Current Research Priorities
The Plastisphere of Pond Ecosystems: Understanding the function and fate of novel carbon in biogeochemical hotspots
Plastics represent a form of novel carbon, solid waste, and debris. Most plastics travel through freshwater environments to the ocean, making ponds an important place to study the impact of this novel carbon source. Ponds are widespread across various landscapes and provide many important services. Most notably, ponds provide resilience by capturing and removing storm water, carbon materials, solid waste, and debris. Depending on size and age, ponds can be sites of where carbon is emitted or stored, which is important regarding emissions of gasses to the atmosphere. Therefore, pond ecosystem services may be altered by captured plastic debris. The prolonged storage of plastic debris in ponds allows for the breakdown of plastic litter into smaller particles recognized as microplastics (particles <5mm). There are no current estimates of how long plastic and microplastic debris are retained in pond ecosystems. Thus, the unknown storage and breakdown of plastics can also release dissolved organic carbon, stimulating or inhibiting microbial activity that governs the ecosystem services ponds render to society.
This award investigates the influence common plastic items have on microbial community structure in ponds, as these novel carbon sources provide a substrate for microorganisms (known as the plastisphere). The project will characterize biofilm succession on plastic and natural items and assess whether plastic-derived organic matter stimulates or inhibits microbial activity that governs ecosystem processes. Lastly, a mass-balance model will be developed to understand pond plastic and microplastic capture and removal. The integrated research and teaching program will promote environmental science to undergraduate students by providing field research opportunities, training in visual arts, and outreach to high school students from historically excluded groups in STEM. As plastic debris in aquatic systems persists due to mismanaged waste and prolonged decomposition rates of plastics, this award will provide foundational knowledge regarding how pond ecosystems respond to plastic pollution and understand the magnitude of response from various levels of ecological organization.
Long-term monitoring of microplastics and polymer identification in intestinal tracts of coastal dolphins
For the first time ever in North America, NCCOS recently reported on microplastics found in thegastrointestinal tracts (GI) of coastal bottlenose dolphins and harbor porpoises. In fact, microplastics, particularly fibers, were identified in every dolphin GI tract examined. However, while the stomach chambers were examined for microplastics, entire intestinal tracts were not. There are numerous hinderances in examining stomachs only, including lining sloughing, adherence of microplastics to prey items, filtration issues, and others. The intestines typically contain a smaller volume of contents that are digested and easier to filter out of a sample during sieving. Currently there are very few studies on microplastics in cetaceans, and no long-term microplastic studies on a localized population of dolphins. This project expands our knowledge on the burden of microplastics on dolphins and the environment they inhabit including monitoring tire wear particle prevalence in dolphins that can indicate expanding impervious surfaces in coastal human communities, and potentially detecting changes in the types of plastics bioaccumulating in apex predators. This project supports innovative and actionable science initiatives that will provide a better understanding of the metabolic and physiological effects of microplastics in marine mammals for future studies.
Toxicokinetic modeling of microplastic uptake and depuration by marine and freshwater bivalves
Microplastic pollution has garnered considerable research attention over the past ten years, with a large focus on marine systems. The ecological effects of microplastics in inland waters are starting to become emphasized more in freshwater sciences. An estimated 80% of coastal plastic debris comes from inland areas, highlighting how freshwater systems, specifically streams, are hotspots for plastics and microplastics. Microplastics have been reported to be acutely toxic to aquatic invertebrates. Despite this, our understanding of the ecological consequence of microplastic pollution is lacking compared to other research priorities (occurrence, distribution, fate). In our lab, we aim to understand how microplastics are accumulated and depurated by bivalves with focus on oysters and Asian clams.
Plastic Derived Carbon as missing piece of the Global Carbon Budget
Fundamental knowledge we have on organic matter processing and carbon cycling is based mainly on principles that do not currently capture alterations happening in the Anthropocene age. Only recently, plastic is considered another source of allochthonous carbon. Our lab's research has shown that inland waters are not just transporters of plastics but are areas where plastic fragmentation is occurring relatively quickly, contributing to MP occurrence, deposition, and DOM. Plastics are considered an allochthonous carbon. Yet, it is not widely understood how plastics impact freshwater ecosystem processes. How influential is plastic and MP storage and degradation towards global carbon cycle budgets? Plastic pollution as an emerging anthropogenic component of the global carbon cycle warrants more research on anthropogenic carbon and biogeochemical cycling dynamics at various ecosystem levels.
Microplastic accumulation in freshwater organisms
As research on microplastics has increased over the past two decades, there is a lack of peer-reviewed research on microplastic retention within freshwater organisms aside from mussels. To truly understand retention rates, it is crucial to examine the base of the food chain. In freshwater ecosystems, aquatic invertebrates have an increased potential for microplastic interaction due to their presence within the water column and sediment, where organisms can feed. The primary candidate of the study is crayfish, and their unique feeding modes make them susceptible to microplastic exposure. Previous work investigating toxicological impacts of microplastics on crayfish conducted by the Gray Lab has shown that crayfish retain ambient levels of microplastics (fibers) from the field as well as higher levels of microplastics when exposed in a controlled setting (fibers, fragments, spheres). Analyses suggest sediment is the major pathway for microplastic retention by crayfish. We aim to better understand this potential of environmental microplastic bioaccumulation within crayfish across various habitat degradations throughout Montgomery County, VA. Understanding a baseline of microplastic abundance and retention in crayfish could provide insights into potential bioaccumulation to upper trophic levels. Additionally, habitat degradation gradients provide potential analysis of areas of greatest concern for microplastic biomagnification.
