Spatiotemporal distribution of free-living marine nematodes in the tidal flats of Nakatsu and Yokohama Umino-Koen

Abstract

The objective of this study was to determine the characteristics of the composition and spatiotemporal distribution of operational taxonomic units (OTUs) of nematodes in two tidal flats, namely, Nakatsu in Oita and Umino-Koen in Kanagawa, which differed in the density of Manila clams (Ruditapes philippinarum) and the other macrobenthos. There was no difference in the median particle size of the sediment between the two tidal flats, but the sorting coefficient was smaller in Umino-Koen, and the amount of organic matter was larger in the Nakatsu tidal flat. The density of nematodes was higher, and the number of OTUs was lower in Umino-Koen, which has a higher clam production than the Nakatsu tidal flat. A total of 219 OTUs were confirmed in both tidal flats, but 16 common OTUs were confirmed even by one individual on both tidal flats. In Nakatsu tidal flats, the OTU presumed to be Daptonema sp., which is common during all seasons at the two stations, was a dominant species that always inhabited extensively. It has been reported that the genus Daptonema is a non-selective deposit feeder (1B feeding type) nematode. In the Umino-Koen, where macrobenthos density is high, the presumed OTU Oncholaimus sp. was the dominant species that stably inhabited every year. Oncholaimus nematodes may thrive in tidal flats with a large amount of benthos because they are omnivore predators (2B feeding type). The characteristics of the composition and spatiotemporal distribution of nematode OTUs in the two tidal flats were different.