MEROMIKTISKA SJÖAR - SÄREGNA OCH SKYDDSVÄRDA / Meromictic Lakes
There are rwo basic lake types, holomictic and meromictic. Holomictic lakes have a complete verrical mixing whereas the circulation ofmeromictic lakes is incomplete. Meromictic condiaons may be due to accumulation of e.g. iron compounds m the deep water or intrusion ofsalt water into fi-eshwater lakes. Meromicuc conditions may also occur in deep coastal inlets which become isolated from the sea due ro land uplift. The deep water or monimolimnion of meromictic lakes is usually anoxic and may be rich in hydrogen sulfide. Phototrophic bacteria and certain algae may have mass development in thin layers at the top ofthe anoxic zone and may be grazed upon by zooplankton. The undisturbed sediments ofmeromictic lakes give valuable paleolimnological information. As meromictic lakes are relatively rare and they have a number ofunique features, they are worth special protection. Several meromictic lakes have been srudied in Norway but very few in Sweden and Finland.