Encounter rates between forage fishes and marine microplastics in the Southern California Bight

Noelle Bowlin, NOAA Southwest Fisheries Science Center, Fisheries Research Division, La Jolla, United States, Julia Chavarry, Scripps Institution of Oceanography, UCSD, Biological Oceanography, La Jolla, CA, United States, Kara L Lavender Law, Sea Education Association, Woods Hole, MA, United States, Andrew David Barton, Scripps Institution of Oceanography, Section of Ecology, Behavior and Evolution, La Jolla, CA, United States, Mark D Ohman, University of California San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States and Anela Choy, Scripps Institution of Oceanography, UCSD, Integrative Oceanography Division, La Jolla, CA, United States
Abstract:
Microplastic particles (net-collected particles < 5mm in size) have reportedly been ingested by more than 1,000 marine species, attesting to the widespread distribution of plastic debris within marine ecosystems. Some of these animals are commercial species directly consumed by humans, while others are important prey items for commercial species. Microplastics have the potential to be consumed by lower trophic species, and then transferred into higher trophic species during foraging. Understanding the amount of marine microplastics available to be transferred throughout marine food webs requires quantifying the encounter rate of lower trophic species with microplastics in the marine environment. To accomplish this, we compiled a 20+ year time series (1984-2007) of the distribution of fish larvae and zooplankton abundance, and microplastic particle concentrations from CalCOFI, the California Cooperative Oceanic Fisheries Investigations. We then designed a simple model to estimate the frequency at which small pelagic fish larvae encounter both live prey and microplastic particles. We focus on two ecologically significant planktivorous coastal pelagic fishes within the Southern California Bight ecosystem, Pacific Sardines (Sardinops sagax) and Northern Anchovies (Engraulis mordax), which are important forage for many commercial species. Our results suggest that sardine and anchovy larvae typically have infrequent encounters with microplastics compared to live prey, with an encounter ratio of 1 microplastic particle per 1 million zooplankton prey. Such estimates do not yet take into consideration nanoplastic particles that are much more abundant than microplastics, or local aggregations of plastic particles. Future work will involve a direct evaluation of forage fish to validate our estimated encounter rates and to ascertain the potential for microplastics to be transferred throughout marine food webs due to forage fish ingestion of plastic particles. We find that forage fish in the Southern California Bight historically had a low microplastics to live prey encounter ratio. However, present forage fish encounter rates with microplastic particles may be higher and continue to increase in the future due to an increasing abundance of marine plastics.
Back to: Impacts of Microplastics on Marine Organisms and Ecosystem Health III