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首页> 外文期刊>Estuarine Coastal and Shelf Science >Decoupling of nutrient and grazer impacts on a benthic estuarine diatom assemblage
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Decoupling of nutrient and grazer impacts on a benthic estuarine diatom assemblage

机译：营养物质和放牧者的解耦影响底栖河口硅藻组合

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摘要

Strong interactions between top-down (consumptive) and bottom-up (resource supply) trophic factors occur in many aquatic communities, but these forces can act independently in some microphytobenthic communities. Within benthic estuarine diatom assemblages, the dynamics of these interactions and how they vary with abiotic environmental conditions are not well understood. We conducted a field experiment at two sites with varying habitat characteristics to investigate the interactive effects of grazers and nutrients on benthic estuarine diatoms. We crossed snail (Cerithidea californica) and nutrient (nitrogen and phosphorus) addition treatments in enclosures on a restored tidal sandflat and a reference tidal mudflat in Mugu Lagoon, southern California. We repeated the study in summer 2000 and spring 2001 to assess temporal variation in the interactions. Snails caused a large decrease in diatom relative abundance and biomass (estimated as surface area); nutrients increased diatom abundance but did not alter diatom biomass. Snails and nutrients both reduced average diatom length, although the nutrient effect was weaker and temporally variable, occurring in the reference mudflat in the spring. There were few interactions between snail and nutrient addition treatments, suggesting that links between top-down and bottom-up forces on the diatom community were weak. There were no consistent differences in diatom assemblage characteristics between the two study sites, despite marked differences in sediment grain size and other abiotic characteristics between the sites. The strong diatom response to herbivores and weaker responses to enrichment differed from the previous studies where cyanobacteria increased in response to nutrient enrichment, further dissolving the "black box" perception of microphytobenthic communities.
机译：自上而下（消费）和自下而上（资源供应）的营养因子之间有很强的相互作用，但在许多微底栖动物群落中，这些力量可以独立发挥作用。在底栖河口硅藻组合物中，这些相互作用的动力学以及它们如何随非生物环境条件而变化还不太清楚。我们在两个具有不同栖息地特征的地点进行了野外实验，以研究食草动物和营养物对底栖河口硅藻的相互作用。我们在加利福尼亚州南部的Mugu Lagoon的恢复潮汐滩涂和参考潮汐滩涂上，将蜗牛（Cerithidea californica）和营养物（氮和磷）添加处理放在封闭的环境中。我们在2000年夏季和2001年春季重复了该研究，以评估相互作用的时间变化。蜗牛导致硅藻相对丰度和生物量（按表面积估算）大大降低；营养物质增加了硅藻的丰度，但没有改变硅藻的生物量。蜗牛和养分均减少了硅藻的平均长度，尽管养分效应较弱且随时间变化，发生在春季的参考泥滩中。蜗牛和营养物的添加处理之间几乎没有相互作用，这表明硅藻群落上自上而下和自下而上的作用力之间的联系较弱。尽管两个研究地点之间的沉积物粒度和其他非生物特征存在显着差异，但两个研究地点之间的硅藻组装特征没有一致的差异。硅藻对草食动物的强烈反应和对富集的较弱反应与以前的研究不同，在先前的研究中，蓝细菌对营养的富集作出了反应，从而增加了对藻类底栖动物群落的“黑匣子”感知。

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