海蜇养殖对池塘底泥营养盐和大型底栖动物群落结构的影响

2009年5-9月,对荣成靖海湾大型养殖池塘海蜇(Rhopilema esculentum Kishinouye)养殖期间与养殖期前后底泥营养盐及大型底栖动物群落结构变化进行了研究。结果表明,7月份海蜇养殖期间,由于海蜇的避光性而产生的上下浮动的行为特征造成了对水体的扰动作用, 与海蜇的生物沉积作用共同导致养殖海区(实验点)与邻近非养殖海区(对照点)之间各项底泥营养盐指标均存在显著性差异,其中,实验点氨氮(NH₄-N)、硝氮(NO₃-N)和沉降速率(sedimentation rate, SR)显著高于对照点,实验点叶绿素a(Chla)、总有机物(TOM)和总有机碳(TOC)含量显著低于对照点。多变量聚类分析结果表明,海蜇养殖对养殖池塘的大型底栖动物群落结构产生显著影响,并且7月份实验点大型底栖动物生物多样性指数(H')和均匀度指数(J) 随海蜇放养显著增大,并显著高于对照点。大型底栖动物群落多样性指数与沉降速率(SR)和底泥TOM含量分别表现出显著正相关和负相关,而与其他营养盐指标无显著相关性。

The effects of jellyfish (Rhopilema esculentum Kishinouye) farming on the sediment nutrients and macrobenthic community

To study the effects of jellyfish (Rhopilema esculentum Kishinouye) farming activities on the sediment nutrients and the structure of macrobenthic community, an experimental station within the farming pond and a reference station adjacent to the farming zone were set in JingHai Bay mariculture zone and samples were collected from both stations between May 2009 and September 2009 to compare the spatio-temporal changes in the biotic and abiotic conditions due to jellyfish farming. NH₄-N, NO₃-N, Chla, TOM, TOC of sediment and sedimentation rate (SR) were analyzed. The macrobenthos (>0.5mm) presented in the sediment were sampled, identified and enumerated. During the three sampling months, significant differences of sediment nutrients except TOC at experimental station and of NH₄-N, NO₃-N and Chla at reference station were observed. In July 2009, when the jellyfish were extensively cultured, the sediment NH₄-N, NO₃-N and SR levels at experimental station were significantly higher than those at reference station, while Chla, TOM and TOC levels were significantly lower than those at reference station. In the other two sampling months, no significant differences of sediment nutrients except Chla in September were observed. As for the structure of the benthic communities, 15 kinds of dominant species were collected in all. Nine kinds of the dominant species were polychaete, two kinds were crustacean and four kinds were mollusc. All the collected macrobenthic invertebrates were common species in intertidal zone in North China. In May 2009, Musculus senhousia Benson accounted for 91.53% and 89.25% at experimental station and reference station respectively. The proportion of polychaete among the macrobenthos at experimental station rised in July and September 2009 due to the farming activity of jellyfish. Shannon-Wiener's diversity index (H') and Pielou's evenness index (J) increased significantly with the cultivation of jellyfish at experimental station in July 2009 and the two indexes were significantly higher than those at reference station. Analysis of similarity for abundance of macrobenthos revealed that the similarity of macrobenthic community between experimental station and reference station was 90% in May 2009 and was approximately 50% in July and September 2009. The similarity of abundance of macrobenthos for both of the experimental station and reference station between July 2009 and September 2009 were approximately 70%. The W values of Abundance-biomass-comparison plots of each sampling month were 0.01, 0.308 and -0.128 for experimental station and 0.015, 0.03 and 0.109 for reference station. The results of ABC plots were consistent with the variation of the Shannon-Wiener's diversity index. Analysis of correlations showed that the Shannon-Wiener's diversity index (H') was remarkably positively correlated with Pielou's evenness index (J). Both the Shannon-Wiener's diversity index (H') and Pielou's evenness index (J) had negative correlations with the TOM and positive correlations with SR. The TOM of sediment was negatively correlated with sedimentation rate.