Boettcher, Hayden2024-02-282024-02-282024https://udspace.udel.edu/handle/19716/34023Microplastics are ubiquitous in the aquatic ecosystems around the world. Coastal and estuarine zooplankton face a particularly high risk of exposure, as they occupy environments near land-based sources of microplastics and have prey size ranges that overlap with microplastic debris. While previous work has been done to characterize microplastic pollution in the waters of the Delaware Bay, we know very little about the interactions between the microplastics and zooplankton residing therein. Additionally, we have yet to fully understand the biological impacts induced by microplastic exposure, particularly across multiple developmental stages. In the present dissertation, these topics were investigated in the larvae of two marine crab species, Atlantic blue crab Callinectes sapidus and Atlantic mud crab Panopeus herbstii. ☐ I first characterized the distributions and interactions of microplastics and blue crab C. sapidus larvae along the Delaware inner continental shelf. Microplastic concentrations ranged between 0.01 and 0.66 pieces m-3 depending on sample region and depth. Rayon, polypropylene, polyethylene, and polyethylene terephthalate were the dominant polymer types in the upper water column. Fibers and fragments were the most common shapes. In surface samples, I found a positive correlation between microplastics and C. sapidus larvae concentrations, suggesting that they are being aggregated by similar physical forces. A subset of the collected larvae were analyzed for evidence of in situ microplastic ingestion. Every group of z1-stage C. sapidus larvae contained microplastics, with an average incidence of 1.4 microplastics individual-1. Having only hatched approximately five days prior to being collected, this level of microplastic ingestion provides evidence that zoeae encounter and ingest microplastics almost immediately upon entering the marine environment. ☐ Given the high proportion of fragments in the water column and ingested microplastics, I next developed a methodology for the production and dosing of microplastic fragments. Utilizing a combination of cryogenic grinding, washing and sieving, the developed method was successful in consistently and accurately preparing fragments of three size classes (53-150, 150-300, and 300-1000 μm). Additionally, the paired dosing technique provided the ability to incorporate the fragments into experiments without the aid of additional chemicals which may alter the experiment. ☐ Finally, the lethal and sublethal impacts of microplastic exposure were investigated through laboratory experiments with mud crab Panopeus herbstii larvae. I found that microplastic exposure was not lethal but did induce a variety of sublethal developmental effects at concentrations of 1 and 10 mp mL-1, including developmental delays on the scale of 2 days and reductions in body length up to 5%. To test whether these effects were specific to microplastics, an additional experiment was conducted with the inclusion of natural sand microparticles. In these experiments, both microplastics and natural microparticles reduced the grazing rates and increased the respiration rates of zoeae, though the effects of microplastic exposure were more pronounced in each case. ☐ The results of this dissertation provide important insights into the in situ interactions between microplastics and zooplankton, as well as the sublethal effects that may arise from high levels of exposure. While microplastics were ubiquitous across the sampling domain and in situ microplastic ingestion was more common than expected, the concentrations required for significant physiological impacts were much higher than what is currently observed in the local environment.EcologyEstuaryPollutionMicroplasticsSublethal effectsThesis1429146259https://doi.org/10.58088/njnw-9x092024-02-26en