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ESR prepress abstract   -  DOI:

Understanding individual and population-level effects of plastic pollution on marine megafauna

Jesse F. Senko*, Sarah E. Nelms, Janie L. Reavis, Blair Witherington, Brendan J. Godley, Bryan P. Wallace

*Corresponding author:

ABSTRACT: Plastic pollution is increasing rapidly throughout the world's oceans and is considered to be a major threat to marine wildlife and ecosystems. Although known to cause lethal or sub-lethal effects to vulnerable marine megafauna, population-level impacts of plastic pollution relative to those of other threats have not been thoroughly investigated. Here, we compile and evaluate available information from published, peer-reviewed studies that reported deleterious individual-level effects of plastic pollution on air-breathing marine megafauna (i.e. seabirds, marine mammals, and sea turtles) worldwide, while highlighting those that assessed potential population-level effects. Lethal and sub-lethal individual-level effects included drowning, starvation, gastrointestinal tract damage, malnutrition, physical injury, reduced mobility, and physiological stress, resulting in reduced energy acquisition and assimilation, compromised health, reproductive impairment, and mortality. We found 47 studies published between 1969 and 2020 that considered population-level effects of plastic entanglement (n = 26), ingestion (n = 19), or both (n = 2). Of these, 7 studies inferred population-level effects (n = 6, entanglement; n = 1, ingestion), whereas 19 lacked evidence for effects (n = 12, entanglement; n = 6, ingestion; n = 1, both). However, no study in the past 50 years reported direct evidence of population-level effects. Despite increased interest in and awareness of the presence of plastic pollution throughout the world's oceans, our review reveals that the extent and magnitude of demographic impacts on marine megafauna remain largely unassessed and therefore unknown, in contrast to well-documented effects on individuals. Addressing this major assessment gap will allow researchers and managers to compare relative effects of multiple threats – including plastic pollution – on marine megafauna populations, thus providing appropriate context for strategic conservation priority-setting.