| 6. Freshwater, Coastal and Marine Environments |
| 6a. Coastal and freshwater environments |
| This session deals with various environmental issues relating to coastal fisheries and freshwater environments. In temperate and subtropical regions, declines in water and sediment quality are serious problems affecting fisheries. For example, in semi-enclosed areas such as estuaries, embayments and harbors, physicochemical and biological processes cause accumulation of organically rich sediments. Further, oxygen-depleted water and hydrogen sulfide are sometimes formed in the sediments and associated waters. Deterioration of coastal conditions may lead to mortality of benthic organisms, which affect the pelagic ecosystems through decline in food chain. Tidal flats and seaweed and seagrass beds have been decreased by reclamations of lands for agriculture, manufacturing and business developments. Destruction of coral reefs and mangrove forests in tropical and subtropical regions are also serious problems for fisheries and biodiversity in coastal areas. Freshwater environments such as lakes, ponds, rivers and artificial lakes have been degraded by eutrophication and pollutions with heavy metals, pesticides, endocrine disturbing chemicals, and other harmful organic chemicals. Eutrophication can lead to cyanobacterial blooms in lakes and ponds, and further deterioration of water quality, fish mortality events and death of other animals. Eutrophication and pollutions have been caused by industrial and domestic sources and also from non-point source pollutions. Constructions of dams have lead to an increase in depositions of sediments and increased phytoplankton blooms that have further decreased key nutrients. Freshwater flows into coastal areas and eventually affects nutrient balance, because of deficiency in key nutrients such as silicate and phosphate in freshwater. A better understanding of coastal and freshwater environments could be achieved through systematic monitoring and development of ecosystem modeling. |
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