The Effects of Ingested Plastic and Other Marine Debris on Seabirds

Seabirds ingest plastic particles and other marine debris more frequently than do any other taxon. Despite considerable speculation as to the adverse effects ingested debris has on seabirds, there have been few experiments designed to test these hypotheses. Initial attempts to demonstrate adverse effects were based on correlations between plastic load and bird condition. However, unless the influence of season and breeding status are removed, negative correlations cannot be used to infer an adverse effect from ingesting plastic. Few statistically significant negative correlations have been found among adequately controlled samples, suggesting that the effects of ingestion are either relatively minor or that they frequently are masked by other variables. To avoid ambiguous results, carefully designed experiments are required to assess the severity of the specific adverse effects that have been hypothesized to result from debris ingestion. Ingested debris may have three specific effects on seabirds: physical damage and blocking of the digestive tract, impairment of foraging efficiency, and the release of toxic chemicals. of debris ingested and their retention time within seabirds. The severity of these effects depends upon the types At present, severe physical damage and obstruction of the digestive tract is infrequent in seabirds, and probably affects only a small proportion of populations. particles were not found to affect the assimilation efficiency of the white-chinned petrel, Procellaria aequinoctialis, but seabird feeding may be affected by large plastic loads that reduce the food storage volume of the stomach, causing reduced meal size and, consequently, the ability to accumulate energy reserves. confirm this, potentially the most serious consequence of plastic ingestion by seabirds. size is required to determine the proportion of populations likely to be affected by reduced food intake. Virgin (raw) plastic Experiments on free-ranging seabirds are required to An estimate of the critical load