REU: Episodic Winterkill, Pulsed Predation, and the Structure of Benthic Assemblages in Lentic Aquatic Ecosytems

罕见的间歇性压力可能会对生态社区产生长期影响。在浅水池塘或湖泊中，冬季间歇性低氧(低氧)可通过直接死亡或通过促进鱼类捕食脉冲影响底栖无脊椎动物群落。在这样的水域中，底栖区域会变得缺氧，而足够的氧气通常会留在冰水界面附近。要想生存下去，底栖动物必须耐受低氧，或者迁移到氧气充足的地区。然而，诸如增加活动或向冰水界面移动等行为，在避免低氧条件下是适应的，在避免鱼类捕食方面是不适应的。尽管在鱼类存在的情况下避免低氧和行为改变已经被单独记录下来，但还没有人研究无脊椎动物如何平衡这些相互冲突的需求。这项研究将研究非生物压力(冬季低氧)和生物因素(鱼类捕食)在构建底栖无脊椎动物组合中的相互作用。在实验室实验中，将检验底栖无脊椎动物平衡避免缺氧和捕食鱼类这两个相互冲突的要求的能力。随着底栖环境变得缺氧，分类群将根据它们对鱼类捕食的脆弱性进行排序。然后，这些预测将在室外池塘中得到验证，在那里，海底区域的缺氧将受到控制。在有鱼和没有鱼的池塘中，底栖无脊椎动物对缺氧的行为反应将使用水下摄像机进行监测。为了确定是否在野外观察到了物种脆弱性的实验室排名，将在底栖生物带变得缺氧之前、期间和之后对鱼类饲料进行量化。底栖低氧前后无脊椎动物类群的丰富程度将使我们能够单独确定冬季低氧的影响，并结合鱼类捕食来构建底栖无脊椎动物群落。

Infrequent, episodic stress can have long-term effects on ecological communities. In shallow ponds or lakes, episodic winter hypoxia (low oxygen) can affect benthic invertebrate communities, either through direct mortality, or by promoting pulses of fish predation. In such waters, benthic areas become hypoxic while adequate oxygen often remains near the ice-water interface. To persist, benthic taxa must tolerate low oxygen or migrate to regions with adequate oxygen. However, behaviors such as increased activity or movement toward the ice-water interface that are adaptive in avoiding low oxygen conditions would be maladaptive in avoiding fish predation. Although avoidance of low oxygen and behavioral changes in the presence of fish have been documented separately, no one has examined how invertebrates balance these conflicting demands. This research will examine the interaction of an abiotic stress (winter hypoxia) and a biotic factor (fish predation) in structuring benthic invertebrate assemblages. In laboratory experiments, the ability of benthic invertebrates to balance the conflicting demands of avoiding both hypoxia and fish predation will be examined. Taxa will be ranked according to their vulnerability to fish predation as the benthic environment becomes hypoxic. These predictions will then be tested in outdoor ponds where hypoxia of the benthic region will be manipulated. The behavioral response of benthic invertebrates to developing hypoxia in ponds with and without fish will be monitored using an underwater video camera. To determine if laboratory rankings of species' vulnerability are observed in the field, fish diets will be be quantified before, during, and after the benthic zone becomes hypoxic. Abundance of invertebrate taxa before and after benthic hypoxia will allow us to determine the effect of winter hypoxia alone and in combination with fish predation in structuring benthic invertebrate assemblages.