采样方法对北塘河口浮游生物多样性分析的影响

Influence of Sampling Method on the Analysis of Plankton Biodiversity in Beitang Estuary

在天津海域的北塘河口,用浮游生物网和球阀采水器采集了浮游植物和浮游动物样品,分析2种采样方法对生物多样性指数的影响。结果表明,北塘河口共检测出浮游植物34种,硅藻占绝对优势;浮游动物17种,桡足类占据优势地位。生物多样性指数和丰度值因采样方法而异。用浮游生物网采集浮游植物样品时,能够获得较多的种类数和较高的Margalef指数、Pielou均匀度指数、Shannon指数和Simpson指数;而优势度指数和分类学差异性指数的结果则较低;用采水器采集的浮游动物样品具有较高的Shannon指数、Pielou均匀度指数、Simpson指数和分类学多样性(Δ);其他指数的结果则相反。网采样品具有较低的生物丰度值。t检验结果显示,种类数和Margalef指数受取样技术的影响显著;而其他几个指数的差异不显著;由于很多指数是按照阈值来评价环境优劣,数值不同依然可能影响评价结果;因而在比较不同研究结果和评价环境时应该注意取样方法的影响。

Biodiversity indices have been used for decades to analyze the stability of communities and assess envi- ronmental conditions. Studies, while limited, have shown that survey results of biological diversity are affected by the method used for sampling. Plankton is an important aspect of ecological research and the two conventional de- vices for plankton sampling are the plankton net and water sampler, but few reports are available about the effect of sampling method on plankton diversity measurements. In late June 2014, we carried out plankton surveys using the two sampling methods in Beitang estuary （ 117.81°E, 39.07°N） in the Tianjin sea area of northern China. The goals were to compare the effects of these two conventional sampling methods on the results of plankton diversity measurements and to provide a reference for ecological evaluation. Phytoplankton and zooplankton samples were collected, using plankton nets （type II for zooplankton and type III for phytoplankton） and water samplers, at the same location and time. The plankton samples were immediately fixed with formaldehyde in situ and later counted in the laboratory. A total of 34 phytoplankton species were identified, dominated by diatoms. Each method collect- ed 26 phytoplankton species, with the 18 species in common accounting for 52.9% of the total species. A total of 17 zooplankton species were collected, dominated by Copepods. Sixteen zooplankton species collected by plankton net and 11 species by water sample, with the 10 species in common accounting for 58.8% of the total species. In addition to the number of species （S） and abundance, eight biological indices, including three taxonomic distinct- ness indices and five traditional diversity indices （ Margalef richness, Pielou evenness, Shannon diversity, Simpson index and dominance） were compared in this study. Results show that the biodiversity indices and the plankton a- bundance are both influenced by sampling method. When a plankton net was used for phytoplankton sampling, the number of species and the Margalef richness, Pielou evenness, Shannon, and Simpson indices gave higher values, whereas the dominance and the taxonomic distinctness indices were lower. When a water sampler was used to col- lect zooplankton samples, the abundance and the Shannon, Pielou evenness, Simpson indices and the taxonomic distinctness （A） were higher, and the other indices were lower than the results obtained with the plankton net. Sta- tistical analysis （T-test） shows that differences resulting from the two sampling methods were significant for species number and Margalef richness index, but not for the other indices. Therefore, the effect of sampling method should be considered when using biodiversity indices to assess water quality and evaluate ecological conditions.