The importance of discourse when discussing microplastic pollution with oyster stakeholders in Massachusetts, USA

Oysters have socioeconomic and environmental importance globally and are currently threatened by microplastic pollution. Whether solutions (e.g., laws, policies, or best management practices) are needed to protect oysters from microplastic pollution is still in question given the complexity of the issue and the multitude of stakeholders involved. Minimal research has been done to examine the public's view of the microplastic problem and, separately, few economic studies have examined non-monetary values for oysters. Here, we employed a discourse-based method (deliberative multicriteria evaluation methodology) to engage with oyster-relevant stakeholders in Massachusetts, USA, to evaluate how the stakeholders discussed and interacted with each other on the topic of 'microplastics polluting oyster habitats' using hypothetical scenarios. Our qualitative analysis indicated that participants discussed human welfare and non-human welfare aspects of oysters when considering what is threatened by microplastic pollution in oyster habitats. In all the workshops, an important theme emerged which is the role of oysters in supporting services (e.g., the concept that microplastic filtration or ingestion by oysters might impact the oysters' role as eco-engineers). Decision-making is not a linear process, especially when complex pollutants (e.g., microplastics) are involved. Here, we learned that both environmental and social data are needed for the oyster stakeholders to make decisions, and discussion among stakeholders can highlight gaps in scientific knowledge. The results were then used to inform the development of a decision-making process for evaluating complex environmental issues, like microplastic pollution.

Microfiber abundance associated with coral tissue varies geographically on the Belize Mesoamerican Barrier Reef System

Ocean plastic pollution is a global problem that causes ecosystem degradation. Crucial knowledge gaps exist concerning patterns in microfiber abundance across regions and ecosystems, as well as the role of these pollutants within the environment. Here, we quantified the abundance of microfibers in coral samples collected from the Belize Mesoamerican Barrier Reef System (MBRS) using a polarized light microscope and identified a subsample of these to the polymer level using an Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy microscope. Microfibers were found in all coral samples with rayon being identified as the most common microfiber, comprising 85% of quantified pollutants. We found a greater average abundance of microfibers in coral samples from the Sapodilla Cayes (296 ± SE 89) than in samples from the Drowned Cayes (75 ± SE 14), indicating spatial variation in microfiber abundance within coral tissue along the MBRS. These results demonstrate that corals on the Belize MBRS interact with microfibers and that microfiber abundance on reefs varies spatially due to point sources of pollution and local oceanography. As rayon from clothing typically enters the ocean through wastewater effluent, alterations to waste water infrastructure may prove useful in decreasing rayon pollution in coastal waters.

Patterns, dynamics and consequences of microplastic ingestion by the temperate coral, Astrangia poculata

Microplastics (less than 5 mm) are a recognized threat to aquatic food webs because they are ingested at multiple trophic levels and may bioaccumulate. In urban coastal environments, high densities of microplastics may disrupt nutritional intake. However, behavioural dynamics and consequences of microparticle ingestion are still poorly understood. As filter or suspension feeders, benthic marine invertebrates are vulnerable to microplastic ingestion. We explored microplastic ingestion by the temperate coral Astrangia poculata. We detected an average of over 100 microplastic particles per polyp in wild-captured colonies from Rhode Island. In the laboratory, corals were fed microbeads to characterize ingestion preference and retention of microplastics and consequences on feeding behaviour. Corals were fed biofilmed microplastics to test whether plastics serve as vectors for microbes. Ingested microplastics were apparent within the mesenterial tissues of the gastrovascular cavity. Corals preferred microplastic beads and declined subsequent offerings of brine shrimp eggs of the same diameter, suggesting that microplastic ingestion can inhibit food intake. The corals co-ingested Escherichia coli cells with microbeads. These findings detail specific mechanisms by which microplastics threaten corals, but also hint that the coral A. poculata, which has a large coastal range, may serve as a useful bioindicator and monitoring tool for microplastic pollution.