Collins Scott F, Wahl David H
Illinois Natural History Survey, Kaskaskia Biological Station, Sullivan, IL, USA.
Oecologia. 2017 Jun;184(2):521-530. doi: 10.1007/s00442-017-3872-x. Epub 2017 Apr 27.
Bighead carp (Hypophthalmichthys nobilis) are an invasive planktivore that can greatly deplete planktonic resources. Due to the inefficient conversion of food into fish tissue, large portions of consumed materials are egested and shunted to benthic habitats. We explored how bighead carp alter pools of organic matter between planktonic and benthic habitats, and across ecosystem boundaries. Here, we report evidence from a manipulative experiment demonstrating that bighead carp greatly reapportion pools of organic matter from planktonic to benthic habitats to such a degree that additional effects propagated across ecological boundaries into terrestrial ecosystems. Strong direct consumption by bighead carp reduced filamentous algae, biomass and production of zooplankton, and production of a native planktivorous fish within planktonic habitats. Reduced herbivory indirectly increased phytoplankton (chlorophyll a). Direct consumption of organic matter by bighead carp supported high carp production and concomitant losses of materials due to egestion. Perhaps in response to organic matter subsidies provided by fish egestion, ponds having bighead carp had higher standing crop biomass of Chironomidae larvae, as well as cross-boundary fluxes of their adult life stage. In contrast, we detected reduced cross-boundary fluxes of adult Chaoboridae midges in ponds having bighead carp. Consideration of bighead carp as mediators of organic matter exchanges provides a clearer framework for predicting the direct and extended impacts of these invasive planktivores in freshwater ecosystems. The perception of bighead carp must evolve beyond competitors for planktonic resources, to mediators and processors of nutrients and energy within and across ecosystems.
鳙鱼（Hypophthalmichthys nobilis）是一种入侵性的浮游生物食性鱼类，会大量消耗浮游生物资源。由于食物转化为鱼体组织的效率低下，大量被消耗的物质会被排出，并转移到底栖生境中。我们探究了鳙鱼如何改变浮游和底栖生境之间以及跨越生态系统边界的有机物质库。在此，我们报告了一项操纵性实验的证据，该实验表明鳙鱼极大地将有机物质库从浮游生境重新分配到底栖生境，以至于其他影响会跨越生态边界传播到陆地生态系统中。鳙鱼的大量直接消耗减少了丝状藻类、浮游动物的生物量和产量，以及浮游生境中一种本地浮游生物食性鱼类的产量。食草作用的减少间接增加了浮游植物（叶绿素a）。鳙鱼对有机物质的直接消耗支持了高鲤鱼产量以及因粪便排出而伴随的物质损失。也许是对鱼类粪便提供的有机物质补贴的响应，有鳙鱼的池塘摇蚊科幼虫的现存量生物量更高，以及它们成虫阶段的跨界通量也更高。相比之下，我们在有鳙鱼的池塘中检测到毛蠓科成虫的跨界通量减少。将鳙鱼视为有机物质交换的调节者，为预测这些入侵性浮游生物食性鱼类在淡水生态系统中的直接和扩展影响提供了一个更清晰的框架。对鳙鱼的认知必须从浮游生物资源的竞争者，转变为生态系统内部和之间营养物质和能量的调节者和处理者。
