Annual Review & Research in Biology 3(4): 873-880, 2013
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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.
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Research Article
Received 17 July 2013 th Accepted 28 July 2013 th Published 4 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 ____________________________________________________________________________________________ *Corresponding author: Email:
[email protected];
Annual Review & Research in Biology, 3(4): 873-880, 2013
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.
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Annual Review & Research in Biology, 3(4): 873-880, 2013
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 + -1 ammonium nitrogen (NH3 + NH4 ):
