Ng Carla A, Berg Martin B, Jude David J, Janssen John, Charlebois Patrice M, Amaral Luis A N, Gray Kimberly A
Department of Chemical and Biological Engineering, Northwestern University, 2145 North Sheridan Road, Evanston, Illinois 60208, USA.
Environ Toxicol Chem. 2008 Oct;27(10):2186-95. doi: 10.1897/07-636.1.
The global spread of invasive species is changing the structure of aquatic food webs worldwide. The North American Great Lakes have proved particularly vulnerable to this threat. In nearshore areas, invasive benthic species such as dreissenid mussels and round gobies (Neogobius melanostomus) have gained dominance in recent years. Such species are driving the flow of energy and material from the water column to the benthic zone, with dramatic effect on nutrient and contaminant cycling. Here, we develop a stage-structured model of a benthified food web in Lake Michigan with seasonal resolution and show how its bioaccumulation patterns differ from expected ones. Our model suggests that contaminant recycling through the consumption of lipid-rich fish eggs and mussel detritus is responsible for these differences. In southern Lake Michigan's Calumet Harbor (Chicago, IL, USA), round gobies have nitrogen isotope signatures with considerable spread, with some values higher than their predators and others lower than their prey. Contrary to patterns observed in linear pelagic systems, we predict that polychlorinated biphenyl (PCB) concentrations in these fish decrease with increasing size due to the lipid- and benthos-enriched diets of smaller fish. We also present here round goby PCB concentrations measured in 2005 after an invasional succession in Calumet Harbor and demonstrate how the change from one invasive mussel species to another may have led to a decrease in round goby PCB accumulation. Our results suggest that benthic-dominated systems differ from pelagic ones chiefly due to the influence of detritus and that these effects are exacerbated in systems with low species diversity and high biomass.
入侵物种的全球扩散正在改变世界各地水生食物网的结构。事实证明，北美五大湖特别容易受到这种威胁。在近岸地区，诸如斑马贻贝和圆口铜鱼（Neogobius melanostomus）等入侵底栖物种近年来占据了主导地位。这些物种正在推动能量和物质从水柱向底栖带流动，对营养物质和污染物循环产生巨大影响。在此，我们构建了一个具有季节分辨率的密歇根湖底栖化食物网的阶段结构模型，并展示其生物累积模式与预期模式的差异。我们的模型表明，通过食用富含脂质的鱼卵和贻贝碎屑进行的污染物循环是造成这些差异的原因。在密歇根湖南部的卡柳梅特港（美国伊利诺伊州芝加哥），圆口铜鱼的氮同位素特征差异很大，一些值高于其捕食者，而另一些值低于其猎物。与线性浮游系统中观察到的模式相反，我们预测这些鱼类体内的多氯联苯（PCB）浓度会随着体型增大而降低，这是因为小鱼的饮食富含脂质和底栖生物。我们还展示了2005年在卡柳梅特港入侵演替后测得的圆口铜鱼PCB浓度，并证明从一种入侵贻贝物种转变为另一种可能导致圆口铜鱼PCB积累量下降。我们的结果表明，以底栖生物为主的系统与浮游系统不同，主要是由于碎屑的影响，而且在物种多样性低和生物量高的系统中，这些影响会加剧。
