Studies Of Meiobenthic Ecology And Community Structure Of Free-living Marine Nematode In The Northwest Jiaozhou Bay

Undisturbed sediment samples of Northwest Jiaozhou Bay were obtained during four cruises:Mar.2011(Spring cruise), July 2011 (Summer cruise), Oct.2011 (Fall cruise) and Dec.2011 (Winter cruise) at 8 stations along three transects. The environmental factors; abundance, biomass, secondary production and Nematode/Copepoda value of meiobenthos; species composition, diversities and community structure of free-living marine nematode were studied in this area. The aims of this dissertation were to provide reference to the pollution condition study of Jiaozhou Bay and benthic dynamic research in the northwest Jiaozhou Bay. Species list of marine free-living nematode was provided to fill the blank of data.Sediment types of the study area were mainly clayey silt (YT), sandy silt (ST) and silty sand (TS). Median partical diameter (MD(?)) ranged from 0.01-0.34mm. The water contents of sediment in four cruises were:41.46%、40.20%、43.43% and 42.56% respectively;organic contents were:0.79%、0.75%、0.83% and 0.82% respectively; chlorophyll a contents were:4.90mg/kg、5.22mg/kg、2.71mg/kg and 2.73mg/kg respectively. Organic matter distributed evenly in three sediment layers:0-2cm、 2-5cm and 5-8cm, while Chlorophyll a dropped as depth increased, but its contents were similar in the first two layers.In total,21 groups of meiobenthos were identified in this study, including: Free-living marine nematode, Copepoda, Polychaetes, Bivalve, Ostracoda, Crustacea larva, Gastropod, Kinorhyncha, Gastrotricha, Tardigrada, Turbellaria, Amphipod, Tanaidacea, Cladocera, Halacaroidea, Isopoda, Opliiuroidea, Cumacea, Rotifera, Insecta and others. The annual mean abundance of meiobenthos was(2290.4±879.9) ind·10 cm-2; the annual mean biomass was (1779.5±522.8)μg dwt·10 cm-2, and the annual mean secondary production was (16015.4±4704.7)μg dwt·10 cm-2·a-1. Nematode dominated in abundance, which was (2138.3±853.1) ind 10 cm-2, then followed by copepode, whose abundance was (79.8±86.0) ind·10 cm-2. The abundance and biomass of Northwest Jiaozhou Bay were higher than those of north Jiaozhou Bay(1510±820ind·10 cm-2,1320±590μg dwt·10 cm-2). The abundance of studied area was higher than other studies according to available literatures.Meiobenthos were unevenly distributed horizontally. Vertically, the proportion of meiobenthos in surface layer, middle layer, and bottom layer were 69.69%,20.07% and 10.24% respectively. Nematode had similar vertical distribution pattern as meiobenthos, whose proportions in three layers were:68.58%,20.87% and 10.55% respectively. Copepode mainly distributed in the surface layer (94.68%). The vertical distribution of meiobenthos showed seasonal variations. In fall, meiobenthos had a tendency to migrate deeper. Abundance of meiobenthos had no significant relationships with environmental factors, further studies were needed to discover the influencing environmental factors. The mean N/C value was 26.79. Summer N/C was highest (159.83) among all cruises, which indicated organic pollution. The other three cruises were in normal conditions. N/C increased as the distance from shoreline increased, the whole study area didn’t show severe pollution disturbance. The horizontal distribution pattern of N/C was similar to organic content.In total,113 species or morpho-species were identified in Oct.2011, which belonged to 104 genera. The dominant species were:Leptolaimus sp.1、Daptonema sp.1、Parodontophora sp.1、Elzalia sp.1 and Spilophorella sp.1. The richness index (d), evenness index (J’), Shannon-Weiner diversity (H’)and dominance index (X)of free-living marine nematode were 10.08、0.73、5.00 and 0.06 respectively. Four groups were identified with CLUSTER under 62% similarity level.Bottom temperature, depth, MD(?), water content and organic content were the most important environmental factors influencing the community structure and diversity according to Spearman’s correlation analysis.