engleski

Effect of eutrophication on benthic communities in the Split area (Adriaitic Sea)

The number of urban inhabitans in cities is rapidly growing, producing further increased amount of waste: bacterial/viral pollutants acting as potential disease pointer, and nutrient generating severe eutrophication of coastal waters. The eutrophication has become an acute environmental problem especially in semi-enclosed areas and gulfs with small exchanges of water with surrounded areas like the Kaštela Bay. The enrichment by nutrients, (especially compound of nitrogen and phosphorous) and other contaminants, causing accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to balance the organisms present in water concerned. Often the total biomass increases, such as, for example, the total amount of chlorophyll in the plankton. Growth rate changes lead to changes in species compositions in both plank-tonic and benthic assemblages. The long-term studies of chemical and biological parame-ters in the Kaštela Bay area point to the fact that, during the past decade, an increase in the eutrophication level has persisted in all the areas of the eastern Adriatic coast. Long-term effect as changes in composition and depth distribution of the benthic flora and vegetation has been recorded by comparing data over time. Likewise, low oxygen condition in the some closed areas, which accompany severe eutrophication often lead to behavioural changes, such as fish leaving the area. Analyses of assemblages showed that there are no significant changes in the catch biomass. There are evident changes regarding of fish species, particularly commercially valid ones. There are also noted changes of basic biometrical characteristics of the species that are surely the consequences of uncontrolled overfishing. Analyses of assemblages would be expected to record some of these changes as a local species extinctions.

coatal waters; eutrophication; canges in the benthic comunity; Split area; Adriatic Sea; Croatia

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