This project will focus on the relationships among novel manufactured nanomaterials, parasitism of a keystone grazer species, and aquatic ecosystem structure and function. Aquatic ecosystems are experiencing increased stress from multiple anthropogenic influences, including alteration of physical habitat and water chemistry, and the introduction of novel materials. The way in which these stressors modify cryptic food web interactions, such as between parasites and their hosts, is largely unexplored. Trematodes are common parasites of freshwater snails that affect their body elemental composition, reproduction, and behaviors that may subsequently influence stream and lake benthic ecosystem processes. Despite their small size, parasites such as trematodes may have a disproportionate effect on ecosystems by altering the cycling of nutrients or flow of energy in aquatic habitats. Engineered nanomaterials are increasingly used in manufacturing, medical applications, and consumer products, and are currently entering ecosystems. These materials have novel properties and unknown consequences on ecological processes. Freshwater communities consisting of bottom-dwelling microbes, plants, and animals will likely be influenced by water soluble nanomaterials such as nanosilver. This project will examine the interactive effects of nanomaterials and trematode parasites on aquatic communities. Field surveys and mechanistic, multi-species and whole community experiments will be used to study how nanomaterials and parasites indirectly alter species interactions and nutrient cycling in simple communities.
This project will advance a broader understanding of how disease ecology is modified by the introduction of novel materials. It will bridge gaps among disease and stress ecology, parasitology, and ecosystem function. A significant broader impact of this project will be to provide opportunities for local high school students to learn about the quality of their own water resources. Relationships between researchers and the local community will be created while integrating basic ecological research with in-depth research experiences for high school students and the development of K-12 classroom and field curricula.
Our project combined two understudied and underappreciated aspects of freshwater ecosystems that we have in our backyards; parasites and small amounts of chemical contaminants. Despite decades of study of ponds, streams, and lakes, our knowledge of what influences and controls the water resources that we use for drinking water and recreation remains limited. One factor that confounds our studies are the increasing use of myriad chemicals, both natural and man-made that potentially influence the plants and animals along with the quality of the water that humans directly use as a necessary resource. Manufactured nanomaterials are examples of a group of chemicals whose use is growing considerably, especially those that are used in consumer products like silver nanoparticles. Silver nanoparticles are applied to prevent bacterial growth in clothing, washing machines, baby toys, and many other products, but inevitably wash out of products and into the environment. One goal of our project was to better understand how plants and animals interact when exposed to environmentally realistic concentrations of silver nanoparticles. The other understudied aspect of aquatic ecosystems that we focused on was how parasites and disease change how animals function, leading to broader changes in the system including possible effects on water quality. Disease ecology is a burgeoning subfield of ecology that aims to include parasites and pathogens into general ecology and environmental biology to not only better understand, predict, and prevent disease outbreaks but also explore the importance of parasites to the normal functioning of ecosystems. Our research contributes to the baseline knowledge of how silver nanoparticles will likely affect aquatic ecosystems as its use increases. Our research and the research of others indicate that silver nanoparticles are found in very low concentrations in streams and ponds, but even these minute concentrations reduce algae survival, alter animal behaviors, and alter the timing and number of offspring that aquatic animals produce. One of the most important results of our research was that the effects of low concentrations of silver nanoparticles on aquatic snails altered how much and how quickly snails ate their algal food and also altered whether they hid from predators. A number of these small changes over time eventually produced systems with different species of algae and different snail population trajectories. In other words, silver nanoparticles are likely to change freshwater ecosystems even at low concentrations because they change the way species interact and the ways and rates at which energy and nutrients travel through ecosystems. Additional laboratory and controlled field experiments revealed the importance of a group of parasites, trematode flatworms, in controlling how rapidly important nutrients move through freshwater systems. Our results indicate that a large portion of the animals that live on the bottom of streams and ponds are parasites that have taken over the tissues of freshwater mollusks. Flatworm parasites can occupy up to 40% of a snail while directing energy and nutrients away from the snail in interesting yet predictable ways. Snails infected with flatworms recycled nutrients at different rates and qualities, ultimately affecting the availability of nutrients to the surrounding organisms. Results from our experiments indicate that flatworms indirectly led to more productive ponds with distinctly different animal and plant communities compared to experimental ponds with fewer or no flatworms. Taken together, our research implicates parasites as important players in ecosystem services such as nutrient cycling and suggests that we will gain a better understanding of these ecosystem services if we explicitly consider parasites. We also combined parasitology and ecotoxicology to study how silver nanoparticles and parasitism together may affect aquatic ecosystems. We found that independently, silver nanoparticles and parasites affected experimental ponds in predictable ways described in the preceding paragraphs. However, combining these major factors resulted in much less predictable indirect impacts on ponds. Parasites led to increases in overall pond production (more algae and faster nutrient cycling), but silver nanoparticles knocked out algae, leading to less productive ponds. While it is not surprising that contaminants such as silver nanoparticles can change ponds, and including understudied groups of organisms such as parasites can refine our ecological understanding, the goal going forward will be to be able to better predict the directions and magnitudes of change that these factor elicit. Overall, our research will lead to more studies of how disease and contaminants interact in real ecosystems and provide a general framework for predicting the levels of each that result in ecosystem changes.
