Spatial distribution of phytopigments and organic matter in surface sediments in Lake Saroma (Hokkaido, Japan)

In Lake Saroma, scallops have been adversely affected by hypoxic events, which are caused by long-term scallop culture in summer. In this study, we were conducive to the spatial distribution of ChI a, phaeopigment, total organic carbon (TO C) and total nitrogen on a grid of 54 stations in surface sediments. The temporal changes in the TOC content of the surface sediments since the initiation of scallop culture in Lake Saroma were also studied. The average ChI a j total pigments was 0.7±0.2 in the organic poor area (PA), which was higher than 0.4 ± 0.2 in the organic rich area (RA). Benthic environments were suited for growing microphytobenthos in the PA. In contrast, the RA has become increasingly eutrophic because of the average TOC was 23±5 mg g- l, which was higher than 6± 3 mg g -l in the PA. During the past 40 years, after the TOC content had decreased in surface sediment owing to the excavation work, it has increased in the RA owing to the concentrated scallop culture facilities . This study concludes that benthic environments in Lake Saroma are directly and indirectly affected by human activities, particularly in the RA