Trophic state and oceanographic conditions of Amvrakikos Gulf: evaluation and monitoring

Abstract

The environmental state of estuaries is often compromised by various processes with direct and indirect ecological impacts such as eutrophication, harmful algal blooms, trophic interactions, and so on. In this paper, the eutrophication state of an important semi-enclosed embayment, the Amvrakikos Gulf, in Western Greece, for the first time will be examined, and the present situation will be compared with previous measurements. Field data used in this study were collected during four sampling cruises (April 2009 to March 2010) in the Amvrakikos Gulf. In compliance with the results, both the rivers’ high discharges and the high evaporation rate lead to strong stratification of the water column throughout the year due to either salinity or temperature fluctuations. In combination with the limited communication with the open sea, this has resulted in different spatial and temporal dissolved oxygen distributions, as the western part of the gulf is seasonally hypoxic, while the eastern part is seasonally anoxic. The use of fertilizers, the load from fish farming, the phosphate geological layers, and other point and nonpoint source pollutions increase the nutrient pollution of the Amvrakikos Gulf. As a consequence, according to Carlson’s trophic state index, the Amvrakikos Gulf varies from mesotrophic to eutrophic.

Keywords:

• Eutrophication
• Stratification
• Hypoxia
• Anoxia
• Trophic state index
• Amvrakikos Gulf

Notes

Third International Conference on Environmental Management, Engineering, Planning and Economics (CEMEPE 2011) & SECOTOX Conference, 19–24 June 2011, Skiathos Island, Greece