牡蛎对浮游植物群落下行控制作用的围隔实验研究

Top-down impacts of Crassostrea gigas on the phytoplankton community:Mesocosm experiments in a eutrophic pond

牡蛎的滤食作用不但能控制浮游植物丰度,还能通过摄食选择性影响群落结构。通过在较高营养水体的围隔实验表明,牡蛎养殖在持续磷限制条件下,促使浮游植物群落由甲藻向小型硅藻优势转变。实验结束时对照组中浮游植物群落由扁压原甲藻主导,占总丰度的77%;而牡蛎养殖组新月柱鞘藻丰度占比达到93%。牡蛎养殖组中,甲藻去除速率随养殖密度增长,但是硅藻最终丰度在高密度牡蛎组最高。研究结果说明大量的贝类养殖能够提升小型链状硅藻的优势度,增加此类赤潮发生风险。

In addition to phytoplankton biomass removal,oyster feeding may also impact the community composition.In our mesocosm experiments,under the continuous phosphorus restriction conditions,oyster feeding promoted a shift in phytoplankton community structure away from dinoflagellates toward the dominance of small diatoms.At the end of cultivation,Prorocentrum compressum prevailed in control treatments,accounting for 77%of the total abundance,whereas Cylindrotheca closterium reached 93%at all oyster densities.In oyster cultivation treatments,while dinoflagellate abundance decreased with oyster density in the initial days,the final diatom abundance was the highest in the high-oyster density treatment.The results indicated that dense bivalve farming can potentially increase the risk of red tide formation by small and chain-forming diatom species.