陵水湾浮游动物群落结构特征及其季节变化

为了探明陵水湾浮游动物饵料情况,本研究依据2014年11月(秋季)、2015年5月(春季)、8月(夏季)和2016年1月(冬季)陵水湾4个航次的调查资料,分析了该海湾浮游动物的种类组成、优势种、丰度和生物量、生物多样性等群落结构特征及其影响因素。调查共发现浮游动物94种和浮游幼虫21类,其中桡足类(Copepoda)最多,有38种,其次是水螅水母类(Hydromedusae)11种,毛颚类(Chaetognatha)8种,其余类群种类数在1～6种之间。浮游动物群落主要由广温广盐类群、暖水沿岸类群和暖水外海类群组成,优势种主要分布在前两个类群,无全年优势种;浮游幼虫是陵水湾的重要类群,丰度呈现为冬季(低温)高于春季(高温)。与亚热带海域不同,低温已不再是制约陵水湾海洋生物生长的主要因子。浮游动物丰度和生物量均呈现为秋季最高,春季最低,冬季高于夏季。浮游动物群落物种Shannon-Wiener指数(H￠)和均匀度指数(J￠)的变化趋势一致,表现为春夏季高,秋冬季低,湾外高,湾内低。聚类分析结果表明,陵水湾浮游动物可分为湾内和湾外两个群落,主要受地形阻隔所致。盐度与浮游动物丰度和生物量均呈显著负相关关系,是浮游动物季节变化的主要影响因子之一。根据陵水湾浮游动物年均生物量估算出浮游动物提供的渔产潜力为2.24×10~4 kg。陵水湾浮游动物丰度呈现剧烈的季节变化,有必要对其进行长期的跟踪监测。

Characteristics of zooplankton community structure and its seasonal variation in Lingshui Bay

Based on the data obtained from four cruises in November (autumn) 2014, May (spring) and August (summer) 2015, and January (winter) 2016, the structure of zooplankton community in Lingshui Bay, including species composition, abundance, dominant species, and species diversity, was studied. A total of 94 zooplankton species and 21 types of pelagic larvae were identified. The most dominant group of zooplankton was copepods (38 species), followed by hydromedusae (11 species), and Chaetognatha (8 species), accounting for 40.43%, 11.70%, and 8.51% of the total species, respectively. The remaining groups were represented by 1 to 6 species per group. Based on species composition and ecological distribution, the zooplankton community in Lingshui Bay mainly comprised three ecological groups, including eurythermal euryhaline group, warm water coastal group, and warm water pelagic group; the dominant species were distributed mainly in the former two groups. No dominant species was widespread throughout all the seasons. Appendiculata was the only dominant group all year-round. Pelagic larvae formed an important group in Lingshui Bay. Their abundance in winter (lower water temperature) was higher than in spring (higher water temperature), which was different from that in subtropical waters. This suggests that in Lingshui Bay, lower seawater temperature was no longer the main factor determining zooplankton abundance. The abundance and biomass of zooplankton were highest in autumn, followed by winter, summer, and finally, spring. Both the species diversity indices were consistent in seasonal and horizontal variation, being higher in spring and summer than in autumn and winter, and higher in the outer bay than the inner bay. Two communities, from the inner and outer bays, were identified by clustering analysis, which can be mainly attributed to the barrier caused by the terrain. Furthermore, we measured temperature, salinity, concentration of chlorophyll a, phytoplankton abundance, and concentration of dissolved oxygen and determined the responses of the zooplankton community to these factors. Salinity was the primary factor influencing zooplankton community structure in Lingshui Bay, based on Pearson''s correlation analysis. Based on the annual biomass of zoo-plankton in Lingshui Bay, potential productivity of zooplankton was estimated to be 2.24×10⁴ kg. The abundance of zooplankton in Lingshui Bay has changed dramatically with different seasons. Thus, it is necessary to continuously monitor zooplankton abundance in Lingshui Bay over a long period to better understand the actual prey situation.