Comparisons of deep-sea sediments and overlying water collected using Multiple Corer and Box Corer

Sediments and overlying water collected using Multiple Corer (MC) and Box Corer (BC) at three stations in Suruga Bay were compared from the view points of meiobenthic and chemical characteristics. Dissolved oxygen, pH, ammonium and nitrite concentrations of the overlying waters were lower, whereas nitrate and phosphate concentrations were higher constantly in the samples collected by MC than those by BC, suggesting contamination of surface seawater in the BC samples. Sediments were sliced into 0–1, 1–2 and 2–3 cm layers, and water content and Eh, and abundance of meiofauna were analyzed. Water content in MC samples was always higher than BC ones. For the whole meiobenthos, MC collected significantly more individuals than BC at only one out of three stations, whereas for harpacticoid copepods, which aggregated to the surface layer of the sediment, MC constantly collected significantly more individuals than BC. In the vertical profiles of both water content and meiofaunal density, data of 0–1, and 1–2 cm layers in the BC samples were similar to those of 1–2 and 2–3 cm layers in the MC samples, respectively. These results suggested only MC can collect the real sediment surface (so called fluffy layer), which was lost due to bow wave effects in the BC samples.