In contemporary ecology, it is becoming increasingly important to consider the effects of human activities on the environment. However, an equally important, but often overlooked, challenge is to consider how ecological interactions may ameliorate these human impacts. At the University of Pittsburgh, we have developed a unique and innovative research program that addresses these contemporary challenges by investigating the interactive effects of anthropogenic perturbations and ecological interactions. Specifically, we are examining the extent to which aquatic plants can mitigate the environmental consequences of anthropogenic stressors that make their way into freshwater ecosystems. While our prior work has shown that aquatic plants dramatically reduce the lethal effects of stressors to ecologically important aquatic species, we still have a poor understanding of whether this phenomenon translates up to complex communities. To take this critical next step, we will examine whether, and to what extent, aquatic plants can mitigate the effects of single exposures to high concentrations of stressors versus repeated exposures to lower concentrations in complex aquatic food webs. This research will advance our understanding of the effects that anthropogenic perturbations are having in biological communities, but also of how common components of most freshwater communities can alter, and potentially reduce, those effects.
In addition to conducting this research and disseminating it within the scientific community, we also engage in a number of activities to promote environmental awareness with the public. For example, we frequently work with K-12 students, where we discuss our research and the importance of the research to conservation. Further, we run annual teacher workshops at the University of Pittsburgh's biological field station, the Pymatuning Laboratory of Ecology, where middle and high school teachers learn how to conduct and integrate scientific experiments into classroom learning experiences for their students. We hope that our studies and efforts to provide students with scientific experiences early in their careers will lead to the development of innovative new strategies for conserving the environment in the future.
An increasingly important global challenge is to understand how and when different factors might mitigate the impacts of anthropogenic contaminants in aquatic ecosystems. In previous laboratory experiments, we have shown that the presence of realistic densities of numerous submerged plant species makes the popular insecticide malathion approximately 10-times less lethal to aquatic animals than when no plants are present. While our previous work has provided a strong foundation for understanding the ability of submerged plants to mitigate insecticide effects, several critical questions still needed to be addressed: 1. What is the primary mechanism by which submerged plants mitigate malathion’s effects? 2. To what extent do aquatic plants also mitigate the effects of other common insecticides? 3. In more realistic ecological communities containing predators and competitors, are the mitigating effects of aquatic plants on insecticide toxicity still evident? With the help of the National Science Foundation Doctoral Dissertation Improvement Grant, we were able to address all of these key questions. We first examined the mechanism by which submerged plants mitigate malathion’s toxic effects. We discovered that the plants mitigate malathion’s toxicity by increasing the pH of water via photosynthesis, causing the rapid breakdown of the insecticide into non-toxic byproducts. This discovery is transformative because while it was already known that high pH levels cause malathion to break down quickly, nobody had ever examined whether this process, called alkaline hydrolysis, could influence malathion’s toxicity. In fact, current models designed to predict the environmental effects of pesticides and current best management practices designed to reduce pesticide loads in runoff don’t even consider alkaline hydrolysis as an important mitigation pathway. Thus, our findings offer a fresh approach for thinking about the influence of plants on the environmental effects of insecticides and suggest that current paradigms employed in toxicological models and best management practices may be ignoring a key pathway for mitigating pesticide effects. Following this study, the critical next step was to examine the extent to which submerged plants mitigate the effects of many different insecticides with different chemical properties to see if generalizable patterns emerge. To do this, we tested the mitigating effects of submerged plants on the toxicity of nine common insecticides to a sensitive aquatic invertebrate. Our prediction was that plants would have the greatest mitigating effects on insecticides that undergo rapid alkaline hydrolysis (as we observed with malathion), because of their rapid breakdown in water, as well as insecticides that are highly hydrophobic, because of their rapid removal from water via binding to plant tissues. While we are still analyzing the results of this study, one preliminary conclusion is that plants were very successful at reducing the toxicity of insecticides susceptible to alkaline hydrolysis such as malathion, carbaryl, and carbofuran. However, hydrophobicity was a surprisingly poor predictor of how well plants would mitigate an insecticide’s toxicity and highly hydrophobic insecticides like permethrin, bifenthrin and lambda-cyhalothrin were not mitigated much at all. Again, the broader impacts of these findings suggest that the current strategies used to mitigate insecticide effects with aquatic plants could strongly benefit from incorporating alkaline hydrolysis. The final question that we wanted to address was whether the presence of submerged plants mitigates malathion’s effects on sensitive species at larger spatial scales and in the presence of realistic ecological interactions like predation. This is an important step as accumulating evidence is revealing that predation can dramatically alter the toxicity of insecticides. While we have not yet formally analyzed the results from this study, so far we have found that, as expected, high concentrations of malathion cause death in sensitive animal species and this toxicity is mitigated by submerged plants. However, we have not yet discerned a clear pattern in the effects that predators have on insecticide toxicity, and how this interaction is influenced by plants. Nonetheless, our studies continue to demonstrate the ability of submerged plants to mitigate malathion’s toxicity at numerous spatial scales. In addition to preparing the aforementioned studies for publication in top-tier ecological and toxicological scientific journals, we have also engaged in several outreach activities to bring these results to the broader public. For example, we have worked with regional Pennsylvania and New York government agencies to coordinate aquatic ecosystem restoration projects performed by over 120 K-12 students. In addition, we have visited Western Pennsylvania high school classrooms on multiple occasions to lead class discussions on the impacts of contaminants in aquatic ecosystems and the mitigation of these impacts. We have used these opportunities to discuss our research and the importance of protecting aquatic ecosystems and we hope that these efforts will inspire the next generation of scientists to engage in this increasingly critical area of research.
