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When are seabirds most vulnerable to exposure to plastic pollution?

Plastics are in widespread use in modern life, from our toothbrushes to our shopping bags. However plastics are also highly persistent and accumulate in the environment, creating potential environmental impacts for wildlife.

Research at Environment and Climate Change Canada (ECCC) is seeking to understand the extent to which plastics are transferred through marine food webs. A newly published research paper by ECCC scientists and their colleagues investigated when seabirds are mostly likely to be exposed to microplastic pollution. Microplastics are tiny particles (less than 5 mm) that result from washing of synthetic fabrics or from the break-down of larger plastic objects. These particles easily enter marine food webs due to their size and number, and, once ingested, they can cause both physical and toxicological damage to marine species.

Researchers modeled the seasonal distribution of a small seabird, the Cassin’s Auklet, against the distribution of microplastics in the ocean.Cassin’s Auklets are a common and characteristic seabird in the North Pacific. Approximately 75% of the global population of Cassin’s Auklets breeds on islands in British Columbia, giving Canada high responsibility for their conservation. Triangle Island, located off the northwestern tip of Vancouver Island within the Scott Islands marine National Wildlife Area, is home to the largest known breeding colony of this species in the world. Cassin’s Auklets may be more likely to be exposed to microplastics because they forage on zooplankton, which are of a similar size to microplastics. The distribution models predicted that auklets were more likely to be exposed to these plastics in the fall and winter than in the spring and summer, most likely because they forage closer to shore where ocean currents concentrate microplastics during those times of year. Limited food availability in the winter may also increase exposure to microplastics because hungry birds will accidentally ingest particles, mistaking them for food sources.

Existing field data show a similar pattern. Microplastics were rarely observed in the food delivered by adult auklets to their chicks at a breeding colony in the spring and summer. These plastics were much more common in the stomach of birds that died in the fall and winter. For example, during an extreme warm-water event in the Pacific Ocean, over the fall and winter of 2014-15, tens of thousands of Cassin’s Auklets died. These birds were malnourished and found to have ingested many microplastics. “We were able to confirm what we previously suspected: Cassin’s Auklets probably ingest more plastic in the winter months, when their exposure is higher, and especially when they are experiencing food stress”, said Dr. Mark Hipfner, a collaborator on the project and Research Scientist for ECCC. “In this winter, the birds were feeding on low quality, warm-water zooplankton prey and may have ingested more plastic in an attempt to compensate”.

This paper, according to Dr. Hipfner, highlights the need for continued research on the ecology of seabirds and other marine life in order to understand how changes to ocean ecosystems, either from climate change or pollution, will impact marine foodwebs.

O'Hara, P.D., S. Avery-Gomm, J. Wood, V. Bowes, L. Wilson, K.H. Morgan, W.S. Boyd, J.M. Hipfner, J.-P. Desforges, D.F. Bertram, C. Hannah, P.S. Ross. Seasonal variability in vulnerability for Cassin's auklets (Ptychoramphus aleuticus) exposed to microplastic pollution in the Canadian Pacific region. Science of the Total Environment 649: 50-60.

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