Meiofaunal Communities In The Study Area Of The Bering Sea And Chukchi Sea In Summer

The Bering Sea and Chukchi Sea are both in the western Arctic, connecting the Arctic Ocean and the Pacific Ocean. Only a few studies have done on meiofauna in the Arctic Seas and meiofaunal studies of these two areas are rather fewer. The present study collected samples from the 5th and 6th Chinese Arctic Research Expedition during the 2012 and 2014 summer, analyzed the meiofaunal taxa composition, abundance, biomass, diversity as well as community similarity in the study areas, and studied the dominant species and feeding types of free-living marine nematodes. This study is a continuation of the domestic research on meiofauna in these areas, which could help increase the contents of meiofauna and marine nematode database in the Arctic Seas, and could enrich people’s understanding of marine biodiversity in the Arctic. The main research results are as followings:1. Totally 16 meiofaunal taxa were identified in the Bering Sea(12 stations) and Chukchi Sea(40 stations), including Nematoda, Polychaeta, Copepoda, Kinorhyncha, Oligochaeta, Tanaidacea, Isopoda, Ostracoda, Amphipoda, Cumacea, Bivalvia, Halacarida, Cladocera, Nauplii, Tardigrada, Tubellari, and undetermined taxa. Nematodes were the most predominant taxa, representing over 90% of total meiofaunal abundance in each study area, polychaetes and copepods followed. Comparison showed that metazoan meiofauna taxa number in the Bering and Chukchi shallow waters were higher than that in the deeper waters, but a little lower than that in other Arctic shelves.2. Meiofaunal abundance in the Bering study area ranged from 1.51 ind./10cm2 to 3522.25 ind./10cm2. There were two stations located in the Bering Basin, which had the lowest abundance(1.51 ind./10cm2 and 67.15 ind./10cm2). Meiofaunal abundance in the Chukchi study area ranged from 59.07 ind./10cm2 to 7243.93 ind./10cm2. Average meiofaunal abundance in the Chukchi shelf was 2084.53±1832.14 ind./10cm2, while average meiofaunal abundance in the Chukchi slope was only 165.20±161.93 ind./10cm2. Stations with high abundance corresponded with “hotspots” of high production and biomass in the study area. Abundance variation in different districts was similar to that at different depths in the Arctic Seas.3. Average taxa number(S), taxa richness index(d), Shannon-Weiner index(H’) and evenness index(J’) in the Chukchi study area were higher than those in the Bering study area. This could mean that diversity of meiofaunal community in the Chukchi Sea was higher than that in the Bering Sea.4. Pearson correlation analysis result between meiofaunal community and environmental factors showed that: Total abundance and total biomass of meiofauna in the Bering and Chukchi study area had a negative correlation with water depth. Correlation between total meiofaunal abundance and other environmental factors was influenced significantly by nematode abundance. Evenness index(J’) of meiofauna had a positive correlation with median size and clay proportion of sediments.5. Marine nematodes from 3 orders in the study areas were identified. In the Bering study area, 25 genera were identified while nematodes from 54 genera were identified. Three genera, including Camacolaimus、Diplopeltula、Subsphaerolaimus were found in the Bering study area but not in the Chukchi study area. The most dominant genus in the Bering and Chukchi study areas was Sabatieria, the dominance was 36.68% and 32.92% respectively. Dominance of several genera was significantly different at different water depths. Proportion of each feeding type of nematodes were rowed from high to low in order: Non-selective deposit feeders(31.579%) > selective deposit feeders(24.561%) = epigrowth feeders(24.561%) > predators(19.298%).6. Meiofaunal abundance in the study area was substantially affected by water depth, which decreased drastically from shelf to slope in the Arctic Seas. Meiofaunal taxa number differed among different shelf areas, yet the common taxa were regularly present. Factors such as sampling method, sediments depth as well as mesh size selection would cause divergence between theoretical meiofaunal study result differences and the actual differences among different areas. Nematode genera composition in the study areas was similar with those from other Arctic areas, but dominant genera differed. Sampling depth may account for this phenomenon.