中华绒螯蟹土池育苗过程中浮游生物群落演替过程及其影响因素

Plankton community succession and its influencing factors on earthen pond cultivation of Eriocheir sinensis larvae

浮游生物在水体生态系统中具有重要功能,其群落结构能影响养殖苗种的健康和产量。但当前尚不清楚它们在中华绒螯蟹(Eriocheir sinensis)育苗池的演替变化及其影响因素。本研究在原位条件下调查了中华绒螯蟹土池育苗过程中水质参数和浮游动植物群落的演替过程,结果发现营养盐总体在养殖后期高于养殖前期。浮游植物检出16种,其中硅藻门种类最多(9种),密度为8.27×10^(8)~4.96×10^(9)ind/L,多样性指数总体随养殖过程呈下降趋势。浮游动物检出11种,密度为2.65×10^(5)~4.78×10^(7)ind/L,多样性指数整体养殖后期高于前期。浮游植物优势种为球等边金藻(Isochrysis galbana)、中肋骨条藻(Skeletonema costatum)、蛋白核小球藻(Chlorella pyrenoidosa)、海洋卡盾藻(Chattonella marina)、长菱形藻(Nitzschia longissimi)、海洋舟形藻(Navicula marina),浮游动物优势种为矮小拟铃虫(Tintinnopsis nana)、急游虫(Strombidium sp.)、华哲水蚤幼体(Sinocalanus larva)、溞状幼体(Zoea)、褶皱臂尾轮虫(Brachionus plicatilis)、卤虫(Artemia nauplii)。浮游植物和浮游动物群落和优势种均随养殖过程呈现明显演替变化。多元统计分析显示饵料、理化环境因子和生物因子的共同作用是育苗池浮游植物和浮游动物群落变化的主要驱动力,饵料、溶解氧和PO43–对其多样性的影响显著。本研究表明调节饵料可作为调控中华绒螯蟹育苗水体浮游生态系统的潜在手段。

The Chinese mitten crab,Eriocheir sinensis,is one of the most important aquaculture species in China,with an annual aquaculture production of 808300 metric tons in 2021.The Chinese mitten crab exhibits six larval stages:Zoeae I-V and Megalopa.These larvae are primarily bred in outdoor earthen ponds;recent studies indicated that the water quality and species composition of the plankton community in these ponds can directly affect the production of breeding.However,little is known about the physical and chemical factors of the E.sinensis larvae-rearing process in breeding earthen ponds;additionally,the characteristics of plankton community succession and its relationship to environmental factors remain unknown.It limits our ability to improve E.sinensis larvae-rearing technology via the control of water quality parameters and plankton communities.Therefore,it is necessary to investigate the water quality paramebers and plankton community succession in E.sinensis breeding earthen ponds.This investigation on the plankton community of E.sinensis breeding earthen ponds was conducted in April 2020.Samples were collected at each larval stage,and the corresponding water environmental factors were determined synchronously.The results showed that the difference in water temperature(WT)and pH at different larval stages was very small,whereas the concentrations of nutrients increased throughout the metamorphic process.Phosphate,total nitrogen,and total phosphorus were significantly different among all larval stages.Additionally,the concentration of nitrogen and phosphorus was significantly correlated with physical factors and the feed used.Overall,16 phytoplankton species were detected,including 9 Bacillariophyta species,4 Pyrrophyta species,3 Cyanophyta species,2 Chlorophyta species,and 1 Chrysophyta species;11 zooplankton species were observed,including 6 Copepod species,3 Protozoa species,1 Rotifera species,and 1 Artemia species(feed).The phytoplankton richness was slightly higher in the Zoe I and megalopa stages than that in the other stages.For phytoplankton,the Margalef index range was 0.26–0.46,Shannon index range was 0.12–0.77,Pielou index range was 0.04–0.29,and the Simpson index range was 0.04–0.50.All diversity indices for the phytoplankton exhibited similar trends,decreasing from Zoeae I to megalopa,indicating that the phytoplankton community became less stable throughout the aquaculture process.The overall diversity index for zooplankton exhibited an opposite trend,with a higher diversity index at the megalopa stage than at the Zoe I stage.For zooplankton,the Margalef index range was 0.26–0.60,the Shannon index range was 0.01–0.66,the Pielou index range was 0.01–0.23,and the Simpson index range was 0.003–0.36.The Mantel test indicated that the diversity of phytoplankton and zooplankton were both significantly affected by the feed,DO,and PO_(4)^(3–).The plankton community and dominant species exhibited a clear succession process.Non-metric multidimensional scaling analysis indicated that both phytoplankton and zooplankton communities were distributed along the NMDS1 axis.Plankton communities were significantly different between larval stages(PERMANOVA,P<0.05).Multivariate analysis indicated that the difference in plankton community distribution was primarily affected by a combination of feed,abiotic factors,and biotic factors.The phytoplankton community was mainly affected by rotifers,PO_(4)^(3–),NH_(4)^(+),DO,NO2–,TP,and WT;the zooplankton community was primarily affected by the feed,WT,DO,and PO_(4)^(3–).The results of variance decomposition analysis demonstrated that the feed was the largest single explanation for the variation in phytoplankton community distribution.Alternatively,environmental factors were the largest single explanation for the variation in zooplankton communities,followed by feed.Biological factors,feed,and environmental factors jointly explained most of the variation in both phytoplankton and zooplankton communities.Isochrysis galbana,Skeletonema costatum,Chlorella pyrenoidosa,Chattonella marina,Nitzschia longissimi,and Navicula marina were the dominant species of phytoplankton;their abundances were affected by the feed and SiO_(3)^(2–).Tintinnopsis nana,Strombidium sp.,Calanoida larva,Zoaea,Brachionus plicatilis,and Artemia nauplii were the dominant species of zooplankton;their abundances were affected by environmental factors(NH_(4)^(+),WT,pH,and NO_(3)^(–))and the diversity of phytoplankton.In conclusion,as the first investigation on plankton community succession in a Chinese mitten crab nursery pond,we revealed that phytoplankton and zooplankton communities both have clear successional processes.During the aquaculture process,the diversity of phytoplankton decreased while that of zooplankton increased.PO_(4)^(3–),feed(rotifers and Artemia nauplii),and DO are the primary factors that affect the plankton community.Our results provide essential data for maintaining the environmental health of E.sinensis larval-rearing ponds and the ecological control of plankton communities in aquaculture farms.