不同采样时期渤海自由生活海洋线虫种类组成的比较

Preliminary Comparative Researches on the Species Composition of Freeliving Marine Nematodes in Different Occasions in the Bohai Sea

在渤海的 3个典型站位 B1、E5和 E1 ,以 3个不同采样时期的沉积物样品 ( 1 997年 6月、1 998年 9～ 1 0月份和 1 999年 4～ 5月份 ) ,研究了渤海自由生活海洋线虫的种类组成变化。结果表明 :自由生活海洋线虫的摄食类型比例在同一个站位 3次不同采样均有变化 ,其中 B1站和 E5站 3个采样时期表现为 3种不同的摄食类型分布 ;将线虫分为 3个时期所进行的年龄结构和雌雄比研究表明 ,在线虫群落中幼龄个体一般占到线虫群落总数的一半以上 ;对 3个站位线虫群落的多样性研究表明 ,离黄河口最近的 B1站 ,出现种类数量最少 ,位于渤海中部的 E5站 ,出现种类数量较多 ;3个不同采样时期的比较 ,以 1 997年 6月份群落中出现的种类数最多 ,1 999年 4～ 5月份出现的最少。对其群落结构的分析表明 ,同一个站位不同采样时期 ,优势种的类型基本相同 ,变化主要表现在优势种丰度大小的差异 。

Meiofaunal communities represent a functional part of the complex marine ecosystem. In almost all marine sediments the nematodes are numerically the dominant group of the meiofauna often comprising more than 90 % of the metazoa. In spite of this, information regarding interannual fluctuations in species composition of nematodes is sparse in China, especially in sublittoral habitats. Free-living marine nematodes were sampled on three occasions, in June 1997 and in September / October 1998 and again in April/May 1999, at three stations B1, E1 and E5, with different sedimentary types in the Bohai Sea. The nematode community structure was investigated in detail including species diversity, feeding groups and age structure. Differences in the nematode fauna of sandy and silty habitats may be due to differences in the type of food available. Wieser (1953) proposed grouping nematodes into four feeding types according to the morphology characteristics of their buccal cavity: 1A with a minute buccal cavity (selective deposit feeders), 1B with a large unarmed buccal cavity (non-selective deposit feeders), 2A with relatively weak oral armament (epigrowth feeders), and 2B with heavy oral armament (predators and omnivores). Nematodes in the feeding group 2B were scarce in all of the Bohai Sea samples. The proportion of the other three feeding groups varied in different sampling occasions even at the same station. At Station B1, three feeding groups 1A, 1B and 2A were almost equally represented in 1997. Non-selective deposit feeders 1B and epigrowth feeders 2A were respectively 53.8 percent and 33.3 percent of total abundance of nematodes in 1998 and epigrowth feeders 2A (56.2 percent) were clearly dominant in 1999. At Station E5, in 1997 non-selective deposit feeders 1B, were the dominant group (48.1 percent) and epigrowth feeders 2A(41.8 percent) ranked second. The selective deposit feeders 1A were dominant in 1998 and epigrowth feeders 2A were dominant in 1999. In Station E1, non-selective deposit feeders 1B and epigrowth feeders 2A, were nearly equal in 1997, and in the other two occasions non-selective deposit feeders were dominant. To some extent, the variations of feeding groups from different seasons can be explained by the suggested theory that nematode abundance increases in spring and summer due to increasing numbers of group 2A nematodes in response to an increase in benthic microflora production and that the number of deposit feeders reaches a maximum in autumn coinciding with an increase in organic detritus (Tietjen 1969). In the Bohai Sea, epigrowth- feeding species reached maximum density at Station B1 and Station E5 in April/May 1999 and June 1997 while non-selective deposit- feeding species reached their maximum densities at Station B1 and Station E1 and the number of selective deposit feeders is comparatively high at Station E5 in September / October 1998 To facilitate interpretation of the age structure of the nematode population, only three cohorts have been represented: mature males (specimens with recognizable spicula), mature females (specimens with developed ovaries) and juveniles. Generally the number of juveniles accounted for above 50 percent of total number of nematodes (except B1 in 1998). The results were similar to observations of Warwick and Price (1979). The ratio of females to males varied from 0.63 to 1.39 at three stations at three occasion. The ratio of females to males was 1.02±0.18 in E1 station by examining six replicates (1779 specimens) (the value determined by Juario was between 1.0 ~1.3). There were a total of 97 putative species in the three sites. The total number of recorded species was lowest in Station B1, and highest in Station E5. Evenness and diversity indices were lowest in Stations B1 and highest in Station E5. The number of species was higher in summer and autumn, lower in spring. The dominant species were generally similar in the three seasons, but the number of dominant species varied. Cluster analysis using group average linking of Bray-Curtis similarities based on