不同鱼类混养组合与饲喂方式对鱼蚌综合养殖水体浮游植物群落结构的影响

摘要

利用三角帆蚌(Hyriopsis cumingii)、草鱼(Ctenoparyngodon idellus)、银鲫(Carassius gibelio)、鲢(Hypopthalmic-hthys molitrix)和鳙(Aristichthys nobilis)构建鱼蚌综合养殖系统，通过155 d围隔(面积32 m2)实验检验两种鱼类组合(草鱼+鲫+鲢+鳙或鲢+鳙)和两种饲喂方式(投喂或不投喂配合饲料)对浮游植物群落结构的影响。采用2×2设计，设4个处理： GISB-F(草鱼+鲫+鲢+鳙+投喂配合饲料)、GISB-NF(草鱼+鲫+鲢+鳙+不投喂配合饲料)、SB-F(鲢+鳙+投喂配合饲料)和SB-NF(鲢+鳙+不投喂配合饲料)。每个围隔内三角帆蚌、草鱼、鲫、鲢和鳙的放养量分别为20、15、5、5和5 ind。结果表明，各处理围隔内浮游植物生物量平均值为3.7×108~6.0×108 cell·L–1。改变鱼类组合和饲喂方式对浮游植物种类组成、优势种优势度、群落多样性、生物量以及浮游植物生物量中蓝藻的比例无显著影响，但投喂配合饲料导致叶绿素 a 增加。浮游植物实验前期主要优势种为十字藻属(Crucigenia)和栅藻属(Scenedesmus)种类，后期为平裂藻属(Merismopedia)和微囊藻属(Microcyslis)种类，表明浮游植物群落演变具有明显的季节性特点以及优势种逐渐演化为蓝藻的规律。水温、氨态氮、总氮和高锰酸钾指数对浮游植物群落结构具有显著影响。各处理围隔内氨态氮、总氮和高锰酸钾指数均随时间延长而增加，说明改变鱼类组合和饲喂方式不会影响围隔内蓝藻水华发生的趋势。%A 155-day enclosure experiment was conducted to evaluate the effects of co-cultured fish species combina-tion (either the combination of grass carp Ctenopharyngodon idellus, gibel carp Carassius gibelio, silver carp Hypoph-thalmichthys molitrix and bighead carp Aristichthys nobilis or the combination of silver carp and bighead carp) and formulated feed supplement regime (with or without feed supplement) on phytoplankton community in the enclosures with integrated culture of freshwater pearl mussel Hyriopsis cumingii and fishes. Four treatments, including stocking of grass carp, gibel carp, silver carp and bighead carp with formulated feed supplement (GISB-F ), stocking of grass carp, gibel carp, silver carp and bighead carp without formulated feed supplement (GISB-NF), stocking of silver carp and bighead carp with formulated feed supplement (SB-F), stocking of silver carp and bighead carp without formulated feed supplement (SB-NF), were examined. In each enclosure, 20 mussel, 15 grass carp, 5 gibel carp, 5 silver carp and 5 big-head carp were stocked, respectively. Results showed that the phytoplankton biomass ranged from 3.7 × 108 to 6.0 × 108 cell·L-1 during the experiment. No significant differences were found in the species composition, biomass and biodiver-sity index of phytoplankton, dominance index of the dominant species, and the ratio of cyanobacteria biomass to phy-toplankton biomass between enclosures GISB-F, GISB-NF, SB-F and SB-NF. However, the concentration of chloro-phyll a was higher in the enclosures fed formulated feed than in the enclosures without formulated feed supplement. Seasonal dynamics in phytoplankton community was observed. The dominant species of phytoplankton was green algae (Crucigenia and Scenedesmus) at the beginning of the experiment, and changed to blue-green algae (Merismopedia and Microcyslis) at the end of the experiment, suggesting the trend of occurrence of blue-green algae bloom. The factors that significantly influenced the alteration of community structure of phytoplankton included water temperature (T), ammonia (NH3-N), total nitrogen (TN) and chemical oxygen demand (CODMn). This result indicated that the changes of co-cultured species combination and formulated feed supplement could not change the trend that blue-green algal bloom finally occurred in the enclosures since NH3-N, TN and CODMn increased with the progress of the experiment.