电厂增温对中小型浮游动物群落结构的影响

为探明电厂增温可能导致邻近海域浮游动物的小型化问题，对小网目（网目77μm）采集的象山港国华电厂排水口附近样品数据进行了分析.结果表明：本次调查共鉴定出75种浮游动物（包括浮游幼体、卵与仔鱼），优势种18种，年平均丰度为27690.0ind/m³.该海域主要由中小型桡足类和浮游幼体组成，且个体体长以<1000μm中小型浮游动物占绝对优势.其中，体长<500μm小型浮游动物丰度在各月份和各断面均最高，平均丰度占总丰度比例>58.2%；体长500~1000μm占比>34.8%；而体长>1000μm所占比例仅为7%.经群落相似性分析（ANOSIM），群落结构具显著的季节性差异（P<0.05），但不同断面的空间结构无显著差异.群落相似性百分比（SIMPER）分析显示，导致群落结构时空差异的主要判别种有大同长腹剑水蚤（Oithona similis）、异体住囊虫（Oikopleura dioica）和砂壳虫（Difflugia sp.）等.电厂增温导致大型浮游动物（>2000μm）全部远离排水口0.2km断面（D02断面），主要幼体类群的桡足类无节幼体和桡足幼体则在增温海域分布较均匀，几乎不受影响.而一些高丰度小型浮游动物，如砂壳虫、短角长腹剑水蚤（Oithona brevicornis）、伪长腹剑水蚤（Oithona fallax）大量聚集于排水口，使D02断面的浮游动物丰度最高，达35704.1ind/m³.多样性分析显示，海域增温与种类数（S）间的线性关系不显著（P>0.05），而与Shannon指数（H'）、Pielou均匀度（J'）、Simpson指数（D'）间均存在显著的线性关系（P<0.01）.据回归方程斜率计算，每增温1℃会导致浮游动物H'、J'、D'和S分别降低5.4%、5.0%、3.8%和2.9%.

Effects of temperature increase on meso-and micro-zooplankton community in thermal discharge seawaters near Guohua Power Plant

To explore whether temperature increase would lead to miniaturization of zooplankton in thermal discharge seawaters near the power plant, samples of zooplankton were collected by the type III net with mesh size of 77μm and data was analyzed. In total 75species (including pelagic larvae, eggs and fish larva) were identified with 18dominant species. The annual average abundance was up to 27690.0ind/m³. These communities were mainly composed of meso-and micro-copepods and pelagic larvae, meanwhile dominanted by meso-and micro-zooplankton with a body length <1000μm. Among them, microzooplankton with a length<500μm had the highest abundance in each month and section, its average accounted for over 58.2% of total abundance. The average of zooplankton with a body length of 500~1000μm accounted for over 34.8%. Zooplankton with a body length >1000μm only accounted for 7%. Analysis of similarity (ANOSIM) showed that community structures among seasons were significant different (P<0.05), while among sections were not significant different. Similarity percentage (SIMPER) analysis found the most important discriminating species causing seasonal differences were Oithona similis, Oikopleura dioica and Difflugia sp., etc. Besides, macrozooplankton (>2000μm) were all away from D02section driven by thermal seawater, major larval groups (copepod nauplii and Copepodites) were almost unaffected evenly distributed in the warming seawater. Moreover, a large number of microzooplankton, such as Difflugia sp., Oithona brevicornis and Oithona fallax gathered to the outfall, resulting in the highest abundance (35704.1ind/m³) at D02section. Diversity analysis showed that significant linear regression relationship existed between water temperature increment and the Shannon index (H'), Pielou evenness (J'), Simpson index (D') of zooplankton (P<0.05), however the relationship between water temperature increment and species number was not significant (P>0.05). Based on slope of regression equation, H' would decrease by 5.4%, J' by 5.0%, D' by 3.8% and S by 2.9% when increasing the temperature by 1℃.