Interhabitat Transport of Nutrients by Detritivorous Fish: Impacts on Phytoplankton Communities

9318452 Vanni这项研究试图了解有害的鱼类是如何通过充当“营养泵”来影响湖泊浮游植物群落的。通过摄食底栖生物碎屑并将营养物质(氮和磷)排泄到湖泊生境中，这些鱼有效地将营养物质从底栖生境输送到湖泊生境，在那里营养物质可以刺激浮游植物的生长并改变浮游植物的群落结构。动物可以以多种方式影响群落，众所周知，在北部湖泊中，鱼类可以通过食物链相互作用对浮游植物群落产生强烈影响。这里提出，在温水湖泊和水库中，鱼类主要通过营养泵机制而不是传统的食物链相互作用来影响浮游植物。具体目标是量化有害食性鱼类对湖泊浮游植物群落的群落水平影响。有待检验的假设包括：1)有害食性鱼类通过营养物质泵机制影响浮游植物，2)营养物质泵机制的影响取决于鱼类种群结构和碎屑营养物质含量，3)在河流流入较少的时期，有害食性鱼类是小型水库浮游植物的主要营养物质来源。这些假设将通过一系列经验观察、现场和实验室实验进行验证。这项研究将增进我们对食物网调节、自上而下和自下而上对群落的控制以及底栖-湖泊耦合的知识。虽然这个项目侧重于社区效应，但它将从个人到生态系统的组织层次整合在一起。此外，由于营养泵可能会影响蓝藻滋生的频率和强度，这项研究对水质管理有一定的意义。***

9318452 Vanni This research seeks to understand how detritivorous fish affect lake phytoplankton communities by acting as "nutrient pumps." By feeding on benthic detritus and excreting nutrients (nitrogen and phosphorus) into the limnetic habitat, these fish effectively pump nutrients from benthic to limnetic habitats, where nutrients can stimulate phytoplankton growth and alter phytoplankton community structure. Animals can affect communities in many ways and it is well known that in northern lakes fish can have strong effects on phytoplankton communities through food chain interactions. It is proposed here that in warm-water lakes and reservoirs, fish affect phytoplankton primarily through the nutrient pump mechanism rather than through conventional food chain interactions. The specific objectives are to quantify the community level effects of detritivorous fish on lake phytoplankton communities. Hypotheses to be tested include: 1) detritivorous fish affect phytoplankton via the nutrient pump mechanism, 2) the effects of the nutrient pump mechanism is dependent on fish population structure, and detrital nutrient content, and 3) detritivorous fish are a major source of nutrients to phytoplankton in small reservoirs during times with stream inflows are low. These hypotheses will be tested using a series of empirical observations, field and laboratory experiments. %%% This research will advance our knowledge of food web regulation, top down versus bottom up controls on communities, and benthic-limnetic coupling. Although this project focuses on community effects, it integrates levels of organization from individual to ecosystem. In addition, because nutrient pumps may have effects on the frequency and intensity of nuisance blooms of blue-green algae, the research has implications for water quality management. ***