Ecological impacts of top-down trophic cascades in combination with bottom-up nutrient enrichment are increasingly being reported. Such effects may be triggered by decline in the abundance and size of piscivore fish leading to a release of smaller-sized mesopredatory fish that are capable of reducing mesograzers and their buffering herbivorous effects, thus intensifying eutrophication symptoms. Hitherto, such mesopredator release has not been studied in controlled manner in macroalgal-dominated rocky shore communities. This study utilised twelve littoral mesocosms in southeastern Norway to investigate the impact of increased nutrient levels and increased abundance of the mesopredatory goldsinny wrasse ( Ctenolabrus rupestris ) over 6 months, from spring (April) to autumn (October). The study mainly revealed typical eutrophication responses in both July and in October with nutrient enrichment leading to more ephemeral algae and less perennial Fucacean and red macroalgae. Significant responses to the addition of mesopredatory fish alone or with nutrients in combination were clearly fewer in July and almost non-existent in October. Mesopredatory fish reduced the number of some mesograzers, but not others, and some herbivores even benefitted. Few joint effects occurred between fish and nutrients and the anticipated negative consequences for perennial macrophytes were largely absent; the possible reasons for these observations are discussed in depth. Curiously, the presence of mesopredatory fish seems to favour some canopy-forming macrophytes. This last finding warrants further investigation as the labrid fishery in coastal waters of southern Norway and western Sweden is increasing and a too heavy reduction of mesopredators may have its own unforeseen ecosystem implications.

中文翻译：

---

与自下而上的养分富集相比，自上而下的中捕食性鱼类的释放是温带岩石海岸群落结构驱动力较弱的驱动力

自上而下的营养级联与自下而上的营养丰富相结合的生态影响越来越多地被报道。这种影响可能是由于食鱼鱼的丰度和大小下降导致释放能够减少中食草动物及其缓冲食草作用的小型中食性鱼类，从而加剧富营养化症状。迄今为止，尚未在大型藻类占主导地位的岩石海岸群落中以受控方式研究这种中掠食性动物的释放。本研究利用挪威东南部的 12 个沿海中生态系统来调查从春季（4 月）到秋季（10 月）的 6 个月内营养水平增加和中掠食性金线鱼（ Ctenolabrus rupestris ）丰度增加的影响。该研究主要揭示了 7 月和 10 月典型的富营养化反应，营养物质富集导致更多的短暂藻类和较少的多年生岩藻类和红色大型藻类。对单独添加中食性鱼类或与营养素结合使用的显着反应在 7 月明显减少，而在 10 月几乎不存在。中掠食性鱼类减少了一些中食草动物的数量，但没有减少其他食草动物的数量，一些食草动物甚至从中受益。鱼类和养分之间几乎没有共同影响，而且对多年生大型植物的预期负面影响基本上不存在；对这些观察结果的可能原因进行了深入讨论。奇怪的是，中食性鱼类的存在似乎有利于一些形成树冠的大型植物。