相模湾真鶴港内におけるメイオベントスおよび自由生活性線虫類を用いた底質環境の評価法の有効性

抄録

To better understand the relationship between human-induced disturbance and the meiobenthic community in a harbor environment, sediment samples were collected at four stations (Sts. MP1 to 4) in Manazuru Port in Sagami Bay on eight occasions, approximately monthly between July, 2003, and March, 2004. Qualitative meiofaunal samples were collected by a simple cylindrical dredge. In addition, chloroplastic pigment equivalents (from October, 2003, to March, 2004), organic carbon and nitrogen content (in April and June, 2004), and grain size composition (in April, 2004) of the sediment were analyzed. Organic carbon and nitrogen were much higher at St. MP2 than at the other three stations. The sediment samples at St. MP2 frequently included dead fish and shellfish, evidently dumped from a nearby fish market. Station MP2 thus was subject to heavy organic loading. Multivariate community structure analyses using only higher taxonomic levels (phylum, order and/or class) of the meiobenthos did not show significant differences among the stations and sampling months. In contrast, based on species and feeding-types of nematodes, a distinct sample group form St. MP2 was revealed by multidimensional scaling (MDS) and cluster analyses. R-type analysis of the species association of dominant nematodes and correspondence analysis of dominant species and feeding-types of nematodes both also clearly showed the distinctness of the sample group from this station, which mainly consisted of facultative predators collected exclusively there. These results suggest that two species of facultative predators, Meyersia sp. and Metaparoncholaimus sp. belonging to the family Oncholaimidae, and four other nematode species are good indicators of a harbor environment affected by heavy organic loading.