鲢鳙+绿狐尾藻处理的罗非鱼养殖池塘浮游植物群落特征及水质评价

Phytoplankton Community Characteristics and Water Quality Evaluation of Tilapia Culture Ponds Treated with Silver Carp, Bighead Carp and Myriophyllum elatinoides Gaudich

【目的】了解鲢(Hypophthalmichthys molitrix)、鳙(Aristichthys nobilis)和绿狐尾藻(Myriophyllum elatinoides Gaudich)组合处理对主养罗非鱼(GIFT Oreochromis niloticus)池塘浮游植物群落及其水质的影响,为评价罗非鱼绿色养殖模式的生态效应提供参考依据。【方法】以放养罗非鱼22 500尾/hm^(2)、鲢2700尾/hm^(2)、鳙300尾/hm^(2)+放置绿狐尾藻浮床1000 m^(2)/hm^(2)为A处理,放养罗非鱼22 500尾/hm^(2)、鲢300尾/hm^(2)、鳙2700尾/hm^(2)+放置绿狐尾藻浮床1000 m^(2)/hm^(2)为B处理,放养罗非鱼22 500尾/hm^(2)、鲢和鳙各1500尾/hm^(2)+放置绿狐尾藻浮床1000 m^(2)/hm^(2)为C处理,以主养罗非鱼22 500尾/hm^(2)池塘为D处理(对照),开展生产试验,采用功能类群(FG)分类法分析各处理池塘的浮游植物群落组成,并在池塘水质监测基础上进行水体综合营养状态指数评价。【结果】试验期内各处理池塘的水质在中—富程度富营养化范围波动,其中C处理的水质最佳。从池塘水体中共检出7门168种浮游植物,群落组成属于绿藻(Chlorophyta)为主的绿藻—裸藻(Euglenophyta)—蓝藻(Cyanophyta)—硅藻(Bacillariophyta)型,A、B和C处理的浮游植物种类数均高于D处理。检出的浮游植物共划分为21个功能群,其中优势度指数(Y)≥0.02的优势功能群9个,分别为C、J、X1、MP、Lo、F、W1、M和Y,优势功能群群落组成是绿藻为主的绿藻—硅藻—蓝藻型,指示的生境特征为富营养化;试验期间,优势功能群组成变化明显,由4-7月的9个优势功能群减少为8-10月的4个共有功能群(J、X1、C和Lo),且这4个共有功能群只有优势度变化而无更替。A、B和C处理优势功能群的总生物量均低于D处理。Y≥0.20的绝对优势功能群有3个,分别为共有功能群J、X1和C,以绿藻为主的J功能群在4个处理中均占绝对优势,以硅藻为主的C功能群在A和B处理中均占绝对优势;对滤食敏感的X1功能群在D处理中占第一绝对优势,在A、B和C处理中不占绝对优势。相关分析结果表明,4-7月优势功能群XI与TN呈显著负相关(P<0.05),8-10月所有优势功能群与环境因子间均无显著相关性(P>0.05)。【结论】鲢鳙+绿狐尾藻组合能增加罗非鱼养殖池塘水体的浮游植物种类及提高其优势功能类群的多样性,降低富营养化程度,稳定水质。根据优势度划分优势功能群的FG分类法适用于评价滤食性动物和水生植物对池塘养殖系统的生态调控效果。

【Objective】The present paper aimed to understand the effects of combined treatments of silver carp(Hypophthalmichthys molitrix),bighead carp(Aristichthys nobilis)and Myriophyllum elatinoides Gaudich on the phytoplankton community and water quality of the main tilapia(GIFT Oreochromis niloticus)ponds,in order to provide a reference for evaluating the ecological effects of green tilapia farming models.【Method】The stocking of tilapia was 22500 ind/hm^(2),silver carp was 2700 ind/hm^(2),bighead carp was 300 ind/hm^(2) and placed on the floating bed of M.elatinoides at 1000 m^(2)/hm^(2) as a treatment A.The tilapia was 22500 ind/hm^(2),silver carp was 300 ind/hm^(2),bighead carp was 2700 ind/hm^(2) and placed the floating bed of M.elatinoides at 1000 m^(2)/hm^(2) as a treatment B.The tilapia was 22500 ind/hm^(2),silver carp 1500 ind/hm^(2),bighead carp 1500 ind/hm^(2) and placed the floating bed of M.elatinoides at 1000 m^(2)/hm^(2) as a treatment C.The pond with main cultivating tilapia 22500 ind/hm^(2) was used as a treatment D(control,CK),and the production experiment was carried out.The functional group(FG)classification method was used to analyze the composition of the phytoplankton community in each treatment pond,and the comprehensive nutritional status index of the water body was evaluated based on the pond water quality monitoring.【Result】During the test period,the water quality of each treatment pond fluctuated in the range of medium-rich eutrophication,and the water quality treated by treatment C was the best.A total of 168 species of phytoplankton in 7 phyla were detected from the pond water quality,and the community composition was mainly Chlorophyta-Euglenophyta-Cyanophyta-Bacillariophyta type,the number of phytoplankton species in A,B and C treatments were higher than that in treatment D.The detected phytoplankton was divided into 21 functional groups,among which 9 were the dominant functional groups with dominance index(Y)≥0.02,namely C,J,X1,MP,Lo,F,W1,M and Y.The dominant functional group was composed of Chlorophyta-Bacillariophyta-Cyanophyta type,and the indicated habitat feature was eutrophication.During the test period,the composition of the dominant functional groups from April to July changed significantly,from 9 to 4 shared functional groups(J,X1,C and Lo)from August to October,and these four shared functional groups had only advantages degree changes without replacement.The biomass of dominant functional groups in A,B and C treatments were lower than that in control group.There were three absolutely dominant functional groups with dominance Y≥0.20,which were common functional groups J,X1 and C.The functional group J,which was dominated by Chlorophyta,had an absolute advantage in the four treatments;The functional group C,which was dominated by Bacillariophyta,had an absolute advantage in both A and B treatments;the X1 functional group,which was sensitive to filter feeding,had the first absolute advantage in treatment D,and did not have an absolute advantage in A,B and C treatments.Correlation analysis results showed that there was a significant negative correlation between X1 and TN from April to July(P<0.05),and there was no significant correlation between all dominant functional groups and environmental factors from August to October(P>0.05).【Conclusion】The combination of silver carp,bighead carp and M.elatinoides could increase phytoplankton species in tilapia breeding ponds,increase the diversity of dominant functional groups,reduce eutrophication and stabilize water quality.The FG functional group classification,which divides the dominant functional groups according to the dominance degree,is suitable for evaluating the ecological regulation effect of filter feeding animals and aquatic plants on the pond culture system.