Temporal variations of ostracods, diatoms, and environmental factors over the past several hundred years in the Seto inland sea, Japan: with relation to anthropogenic influence

Abstract

The Seto Inland Sea (SIS) is the largest enclosed sea in Japan, and has nine basins called “Nada” or “Wan”(bays) and three channels (Suido or Seto) (Fig. 1). During a period of strong economic growth from 1955 to 1973 (“economic miracle”), industrialization, reclamation, and sand collection for construction material intensified and a rapid increase in various effluents caused intensive water pollution, red tides, and organic pollution in sediment. Since then effluents have been regulated in the SIS. Water quality has been measured widely in the SIS since the 1970s or 1980s. Temporal changes of ostracods and diatoms with relation to anthropogenic impacts in the SIS have been recently studied (e.g. YASUHARA et al., 2003, 2007; HIROSE et al., 2008; IRIZUKI et al., 2011; YOSHIOKA et al., 2012). We continue conducting such studies at many sites of the SIS. In this study we compiled these data and elucidated quantitatively the relations of ostracods to several environmental factors (e.g. TOC, TN, COD) and planktic and benthic diatoms, which seem to be one of foods for ostra…