Mismatch between periphyton and macrophyte development in spring: crucial for submerged macrophyte recolonization in eutrophic shallow lakes?

淹没的大型植物稳定了浅水湖泊的清澈水状态，但在富营养化过程中往往完全消失，导致转向浑浊，浮游植物主导的状态。浅水湖泊再富营养化后，淹没植物的再定殖常常失败，尽管春季光照供应增加。由外生植物造成的遮阳被认为是原因之一。富营养化湖泊中的浮游生物生物量可能受到鱼类捕食对以浮游生物为食的无脊椎动物的级联效应的控制。然而，直接的实验证据表明，这种自上而下的对周围植物的控制及其与沉水植物再定植的相关性仍然缺乏。我们计划结合野外和实验室实验和建模来揭示水生植物遮阳对淹没植物发展的作用，作为浅层富营养化湖泊可持续管理的基础。重点是鱼类-无脊椎动物-级联自上而下控制周围植物生长的原位证据，大型植物发育早期阶段的遮荫影响，以及春季清水期和块茎发芽时间对周围植物和大型植物生长不匹配的影响。

Submerged macrophytes stabilize the clear water regime in shallow lakes, but were often completely lost during eutrophication resulting in a shift to the turbid, phytoplankton-dominated regime. Re-colonization of submerged macrophytes often failed after reoligotrophication of shallow lakes despite an increased light availability in spring. Shading by periphyton is supposed to be one of the reasons. Periphyton biomass in eutrophic lakes has been suggested to be potentially controlled by a cascading effect of fish predation on periphyton-grazing invertebrates. Direct experimental evidence of this top-down control of periphyton and its relevance for submerged macrophyte re-colonization, however, is still lacking. We plan a combination of field and laboratory experiments and modeling to unravel the role of periphyton shading for the development of submerged macrophytes as a base for sustainable management of shallow eutrophic lakes. The focus is on in situ evidence of topdown control of periphyton by a fish-invertebrates-cascade, the shading impact during early stages of macrophyte development and the impact of timing of the clear water phase and tuber sprouting in spring for a mismatch between periphyton and macrophyte growth.