Marine Debris: Microplastics

Aside from the eyesore marine debris evokes, plastics may have acute and chronic effects on the marine ecosystem and its inhabitants. Debris entangles whales, is ingested by wildlife, disturbs the seafloor, and releases harmful chemicals during decay. As plastics in the ocean break down into smaller pieces, they eventually become microplastics: plastic that measures less than 5 millimeters across (smaller than a grain of rice). Microplastics also come from personal care products, or from synthetic microfibers sloughed off clothing in the washing machine.

Microplastics are a significant threat to both human health and the marine ecosystem, and their distribution is global. For example, Monterey Bay National Marine Sanctuary staff and partners detected microplastics in every ocean sample taken from nearshore and offshore locations of the sanctuary (Kashiwabara et al. 2021). Fish and shellfish consume microplastics, which then make their way into our food supply. Ingestion of microplastics by marine wildlife may lead to starvation and even endocrine disruption, which can alter the normal functioning of hormones in their bodies and result in several health problems. The vertical distribution (5-1000 meters) of microplastics in Monterey Bay National Marine Sanctuary has been recently reported with the highest concentrations (15 particles per cubic meter) at a depth of 200 meters, with higher concentrations of microplastics in offshore samples as compared to nearshore samples (Choy et al. 2019).

Marine Debris Action Plan

The sanctuary’s most recent management plan includes a dedicated section for this emerging problem: the Marine Debris Action Plan. The goal of this action plan is to use research to assess marine debris in the sanctuary to reduce its prevalence and impacts on sanctuary resources. Sanctuary staff aim to understand the amount, types, and sources of marine debris through research, and focus on ways to work with coastal and inland communities to reduce these inputs. The sanctuary is coordinating with coordinating with NOAA’s Marine Debris Program and local farmers to reduce the amount of agricultural plastics to reduce the amount of agricultural plastics that enter Monterey Bay National Marine Sanctuary.

In August 2023, the sanctuary and its partners were awarded a $350,000 grant (California Sea Grant and Ocean Protection Council) to conduct a two-year study (titled, “From Watershed to Whales”) that will characterize the amount and sources of microplastics in Monterey Bay. This project involves sampling water from four rivers in Monterey Bay, sand from beaches adjacent to those rivers, and ocean water just offshore of those rivers three to four times annually. Krill and whale fecal material will also be analyzed. Microplastics will be isolated from all samples and cataloged by their size, color, and shape. Some microplastics will be chemically analyzed, which could isolate the type and source of plastic.

References

Choy, C.A., B.H.Robison, T.O. Gagne, B. Erwin, E. Firl, R.U. Halden, J.A. Hamilton, K. Katija, S.E. Lisin, C. Rolsky, and K.S. Van Houtan. 2019. The vertical distribution and biological transport of marine microplastics across the epipelagic and mesopelagic water column. Scientific Reports 9:7843. https://doi.org/10.1038/s41598-019-44117-2

Kashiwabara L.M., S.R. Kahane-Rapport, C. King, M. DeVogelaere, J.A. Goldbogen, and M.S. Savoca. 2021. Microplastics and microfibers in surface waters of Monterey Bay National Marine Sanctuary, California. Marine Pollution Bulletin 165:112148. https://doi.org/10.1016/j.marpolbul.2021.112148