海南西北部近岸海域浮游植物的生态特征

基于2012年9月(丰水期)和2013年1月(枯水期)海南西北部近岸海域的调查资料,分析该海域浮游植物的种类组成、优势种、细胞数量及其群落结构多样性。共鉴定浮游植物4门42属151种,硅藻为最主要优势类群。丰水期与枯水期共有种类90种,物种相似性指数为59.60%,表明种类组成不存在明显的季节性差异。丰水期优势种有3种,分别为旋链角毛藻(Chaetoceros curvisetus)、洛氏角毛藻(Chaetoceros lorenzianus)和柔弱菱形藻(Nitzschia delicatissima),其中以旋链角毛藻优势度最高(0.464);枯水期优势种有两种,为金藻门的球形棕囊藻(Phaeoecystis globosa)和硅藻门的细弱海链藻(Thalassiosira subtilis),优势度分别为0.217和0.062。枯水期和丰水期浮游植物平均细胞数量分别为3.250104/L和0.133104/L,细胞数量分布表现出明显的时间和空间异质性,主要密集区为海口市和临高县沿岸海域;与枯水期浮游植物细胞数量相比较,丰水期在海口市至儋州市沿岸细胞数量较低,而在东方市沿岸细胞数量较高。调查海域浮游植物群落结构多样性总体较好,丰水期和枯水期的Shannon-Wiener指数和Pielou均匀度指数分别为3.378,0.679和2.795,0.578;多样性水平季节变化呈现为临高县沿岸枯水期较高,而其他调查海域丰水期较高。相关分析表明:丰水期浮游植物细胞数量与无机氮(DIN)(P0.01)和Chl a(P0.05)呈正相关;枯水期浮游植物细胞数量与BOD5(P0.01)和DO(P0.05)呈正相关,而与盐度(P0.01)呈显著负相关。

Ecological characteristics of phytoplankton community structure in Northwest Hainan coastal areas

This study analyzed the species composition, dominant species, abundance, and community diversity of phytoplankton, based on the data collected from the ecological investigation of coastal waters in Northwest Hainan Island in both wet season (September, 2012) and dry season (January, 2013).The results showed that a total of 151 species among 42 genera belonging to 4 phyla were identified in the surveyed areas.Diatom was the predominant group of all the phyla.There were 90 species common between wet and dry seasons, and the species similarity index between two seasons was 59.60%, suggesting no significant seasonal variations in the species composition.During the wet season, there were 3 dominant species, Chaetoceros curvisetus (C.curvisetus), C.lorenzianus, and Nitzschia delicatissima, while C.curvisetus was with the highest dominance index (0.464).Phaeoecystis globosa and Thalassiosira subtilis were the dominant species in dry season, with dominance indices of 0.217 and 0.062 respectively.The average cells densities of phytoplankton in dry and wet seasons were 3.250104/L and 0.133104/L respectively.The abundance of phytoplankton cells showed significant regional and seasonal differences, and the main concentrated areas were Haikou and Lingao coastal waters.However, compared with dry season, in wet season, the phytoplankton density was relatively low in Haikou and Danzhou coastal waters but higher in Dongfang coastal area.In general, the Shannon-Wiener index (H') and the Pielou's evenness index (J) were 3.378 and 0.679 respectively during wet season and 2.795 and 0.578 respectively in dry season, suggesting a high diversity of the phytoplankton community.The phytoplankton diversity showed a higher seasonal variation in Lingao coastal area compared with other areas during dry season, but the opposite was observed in wet season.Correlation analysis demonstrated that the density of phytoplankton community had definite correlations to environment factors.During wet season, phytoplankton density significantly positively correlated with the dissolved inorganic nitrogen (P0.01) and chlorophyll a (P0.05); however, during dry season, it significantly positively correlated with biochemical oxygen demand (P0.01) and dissolved oxygen (P0.05), but significantly negatively correlated with salinity (P0.01).