菲律宾蛤仔稚贝对浮游微藻的滤食选择及对水体水色的影响

Effect of Filter-feeding in the Juveniles of Ruditapes philippinarum on Phytoplankton and Water Color

为研究菲律宾蛤仔(Ruditapes philippinarum)稚贝对浮游微藻的滤食选择及生物沉降作用,分别在稚贝滤食0、3、6、10 h后采集育苗池中的微藻水样,分析浮游微藻的种类和数量变化,测定水体透明度、悬浮物、叶绿素a等理化因子的变化。结果显示:调查期间共观察到近50种浮游微藻,主要包括硅藻门、绿藻门、蓝藻门等。对比滤食前后微藻的种类和数量,发现菲律宾蛤仔稚贝对硅藻门藻类具有显著的滤食效应,其中梅尼小环藻在投喂后10 h平均生物量下降了94.02%,占微藻平均总减少量的39.97%,为筛寻一种优质高效的稚贝生物饵料提供了重要思路。同时稚贝的滤食作用使浮游微藻及悬浮物含量迅速减少,水体水色变化明显,悬浮物含量下降85.6%,叶绿素a的含量下降72.9%,水体透明度增加96.7%,证明菲律宾蛤仔稚贝滤食能够在一定程度上改善水质。

Polyculture model can improve the economic benefits of aquaculture and reduce the pollution of aquarium water.Using shellfish to ingest microalgae is an important link in this model.Due to incomplete development of filter-feeding structures,juveniles of shellfish have high filter-feeding selectivity for phytoplankton.Besides,the filter-feeding of shellfish will cause the sedimentation of suspended solids,which is helpful to improve water quality.In order to study the filter-feeding selection effect on phytoplankton and biodeposition effect of juvenile short necked clam(Ruditapes philippinarum),samples of phytoplankton in the ponds culturing juvenile short necked clam were collected at 0 h,3 h,6 h and 10 h after feeding for analysis of their changes in the species and density of phytoplankton.Water transparency,suspended solids,and chlorophyll-a content were measured to observe the change of water color.The results showed that about 50 species of phytoplankton were observed during the survey,mainly including Bacillariophyta,Chlorophyta,and Cyanophyta among others.Comparison of the species and biomass of phytoplankton before and after filtering showed that the juveniles of the short necked clam had a significant filter-feeding selection on the species in the phylum Bacillariophyta.Cyclotella meneghiniana is expected to be a high-quality and efficient juvenile bait.After 10 hours of feeding,the mean biomass of C.meneghiniana decreased by 94.02%,accounting for 39.97%of the mean total loss of phytoplankton.And the suspended solids settled rapidly due to filtering by the juveniles,reducing the cell density of phytoplankton.The water color changed significantly after filtering.The suspended solids decreased by 85.6%,the chlorophyll-a content decreased by 72.9%,and the transparency of the water body increased by 96.7%,which proved that the juvenile short necked clam can improve water quality via filter feeding.