Effects of grazer richness and composition on algal biomass in a closed and open marine system.
Effects of grazer richness and composition on algal biomass in a closed and open marine system.
复制标题
封闭和开放海洋系统中食草动物丰富度和组成对藻类生物量的影响。
作者：
B. Matthiessen;Lars Gamfeldt;P. Jonsson;H. Hillebrand
大多数自然局部系统通过迁移和扩散与区域物种库交换生物体。这种相互关联的多物种组合的元群落过程可能会影响物种和过程的局部动态。我们展示了人工海洋室外岩石池系统的结果，其中我们研究了以下因素：（1）当地食草动物的丰富度和组成，以及（2）当地斑块与区域物种池的连通性及其对藻类生物量的影响。六种食草动物的当地物种丰富度在开放池和封闭池中进行控制，这些池嵌入包含所有六种食草动物的区域物种池中。食草动物丰富度对封闭系统中的放牧显示出显着的净生物多样性影响，但在开放系统中则不然。另一方面，放牧动物的组成对开放和封闭系统中的放牧都有显着影响，具体取决于最初存在的物种。两种效率最高的食草动物能够补偿物种混合物中效率较低的食草动物，从而确保放牧功能。因此，开放系统中藻类生物量自上而下控制的效率取决于丢失的特定物种。此外，由于放牧动物组成的时间动态，开放系统和封闭系统之间的放牧差异随着时间的推移而变化。结果强调了在实验设计中纳入系统连通性的重要性，以便推断生物多样性生态系统功能与自然系统的关系。
Most natural local systems exchange organisms with a regional pool of species through migration and dispersal. Such metacommunity processes of interconnected multispecies assemblages are likely to affect local dynamics of both species and processes. We present results from an artificial marine outdoor rock pool system in which we investigated the factors of (1) local grazer richness and composition, and (2) connectivity of local patches to a regional species pool, and their effects on algal biomass. Local species richness of six grazers was manipulated in both open and closed pools, which were embedded in a regional species pool containing all six grazers. Grazer richness showed significant net biodiversity effects on grazing in the closed, but not in the open, system. Grazer composition, on the other hand, showed significant effects on grazing in both open and closed systems, depending on which species were initially present. The two most efficient grazers were able to compensate for less efficient grazers in species mixtures, hence ensuring the function of grazing. The efficiency of top-down control of algal biomass in open systems thus depends on which particular species are lost. Further, differences in grazing between the open and closed system changed over time due to temporal dynamics in grazer composition. The results emphasize the importance of including system connectivity in experimental designs to allow an extrapolation of biodiversity ecosystem-functioning relationships to natural systems.