Mehmet Aksu

Impacts of the fish farms on the water column nutrient concentrations and accumulation of heavy metals in the sediments in the eastern Aegean Sea (Turkey).

We investigated potential effects of the fish farms on water column and sediment around Salih Island in the Gulluk Bay (Aegean Sea, Turkey) where four seasonal samplings were performed from October 2001 to August 2002. One measured physicochemical variables in water column including dissolved oxygen, nutrients (nitrite, nitrate, ammonium, phosphate and silicate), particulate organic carbon (POC) and chlorophyll a. Organic matter, total organic carbon (TOC) and heavy metals (Zn, Cu and Fe) were measured in sediment samples. Although occasional increases in ammonium and chlorophyll a concentrations were observed at the cage stations as compared to the control one, no statistically significant differences were detected among the stations in terms of nutrients, chlorophyll a and POC. On the other hand, significant differences were found in organic matter, TOC and heavy metals (Zn and Fe) of the sediments among the sampling stations. Despite these differences, our results indicate that concentrations of physicochemical variables and heavy metals were within the range of tolerable levels for the marine ecosystem, and the oligotrophic nature of the water column in the study area was able to assimilate organic and inorganic loads caused by the fish farms.

Long-term monitoring of the impact of a capture-based bluefin tuna aquaculture on water column nutrient levels in the Eastern Aegean Sea, Turkey.

Capture-based aquaculture of Atlantic bluefin tuna in the Mediterranean has been expanding rapidly but little is known about its environmental impact. In order to understand the consequences of this new sector, long-term monitoring is needed. For this purpose, we investigated the impact of a capture-based tuna farm located in the Gerence Bay (Aegean Sea) on the water column on a seasonal basis from 2005 to 2008, where in the water column, temperature, salinity, pH, dissolved oxygen, nutrients (nitrite, nitrate, ammonium, and phosphate), and chlorophyll a, in the sediment organic carbon variables were measured. Although highest nutrient concentrations were observed at the cage station as compared to the two controls in the production period, differences were not statistically significant between stations. Monitoring of physico-chemical parameters, nutrients, and chlorophyll a in water column together with organic carbon in sediment did not show detectable impact of fattening of Atlantic bluefin tuna. This was probably caused by strong currents present in the area, location of the cages away from the coast, hence high water depth, controlled feeding, and periodic presence of tuna farming activity in the study area.

Effects of Wastewater Treatment Plant on Water Column and Sediment Quality in Izmir Bay (Eastearn Aegean Sea)

Economic and social consequences of damage to the marine environment are becoming increasingly evident. Unless seas and oceans are carefully protected, their economic potential can not be sustainable. The marine environment is one of humanity’s most precious assets. Oceans and seas cover 71% of the earth’s surface and are the greatest sources of biodiversity, containing 90% of the biosphere. Marine ecosystems play a key role in climate and weather patterns. They also contribute to economic prosperity, social wellbeing and quality of life and are literally a source of survival for coastal communities. However, this environment is under intense pressure. The pace of degradation of biodiversity and habitats; the level of contamination by dangerous substances and the emerging consequences of climate change are some of the most visible warning signals (Environment for Europeans 2005). Only recently marine eutrophication is being regarded as pollution, particularly in near shore environments where more often low water transparency, oxygen depletion and algal blooms occur. Nutrient concentrations in sea water and sediment increase remarkably going from offshore to inshore, due to the proximity of terrestrial and domestic inputs and to the increase of biotic and abiotic processes strictly related to the progressive decrease of water depth. The Bay of Izmir is in a state of pollution centre in Turkish Aegean coast region in respect of aesthetic and welfare where pollution increased in the course of time from what it used to be in 1960s. The most important factors of this current status are; domestic wastes of more than 3 million people; industrial wastes from 1,500 factories; wastewater discharge during maritime transportation and shipyard services filling materials arisen from the recreation of seaside alluvions carried with rivers and valleys. Izmir Bay is surrounded by major agricultural plateau. Menemen plateau in the North–North West of Izmir is one of the most important production fields where agricultural irrigation is utilized. The Bay is also influenced by the pollution caused by the agricultural activities in the Gediz River water shed and erosion of a large area by Gediz River. The bay of Izmir, which is the biggest harbour on the Aegean Sea, is of economical importance for Izmir, the third largest city in Turkey. The Bay is divided into inner, middle and outer bays in terms of topographical and hydrographical characteristics. The inner bay