Marine debris is a global problem, injuring and killing marine life and damaging their habitats. Items as small as cigarette butts and plastic bags and as large as tires and even sunken vessels litter the oceans from the surface to the floor. Some marine debris results directly from human activity, while storms sweep yet more debris into the water. How does marine debris affect ecosystems along the Mississippi Sound? That is the question that Drs. Benedict "Ben" Posadas and Mark Woodrey, MAFES scientists stationed at the Coastal Research and Extension Center in Biloxi, are hoping to answer.

Trawling for Trash

Marine debris is a known stressor to commercial fishing, and local shrimpers working in waters off of the Mississippi Gulf Coast commonly suffer from encounters with marine debris, primarily derelict crab traps.

In 2018, Posadas, a research and extension marine and horticultural economist in the Department of Agricultural Economics, launched a three-year incentivized program working with local shrimpers to collect abandoned crab traps. The study was funded by the Environmental Protection Agency Gulf of Mexico Program. The project documented the impacts of marine debris on the shrimpers' hauls. Posadas collaborated with Dr. Eric Sparks, MSU associate extension professor and coastal ecology specialist; Dr. Caitlin Wessel, NOAA marine debris program coordinator; Mississippi Coalition for Vietnamese-American Fisher Folks and Families (MCVAFF), Mississippi Commercial Fisheries United (MCFU); and Mississippi commercial shrimpers.

For decades, studies have noted the presence of marine debris in waters, but scientists have never quantified its reach on the commercial fishing industry. At the start of the program, Posadas and his team held workshops to train participating shrimpers on where to deposit derelict crab traps caught in their trawls to sites along the Mississippi coast. In addition, for each tow, the shrimpers kept a log to estimate the loss of shrimp, in weight, due to marine debris; loss of time spent handling and disposing of marine debris; and expenses resulting from damage to their equipment.

Posadas estimated that during the 2019 season, shrimpers lost a total of about 17% of what would have been the total shrimp catch. In 2020, the estimated total forgone shrimp catch due to marine debris encounters approached $1 million in lost revenue. This loss due to marine debris encounters amounts to significant quantities of shrimp catch and equivalent dockside sales. He also noted that the damage to the shrimpers' bottom line also ripples out into other segments of the local economy.

"For every $1 million lost in shrimp dockside sales, about $280,000 in income is also lost for shrimpers. That is significantly fewer pounds of shrimp to be processed, resulting in lost hours, wages, and jobs for the processing plants," Posadas said. "And it goes on into the seafood markets and restaurants. To keep costs down and meet consumer demand, local markets must purchase more imported shrimp."

Although further studies must be conducted before scientists have a clear picture of the large-scale effects of marine debris on the fishing industry, Posadas sees this study as a promising start with room to expand.

In the United States, 30 states have a coastline: 23 on the Arctic Ocean, Atlantic Ocean (including the Gulf of Mexico and Gulf of Maine), and/or Pacific Ocean, and eight with a Great Lakes shoreline.

"Once we publish our research, these methods would serve as a template that every state could adapt to measure the economic impacts of marine debris on their fishing industry," Posadas said.

Life in the Plastisphere

Americans generate 35.7 million tons of plastic each year, and much of that plastic ends up in the ocean, to the tune of 5.25 trillion pieces. With about 269,000 tons of plastic floating on the surface and an estimated 14 million tons of plastic microfibers in the depths below, scientists have defined a new marine microbial habitat known as plastisphere.

While the science is emerging, there is hard evidence that plastics have clear and quantifiable effects on the marine resources that also sustain our lives. Less visible, but equally concerning, are the consequences of plastic debris on estuaries, coastal ecosystems where freshwater from rivers and streams mixes with salt water from the ocean.

Dr. Mark Woodrey, assistant research professor in the Department of Wildlife, Fisheries and Aquaculture and MAFES scientist, has been investigating the effects of microplastics on marsh birds that live in estuarine environments along the Mississippi coast.

Plastics can take anywhere from 20 to 500 years to decompose, depending on the material and structure, and exposure to sunlight speeds up the process. As plastic debris enters the ocean, it not only decomposes but simultaneously travels along ocean currents and accumulates in environmental accumulation zones, or "sinks." Closer to home, items such as abandoned plastic bottles, bags, and even small particles shed from fleece jackets enter the ocean and wash into sinks along the coast. The breakdown of plastic materials accelerates even more quickly in a marsh environment than in open water, resulting in an abundance of microplastics, or pieces of plastic smaller than five millimeters, in these coastal ecosystems.

Woodrey's study was funded, in part, by the National Institute of Food and Agriculture, National Oceanic and Atmospheric Administration, National Fish and Wildlife Foundation, Mississippi Department of Marine Resources, and Mississippi Department of Environmental Quality. The idea began when Sparks was conducting surveys along the Mississippi coast and found high concentrations of microplastics. At the same time, Woodrey's graduate student, Spencer Weitzel, approached him with an interest in studying this topic. Woodrey, who has studied Mississippi coastal birds for over 30 years, found a lack of studies documenting the ingestion of micro-plastics in coastal birds including secretive marsh birds, although several studies had examined the harmful consequences of plastic pollution on marine life.

Woodrey and his research team set out to document the presence and abundance of microplastics in estuaries and to measure and document the presence of microplastics in the clapper rail and the seaside sparrow, two common Mississippi coastal species. These estuarine birds share the same habitat but eat different diets. Clapper rails forage in the mud for fiddler crabs, which are known to contain elevated levels of microplastics. Seaside sparrows feed on spiders and other insects residing on the muddy marsh surface.

The study detected microplastics in 64% of marsh sediment samples and in 83% of clapper rail and 69% of seaside sparrow stomach content samples. Although this study only scratches the surface of the impact of plastics on avian wildlife, it is important because it provides the first documented evidence that birds are ingesting these plastic fibers because of their presence in the birds' environment and diet. It also adds to the growing body of literature examining the harmful effects of plastic-derived chemicals on animals and ecosystems.

"For us, it's the first and only bird study for the Gulf of Mexico. There have been studies documenting where these plastics are along the Gulf Coast, but now we're thinking about the larger-scale consequences of microplastics in the environment," Woodrey said.

To more clearly understand how these fibers move through the estuarine food chain, Woodrey hopes to expand his samples of estuarine ecosystems to include broader geographical areas in the northern Gulf Coast region.

"I'm interested in monitoring across the entire Gulf of Mexico," he said. "The Mississippi coast is only about 75 miles long and doesn't exist in isolation, so I'm interested in where the hotspots are in Alabama, Florida, Louisiana, and Texas."

Woodrey aims not only to broaden the scope of the study but also to more clearly understand any possible health impacts on birds who ingest these materials. He is now working with ecotoxicologists to test his hypotheses on how ingesting microplastic fibers may disrupt the birds' hormonal and digestive systems.

"The science is in its early stages, and we don't really have a good feeling for what the impacts are. Understanding the impacts of ingesting plastics is the next step," Woodrey said.

Posadas and Woodrey are pioneering studies that shed light on how trash in the Gulf—the proverbial backyard of coastal Mississippians—is not "out of sight, out of mind" after all. The work these scientists are doing to educate and to mitigate damage to these fragile coastal ecosystems will lead to more mindful treatment of all resources, whether natural or manufactured.

Trawling for Trash was funded by the Environmental Protection Agency Gulf of Mexico Program. Life in the Plastisphere was funded by the National Institute of Food and Agriculture, National Oceanic and Atmospheric Administration, National Fish and Wildlife Foundation, Mississippi Department of Marine Resources, and Mississippi Department of Environmental Quality.