1. ____________________________________________________________________________________________
*Corresponding author: Email: cosmasfax@yahoo.com;
Annual Review & Research in Biology
3(4): 873-880, 2013
SCIENCEDOMAIN international
www.sciencedomain.org
Dispersal and Variability of Chemical and
Biological Indices of Aquaculture Pollution in
Igoumenitsa Bay (NW Greece)
Paraskeyi Mpeza1
, Theodoros Mavraganis1
and Cosmas Nathanailides1*
1
Department Aquaculture and Fisheries, Technological Educational Institute of Epirus, Irinis
and Filiaw 1, Igoumenitsa, Greece GR 46100e, Greece.
Authors’ contributions
This work was carried out in collaboration between all authors. All authors contributed
equally for designing the study, laboratory analysis, statistical analysis, writing the
manuscript. All authors read and approved the final manuscript.
Received 17
th
July 2013
Accepted 28
th
July 2013
Published 4
th
August 2013
ABSTRACT
The purpose of this work was to monitor nutrient enrichment around a fish farm site in
Igoumenitsa Bay (NW Greece). Seasonal samples were collected from the waters and
benthos surrounding fish farms in Igoumenitsa Bay, NW Greece. The study was carried
out in Igoumenitsa bay between May 2011 and Dec 2012). Seawater samples were
collected every month from different sampling sites which were: the open Ioanian sea, 60
meter south and North of the fish farms as well as in the water adjucent to the floating
cages. The waters surrounding the fish farms exhibited profound increased mean annual
content of phosphorus, which peaked during the summer months. This increase in
phosphorus was also reflected in high primary productivity as indicated by increased chl-a
content at the sites of the fish farms. A model of dispersion of wastes generated by the fish
farms indicates that the major path of dispersion is towards the coast and over a range of
more than 120 meters. The directions and velocity of water currents may result in the
diffusion of nutrient from point sources such as the fish farms towards deepest part of the
bay (South). The results indicate that benthic ecosystem around the fish farms is not
significantly disturbed. Nevertheless, the levels of nutrients in the water body and the
AZTI’s marine biotic index (AMBI) of the sampling points indicate a potential ecological risk
during the summer period. Increased feeding and metabolism of the farmed fish during the
growing season is combined with the natural seasonal hydrological conditions and result in
Research Article

2. Annual Review & Research in Biology, 3(4): 873-880, 2013
874
a highly localized aquaculture induced eutrophication.
Keywords: Aquaculture; aquatic pollution; eutrophication.
1. INTRODUCTION
Eutrophication in coastal zones is a major environmental problem because it can lead to
harmful algal blooms, shellfish contamination, anoxic and hypoxic induced fish kills,
ecosystem degradation, changes in biodiversity. In turn this can result in economic losses
[1,2]. Fish farming often results in a generation of a nutrient load which contain uneaten
feed, faeces, and both organic and inorganic elements, such as nitrogen (NHX, NOx), and
phosphorus containing molecules [3,4,5,6]. This organic load can in several cases result in
oxygen deficiency, generation of hydrogen sulphide, and blooms of harmful plankton. Waste
solids can form sediments, for example below the cages, which can alter the benthic
ecosystem with consequences to the ecology of the aquatic body [7].
Several biological and chemical parameters can be used to identify the level of pollution
impacts on the marine environment due to the increase in anthropogenic activities, such as
aquaculture. A range of direct physico-chemical measurements can indicate disturbances of
water quality due to aquaculture generated organic load but the biotic indices, which based
on the benthic invertebrate community structure, can provide information about the Biotic
community present at seabed sites below fish farms and they particularly emphasise the
trophic distributions of species and their relative abundance, which can be used as an
indication of environmental quality [8]. AMBI (AZTI’s marine biotic index) is a biotic index ex)
assigns a score on the basis of interactions and presence of species from different trophic
levels. The score is directly related to good or poor quality environmental conditions [9].
The selection of sites suitable for marine floating cages for aquaculture is based on several
criteria including the presence of water currents and the depth of the water bodies. Feeding
management of aquaculture requires adjustment of feeding regimes according to fish
size/age, fish biomass and temperature. Bioenergetic models can be used to estimate the
feeding required and the metabolic wastes generated by a fish farm [10]. Organic wastes
from floating aquaculture cages include uneaten feed and fish faeces [11]). The water
current can disperse the wastes but that depends on the settling velocity of the wastes and
the depth. This relationship can be used to calculate the dispersion of wastes around a
particular fish farm. Perez et al. [12] used bioenergetic models, current velocities and
direction to illustrate the particulate waste distribution at marine fish cages.
Igoumenitsa bay has an opening to the Ioanian sea facing the Corfu strait, and is protected
by high waves by a narrow landline (Drepanos). Three fish farms operate in the Bay. Several
fish species are cultivated in the region but production (annually reaching 450 tonnes) is
mainly based on the farming of sea bass (Dicentrarchus labrax) and gilthead sea bream
(Sparus auratus). The purpose of the present work is to estimate organic load generated
from from aquaculture floating cages in Igoumenitsa bay and to predict the particulate waste
distribution around the fish cages.

3. Annual Review & Research in Biology, 3(4): 873-880, 2013
875
2. MATERIALS AND METHODS
The study was carried out between May 2011 and Dec 2012). Seasonal seawater samples
were collected from different sampling sites which were: the open Ionian sea, 60 meter south
and North of the fish farms as well in the water adjacent to the floating cages F). The
stations were reached by boat and the exact position of each sampled station was confirmed
by a Geographic positioning system. Oxygen, temperature, pH and salinity of the water
samples, were measured in situ at the field with portable multi parameter YSI (YSI 6600)
equipment. Chl-a was measured with trichromatic spectrophometic method [13].
Benthic macrofauna were sampled from the spring of 2011 to the winter of 2012, using a
standard size grab sampler (Van Veen 0.025 m2) from beneath the floating cages and from
two sampling stations south and north of the fish farms. Species richness and abundance
counts per unit area calculated after sorting by eye. Using the macrofauna data, the values
of AMBI (AZTI’s marine biotic index) were calculated [14].
Current speed and direction were measured approximately 50 m from the fish cages using a
Valeport BFM105 self recording current meter deployed 3 m below the surface. A solid
phase waste deposition model developed by Pérez et al. [12] was used to calculate the
dispersion of the wastes.
3. RESULTS AND DISCUSSION
Temperature followed the expected seasonal pattern with the lowest values in March
(14,8ºC to 15.5ºC) and the highest in August (26,6ºC). Salinity values ranged from 37 psu to
38,95 psu, with the lowest values in April and the highest in August. The pH varied from
7,59 to 8,6. The observed pH values are commonly observed in other similar systems in
Greece [15,16]. The dissolved oxygen concentrations indicated values from 7,1 mg/l at
sampling site B1 on May to 12,5 mg/l on March at sampling site (L) near a small lagoon.
Throughout the year, the minimum and maximum amounts of nutrients were: Total
ammonium nitrogen (NH3 + NH4
+
): <0,01–0,62 mg-at l
-1
, Phosphate (PO4): <0,01 - 0,14 mg-
at l
-1
. Chl-a content (mg m
-3
) ranged from 0,0189 at surface waters, to 26,63 and 7,23 at 5m
depth during April and June respectively.
The macroinvertebrate abundance 60 meters South and North of the flaoting cages (but not
beneath the cages) remained similar over the period of the study, on the contrary the
abudance varied between the different sampling sites. More specifically, The AMBI index
(Fig. 2) varied significantly spatially between the North sampling site and the other two
sampling sites (P<0.001, DF=2, F=23.04) but not seasonally (P>0.05, DF=3, F=2.84)
A model of solid phase waste deposition for fish wastes [12] was used to calculate the
dispersion of the wastes (Fig. 1).

4. Annual Review & Research in Biology, 3(4): 873-880, 2013
876
Fig. 1. Dispersion model of fish faeces calculated according to depth, water flow
velocity and direction using faeces settling velocity u=0,04 [12]. The arrow indicates
the magnetic North (N). White boxes indicate the North and South sampling points for
the Benthic Ecosystem analysis
Phytoplankton production depends on supplies of nitrate-N and phosphate-P, an increase in
these nutrients usually results in eutrophic conditions with seasonal algal blooms. Coastal
waters eutrophication, results from a combination of natural and anthropogenic influences
[17]. Anthropogenic enrichment of water with nutrients, especially nitrogen and/or
phosphorus and organic matter in aquatic ecosystems can result in increased growth of
algae and higher forms of plant life. In turn, these eutrophication results in an unacceptable
deviation in structure, function and stability of the ecosystem and to the quality of water [18].
Apart from the ecological issue, eutrophication is a serious economic problem in coastal
marine ecosystems worldwide [19]. A key element of nutrients inflow-outflow in a bay
involves the natural flow of nutrients from the land and the outflow of nutrients to the open
sea. In addition to a natural flow of nutrients, anthropogenic sources result in an increased
nutrient content of bay's aquatic ecosystems. Agricultural runoff of nitrate, olive-processing
plants, domestic sewage plants, can result in increased nutrient content and Eutrophication.
Furthermore, resuspension of the sediment by water currents and winds and decomposition
of algae can further increase the available nutrients for primary production. Measurements of
nutrient concentrations such as total nitrogen and total phosphorus and algal growth are
essential parameters in efforts to manage and monitor coastal zone eutrophication [20]. The
result indicate a seasonal element of high primary productivity of the Bay, with a strong
spatial element of variability attributed to the sampling locations of the fish farming site. Fish
farms can generate nutrient waste (uneaten food and metabolic waste). Changes in the Chl-
a content can be an indicator of changes in plankton primary productivity [23,24]. The levels
of Chl-a observed here indicate a medium status of Eutrophication in the bay [20], but PO4
levels reached) of fish farms during summer are usually resulting in increased nutrient
loading of the nearby water bodies [21,22] such an increase was observed in the increased
chl-a content in the fish farms samples of August. The content of chl-a is a more reliable
indicator of organic enrichment in a bay.

5. Annual Review & Research in Biology, 3(4): 873-880, 2013
877
Currents may wash and dilute a poit source of organic enrichement but increased primary
production remains over a significant period and is reflected in the Chl-a content of the
samples. Changes in the Chl-a content can be an indicator of changes in plankton primary
productivity. The levels of Chl-a observed here indicate a medium status of Eutrophication in
the bay [20] but organic wastes generated by the fish farms may explain the high peaks of
chl-a content in the location of fish farms.
Table 1. Variability in DO2; TAN(total ammonium nitrogen); PO4; Chl-a ,& salinity of
surface waters in Igoumenitsa Bay
Parameter Significance of differences (ANOVA)
PO4 P<0,001
TAN P<0.001
DO2 P<0.001
Chl-a P=0,031
Salinity P<0,001
2,14
2,16
2,18
2,20
2,22
2,24
2,26
2,28
Spring Summer Autumn Winter
North South Ffarm
Fig. 2. The AMBI index values of the benthic community at the Fish Farms site: FF
(circles): in the waters adjacent to the floating cages, S(squares): 60 meters south,
N(triangles): 60 meters north of the floating cages. The AMBI index varied
significantly spatially between the North sampling site and the other two sampling
sites (P<0.001, DF=2, F=23.04) but not seasonally (P>0.05, DF=3, F=2.84)
The model of dispersion of wastes generated by the fish farms indicates that the major path
of dispersion is towards the coast and over a range of more than 120 meters. The location of
the fish farms and the directions and velocity of water currents may result in the diffusion of
nutrient from point sources such as the fish farms towards deepest part of the bay (South).
The results of the present work indicate that chemical and biological parameters which were
investigated in the present work can provide important information for the aquatic ecosystem

6. Annual Review & Research in Biology, 3(4): 873-880, 2013
878
of Igoumenitsa bay. This information is useful for both monitoring the ecological conditions of
the bay but also for offering the fish farm industry valuable information for the water quality of
the aquaculture site, a parameter which is important for ensuring the welfare of the growing
fish and for minimising the risk of exposure to stressfull environmental conditions of the
farmed fish with consequences for the welfare and the quality of the final fish product of the
aquaculture industry operating at the site.
4. CONCLUSION
The results indicate a potential ecological risk of aquaculture pollution during the summer
period. During the summer, fish farms may intensify feeding rate and the metabolism of the
farmed fish may peak. The bay appears to exhibit a natural seasonal hydrological cycle of
nutrients and a highly localized aquaculture induced eutrophication. The modelling of particle
diffusion used in the present work can provide extremely useful information for r
environmental management of finfish culture.
Although the results of this study indicate minimal environmental effect of aquaculture
activity in the Bay, a potential eutrophication, especially if the fish farming activity is
intensified and the usage of aquaculture chemicals increase may occur.
In addition to the AMBI index, the nutrient load offers an additional parameter for monitoring
the ecosystem of the bay. This information can be useful for the management of aquaculture
development in Igoumenitsa Bay.
ACKNOWLEDGEMENTS
This research has been co-financed by the European Union (European Social Fund – ESF)
and Greek national funds through the Operational Program "Education and Lifelong
Learning" of the National Strategic Reference Framework (NSRF) - Research Funding
Program: ARCHIMEDES III. Investing in knowledge society through the European Social
Fund.
COMPETING INTERESTS
Authors have declared that no competing interests exist.
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_________________________________________________________________________
© 2013 Mpeza et al.; This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
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