Nippon Suisan Gakkaishi 75 (4), 674-683 (2009)

Zoning of the inner part of Ariake Sound based on principal component analysis of sediment factors

HISASHI YOKOYAMA* AND YUKA ISHIHI

National Research Institute of Aquaculture, Fisheries Research Agency, Minami-Ise, Mie 516-0193, Japan

To determine the environmental factors which have led to the decline of bivalve resources in the inner part of Ariake Sound, surface sediments and near-sediment-surface water were obtained from 48 stations in the summer of 2007. Principal component analysis based on 8 sediment factors (median diameter, quartile deviation, total organic carbon, total nitrogen, C:N ratio, δ13C, δ15N and acid-volatile sulfides) showed 4 zones in the study area. A decrease in the particle size of sediments, production of sulfides, significant contribution of coastal phytoplankton to sedimentary organic matter, increase in the amount of sedimentary organic matter and deoxygenation of the bottom water were found in the 2 zones off the western coast in the inner part of the Sound, suggesting that the weakened tidal currents and an increase in phytoplankton-derived organic matter loads are key factors related to the environmental deterioration.


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