3.4.2. Bivalves
The Bivalvia class, however, is the second largest of the molluscan classes (Giribet, 2008).
Bivalves consist of a compressed body enclosed by two aragonite and/or calcite valves
(Figure 3). These valves are hinged together dorsally by adductor muscles and by
interlocking teeth (Tunnel, et al., 2010). The shape of the valve however varies between
species and can be either equilateral, inequivalve, or a combination of the both.
Figure 3. Diagram of a generalized bivalve, with the main features labelled. Note that when
the adductor muscles relax the hinge ligaments expands and the shell opens (Little, 2008)
Figure 2. Diagram of a generalized
gastropod. The operculum is a corneous
plate that molluscs secrete over their shell
opening to survive predators and periods of
drought (Ghesquiere, 2011).

21
Freshwater molluscs have gained scientific attention since the 17th
century. Merrett (1666),
listed the plants and animals of The British Isles and recorded six species of mollusc. The
study of molluscs remained a lively topic throughout this century and Lister (1678) recorded
the geographical distribution of molluscs within the British Isles. Jeffreys (1982), who
synthesized all existing literature regarding the classification and distribution of molluscs,
significantly advanced this research area. However, Merrett (1666), Lister (1678) and
Jeffreys (1982) have been strongly criticised as being too descriptive (Ložek, 1986). In the
early 1950s, there was a growing sense that the existing paradigm of molluscan study was
unscientific and lacked purpose. A more theoretical approach subsequently occurred,
emphasizing the quantification of data. Studies therefore grow in complexity with the
advance of technology (Miller and Tevesz, 2001). A highlight of this time was the work of
Sparks (1961) which documented the great biostratigraphical significance of molluscs. Talyor
(1960), Ložek (1986) and Keen (1990) also recognised the paleoenvironmental advantages
of the study of molluscs.
Molluscs are an ideal proxy to study the effects of cultural eutrophication. A great body of
literature has accumulated documenting that freshwater molluscs can be used as an
indicator of eutrophic conditions (e.g. Arter, 1989; Nakamura and Kerciku, 2000; Carlsson
2001; Jou and Liao, 2006; Timm, et al. 2006). Furthermore, Dussart (1979) documents that
the abundance of some mollusc species is positively correlated to the concentration of
potassium and negatively correlated to the concentration of sodium. Molluscs are also
advantageous in the field of palaeoecology as they are extremely numerous (Bignot, 1982).
Molluscs inhibit a wide range of sedimentary deposits such as windblown (Miller, et al.,
1994), fissures (Miller, et al., 1994b) and fen peat deposits (Miller and Thompson, 1987). An
additional advantage is that they exhibit wonderful patterns of variation between and
within species. For example, the shape of the operculum and the pattern of the suture can
vary between species. As a result, molluscs can be used for stratigraphic zonation and to
reconstruct former habitat and climatic conditions (Miller, et al., 1985). The most important
advantage, however, is that molluscs are preserved in situ in a long and complete fossil
record. This allows an in depth analysis over a many epochs.

22
3.5. Summary
Scientific investigations focusing upon cultural eutrophication have been limited in recent
years. This has resulted in a poor historical record of this phenomenon (Cheng, et. al., 2007).
Furthermore, there is an uncertainty regarding the extent to which anthropogenic activities
influence natural eutrophication (Cheng, et. al., 2007). There is therefore considerable
scope for more palaeoecological and paleolimnological studies regarding cultural
eutrophication. In order to reduce this phenomenon in the future, greater studies into the
past need to be undertaken. A fuller understanding of the topic will therefore be achieved.
Consequently, anthropogenic activities, that promote cultural eutrophication, will be able to
be successfully managed.
In order to determine the process of cultural eutrophication at Quidenham Mere, the
potassium and sodium content was measured (Grigorovich, et al., 2005). The organic
material content was also measured due to its direct relationship with this phenomenon
(Nixon, 1995). Ongley (2006) and Ortega, et al., (2006), who reveal that the organic matter
content of the sediment increases during eutrophication, support this idea. Rabalais (2010)
further supports this idea by documenting Grigorovich that the increase of organic matter
during eutrophication is due to soil erosion, natural weathering, or human activity. This
multi-proxy method is ideal as it can abolish misleading information provided by single-
proxy studies (Engstrom and Wright, 1984; Boyle, 2001: Birks and Birks, 2006). An increase
in the concentration of sodium is used as an indication to the start of the phenomenon, and
a decrease in the concentration of potassium is used as an indication to the restoration of
the lake. The population of molluscs in the sediment at Quidenham Mere was also studied
in order to evaluate the effects of anthropogenic activities. Molluscs were chosen as they
are susceptible to environmental change, and can therefore produce informative results.
This literature will provide a greater insight into the process of cultural eutrophication, as it
is clear that there are gaps in the knowledge in this field. It will help further the current
state of knowledge by highlighting what effect anthropogenic activities have upon the
population of molluscs at Quidenham Mere. This literature will also aid the development in
this research field.

23
Chapter 4: The study area
4.1. Site location and description
Quidenham Mere is a small shallow lake
located on the eastern edge of Breckland
in south Norfolk, UK (52°30’ N, 1°0’E;
National Grid Reference: TM 040875).
The area is composed of chalky boulder
clay deposited by the Anglian glaciations,
overlying chalk bedrock (Perrin, et al.,
1979) (Figure 4). The lake sediments are
calcareous marls (approximately 12 m),
with abundant shell and Characeae
remains (Cheng, et al., 2007). A thick
layer of dark peat (>2 m) overlies the
calcareous marls.
Quidenham Mere is extraordinary among East
Anglian Meres as it has an inflowing stream,
which drains from approximately 5km to the
south and east (Lewis, et al., 1991). A drainage
network has therefore been added to the fen
woods of the east and north of the Mere (Figure).
The present lake is roughly oval, with a short axis
of 200 m and long axis of about 300m (Lewis, et
al., 1991). There is however evidence that the lake
was greater in size at the onset of the Holocene
epoch (Bennett, et al., 1991).
Figure 4. A geological map of East
Anglia, with the location of Quidenham
Mere indicated (Peglar, 1993).
Figure 5. The local topography of
Quidenham Mere and the local
landmarks (Peglar, 1993).

24
4.2. Site Selection
Quidenham Mere was chosen as the study site for numerous reasons. Previous work at
Quidenham Mere, for example, has only focused upon the fossil pollen and charcoal content
of the sediments. There has been no work, however, focussing upon the nutrient
concentration of the sediments. This is an important variable to investigate in order to
further our knowledge of the eutrophication event at Quidenham Mere. Furthermore,
Cheng, et al., (2007) lacks detail of which species of mollusc where effected by the medieval
eutrophication event. Adding to this, there has been no work focusing upon the top 200m of
the sediment sequence. This literature will therefore give a greater insight into the cultural
eutrophication process and provide a basis for further study of the recent eutrophication
event at Quidenham Mere.
4.3. Limitations of study site
The main limitation of the study site is that the site cannot be accurately dated. The
sediments of Quidenham Mere are highly calcareous and are therefore unsuitable for
radiocarbon dating (Peglar, 1993). This is because ‘hard-water’ errors are likely to occur. The
sediments of Quidenham Mere are also unsuitable for accelerator mass spectrometry (AMS)
as not enough material can be extracted. However, this problem can be overcome by
comparing the sediment composition of Quidenham Mere with the sediment composition
of Peglar (1993) (Chapter 5 provides a full explanation for this criterion).

25
Chapter 5: Methodology
5.1. Coring procedure
Members of The University of Leeds Geography Department, following the standard
procedure of Wright (1967), extracted the Quidenham Mere Core. 8.3 m of core was
recovered using a 5 cm diameter Livingstone corer. However, the exact location of the
coring site at Quidenham Mere is unknown.
5.2. Sediment lithology
Valuable information about former climates and environments can be derived from the
nature of Late Quaternary sediments. For example, the biological, chemical and physical
properties of the sediment can provide information on the environment of deposition.
Furthermore, stratigraphic relationships can provide information on depositional changes
through time, while sediment accumulation rates can provide a proxy record of climate
change (Bell and Walker, 2005). A sediment description was therefore performed prior to
sediment sampling to address all three aims of this literature. Lowe and Walker (1997) agree
that sediment lithology is an important topic to investigate.
The sediment lithology of the core was analysed using the system of Troels-Smith (1955).
The Troels-Smith system was chosen, as other systems for describing organic sediments are
genetic in their character (West, 1977; Birks and Birks, 1980). Furthermore, it recognizes
that sediments are frequently mixtures of elements, thus making it a logical and versatile
approach (Birks and Birks, 1980). The sediment lithology of the core was therefore
described on a five-point scale (0, 1, 2, 3, 4, +) by:
1. The physical properties (colour, dryness, stratification etc.)
2. The composition of the core (silt, marl, lake mud etc.)
(Birks and Birks, 1980).

26
5.3. Sediment composition
Gravimetric analysis’ are of considerable importance in palaeolimnology as they are able to
provide an index of the biological productivity in former lake basins, (Lowe and Walker,
1997). The organic matter content and carbonate content of the core was measured to
calculate the age of the core (section 5.4). The organic content was also measured to
determine the timing of eutrophication at Quidenham Mere. By analysing the organic
matter content and carbonate content of the core, aim number one and two will be
addressed.
Loss-on-ignition was performed at 450°C and 950°C to calculate these variables following
the standard procedure of Hesse (1971). A full description of this method is provided in
Appendix 10.1.1. This method was chosen as Boyle (2001) documents that it is simple and
reliable method to perform. Samples were taken every 5 centimetres, to allow an accurate
comparison with Peglar (1993). The temperature of 450°C was chosen as Ball (1964)
documents that this is an appropriate temperature for the oxidation of organic matter.
Furthermore, Jordan, et al., (2002) documents that this is a sufficient temperature for this
aim. The temperature of 950°C was chosen as Heiri, et al., (2001) documents that this is an
appropriate temperature for carbon dioxide to be evolved from carbonate. Furthermore,
Dean (1974) shows a strong correlation between LOI at 950°C and the carbonate content in
lake sediments. A consistency in the LOI method was implemented in relation to the ignition
temperatures, exposure times and sample size, as recommended by Heiri, et al., (2002).
5.4. Chronology
The chronology of the sediments at Quidenham Mere is an important subject to identify,
and a technique that is frequently used in palaeoenvironmental research. It is particularly
important in this study, as it can help explain why Quidenham Mere experienced
eutrophication. For example, it is possible to determine, by knowing when the phenomenon
occurred, whether it was human induced or whether it was a natural occurrence. This
method therefore corresponds with aim number one, but can also add weight to the other
aims of this literature.

27
The sediments at Quidenham Mere are unsuitable for traditional dating methods. However,
Peglar (1993) provides a tentative chronology for the sediments of Quidenham Mere. This
work is based on the literature of Bennett (1983, 1986, 1988) which provides radiocarbon
dates for similar sites close to Quidenham. It is therefore possible, by comparing the organic
and carbonate peaks on the sediment composition diagram of Peglar (1993) and QUID1, to
calculate approximate age boundaries for QUID1. The results of the dating are shown in
section 6.1.
5.5. Geochemistry
Geochemical analysis of lake sediments has been a crucial technique in paleolimnology since
the work of Mackereth (1966). It plays a valuable role in determining a link between
sediment composition and the environment (Boyle, 2001).
A great body of literature has accumulated documenting that the concentration of
potassium and sodium in sediments can be used to indicate eutrophication (Leentvaar,
1980; Livingstone and Boykin, 1962; NAS, 1969). The concentration of potassium and
sodium of the sediment was therefore recorded to address aims one and two. The
concentration of potassium and sodium were measured using flame atomic absorption
spectrometry (FAAS). Boyle (2001) documents that FAAS is an ideal instrument for
measuring alkali metals as it is simple and produces robust results. Electrothermal atomic
absorption spectrometry (EAAS) was not chosen due to the matrix interference effects of
this apparatus (Boyle, 2001).
The pH of the sediment was measured in order to decide an appropriate method for cation
extraction. If the sample had a pH > 5, ammonium acetate would have been used for the
cation extraction (Gillman, 1979). It the sample had a pH < 5, ammonium chloride would
have been used for cation extraction (Narin, et al., 2000). The pH was recorded at 2 cm
intervals throughout the core using the electrometric method. The samples were then
analysed using FAAS to answer aim two. A full description of this method is provided in
Appendix 10.1.2. This is a sufficient method for interfering past nutrient levels and provides
valuable information on past processes (Boyle, 2001).

28
5.6. Magnetic susceptibility
The concentration of magnetic mineral can be reliably recorded by measuring the magnetic
susceptibility of sediments (Nowaczyk, 2001). This technique is an important
palaeoenvironmental indicator and has grown in popularity over the last two decades
(Mackereth, 1966; Bengtsson and Enell, 1986; Nowaczyk, 2001). Variations in the magnetic
properties of sediments have been used to make conclusions about a number of
environmental process including sediment flux and erosion in lake catchments (Dearing, et
al., 1981; Hirons and Thompson, 1986; Lowe and Walker, 1997). This method was therefore
performed to address aim number two.
For this investigation, the ‘whole core logging technique’ was used, as the recovery rate
from the coring procedure was very good. A MS2C sensor was used, as Dearing (1999)
documents that it is the appropriate apparatus for this study (Figure 6). Furthermore, this
method is a non-destructive technique and simple to perform. The first step of the
procedure was to measure the calibration sample provided by the manufacturer. The
calibration sample is a ferromagnetic material with a high magnetic susceptibility and can
confirm the long-term calibration of the MS2C meter (Dearing, 1999). The susceptibility
meter was subsequently correlated to zero against the magnetic background (Nowaczyk,
2001). Following this step, the whole core was placed into the loop sensor and recordings
were taken every 2 cm. This stratified sampling technique was designed in order to produce
a large and robust data set.
Figure 6. Diagram of the Bartington
system designed to measure the magnetic
susceptibility of sediments (Nowaczyk,
2001). The loop sensor should be a similar
size to the core in order to produce
accurate results.

29
5.7. Mollusc Analysis
Mollusc shells are one of the most common fossil remains in terrestrial Quaternary
sediments and are therefore useful palaeoenvironmental indicators (Lowe and Walker,
1997). An analysis of the mollusc shells was undertaken in order to address aim number
three. The interval and thickness of each sample depends on a variety of factors including
the concentration of molluscs in the sediment and the frequency of the sampling method.
Due to the variation in concentration of molluscs throughout the core, there are no
documented guidelines for the weight or volume of sediment required. A pilot study was
therefore performed to produce a species acquisition curve (Henderson, 1990). A small
subsample of sediment was taken and the number of species present was recorded. The
sample size was then increased in small additions until the plot for number of species
reached asymptote (Griffiths and Holmes, 2000). It is then possible to estimate the mass of
sediment required to achieve full species representation. The results of this investigation
are shown in figure 7.
Figure 7: A mollusc acquisition curve for the QUID1 core. In order to produce an accurate
acquisition curve, 10 samples were taken from the core at each weight, and the average was
recorded. The plot reaches asymptote at 12 individuals per sample weight. It is therefore
clear that a sample of 20 g should be extracted to achieve a full species representation.

30
The molluscan remains were extracted under laboratory conditions following the standard
procedure of De Deckker and Forester (1982). Ložek (1986) and Griffiths (1995) have proved
this method successful. Furthermore, Sparks (1964) documents the high level of accuracy of
this method. Sediment samples were taken every ten centimetres along the core to provide
an extensive data set. All samples were taken from the middle of the core where
disturbance is minimal. Furthermore, the surface of the sediment was carefully removed in
order to avoid contamination (Birks and Birks, 2004). The identification of the molluscan
remains was based on the work of Macan (1977) and Kerney (1999). A full description of this
method is provided in Appendix 10.1.3/
5.8. Statistics
Statistical analyses were performed upon the data, using Minitab 1.6, to prove that the
conclusions of this literature are statistically significant. Anderson-Darling normality tests
were initially performed to determine if the data sets are normally distributed (Dytham,
2011). Following this, Spearman’s rho tests were performed as the data sets, as indicated by
the Anderson-Darling tests, were not normally distributed (section 6.4). Furthermore, the
control variables and the response variables are continuous variables.
In order to address aim one, a Spearman’s rho test was performed using the potassium and
sodium data. In order to address aim two, a Spearman’s rho test was performed using the
silica and magnetic susceptibility data. This was undertaken to determine if the magnetic
susceptibility results can be used to indicate periods of soil erosion, or if the results are
controlled by the input of silica. To address the third aim of this literature, a Spearman’s rho
test was performed upon the mollusc data and the organic, potassium and sodium data. The
aim of this test was to identify if the population of molluscs at Quidenham Mere changed in
response to the episodes of cultural eutrophication.
Quantitative zonation was also performed upon the mollusc data to prove that there is a
significant statistical difference between groups of molluscs. The quantitative zonation was
performed using Psimpoll software and the optimal splitting by information content’ option
was chosen. This is method was chosen because it is robust and reliable (Lawson, 2011).

31
5.9. Limitations of methods
Several limitations regarding the Troels-Smith method, the mollusc extraction and
identification and the magnetic susceptibility method have been identified. The Troels-
Smith sediment description system can sometimes be problematic for the reason that it
relies on descriptive results (Birks and Birks, 1980). The method can therefore lead to
different interpretation by different researchers. However, if the process if followed
accurately, differing results can be kept minimal.
The mollusc extraction method can prove to be difficult due to the use of hydrogen
peroxide. Even though hydrogen peroxide is frequently used for non-marine Mollusca
analysis, several pieces of literature argue that hydrogen peroxide can destroy fragile shells
(Sohn, 1961; Hodgkinson, 1991; Slipper, 1996). Extreme care was therefore taken to ensure
that the mollusc shells were not damaged.
Additionally, the identification of molluscs can be complicated. For example, many mollusc
species vary in their morphology and markings from juvenile to adult stage and their
colouring and fine sculpture due to local environmental conditions (Lowe and Walker, 1997)
Furthermore, fossil remains can be damaged during sediment compaction or by the washing
down of the sediment (Sparks, 1964). Large bivalves for example, are rarely recovered in an
identifiable condition from compacted sediment as they shatter easily (Sparks, 1964). An
additional point to note is the over representation of Bithynia sp. This is because this genus
is more readily preserved in comparison to other genuses due to its think operculum (Figure
2) (Sparks, 1964).
The magnetic susceptibility method can also be difficult to perform accurately. This is
because the sensors are affected by electromagnetic fields, the presence of magnetic
materials and changes in temperature (Dearing, 1999). In order to produce accurate results,
the system of Dearing (1999) was followed precisely.

32
5.10. Ethical Issues
Environmental issues and health and safety issues have been acknowledged in the design of
the methods for this study (Appendix 10.6). For example, laboratory wastes were placed in
waste bags for incineration and all sharp instruments were placed in sharp bins after use.
Furthermore, the findings of the literature are not harmful to others and cannot be used in
a negative way. The findings shall instead add to the literature of paleoenvironments in
Norfolk during the Holocene epoch.
5.11. Summary
The methods have also been designed to address the aims and objectives of this literature.
For example, sections 5.3 – 5.5 have been designed to address aim number one, section 5.6
to address aim number two and section 5.7 to address aim number three. Section 5.2 and
the statistical analysis have been designed, however, to address the three aims of the
literature.

33
Chapter 6: Results
6.1. Sediment Lithology
The sediment lithology of the core has been determined to explain the three aims of this
literature. The results of this analysis are displayed in Figure 8 and 9, and further described
in Appendix 10.2.2. The bottom of core QUID1 is composed largely of calcium carbonate.
Particulate testarum molluscorum become present at 802 cm and remains throughout the
core. The calcareous marl varies in stratification from values 1 – 3 and undergoes a rapid
transition into peat at 360 cm, which remains until 125 cm. The base of the peat is very dark
brown/black and is composed of Sphagnum leaves. In the middle part of this section, the
peat becomes lighter, coarser and contains fragments of herbaceous plants and wood
segments such as Betula. The peat continues becoming lighter above this section and
herbaceous plants and wood segments dominate. The peat then gradually changes to a dark
brown herbaceous peat at approximately 161 cm.
Aim 1: Approximately, when did cultural eutrophication happen at Quidenham Mere?
6.2. Sediment composition
There is a similarity between the trends of the organic and carbonate content throughout
the two cores, however the major features occur at different depths. For example, the
organic content of the QUID1 core first peaks at 770 cm to approximately 34%, while the
organic content of Peglar’s (1993) core peaks at 790cm to approximately 38%. Furthermore,
the carbonate content of the QUID1 core declines to 680 cm, while Peglar (1993) shows that
it declines to 720 cm. Peglar (1993) also shows a slight decline in the organic content at 510
cm, followed by a rise in the carbonate content. This study also found this trend, however
the organic content of QUID1 declines at 420 cm. It is therefore clear that QUID1 differs to
Peglar’s (1993) sediment composition by 40-90 cm.

34
Key to lithology
Figure 8. A comparison between Peglar’s (1993) sediment composition diagram (434 – 1240
cm) and the QUID1 sediment composition diagram (125-830 cm). The key follows the
classification system of Troels-Smith (1955). The coloured lines indicate where the organic
and carbonate component correspond. Red indicates a comparison between the organic
variables and blue indicates a comparison between the carbonate variables. The silica
content is the first variable on the x-axis to allow a clear comparison between the organic
and carbonate variables.

35
Figure 9. Sediment lithology, sediment composition and tentative chronology at
Quidenham Mere. See Key from figure 8 for the sediment lithology.

36
6.3. Geochemical analysis
Figure 10. Geochemical analysis of Quidenham Mere, focusing upon the concentrations
of potassium and sodium.
Two peaks are prominent in the concentration of both potassium and sodium. From the
base of QUID1, the concentration of potassium is approximately 17 mg/kg. The
concentration of potassium peaks at 745 cm (approximately 80 mg/kg) before gradually
decline to approximately 15 mg/kg. This variable then fluctuates greatly between 3 and
21 mg/kg, before rapidly rising to approximately 160 mg/kg. Following a rapid decline in
the concentration of potassium, a peak is prominent at 345 cm (approximately 160
mg/kg). The concentration of potassium then quickly declines and fluctuates between 10
and 20 mg/kg between 325 cm – 125 cm.
The concentration of sodium throughout QUID1 is greater than that of potassium, yet
follows a similar pattern. From the base of QUID1, the concentration of sodium is
approximately 131 mg/kg until it gradually peaks at 765 cm to approximately 200 mg/kg.
This variable then rapidly declines and fluctuates greatly between 50 mg/kg and 140
mg/kg until 455 cm. At 455 cm, the concentration of sodium sharply rises to 310 mg/kg,
before declining rapidly to 150 mg/kg. This is followed by another rapid increase at 395
cm to 342 mg/kg. Following this rise, the concentration of sodium rapidly declines and
greatly fluctuates between 60 and 133 mg/kg throughout the rest of the core.
0
50
100
150
200
250
300
350
400
125
155
185
215
245
275
305
335
365
395
425
455
485
515
545
575
605
635
665
695
725
755
785
815
Concentration(mg/kg)
Depth (cm)
Distribution in depth of the concentration of sodium and potassium in
the sediments of Quidenham Mere.
Potassium
Sodium

37
6.4. Non-parametric analysis (1)
Table 1. A summary of statistical analysis performed to address aim number one. For the
Anderson-darling test, the data is normally distributed if p > 0.05. For the Spearman’s
rho test, the two variables are statistically correlated, to a 95% confidence level, if p <
0.05
The result of the Spearman’s rho test for the sodium and potassium variable shows that
p = 0.758. 0.758 > 0.05, indicating that there is no statistical significant correlation
between these two variables. Ho number one is therefore accepted. This finding was
expected as an increase in the concentration of sodium indicates the onset of the
eutrophication process, while an increase in the concentration of potassium indicates
the onset of the restoration process. The concentration of sodium and potassium can
therefore be used to identify eutrophication at Quidenham Mere.

38
Aim 2: Why did the eutrophication events at Quidenham Mere occur?
6.5. Magnetic susceptibility
Figure 11. The magnetic susceptible elements in the sediments of Quidenham Mere.
The magnetic susceptibility results are displayed in Figure 11. The results reveal a
general increase in magnetic susceptible elements from 830 cm to zero cm. Figure 11
also shows that the core is rich in diamagnetic substances due to the negative values on
the y-axis (Dearing, 1999). One of the diamagnetic substances in the core may be
carbonate. A reason for this suggestion is that the sediment analysis (Figure 8) shows
that QUID1, especially in the lower parts, is highly composed of carbonate. However,
water may also be present in the core, leading to the negative values. On closer
analysis, the results reveal a relatively steady input of magnetic susceptible elements
from 830 cm to 690 cm, with minor fluctuations. Following this, the rate of input rapidly
increases between 690 and 530 cm. The input of magnetic susceptible elements then
becomes relatively steady, with minor fluctuations, between 530 cm and 0 cm.
-16
-14
-12
-10
-8
-6
-4
-2
0
125
151
177
203
229
255
281
307
333
359
385
411
437
463
489
515
541
567
593
619
645
671
697
723
749
775
801
827
Magneticsusceptibility
Depth (cm)
Distribution in depth of the magnetic susceptible
elements at Quidenham Mere.

39
A Spearman’s rho test was performed using the silica and magnetic susceptibility data.
The test shows that r = 0.356, which indicates a weak positive correlation between the
two variables. The results also reveal that p = 0.002. 0.002 < 0.05, which indicates that
there is a statistical significant correlation to a 95% confidence level. H1 number two is
therefore accepted.
Aim 3: To examine the abundance of molluscs at Quidenham mere, in order to
determine how the molluscs responded to cultural eutrophication.
6.7. Mollusc Analysis
At least five species of molluscs are present in the sediment of Quidenham Mere since
the medieval period. These are Bithynia tentaculata, Gyraulus laevis, Lymnaea peregra,
Valvata macrostoma and Valvata piscinalis (Figure 12 - 17). Other genuses were
identified in the sediment, but could not be identified to species level due to damage of
the shell. These are Lymnaeidae sp., Gyraulus sp. and Pisidium sp.
Figure 12. Bithynia tentaculata: Belonging to the
gastropod class, this is a common prosobranch
found in slow-moving, well-oxygenated lakes
(Kerney, 1999). It can survive well in lakes with
high concentrations of calcium and potassium
(Jokinen, 1992).

40
Figure 13. Gyraulus laevis: Belonging to the
gastropod class, these pulmonates are
extremely common in clean, quite water
(Alder, 1838; Kerney, 1999).
Figure 14. Lymnaea peregra: Belonging to
the gastropod class, these pulmonates are
found in a variety of environments, such as
rivers, canals and ephemeral ponds (Kerney,
1999). There is controversy, however, as to
whether these snails can survive in
eutrophic conditions.
Figure 15. Valvata macrostoma: Belonging
to the gastropod class, these prosobranchs
are found in slow moving, well-vegetated,
calcium rich waters (Kerney, 1999). They
are, however, extremely rare in The British
Isles.

41
Figure 16. Valvata piscinalis: Belonging to the
gastropod class, this is a common prosobranch
found in muddy or silty substrates (Kerney,
(1999). Furthermore, this snail is tolerant of
oligotrophic zones and varying carbonate
concentrations (Fretter and Graham, 1978;
Grigorovich, et al., 2005).
Figure 17. Pisidium sp.: Belonging to the
bivalve class, this species is found in a variety
of environments (Kerney, 1999). The diagram
shows a generalized Pisidium species.
The preferred way of displaying mollusc data is by calculating influx rates, using the
following formula: ia = ca/d where ia = influx rate, ca = concentration of molluscs and d =
sediment deposition rate. However, because the sediment deposition rate for
Quidenham Mere is unknown, concentration values have been reported. Proportion
data has not been included in this literature, as this data is affected by the total sum.
Proportion data does not therefore accurately represent the sample.

42
6.8. Quantitative Zonation
Quantitative zonation shows that the mollusc concentration data can be divided into
four statistical significant zones for the mollusc concentration data (Figure 18). These are
from the base upwards:
Zone Q-1: Zone Q-1 is characterised by a low abundance of molluscs. Only Gyraulus sp.
and Pisidium sp. are present in this zone.
Zone Q-2: Bithynia tentaculata is the prominent mollusc species in zone Q-2. The
concentration of Bithynia tentaculata at the base of zone Q-2 is relatively high.
Throughout the zone, the concentration of this mollusc increases, before declining
towards the boundary of zone Q-3. The concentration of Gyraulus laevis, Valvata
macrostoma and Valvata piscinalis increases throughout the zone, while the
concentration of Pisidium sp. remains relatively constant. Lymnaea peregra and
Gyraulus sp. however are relatively scarce within this zone.
Zone Q-3: At the base of the zone, the concentration of molluscs in the sediment is
relatively high. Bithynia tentaculata, Valvata piscinalis, Valvata macrostoma, Lymnaea
peregra, Lymnaea sp. and Gyraulus laevis remain high until 745 cm before declining.
Following this decline, the concentrations of these species remains roughly constant,
with minor fluctuations, throughout the rest of the core. It is important to note that
Gyraulus laevis is not present in every sample throughout zone Q-3. The concentration
of Gyraulus sp. shows a general decline until 635 cm, where the concentration of this
variable is zero. Following this decline, this variable fluctuates around 0.2 individuals per
gram for the rest of the zone. The concentration of Pisidium sp., however, far exceeds
the concentrations of the other molluscs in this zone. Pisidium sp. fluctuates around 0.3
individuals per gram throughout this zone, showing no clear trend.

43
Zone Q-4: Until 395 cm, the concentration of molluscs in the sediment is relatively
steady. At 395 cm, the concentration rapidly increases until a depth of 320 cm. Lymnaea
peregra and Lymnaea sp. show the largest increase, while Pisidium sp. shows the
smallest increase. The concentration of Bithynia tentaculata, Gyraulus sp., Valvata
piscinalis and Lymnaea sp. fluctuates around 0.2 individuals per gram throughout the
rest of the core. Lymnaea peregra, Valvata macrostoma and Pisidium sp. however,
remain relatively constant until 205 cm where the concentrations increase. Following
this rise, the concentrations of these species remains steady, with minor fluctuations
until the top of the core. After the rise in the concentration of Gyraulus laevis between
390 and 320 cm, the concentration of this species remains approximately 0.2 individuals
per gram until the upper boundary of Zone Q-4. This species, however, is absent from
the sample of 275 cm.

44
Figure 18. The concentrations of the molluscs at Quidenham Mere, divided by
quantitative zonation. The graph shows that the concentrations of the molluscs increase
between the first (800 – 685) and second (455 -325) episode of cultural eutrophication.
The results of the Spearman’s rho test show that there is a significant mild positive
correlation between the number of molluscs in the sediment and the organic matter
content. H1 number three is therefore accepted. When analysing the individual species
however, H1 number three is accepted for all species bar Gyraulus laevis and Lymnaea
peregra. The results of the Spearman’s rho test show that there is a significant weak
positive correlation between the number of molluscs in the sediment and the
concentration of potassium. H1 number four is therefore accepted. When analysing the
individual species however, H1 number four is accepted for all species bar Gyraulus laevis
and Lymnaea peregra. The results of the Spearman’s rho test show that there is not a

45
significant correlation between the number of molluscs in the sediment and the
concentration of sodium. Ho number five is therefore accepted. The results also reveal
that that there is no correlation between the number of the individual species of mollusc
in the sediment and the concentration of sodium. Ho number five is therefore accepted
for all species.
6.10. Summary
The results have been discussed in way to support the aims of the literature and the
structure of this section has been designed to reflect this. For example, sections 6.2 – 6.3
have been designed to address aim number one, sections 6.4 - 6.6 have been designed
to address aim number two and sections 6.7 – 6.9 have been designed to address aim
number three. The objectives of this literature have also been achieved by the
documented results.
.

46
Variable Bithynia
tentaculata
Gyraulus laevis Gyraulus sp. Lymnaea peregra Lymnaea sp. Valvata
piscinalis
Valvata
macrostoma
Pisidium sp. Total
Anderson-
darling
<0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005
Organic
matter
content
Mild positive
correlation (R
= 0.507, P =
0.000)
Not correlated (P
= 0325)
Mild positive
correlation (R
= 0.478, P =
0.000)
Not correlated (P
= 0.473
Mild positive
correlation (R
= 0.432, P =
0.000)
Mild positive
correlation (R
= 0.417, P =
0.000)
Mild positive
correlation (R =
0.490, P = 0.000)
Weak
positive
correlation
(R =0.315, P
= 0.007)
Mild positive
correlation (R
= 0.487, P=
0.000)
Potassium Mild positive
correlation (R
= 0.447, P =
0.000)
Not correlated (P
= 0.119)
Weak positive
correlation (R
= 0.315, P =
0.008)
Not correlated
(P = 0.499)
Weak positive
correlation (R
= 0.292, P =
0.014)
Weak positive
correlation (R
= 0.281, P =
0.018)
Mild positive
correlation (R =
0.538, P = 0.000)
Mild
correlated (R
= 0.479, P =
0.000)
Weak positive
correlated (R
= 0.343, P =
0.003)
Sodium Not correlated
(P = 0.338)
Not correlated (P
= 0.619)
Not correlated
(P = 0.836)
Not correlated (P
= 0.415)
Not correlated
(P = 0.450)
Not correlated
(P = 0.219)
Not correlated (P
= 0.805)
Not
correlated (P
= 0.840)
Not correlated
(P = 0.825)
Table 2. A summary of the statistical analyses performed on the mollusc data and environmental data. For the Anderson-darling test, the data
is normally distributed if p > 0.05. For the Spearman’s rho test, the two variables are statistically correlated if p < 0.05.

47
Chapter 7: Discussion
7.1. When did the eutrophication events happen at Quidenham Mere?
The results reveal that two episodes of eutrophication occurred at Quidenham Mere since
the medieval period. The first episode of eutrophication occurred at approximately 800 –
685 cm (medieval/ post-medieval period). This idea coincides with the work of Cheng, et al.,
(2007) who also documented this event. The second episode of eutrophication occurred at
approximately 455 – 325 cm (the last 200 years). No previous literature has focused upon
the 450 – 0 cm section of the profile before, therefore the latter is a new finding.
7.1.1. The onset of the eutrophication process
There is evidence to suggest that the onset of eutrophication at Quidenham Mere occurred
at 800 cm and at 455 cm. The reason for this statement is that the concentration of sodium
increases at these depths. Sharp (1969), Provasoli (1971), Baybutt and Makarewicz (1981)
and Makarewicz and McKellar (1985) support this idea. Furthermore, the organic matter
content increases after the increased concentration of sodium (Figure 8). These depths have
therefore been used as the onset of cultural eutrophication at Quidenham Mere in this
literature. Ongley (2006), Ortega, et al., (2006) and Rabalais (2010) support this idea.
7.1.2. The onset of the restoration process
There is evidence to suggest that the onset of the restoration process at Quidenham Mere
occurred at 685 cm and at 325 cm. The reason for this statement is that the concentration
of potassium declines at these depths. Leentvaar (1980), who documents that the
concentration of potassium can be used as a proxy of eutrophication, supports this idea.
Emerson and Lewis (1942), Allen (1952), Kratz and Myers (1955) and Wist, et al., (2009),
who document that an increased concentration of potassium indicates a change of trophic
levels, supports this idea. Furthermore, the organic matter content is low after the
decreased concentration of potassium (Figure 8). These depths have therefore been used as

48
the onset of cultural eutrophication at Quidenham Mere in this literature. Ongley (2006),
Ortega, et al., (2006) and Rabalais (2010) support this idea.
7.1.3. Summary
Previous paleolimnological studies document that the organic matter content, the
concentration of potassium and the concentration of sodium can be used to identify
eutrophication. This study agrees this knowledge. This is because there is not a significant
statistical correlation between the potassium concentration and the sodium concentration.
Furthermore, the organic matter content increases following a rise in the concentration of
sodium. Therefore, there is sufficient evidence to suggest that cultural eutrophication
occurred between 800 – 685 cm (medieval/post-medieval) and between 455 – 325 cm (the
last two hundred year). These depths and dates have therefore been used throughout the
rest of the study.

49
7.2. Possible causes of cultural eutrophication at Quidenham Mere
Both episodes of eutrophication will be discussed to gain a fuller understanding of the
impacts of anthropogenic activities at Quidenham Mere.
7.2.1. Possible causes of the medieval/ post-medieval eutrophication event
Cheng, et al., (2007) documents that hemp retting caused Quidenham Mere to become
eutrophic during the medieval/ post-medieval (M/P-M) period. This relationship occurs
because the process of hemp retting causes the organic matter content and nutrient
concentration of the lake to increase. This is because hemp retting involves depositing
bundles of mature Cannabis sativa stems (a member of the Cannabaceae family) into a lake.
Microorganisms in the lake then consume the cellular tissue of the hemp, and the fibre of
the stem becomes available to make sails, ropes, clothes and fishing nets. The results of this
study provide evidence to support this idea. A similar view of Cheng, et al., (2007) is shared
by Yang (2010) who documents that hemp retting caused Quidenham Mere to become
contaminated. Furthermore, Peglar (1993) reports that the percentage of Cannabaceae
increased during the M/P-M period, thus suggesting hemp retting (Figure 19). Cox, et al.,
(2001) who reveal that the process of hemp retting significant effects the local environment,
also advances this suggestion.
Figure 19. Peglar’s (1993) pollen stratigraphy of Quidenham Mere. There is a rapid increase
in Cannabaceae during the medieval period (QM–9b). After a gentle decline of Cannabaceae
at the end of subzone QM-9b, Cannabaceae increases rapidly to a maximum of 94% during
the post-medieval (QM-9c).

50
There is also evidence, however, to suggest that forest clearance may be a possible
explanation for the M/P-M eutrophication event. This relationship occurs as forest
clearance increases the total surface area of bare soil. The rate of erosion therefore
increases, as there is no vegetation to anchor the soil. It is then possible that a weathering
pulse would release chemical ions, such as sodium and potassium, from the sediment into
the lake, thus causing eutrophication (Figure 20) (Palmer, 2011). The geochemical data
shows that the concentration of potassium and sodium in the sediment increases between
800 - 685 cm, thus supporting the idea. Mackereth (1966), who documents that an
increased concentration of potassium and sodium in the geochemical record is an indication
of intense erosion, supports this idea. This view is also supported by Engstrom and Wight
(1984), Brubaker and Anderson (1993) and Foster and Lees (1999) who record that the
geochemistry of lake sediments can be used to deduce the stability of the surrounding area.
Furthermore, Boyle (2001) strongly argues that mineral enrichment, and thus the
concentration of sodium and potassium, is a fundamental indicator of soil erosion. The
magnetic susceptibility data, however, cannot be used to support this idea. This is because
there is a positive correlation between the concentration of magnetically susceptible
elements and the concentration of silica in the sediment. The magnetically susceptible
elements in the sediment do not therefore increase with soil erosion.
Figure 20. A proposed explanation of the medieval/post-medieval eutrophication event at
Quidenham Mere.

51
7.2.2. Possible causes of the second eutrophication event
There is evidence to suggest that anthropogenic activities are the cause of the second
eutrophication event at Quidenham Mere. This paper suggests that vegetation burning, due
to the development of Quidenham Mere, is a possible cause of this event. Peglar (1993),
who documents the high concentration of charcoal in the sediment at this time, supports
this idea. There are two reasons why this relationship exists. The first reason is that the
burning of vegetation would have caused an excessive input of nutrients to enter the Mere
(Figure 21). This idea coincides with Perrow (2002) who reveals that following vegetation
burning, a high proportion of the deposited nutrients are leached from the soil. Chapman
(1989), who documents that phosphorus is leached from the soil after vegetation burning,
advances this idea. Furthermore, Kenworthy (1964) reveals that potassium is rapidly
leached from the soil after burning. It is therefore possible that the excessive input of
nutrients into the Mere, due to vegetation burning, would have resulted in the second
eutrophication event at Quidenham Mere. The second reason to explain this relationship is
that the burning of vegetation would have caused an increased rate of soil erosion and thus
eutrophication (section 7.2.1) (Holden, 2008). The geochemical analysis supports this idea.
Figure 21. A proposed explanation of the most recent eutrophication event at Quidenham
Mere.

52
7.2.3. Summary
There is sufficient evidence to suggest that anthropogenic activities were the cause of both
eutrophication events at Quidenham Mere. A possible cause of the first eutrophication
event was hemp retting and/or forest clearance. A possible cause of the second
eutrophication event was vegetation burning. Anthropogenic activates are therefore a
legitimate explanation.
7.3. The effect of cultural eutrophication at Quidenham Mere upon the Mollusca phylum.
The concentration of molluscs in the sediment at Quidenham Mere is lowest in zone Q-1,
where only Gyraulus sp. and Pisidium sp. are present. A reason for this outcome is that this
zone, as documented in the work of Cheng, et al., (2007), resembles oligotrophic conditions.
The greatest concentration change of molluscs in the sediment occurred in zones Q-3 and
Q-4. A possible reason for this outcome is anthropogenic activities. The statistical testing
supports this idea as it shows that there is a mild positive correlation, to a 95% confidence
level, between the abundance of molluscs in the sediment and organic matter content.
Statistical testing however showed that there is a weak correlation, to a 95% confidence
level, between the abundance of molluscs in the sediment and the concentration of
potassium. This therefore suggests that the organic matter content had the greatest effect
upon the mollusc population out of these two variables. Statistical testing also showed that
there is no correlation between the population of molluscs in the sediment and the
concentration of sodium. This therefore suggests that the onset of the eutrophication
process did not affect the abundance of molluscs at Quidenham Mere. The species of
molluscs found at this location shall therefore be discussed to gain a fuller understanding of
the impacts of cultural eutrophication.

53
7.3.1. Bithynia tentaculata
Evidence suggests that the population of Bithynia tentaculata was affected by changes in
the organic matter content and the concentration of potassium in the sediment. Figure 18
shows that the population of Bithynia tentaculata initially increased during both episodes of
eutrophication at Quidenham Mere, but decreased towards the restoration process of the
Mere. The statistical analysis confirms this. The results therefore imply that the abundance
of this mollusc was altered by the episodes of cultural eutrophication at Quidenham Mere. A
possible explanation for the increased population of this mollusc is their ability to filter feed
in eutrophic waters (Brendelberger and Jiirgens, 1993). Legitimate reasons for the
decreased population of Bithynia tentaculata, however, include:
(i) Bithynia tentaculata are gill breathing and can only survive in well-oxygenated water
(Kerney, 1999; Dillon Jr., 2000),
(iI) Bithynia tentaculata are not able to migrate from their microhabitat after rapid
environmental change,
(iii) Bithynia tentaculata are intolerant to the toxic by-products of hemp retting, such as
hydrogen sulphide (Cheng, et al., 2007).
Cheng, et al., (2007) came to a similar outcome during their work on Bithynia tentaculata at
Quidenham Mere. Dussart (1979), who found a positive relationship between the
abundance of Bithynia tentaculata and the concentration of potassium, also came to a
similar conclusion. Furthermore, these results are in agreement with Ritcher (2001) who
documents an increased depth rate among the Bithynia tentaculata population following a
reduction in the concentration of dissolved oxygen (DO).
7.3.2. Gyraulus
Gyraulus laevis and Gyraulus sp. are discussed to identify the effects of cultural
eutrophication. Evidence suggests that the population of Gyraulus laevis was not affected by
changes in the organic matter content and the concentration of potassium in the sediment.
The statistical analysis confirms this. In other words, the abundance of mollusc was not
significantly altered by episodes of cultural eutrophication at Quidenham Mere. This finding,

54
however, contradicts Arter (1989), Nakamura and Kerciku (2000), Carlsson (2001), Salanki,
et al., (2003,) Jou and Liao (2006) and Timm, et al., (2006) which document that mollusc can
be used as an indicator of eutrophic conditions. This finding also contradicts Dussart (1979)
who found a negative correlation between this variable and the concentration of potassium
and a positive correlation between this variable and the concentration of sodium.
There is also evidence to suggest that the population of Gyraulus sp. was affected by
Figure 18 shows that the population of Gyraulus sp. initially increased during both episodes
of eutrophication at Quidenham Mere, but decreased towards the restoration process of
the Mere. The statistical analysis confirms this. The results therefore imply that the
abundance of this mollusc was altered by the episodes of cultural eutrophication at
Quidenham Mere. A possible explanation for the increased population of this mollusc is that
they are tolerant to slight eutrophic conditions (Lsyne and Clark, 2009). A legitimate reason
for the decreased population of Gyraulus sp., however, is that they cannot survive in
oxygen-depleted waters (Alder, 1838). Furthermore, these molluscs are intolerant to
hydrogen sulphide (Caldwell, 1975).
7.3.3. Lymnaea
Lymnaea peregra and Lymnaea sp. are discussed to identify the effects of cultural
eutrophication. In recent years, a dispute has arisen as to whether this species can be used
as an indicator of eutrophication. The results from this study shall therefore advance our
knowledge in this field.
Evidence suggests that the population of Lymnaea peregra was not affected by changes in
the organic matter content or the concentration of potassium and sodium. The abundance
of this mollusc was therefore not significantly altered by the episodes of cultural
eutrophication at Quidenham Mere. This finding coincides with Fitter and Manuel (1986)
who document that this species of mollusc are able to survive in a wide variety of
freshwater habitats. This finding, however, contradicts Dussart (1979) who found a positive

55
correlation between the population of Lymnaea peregra and the concentration of
potassium. Dussart (1979) also found a negative correlation between this variable and the
concentration of sodium. This finding therefore challenges existing literature.
There is evidence however to suggests that the population of Lymnaea sp. was affected by
Figure 18 reveals that the population of Lymnaea sp. initially increased during both episodes
of eutrophication at Quidenham Mere, but decreased towards the restoration process of
the mere. The statistical analysis confirms this. It is therefore likely that the abundance of
this mollusc was altered by the episodes of cultural eutrophication at Quidenham Mere. A
possible explanation for the increased population of this mollusc is that they are able to
survive in oxygen-depleted waters. This is because they are able to hang from the surface of
the water and take in oxygen through its pneumostome (Figure 22 and 23) (Clifford, 1991).
Furthermore, the snail is able to undergo phonological plasticity in order to responds to
periods of low DO (Lodge and Kelly, 1985). A possible explanation for the decreased
population of this mollusc is that they are intolerant to hydrogen sulphide (Calderwell,
1975). Dussart (1979) came to a similar outcome when studying this snail in North West
England.
Figure 22. Diagram of a Lymnaea snail
with the main features labelled.

56
Figure 23. In order to survive in periods
of low DO, the snail hangs suspended
from the upper surface of the water by
its foot. The snail subsequently takes in
oxygen by opening its pneumostome
(Clifford, 1991).
7.3.4. Valvata
Valvata piscinalis and Valvata macrostoma are discussed to identify the effects of cultural
eutrophication. These molluscs have been discussed under the title Valvata, as the results of
the statistical analysis are the same for both species.
Evidence suggests that the population of Valvata was affected by changes in the organic
matter content and the concentration of potassium. Figure 18 shows that the population of
Valvata initially increased during both episodes of eutrophication at Quidenham Mere, but
decreased towards the restoration process of the Mere. The statistical analysis confirms this
(Table 2). It is therefore likely that the abundance of this mollusc was altered by the
episodes of cultural eutrophication at Quidenham Mere. A possible explanation for the
increased population of this mollusc is that the snail is able to survive periods of
eutrophication due to behavioural and physiological plasticity (Lodge and Kelly, 1985).
Furthermore, these molluscs are effective competitors in eutrophic waters, as they can feed
on suspended particles (Grigorovich, et al., 2005). A key explanation for the decreased
population of this mollusc is that it is intolerant to hydrogen sulphide (Calderwell, 1975).
Foot

57
7.3.5. Pisidium
Evidence suggests that the population of Pisidium sp. was affected by changes in the organic
matter content and the concentration of potassium. Figure 18 shows that the population of
Pisidium sp. initially increased during both episodes of eutrophication at Quidenham Mere,
but decreased towards the restoration process of the mere. The statistical analysis confirms
this (Table 2). It is therefore likely that the abundance of this mollusc was altered by the
episodes of cultural eutrophication at Quidenham Mere.
7.3.6. Summary
There is sufficient evidence to suggest that anthropogenic activities at Quidenham Mere
initially caused the population of Bithynia tentaculata, Gyraulus sp, Lymnaea sp., Valvata
piscinalis, Valvata macrostoma and Pisidium sp. to increase. This finding coincides with
Cheng, et al., (2007) who found that an increased concentration of nutrients at Quidenham
Mere caused the population of molluscs to enlarge. There is also evidence to suggest that
the eutrophication process caused the population of these molluscs to decline. A wide range
of literature supports this finding.

58
Chapter 8: Conclusion
8.1. Summary of main findings
The information presented in this paper represents a substantial increase in the range and
quality of data from Quidenham Mere. A new geochemical record provides the
environmental history of Quidenham Mere since the medieval period. This geochemical
record suggests the occurrence of two episodes of cultural eutrophication at Quidenham
since the medieval period. This challenges previous literature, as only one episode of
cultural eutrophication has been recorded at Quidenham Mere. This is therefore a
significant new finding.
The first episode of eutrophication occurred at approximately 800 – 685 cm (medieval/post-
medieval period). Reasons for this outcome include the use of Quidenham Mere as a hemp-
retting pit. Hemp retting would have released a great quantity of nutrients and organic
matter into the Mere, thus causing eutrophication (Cox, et al., 2001; Cheng, et al., 2007).
An additional reason is the clearance of Quercus and Corylus avellana, which would have
resulted in an increased rate of soil erosion into the Mere. The increased input of nutrients
into the Mere, due to soil erosion, may have then promoted eutrophication. This idea
coincides with Peglar (1993) and the geochemical data.
The second episode of eutrophication occurred at approximately 455 – 325 cm (the last 200
years). A reason for this outcome is the burning of vegetation due to the development of
Quidenham Mere Parkland. This idea coincides with the work of Peglar (1993). An increased
rate of soil erosion, due to the clearance of vegetation, may have caused the eutrophication
process. The burning of vegetation may have also caused the leaching of an excessive
quantity of nutrients into the Mere, thus causing eutrophication.
This investigation also provides an accurate mollusc record of Quidenham Mere since the
medieval period. The data shows that Bithynia tentaculata, Gyraulus sp., Valvata piscinalis,
Valvata macrostoma, and Pisidium sp. were affected by anthropogenic activities at
Quidenham Mere. Changes in the percentage of organic matter content caused the greatest
change to the abundance of molluscs. The ending period of the eutrophication process, as
indicated by increased potassium levels, caused the next greatest change to the population

59
of these molluscs. The beginning period of the eutrophication process, as indicated by
increased sodium levels, did not cause a significant change to the population of molluscs.
8.2. The aims of the literature
Overall, the three aims of this literature have been fulfilled to the highest ability possible.
The objectives of this literature have also been fully achieved. Episodes of cultural
eutrophication have been identified by the analysis of the organic matter content, the
potassium concentration and the sodium concentration. Statistical testing also provided
further confirmation. The dating of the eutrophication process, however, requires further
investigation. The first reason for this outcome is that the sediments of Quidenham Mere
cannot be accurately dated. Comparing the sediment composition of Quidenham Mere
with the sediment composition of Peglar (1993) only provided a tentative chronology.
Furthermore, as the phenomenon of eutrophication is a process, a start and end cannot be
identified, and thus dated. Despite this criticism, there is strong evidence to suggest that the
dates recorded in this literature can be used to determine when the Mere experienced
eutrophic conditions, and hence aim number one has been addressed.
Possible explanations as to why the mere experienced cultural eutrophication have been
determined by the analysis of the geochemical record. The magnetic susceptibility results
were, however, unable to add additional support to the conclusions proposed. Nonetheless,
this paper fully supports the idea that anthropogenic activities were the key cause of
eutrophication at Quidenham Mere. Several explanations for each episode of
eutrophication have been documented, and there is strong evidence to accept that the
explanations provided in this literature are legitimate. Furthermore, Peglar (1993) and
Cheng, et al., (2007) supports several of the conclusions proposed in this literature. Aim
number two has therefore been addressed an answered successfully.

60
Changes in the abundance of molluscs have been recorded at Quidenham Mere since the
medieval period. There is evidence to suggest that these changes were caused by cultural
eutrophication. This is because the quantitative zonation analysis places zone boundaries at
the onset of the eutrophication process. The Spearman’s rho test furthers this idea.
However, due to the limitations of the statistical testing (section 8.2) one cannot conclude
that the mollusc population changed due to episodes of cultural eutrophication. Additional
factors may have caused this correlation to be present. Aim number three has therefore
been addressed, but conclusion regarding this aim cannot be produced.
8.2. Limitations of the study
The recognised limitations of this study regard the third aim. For example, the total number
of species extracted from the sample was relatively low. This could not be prevented,
however, as the species acquisition curve revealed that 20 g of sediment was the optimum
sample weight to extract. Additionally, Bithynia sp. may be over represented due to their
thick operculum (Sparks, 1964). Conclusions regarding aim three, therefore, may not be
accurate. Furthermore, correlations and associations do not necessarily imply causation.
Therefore, the results of this study cannot be used to prove that cultural eutrophication
caused the population of molluscs to change; one can only state that there is a correlation
between these two variables.
8.3. Significance of the findings
The overall aim of this paper was to identify the causes of cultural eutrophication at
Quidenham Mere and to document the effects this phenomenon had upon the mollusc
population. In interpretation of the data, it must be realised that the results are only
representative of this location. The conclusions proposed are therefore only legitimate for
Quidenham Mere. Despite this, a significant body of work has accumulated documenting
the negative effects of cultural eutrophication upon the abundance of molluscs, in various
locations. This paper therefore supports this correlation. Furthermore, this paper adds to
the wider issue of environmental change. This is because there is a growing concern that
anthropogenic activities are causing a decline in biodiversity (Huggett, 2010). Future

61
management issues regarding anthropogenic activities can therefore be addressed
appropriately with knowledge of this paper and similar studies.
8.4. Scope for further study
Regarding Quidenham Mere, further studies incorporating a larger population of molluscs is
needed to understand fully the effects of cultural eutrophication. Furthermore, an accurate
dating technique is needed to allow a greater understanding of the causes of cultural
eutrophication at this location. There is also significant scope for further studies regarding
the topic of cultural eutrophication. This is because the interest in this area declined in the
1980s due to a heightened interest in acidification (Smol, 2002). Further studies in this area
will enhance the knowledge of the impacts of cultural eutrophication and allow the field to
become more predictive. Additionally, it will act as a basis of how to manage future cultural
eutrophication problems, and thus prevent environmental change.

The causes and effects of cultural eutrophication at Quidenham Mere, Norfolk, UK. 2011

The causes and effects of cultural eutrophication at Quidenham Mere, Norfolk, UK. 2011

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