鄱阳湖子湖“堑秋湖”过程中水位变化对浮游动物群落结构的影响

EFFECTS OF WATER LEVEL ON ZOOPLANKTON COMMUNITY DURING “PLATE-SHAPED LAKE ENCLOSED IN AUTUMN” IN A SUB-LAKE OF THE POYANG LAKE

"堑秋湖"是鄱阳湖区渔民根据湖泊水位季节性涨退变化,利用人工闸门控制子湖水位进行捕鱼的一种渔业方式。研究分析了"堑秋湖"过程中浮游动物群落结构的变化,探讨水位变化对浮游动物群落结构的影响及其他可能的影响因素,以期为合理管控鄱阳湖区"堑秋湖"渔业活动提供科学依据。鄱阳湖"堑秋湖"捕鱼期间(2014年11月9日至2015年1月4日),在鄱阳湖国家级自然保护区内子湖——大湖池的敞水区设置了7个采样点进行了8次浮游动物定性、定量采集和分析。研究共发现浮游动物77种,其中轮虫53种,枝角类10种,桡足类14种。在"堑秋湖"捕鱼过程中,浮游动物物种数随水位的连续下降呈现逐渐减少趋势,多样性指数也呈逐渐下降趋势,密度和生物量呈现先增加后减少的变化趋势。浮游动物优势物种的密度变化具有明显的种属差异,前节晶囊轮虫和中华窄腹剑水蚤的密度呈逐渐增加的趋势,广布多肢轮虫、广布中剑水蚤、长额象鼻溞和桡足类无节幼体的密度呈逐渐减少的趋势。冗余分析表明:水位、电导率、水温、溶氧、营养盐等环境因子均对浮游动物群落结构产生显著影响,其中溶解氧是最强的影响因子。此外,根据"堑秋湖"鱼类渔获量的变化情况推测,捕鱼活动导致的浮游食性鱼类减少也对浮游动物的密度变化产生了影响。在"堑秋湖"过程中,随着水位的持续下降水体理化因子发生了不同变化。浮游动物的种类和多样性指数逐渐降低,浮游动物的密度呈现先升高后降低的变化趋势。浮游动物的群落结构主要受溶解氧、氨氮和水位的影响。捕鱼活动导致的浮游食性鱼类减少也对浮游动物的密度变化产生了影响。

"Plate-shaped Lake Enclosed in Autumn"is a fishing method used by fishermen in the Poyang Lake.According to seasonal water level,fishermen use artificial gates to control sub-lake water level for fishing.This study analyzed the zooplankton community structure during the"Plate-shaped Lake Enclosed in Autumn"and discussed the impact of water level and other possible influencing factors on the zooplankton community structure.From 9th November,2014 to 4th January,2015,we conducted 8 times qualitative and quantitative zooplankton acquisitions from seven sampling sites in the open water area of Dahuchi Lake,a sub-lake located in the Poyang Lake National Nature Reserve.A total of 77 species of zooplankton were identified,which consisted of 53 species of Rotifera,10 species of Cladocera and 14 species of Copepoda.During the"Plate-shaped Lake Enclosed in Autumn"fishing process,the specie richness of zooplankton gradually decreased with the decrease of water level.The diversity index of zooplankton also showed a decreasing tendency.Zooplankton density and biomass increased first and then decreased.However,the density variation of dominant species in zooplankton has obvious species differences.The density of Asplanchna priodonta and Limnoithona sinensis gradually increased during"Plate-shaped Lake Enclosed in Autumn".The density of Polyarthra vulgaris,Mesocyclops leuckarti,Bosmina longirostris and Copepod nauplii continuously decreased.Redundancy analysis(RDA)showed that several environmental factors such as water level,conductivity,water temperature,dissolved oxygen and nutrient had significant effect on the zooplankton community structure with the strongest effect by dissolved oxygen.In addition,according to the information of fishing catch during"Plate-shaped Lake Enclosed in Autumn",we propose that the decrease in planktonic fish caused by fishing activities can impact zooplankton density.