南沙群岛重点岛礁潟湖微型浮游动物的群落结构与摄食

Community structure and grazing of microzooplankton in the key islands and reefs of Nansha Islands

摘要:

潟湖是岛礁生物多样性演变的重要环境场，在岛礁水生态系统的物质循环和能量流动中发挥重要作用，而微型浮游动物的生态功能研究是解析南沙群岛岛礁水域潟湖生态系统初级生产力组成、流向、能量流动效率的重要研究内容之一。实验通过对南沙群岛重点岛礁渚碧礁、美济礁与永暑礁潟湖表层水域中微型浮游动物与生态环境调查，研究了其群落结构及其与环境因子的关系，并通过稀释培养实验研究了微型浮游动物的摄食压力。结果显示，调查水域共发现微型浮游动物20种，总丰度的范围为320~1460个/L，以无壳纤毛虫丰度最高。无壳纤毛虫在渚碧礁潟湖西部水域(ZB-1)丰度最高，砂壳纤毛虫峰值则出现在永暑礁潟湖中部水域(YS-3)，桡足类幼体丰度最大值出现在美济礁潟湖北部水域(MJ-2)。聚类分析结果显示，3个岛礁潟湖中部区域的微型浮游动物群落相似度较高，溶解氧是影响群落结构的最重要因素，特别是对MJ-3站位影响最为突出。摄食实验结果显示，3个岛礁潟湖水域浮游植物生长率为0.22~1.36 d⁻¹；微型浮游动物摄食率范围为0.22~0.60 d⁻¹，微型浮游动物每天约摄食浮游植物现存量的20.5%~45.1%，相当于初级生产力的37.1%~222.9%。研究表明，南沙群岛3个岛礁不同的环境和生物因子共同影响着潟湖内微型浮游动物的摄食压力，从而使3个岛礁形成了不同的微型浮游动物生物多样性演化机制或方向。

关键词:微型浮游动物;摄食压力;能量流动;生境演化;南沙岛礁

Abstract:

Island and reef lagoon is an important environmental field for the evolution of island and reef biodiversity, and plays an important role in the material circulation and energy flow of island and reef water ecosystem. The ecological function of microzooplankton is one of the important research contents to analyze the composition, flow direction and energy flow efficiency of primary productivity of lagoon ecosystem in Nansha Islands waters. In this paper, microzooplankton and ecological environment were investigated in the surface waters of Zhubi Reef, Meiji Reef and Yongshu Reef lagoon, the key islands and reefs of Nansha Islands, and the community structure and its relationship with environmental factors were studied, and the grazing pressure of microzooplankton was studied by dilution culture experiment. There are 20 species of microzooplankton in the investigated waters, with the total abundance ranging from 320 to 1 460 ind/L, among which the abundance of Ciliated ciliate is the highest. The abundance of C. ciliate is highest in the western waters of Zhubi Reef lagoon (ZB-1), while the abundance of A. ciliate appears in the middle waters of Yongshu Reef lagoon (YS-3), and the maximum value of Nauplius larva appears in the northern waters of Meiji Reef lagoon (MJ-2). The cluster analysis shows that the community similarity of microzooplankton in the middle area of lagoon was relatively high, and dissolved oxygen is the most important factor affecting microzooplankton community structure in these islands and reefs, with its most obvious influence on MJ-3 station. The growth rate of phytoplankton in the lagoon waters of the three major islands and reefs was 0.22-1.36 d⁻¹. The grazing rate of microzooplankton ranged from 0.22 to 0.60 d⁻¹, and the micro-zooplankton consumed about 20.5%-45.1% of the existing phytoplankton every day, equivalent to 37.1%-222.9% of the primary productivity. This study shows that different environmental and biological factors on the three major islands and reefs of Nansha Islands have influenced the different grazing pressures of microzooplankton, thus forming different evolution mechanisms of microzooplankton biodiversity on each island and reef. This study provides data support for the energy flow of microbial loops in the lagoon ecosystem under the ecological effects of islands and reefs.

Key words:microzooplankton;grazing pressure;energy flow;habitat evolution;Nansha Island reefs