Effect of human activity on Lake Saroma (Japan) during the past 150 years: evidence by variation of diatom assemblages.

摘要: Abstract Diatom assemblages of the surface and in core sediment samples from Lake Saroma (Japan) were examined for purpose evaluating anthropogenic effect on coastal environmental changes. Before first inlet excavation, lake's water quality ecology controlled by exchange with Okhotsk Sea as well lake-level variation. However, large-scale ecological modification occurred, mainly due to artificial excavation shellfish industrial farms. A distinct record succession dominant diatom taxa was preserved sediments. Low-oxygen prevalent lake 1929, before excavation. Immediately after low-oxygen western basin began disappear, a trend that became increasing transparent, which has been attributed an rate exchange. lacustrine environment bottom sediments resumes deterioration 20 years since excavation: resultant deposition river-mouth materials into deep caused eutrophication disturbance bottom. At same time, intensified onset intense scallop culturing beginning 1966. Increasing organic loads deposited onto layer form excreta nursery led more oxygen deficiency elution nitrogen phosphorus sediment, again brought about layer. Such change reflected decrease benthic increase planktonic taxa, trends have continued until today. Particularly, numbers assemblage decreasing all over during last 10 years, suggests Saroma's present-day will continue or become even worse.