北部湾近岸海域浮游动物群落结构特征及季节变化

2017年3月(枯水期)、7月(丰水期)和10月(平水期)分别对北部湾近岸海域44个站位的浮游动物进行了调查。结果共检出浮游动物251种和浮游幼体24类,其中枯水期138种(类),丰水期134种(类),平水期191种(类),分属河口低盐、近岸暖温、近岸暖水和外海暖水4个生态类群。优势种9种,其中枯水期以原生动物占绝对优势,丰水期以枝角类、桡足类和浮游幼体类占优势,平水期以十足类和浮游幼体类占优势。浮游动物丰度年均值为789.95个/m~3,呈现出枯水期(1540.19个/m~3)明显高于平水期(457.58个/m~3)和丰水期(372.08个/m~3)的季节变化特征;浮游动物生物量年均值为252.40 mg/m~3,生物量的季节变化与丰度变化不一致,平水期生物量(385.01 mg/m~3)明显高于枯水期(221.41 mg/m~3)和丰水期(150.78 mg/m~3)。多样性指数平水期最高(3.16),丰水期(2.35)次之,枯水期(2.22)最低。枯水期和丰水期北部湾近岸海域浮游动物生物量和丰度水平分布特征基本呈现自河口近岸海域向外海递增的趋势,平水期浮游动物生物量与丰度的空间分布较为均匀。浮游动物的种类组成结构以及优势种的演替对浮游动物的生物量和丰度季节变化有着重要的决定作用。径流导致的悬浮物、营养盐等的变化可能是决定北部湾近岸海域浮游动物生物量和丰度空间分布的主要因素。研究还表明与其他海湾相比,北部湾近岸海域浮游动物群落结构趋于小型化,需加大关注。

Community structure and seasonal variation of zooplankton in coastal Beibu Gulf

A comprehensive investigation on the population of zooplankton was conducted at 44 stations in the Beibu Gulf coastal area in the dry,wet and normal seasons in 2017. In total,251 zooplankton species including 24 larvae were identified during the investigation,among which 138,134,and 191 species occurred in the dry,wet and normal seasons,respectively. All zooplankton could be grouped into four ecotypes:estuary,offshore warm-water, offshore warm-temperature and eurytopic. There were 9 dominant species during the sampling period,with protozoa dominating the community in dry season,Cladocera,Copepoda and pelagic larvae dominating in the wet season, Decapoda and pelagic larvae in the normal season.The annual average abundance of zooplankton was 789.95 ind./m³. Dry season had the largest abundance (1540.19 ind./m³), followed by normal (457.58 ind./m³) and wet (372.08 ind./m³) seasons. The annual average biomass of zooplankton was 252.40 mg/m³, with the highest biomass during normal season (385.01 mg/m³),followed by dry (221.41 mg/m³) and wet (150.78 mg/m³) seasons.The highest diversity index (3.16) was found in normal season, followed by wet season (2.35), while the least diversity (2.22) presented in the dry season. Both the horizontal distribution of biomass and abundance of zooplankton increased gradually moving offshore in dry and wet seasons, while remaining relatively evenly distributed in normal season. Seasonal variation of biomass and abundance was determined by composition and dominant species. Correlation analysis shows that the distribution of biomass and abundance of zooplankton in the coastal waters of Beibu gulf are influenced by suspended matter and nutrients. Compared with the other bays, the population structure of zooplankton in the coast of the Beibu Gulf exhibited a clear tendency toward miniaturization that require additional attention.