Current Research Priorities

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. 

Degradation of microplastics in urban freshwater

Due to the pressing issue of microplastics pollution, there is a great deal of work looking into their toxicological impact on aquatic organisms. Less known, is the rate of degradation of plastics. Previous work has demonstrated that plastics can start producing microplastics in as little as 4-8 weeks. Those findings are specific to salt-marsh habitats. We are now assessing degradation of different polymers in streams that are influenced by different land use types. 

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.