Abstract

Human activities alter biodiversity, influencing bottom-up and top-down control on food webs which can affect ecosystem functioning. In marine ecosystems, large bivalves play a critical role in benthic–pelagic coupling including nutrient cycling; however, their influence on the uptake of detrital organic matter by benthic communities is less understood. In a replicated factorial field experiment, we examined how the presence or absence (overharvesting scenario) of a large suspension-feeding clam on an intertidal sandflat and the addition of isotopically enriched macroalgal (Ulva sp.) detritus (eutrophication scenario) influenced infaunal biodiversity, and how changes in trophic interactions influenced key ecosystem functions (nutrient cycling and benthic metabolism and primary production). Both clams and Ulva increased community metabolism, but only clams had an effect on nutrient regeneration. We used the ¹³C- and ¹⁵N-enriched Ulva to quantify the effect of clams on detritus uptake in fauna and recovery in sediment. Due to their large biomass, nitrogen incorporation by clams constituted one-third of the infaunal community uptake after 14 days. Clam uptake likely resulted from ingestion of resuspended microphytobentos which had utilized ¹⁵N leaking out from decomposing Ulva. In plots without Ulva addition, the effect of clams on the overall resource utilization by the benthic community using natural abundance isotope niche metrics were tested. In plots without clams, the isotope niche of the community was reduced, and less carbon of pelagic origin was channelled into the infaunal food web. Our results imply that the loss of clams changes trophic pathways and reduces community uptake of macroalgal detritus, potentially exacerbating eutrophication.

Graphic Abstract

中文翻译：

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大型的双足双壳类动物决定了巨藻碎屑和食物网途径的社区吸收

摘要

人类活动改变了生物多样性，影响了食物网自下而上和自上而下的控制，这可能影响生态系统的功能。在海洋生态系统中，大型双壳类动物在底栖-上层耦合（包括养分循环）中发挥关键作用。但是，它们对底栖生物对碎屑有机质吸收的影响了解较少。在重复的析因田间实验中，我们研究了潮间带沙滩上是否存在大型悬浮饲料喂养蛤，以及同位素富集的巨藻（Ulva sp。）碎屑（富营养化）的存在如何影响非生物多样性，营养相互作用的变化如何影响关键的生态系统功能（营养循环，底栖生物代谢和初级生产）。蛤和Ulva增加了社区的新陈代谢，但是只有蛤on对营养物的再生有影响。我们使用了富含¹³ C和 ¹⁵ N的Ulva来量化蛤c对动物碎屑摄取和沉积物回收的影响。由于它们大量的生物量，在14天后，蛤中的氮吸收量占该臭名昭著的群落吸收量的三分之一。蛤摄取可能导致从其中已经利用悬浮microphytobentos的摄取¹⁵ n的分解漏出石莼。在没有Ulva的地块中此外，还测试了蛤类对底栖生物利用自然丰度同位素生态位指标的整体资源利用的影响。在没有蛤lam的地块中，群落的同位素生态位减少了，更少的中上层碳被带到了臭名昭著的食物网中。我们的结果表明，蛤类的流失会改变营养途径，并减少群落对巨藻碎屑的吸收，从而可能加剧富营养化。

图形摘要