Brogan William R, Relyea Rick A
Smithsonian Environmental Research Center, Edgewater, Maryland, 21037, United States of America.
Rensselaer Polytechnic Institute, Troy, New York, 12180, United States of America.
PLoS One. 2015 May 15;10(5):e0126677. doi: 10.1371/journal.pone.0126677. eCollection 2015.
Understanding how ecological interactions mitigate the impacts of perturbations such as pesticides in biological communities is an important basic and applied question for ecologists. In aquatic ecosystems, new evidence from microcosm experiments suggests that submerged macrophytes can buffer cladocerans from pulse exposures to the widely used insecticide malathion, and that mitigation increases with macrophyte density. However, whether these results scale up to more complex aquatic communities where ecological interactions such as competition can alter toxicity is unknown. Further, macrophyte abilities to mitigate different insecticide exposure scenarios (i.e. single versus repeated pulses) have never been tested. To address these gaps, we performed a factorial mesocosm experiment examining the influence of four macrophyte treatments (0, 10, 50, or 100 Elodea Canadensis shoots planted per mesocosm) crossed with three malathion exposure scenarios (no insecticide, single pulse, repeated pulses) on aquatic communities containing zooplankton, phytoplankton, periphyton, two snail species, and larval amphibians. In the absence of macrophytes, single malathion pulses caused short-term declines in cladoceran abundance followed by their rapid recovery, which precluded any indirect effects (i.e. trophic cascades). However, repeated malathion pulses caused cladoceran extinctions, resulting in persistent phytoplankton blooms and reduced abundance of one snail species. In contrast, with macrophytes present, even at low density, malathion had no effect on any taxa. We also discovered novel effects of macrophytes on the benthic food web. In the two highest macrophyte treatments, we observed trends of reduced periphyton biomass, decreased abundance of one snail species, and decreased amphibian time to and mass at metamorphosis. To our knowledge, this is the first evidence of negative submerged macrophyte effects on amphibians, a taxa of global conservation concern. Our findings suggest that facilitating macrophytes could be an important strategy for buffering freshwater communities from insecticides, though consideration of their impacts on animal species is necessary.
了解生态相互作用如何减轻诸如农药等扰动对生物群落的影响，是生态学家面临的一个重要的基础和应用问题。在水生生态系统中，微观实验的新证据表明，沉水大型植物可以缓冲枝角类动物免受脉冲式接触广泛使用的杀虫剂马拉硫磷的影响，并且这种缓解作用会随着大型植物密度的增加而增强。然而，这些结果是否适用于更复杂的水生群落，在这些群落中，诸如竞争等生态相互作用会改变毒性，目前尚不清楚。此外，大型植物减轻不同杀虫剂暴露情景（即单次脉冲与重复脉冲）影响的能力从未经过测试。为了填补这些空白，我们进行了一项析因中宇宙实验，研究了四种大型植物处理（每个中宇宙种植0、10、50或100株加拿大伊乐藻）与三种马拉硫磷暴露情景（无杀虫剂、单次脉冲、重复脉冲）对包含浮游动物、浮游植物、周丛生物、两种蜗牛物种和两栖类幼体的水生群落的影响。在没有大型植物的情况下，单次马拉硫磷脉冲导致枝角类动物数量短期下降，随后迅速恢复，这排除了任何间接影响（即营养级联效应）。然而，重复的马拉硫磷脉冲导致枝角类动物灭绝，导致浮游植物持续大量繁殖，并减少了一种蜗牛物种的数量。相比之下，在有大型植物的情况下，即使密度很低，马拉硫磷对任何分类单元都没有影响。我们还发现了大型植物对底栖食物网的新影响。在大型植物处理的两个最高水平中，我们观察到周丛生物量减少、一种蜗牛物种数量减少以及两栖动物变态时间和变态时体重下降的趋势。据我们所知，这是沉水大型植物对两栖动物产生负面影响的首个证据，两栖动物是全球关注的保护类群。我们的研究结果表明，促进大型植物生长可能是缓冲淡水群落免受杀虫剂影响的重要策略，不过有必要考虑它们对动物物种的影响。
