| Meiofauna was investigated in the sandy beaches of Dadeji and Huangcuo, Xiamen in 2010 and 2011 at four quarterly months. The sedimentary environment, abundance and biomass of meiofauna were quantitatively studied during the periods of investigation.The results showed that the sediment type of Dadeji was GS, VCS was the highest, followed by gravel, silt and clay contents were very low, sorting was good. The sediment type of Huangcuo was coarse sand, too, but the content of gravel and coarse sand were less than the sandy beaches of Dadeji , Medium sand and fine sand were higher than Dadeji, silt and clay content were extremely low. Sediment characteristic parameters had significant correlations with each other. The average content of chlorophyll a in the sediment of Dadeji and Huangcuo were 0.0142mg/kg and 0.0045mg/kg, respectively. The high value appeared in summer of the two beaches. The average content of organic matter in the sediment of Dadeji and Huangcuo were 0.0162% and 0.0127%, respectively. Except the D1 section had the highest value in winter, others had the highest value in summer. Correlation analysis showed that dissolved oxygen correlated with temperature positively, Chl-a content correlated with silt and clay positively.A total of 17 groups of meiofauna were identified in the sandy beach of Dadeji: Nematoda, Copepoda, Tubellaria, Polychaeta, Tardigrade, Rotifera, Gastrotricha, Ostracoda, Cnidaria, Isopoda, Halacaroidea, Kinorhyncha, Amphipoda, Cladocera, Ophiura, Bivalvia, and other unidentified meiofauna. A total of 12 groups of meiofauna were identified in the sandy beach of Huangcuo. Five groups did not appear in this beach were Kinorhyncha, Amphipoda, Cladocera, Ophiura, Bivalvia compared to Dadeji. The average abundance of meiofauna were(660.23±192.44)ind·10cm-2 and(521.86±146.30)ind·10cm-2, respectively. The most dominant group was Copepoda in the sandy beach of Dadeji, accounting for 44.33% of the total abundance of meiofauna; with free-living marine nematode being the second, accounting for 35.10%. Nematode was the most dominant group in the sandy beach of Huangcuo, accounting for 72.56% of total abundance of meiofauna, with Copepoda being the second, accounting for 18.46%. The mean biomass of meiofauna were (1908.19±835.40)μg·dwt·10cm-2 and(654.54±349.87)μg·dwt·10cm-2 for the Dadeji and Huangcuo respectively . The mean production of meiofauna were(17173.70±7518.60)μg·dwt·10cm-2·a-1 and(5890.89±3148.81)μg·dwt·10cm-2·a-1 respectively. The biomass of Copepoda accounted for 28.53% of the total meiofauna biomass, Polychaeta ranked second, Ostracoda ranked third of Dadeji. Copepoda also had the highest biomass of Huangcuo, accounting for 26.74% of total biomass of meiofauna, Polychaeta ranked second, Nematode ranked third.Meiofaunal abundance showed obvious seasonal fluctuations. Both beaches had the highest abundance in summer, followed by spring fall and winter. Meiofaunal biomass also showed a significant seasonal difference of the two beaches.The horizontal distribution among the tidal zone was different between the two beaches. The highest abundance was in the middle intertidal zone of Dadeji. In Huangcuo, the highest abundance was in lower intertidal zone. But in generally, the changes of the two beaches among tide zone were not significant, the diffference of abundance among tide zone was not significant(P>0.05). The highest biomass was in the middle intertidal zone of Dadeji, the same with abundance, but in Huangcuo, the changes pattern of biomass among tide zone were different from the abundance, the highest biomass was in high intertidal zone, which was different from abundance.The top 0～4cm had the fewest meiofauna compared to other layers in the sandy beach of Dadeji, the other layers were distributed evenly, the distribution of Nematodes and Copepods were the same with the meiofauna. Most of the meiofauna concentrated in the top 0～4cm in the sandy beach of Huangcuo, decreased with depth down, the distribution of Nematodes was the same with the meiofauna, but the trend of Copepods was contrary to the meiofauna, the distribution gradually increased with depth down. In addition, meiofauna had shown a seasonal vertical migration with depth in the sediments in both beaches.The combination of temperature, medium size and the content of silty and clay could explained the distribution pattern of meiofauna in the sandy beach of Dadeji by the analysis of BIOENV, and the coefficient were 0.458. And the combination of DO, the content of sand and the content of silty and clay could explained the distribution pattern of meiofauna in the sandy beach of Huangcuo by the analysis of BIOENV, and the coefficient were 0.583. |
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