Abstract
We analyzed the depth profiles of phosphorous and heavy metal ions (Cr, Zn, Pb, Cd, Co, Ni, and Cu), sedimentary pigments, and fossil diatoms in the sediment cores collected from Lake Sanaru in Hamamatsu, Shizuoka Prefecture, to estimate anthropogenic effects in the lake. The concentration of P and heavy metals were significantly higher in the upper parts of the cores, indicating anthropogenic inputs into the lake. We referred their concentrations in the lower parts of the cores to the background concentrations without anthropogenic effects, and estimated the excess amounts of the elements preserved in the sediment in Lake Sanaru. The concentrations of total chlorophyll a and total carotenoids were also higher in the upper parts of the cores with dramatic changes in the relative carotenoids, suggesting eutrophication accompanying abrupt alteration in algal assemblages. Analyses of fossil diatoms and Cl− ion in the interstitial waters suggest an increase in the lake salinity, probably due to the construction of the Shinkawa drainage channel and a decrease in freshwater supply into the lake by urbanization of the watershed. This study demonstrates, using multi-proxies in the sediment cores, impact of anthropogenic effects on aquatic environments and the ecosystems.
