Foraminifera are single-celled organisms that live in marine environments and produce shells or tests. Their tests can be preserved as fossils and used to reconstruct past environments. Foraminifera inhabit different zones within salt marshes and mangroves based on tidal levels, making them useful indicators for paleoenvironmental studies. Studies of foraminifera distribution in the Severn Estuary, UK showed distinct zones related to tide levels that allow reconstruction of past sea levels and salt marsh evolution. Foraminifera also have potential as indicators of coastal pollution and sediment transport.

1. Foraminifera in coastal studiesProfessor Simon K. HaslettCentre for Excellence in Learning and TeachingSimon.haslett@newport.ac.uk5th July 2010

2. IntroductionForaminifera are marine Sarcodine Protozoa that possess tests (shells) that are preservable in the fossil record.These tests may either be constructed using cemented detritus (agglutinating or arenaceous forms), or secreted using calcium carbonate (calcareous forms).Their life habits embrace planktonic and benthonic modes , although planktonic forms generally inhabit the open ocean and seldom live in coastal waters in any abundance, whilst benthonic foraminifera exist on substrates from abyssal plains to high intertidal areas.There are many species of foraminifera which have narrowly defined niches, making them ideal for palaeoenvironmental analysis (Murray, 1991).In this presentation, several examples of how foraminifera have been employed for coastal studies are described.

3. Using foraminifera in palaeoenvironmental analysisThe application of foraminifera to sea-level studies is well-established (e.g. Scott and Medioli, 1978, 1986).Salt marsh foraminifera have been shown to occur within specific vertical zones on modern salt marshes from eastern North America (e.g. Gehrels, 1994, 2000) which can be related to tide levels and accurately employed as tide level indicators in palaeo-salt marsh sediments.Of greatest significance is recognition that in micro- and meso-tidal salt marshes of eastern North America, foraminifera extend up to Highest High Water (HHW), with the highest zone (Zone 1A) characterised by a monospecific assemblage of Jadamminamacrescens, which extends down to Mean Highest High Water (MHHW).Recognition of Zone 1A in palaeo-salt marsh sediments is thus a very useful indication of palaeo-tidal levels (Gehrels, 2002).

4. Foraminifera distribution in the Severn Estuary (UK) 1Haslett et al. (1998) report the results of a modern foraminifera distribution survey across salt marshes in the Severn Estuary, indicating that as in North America, foraminifera possess restricted vertical ranges related to position within the tidal frame.Salt marshes of the Severn Estuary.

5. Foraminifera distribution in the Severn Estuary (UK) 2The results indicate that a zone roughly equivalent to Mean High Water Spring Tide (MHWST) – Highest Astronomical Tide (HAT) is barren of foraminifera (contains a few Jadamminamacrescens).This is possibly due to the severe macrotidal nature of the inner Severn Estuary.Below MHWST, Jadaminnamacrescensand Trochamminainflatacharacterise the zone, followed by the Ammonia beccariizone and Haynesinagermanicazone, extending from just above Mean High Water Neap Tide (MHWNT) towards Mean Tide Level (MTL).Source: Haslett et al. (1998).

6. Vertical salt marsh accretionRecognition of these foraminiferal zones allows, for the first time in the Severn Estuary, the establishment of the relationship of salt marsh surfaces to sea-level.Haslett et al. (2001) have subsequently applied this knowledge to the study of downcore historic salt marsh sediments.Allen and Haslett (2002) have used foraminifera to reconstruct Holocene salt marsh palaeogeomorphology.In addition to salt marsh studies, foraminifera have also shown potential as indicators of coastal pollution (Alve, 1995) and sediment transport (Haslett et al., 2000).

7. Foraminifera and mangrovesAs well as in temperate salt marshes, foraminifera also appear to be useful in tropical mangrove settings (e.g. Haslett, 2001).The relationship of foraminifera distribution to tidal levels in Thomatis Creek, a tidal tributary of the Barron River estuary, north Queesnsland, Australia. Source: Haslett (2001).

8. Practical: estuarine sediment and foraminifera study 1It will take 3 weeks to process samples for this practical, and a further 3 weeks to analyse them. At the end of this period, you will be supplied with a data tablethat will include the sample numbers, water depth (m), foraminifera species abundance, and particle size data. Using samples taken from a local salt marsh, be sure to sketch a location map and record details of the water depth at each sample site.The aims of this practical are for students:To develop a familiarity with the study of foraminifera, including sample processing techniques, drawings, anatomical descriptions, and notes on ecology for each of the main species you are introduced to;To analyse the modern distribution of foraminifera within an estuarine habitat and relate it to estuarine environments; andTo appreciate the range of sediment types found within an estuary.From the data available you may be able to explore the relationship between foraminifera and sediment and estuarine parameters. You will be able to explore the foraminifera and sediment data (use raw counts or convert to percentages) by plotting it against water depth, and/or distance along the estuary. Get ideas from the examples and references provided in this presentation.

9. Practical: estuarine sediment and foraminifera study 2Method for sample preparation:Week 1 of practicalPut an empty aluminium sample tray onto an electronic balance and record its weight to 2 decimal places (use the table below to record weights).Then put the wet sample onto the LABELLED aluminium tray (label tray with ‘sample no.’ (and your name if necessary)), and weigh and record to 2 decimal places (leave a little bit of wet sediment in the original bag).Leave the sample on the tray to air dry on a side bench in the lab for 1 week.Week 2 of practicalWhen the sample is dry, weigh and record the tray + sample to 2 decimal places.Put the sample in a LABELLED glass beaker and generously cover with water (label beaker with ‘sample no.’ (and your name if necessary)). Stir and leave for 10-30 minutes (until the sediment is loose).Sieve at 63μm at the sink and retain the fraction left on the sieve (> 63μm).Wash out the original beaker used to soak the sample.Gently wash the >63μm fraction back into the original LABELLED beaker (add ‘> 63μm fraction’ to the beaker label) with the minimum amount of water.Leave sample in beaker to air dry for 2-3 weeks.

10. Practical: estuarine sediment and foraminifera study 3Week 3 of practicalPut an empty LABELLED sample bag on an electronic balance and zero the balance.Once the sample is dry, carefully transfer the sediment contents of each beaker into the LABELLED SAMPLE BAG (labelled with ‘sample no.’, your name if necessary, and ‘> 63μm fraction’).Weigh the bag using an electronic balance to 2 decimal places and write the weights on the bag.Search the > 63μm fraction under the microscope for foraminifera, pick using 000 paintbrush, and mount onto gummed LABELLED microslides – the aim is to pick around 100 specimens.Keep sediment that you have searched through separate from the sediment you haven’t yet looked at.Keep all materials relating to a sample in a large LABELLED sample bag i.e. it should contain the original sample bag and sediment, a sample bag with processed sediment, a sample bag of searched sediment, the microslide with picked foraminifera mounted on it, and , if you want to, your picking brush and picking tray.Week 4 of practicalContinue picking foraminifera specimens and mounting them onto microslides.Week 5 of practicalIdentify foraminifera specimens.Week 6 of practicalCollate foraminifera and sedimentological data.In weeks 1 & 2, while the samples are processing, look at foraminifera reference collections; drawing specimens,make notes about anatomy and ecology. Also, sediment will be available to practice picking through.

11. SummaryThe fossil record of foraminifera is founded entirely on their preserved tests.Both planktonic and benthic types.Salt marsh and mangrove foraminifera occupy different vertical zones within the sediment based on the environmental conditions in which they live.Zones can be related to tide-levels and accurately employed as tide-level indicators in palaeo-salt marsh sediments.The restricted altitudinal ranges make foraminifera excellent tools for reconstructing past sea levels and salt marsh environments.Foraminifera have also shown potential as indicators of coastal pollution and sediment transport.

12. ReferencesAllen, J.R.L. and Haslett, S.K. 2002. Buried salt-marsh edges and tide-level cycles in the mid-Holocene of the Caldicot Level (Gwent), South Wales, UK. The Holocene, 12: 303-324.Alve, E. 1995. Benthic foraminiferal responses to estuarine pollution: a review. Journal of Foraminiferal Research, 25: 190-203.Gehrels, W.R. 1994. Determining relative sea-level change from salt-marsh Foraminifera and plant zones on the coast of Maine, USA. Journal of Coastal Research, 10: 990-1009.Gehrels, W.R. 2000. Using foraminiferal transfer functions to produce high-resolution sea-level records from salt-marsh deposits, Maine, USA. The Holocene, 10: 367-376.Gehrels, W.R. 2002. Intertidal foraminifera as palaeoenvironmental indicators. In: Haslett, S.K. (ed.). 2002. Quaternary Environmental Micropalaeontology. Arnold, London, pp. 91-114.Haslett, S.K., Davies, P. and Strawbridge, F. 1998. Reconstructing Holocene sea-level change in the Severn Estuary and Somerset Levels: the foraminifera connection. Archaeology in the Severn Estuary, 8(for 1997): 29-40.Haslett, S.K., Curr, R.H.F. and Bryant, E.A. 2000. Tracing beach sand provenance and transport using foraminifera: preliminary examples from north-west Europe and south-east Australia. In: Foster, I.D.L. (ed.). Tracers in Geomorphology. Wiley, Chichester, 437-452.Haslett, S.K. 2001. The palaeoenvironmental implications of the distribution of intertidal foraminifera in a tropical Australian estuary: a reconnaissance study. Australian Geographical Studies, 39: 67-74.Haslett, S.K., Strawbridge, F., Martin, N.A. and Davies, C.F.C. 2001. Vertical saltmarsh accretion and its relationship to sea-level in the Severn Estuary, UK: an investigation using foraminifera as tidal indicators. Estuarine, Coastal and Shelf Science, 52: 143-153.Murray, J.W. 1991. Ecology and Palaeoecology of Benthic Foraminifera. Longmans.Scott, D.B. and Medioli, F.S. 1978. Vertical zonations of marsh foraminifera as accurate indicators of former sea-levels. Nature, 272: 528-531.Scott, D.B. and Medioli, F.S. 1986. Foraminifera as sea-level indicators. In: Van de Plassche, O. (ed.). Sea-level Research: a manual for the collection and evaluation of data. Geo Books, pp. 435-456.

13. This resource was created by the University of Wales, Newport and released as an open educational resource through the 'C-change in GEES' project exploring the open licensing of climate change and sustainability resources in the Geography, Earth and Environmental Sciences. The C-change in GEES project was funded by HEFCE as part of the JISC/HE Academy UKOER programme and coordinated by the GEES Subject Centre. This resource is licensed under the terms of the Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales license (http://creativecommons.org/licenses/by-nc-sa/2.0/uk/). All images courtesy of Professor Simon Haslett. However the resource, where specified below, contains other 3rd party materials under their own licenses. The licenses and attributions are outlined below:The name of the University of Wales, Newport and its logos are unregistered trade marks of the University. The University reserves all rights to these items beyond their inclusion in these CC resources. The JISC logo, the C-change logo and the logo of the Higher Education Academy Subject Centre for the Geography, Earth and Environmental Sciences are licensed under the terms of the Creative Commons Attribution -non-commercial-No Derivative Works 2.0 UK England & Wales license. All reproductions must comply with the terms of that license.