Trophic Interactions between Phagotrophic Protozoa and Bacterioplankton in Coastal Waters

现在已经确定，异养微生物、细菌和吞噬原生动物是海洋食物网中大部分碳/能量流动的原因。利用从天然浮游细菌组合中制备的荧光标记细菌，已经证明来自盐沼泽河口水域和地中海西北部沿海水域的20万只纤毛虫可以以高清除率捕食细菌。这些纤毛虫优先摄取自由悬浮的细菌，而不是附着在颗粒上的细菌。以往的研究为细菌原生动物对细菌生长的正反馈效应提供了间接证据。将继续对沿海远洋食物网中原生动物-细菌营养相互作用进行研究，重点是：1)评估离散水体中浮游细菌生产力和原生动物象牙质的短期和精细空间尺度变化；2)检查食菌原生动物之间的资源分配程度，特别是关于鞭毛虫和纤毛虫食草细菌的大小光谱；3)测定摄取的细菌转化为原生动物生物量的效率；4)验证了将河口细菌与其原生食草动物分离导致细菌代谢变化的假设。

It is now firmly established that heterotrophic microbes, bacteria and phagotrophic protozoa are responsible for a largepart of carbon/energy flow in marine food webs. Using fluorescently labeled bacteria prepared from naturalbacterioplankton assemblages, it has been demonstrated that 20um ciliates, from waters in a salt marsh estuary and fromcoastal waters in the NWMediterranean Sea, could grazebacteria at high clearance rates. And these ciliatespreferentially ingest freely suspended, rather that particle-attached, bacteria. Previous studies have provided indirectevidence for a positive feedback effect of bacterivorousprotozoa on bacterial growth. Continued investigations will beconducted on protozoa-bacteria trophic interactions in coastal pelagic food webs emphasizing the: 1) evaluation of short-termand fine spatial scale variations in both bacterioplanktonproductivity and protozoan bacterivory within discrete watermasses; 2) examination of the extent of resource partitioningamong bacterivorous protozoa, especially with respect to the size spectra of bacteria grazed by flagellates and ciliates; 3)determination of the efficiency of conversion of ingestedbacteria into protozoan biomass; and 4) testing the hypothesisthat decoupling estuarine bacteria from their protozoan grazersresults in a change in bacterial metabolism.