Sediment signature inside and outside of breakwaters at the planting area with Nymphoides peltata in Lake Kasumigaura

Planting Nymphoides peltata may deteriorate sediment quality in terms of organic content through increase the supply of organic materials. Because breakwaters are often constructed at the planting of N. peltata, changing wave action may also alter the sediment quality. To examine the possible effect of N. peltata plantation, we analyzed the quality of sediments on both the landward and offshore sides of the breakwaters. Surface sediments sampled from the landward side of the breakwaters, where plantation of N. peltata had operated and disappeared afterwards, showed higher contents of fine particles, organic carbons and total sulfur compared to the offshore side. Surface sediments sampled from the landward side of the breakwaters, where natural populations of N. peltata had been remaining showed equivalent contents of fine particles, organic carbons and total sulfur with that of the offshore side s. Since the breakwaters constructed at the area where natural populations of N. peltata exist had wide openings, we assumed that these areas experienced less effects brought about by the breakwaters. Keyword:Core sediment, total sulfur, organic carbon, total nitrogen, silt clay content (2015年4月7日受付:2015年5月8日受理)