胶州湾底栖软体动物与环境因子的关系

MACROBENTHIC MOLLUSCA FAUNA AND ITS RELATIONS TO ENVIRONMENTAL FACTORS IN JIAOZHOU BAY

采用1998年2月—2002年11月,共5年19个季度月对胶州湾10个站进行综合调查的资料,对胶州湾大型底栖软体动物的种数、生物量和栖息密度三项数量指标与温度、盐度、底层初级生产力、底质四项生态因子的关系进行了研究。结果表明,胶州湾底栖软体动物是胶州湾重要的生物类群,共发现了51种。生物量和栖息密度最高的站均为2号站,分别为1015.6g/m2和1041ind/m2。软体动物的数量分布和季节变化与底质、温度存在较为密切的关系,同时底栖软体动物的出现种数和平均栖息密度与底层初级生产力呈线形相关,但三者与盐度的关系不明显。

Mollusca are one of the common marine populations in Jiaozhou Bay. They play a very important role in food chains in the area, because of its huge biomass. Rich ecological researches on of Jiaozhou Bay have been performed in the past. However, the relationship of macrobenthic mollusca fauna to the environmental factors is still unclear. Environmental factors included temperature, salinity, sediment, and bottom primary product. Ten stations were set up for observation and sampling. Sampling were performed in each season (spring-May, summer-August, autumn-November, winter-February) from Feb. 1998 to Nov. 2002, and collected by 0.1m2 grabber. The samples were preserved in alcohol, then classified, counted, and weighed later. Fifty-one mollusk species were identified that dominated by Ruditapes philippinarum. Other species were common including Raetellops pulchella, Nassarius festivus, Philine argentata, Theora lubrica, and Cadella narutoensis. Results from this study are followed. The maximum number of species was 26, found at Station 1, and the lowest number was 7, at Station 9. The highest average biomass was 1015.6g/m2 at Station 2, the lowest average biomass was 2.0 g/m2 at Station 9. Density of benthic mollusk varied greatly in different samples, the highest density was 1041 ind/m2 at Station 2, which is due to a large amount of R. philippinarum, and the lowest density was only 27 ind/m2 at Station 9. In spring, the density was highest, 116.6 ind/m2; in autumn, the biomass was highest, 120.5g/m2. Data analysis revealed that average density and biomass of mollusk in this study were closely related to sediment feature. Sediments in Stations 1, 2, 4 and 8 were mixture of fine sand and clay. All the indicators, such as average number of species, density and biomass of mollusk lived were higher than that in Stations 9 and 10, where the sediment was coarse sand. The result accorded with the finding of Gray (1974) and Sander (1956). In terms of temperature, because Jiaozhou Bay is classified meteorologically as warm temperate zone, and the depth is shallow (average 7m, maximum 70m), so the bottom temperature would greatly fluctuate in different season, which then had a enormous effect on the biomass and density of macrobenthic mollusca. In spring, R. philippinarum grew very fast, then matured and reproduced. Therefore, the biomass they live on began to decrease, but the density was high; in autumn, they grew very fast although some young mollusks were taken by predators, so the density still decreased rapidly, but the biomass increased. In Jiaozhou Bay, the salinity change is relatively even, 31.8 in most of the regions. This small fluctuation had minor effect on macrobenthic mollusk fauna. Most of the macrobenthic mollusks are filter and deposit feeders, which intake food from bottom waters and detritus. Regressive analysis revealed that the average density and biomass had correlativity with bottom primary product in Jiaozhou Bay, while their relation to salinity was indistinct.