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Marine Ecology Progress Series

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MEPS 737:161-181 (2024)  -  DOI:

Marine bird mass mortality events as an indicator of the impacts of ocean warming

Timothy Jones1,*, Julia K. Parrish1, Jacqueline Lindsey1, Charlie Wright1, Hillary K. Burgess1, Jane Dolliver1, Lauren Divine2, Robert Kaler3, David Bradley4, Graham Sorenson4, Rémi Torrenta4, Stacia Backensto5, Heather A. Coletti5, James T. Harvey6, Hannahrose M. Nevins6, Erica Donnelly-Greenan6, David L. Sherer7, Jan Roletto8, Kirsten Lindquist8,9

1School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington 98105, USA
2Ecosystem Conservation Office, Aleut Community of St. Paul, Anchorage, Alaska 99503, USA
3Migratory Bird Management, US Fish and Wildlife Service, Anchorage, Alaska 99503, USA
4Birds Canada/Oiseaux Canada, Delta, British Columbia V4G 2T9, Canada
5Inventory and Monitoring Program, National Park Service, Fairbanks, Alaska 99709, USA
6BeachCOMBERS, Moss Landing Marine Laboratories, Moss Landing, California 95039, USA
7BeachCOMBERS, US Fish and Wildlife Service, Ventura, California 93003, USA
8Greater Farallones National Marine Sanctuary, NOAA, NOS, ONMS, San Francisco, California 94129, USA
9Greater Farallones Association, affiliate NOAA, NOS, ONMS, Greater Farallones National Marine Sanctuary, San Francisco, California 94129, USA
*Corresponding author:

ABSTRACT: The frequency and severity of marine heatwaves (MHWs), an emergent property of global warming, has led to large-scale disruptions to marine ecosystems. As upper trophic species, marine birds reflect shifts in trophic structure and stability; therefore, a sharp increase in marine bird mortality is a clear signal of ecosystem impact. In this study, we analyzed 29 yr (1993-2021) of beached bird monitoring data (~90000 surveys) to identify marine bird mortality events throughout the Northeast Pacific and Alaska, USA, and examined linkages to ocean-climate variability. Mortality events were documented throughout the study period, but massive events (>500 km in extent, >10 carcasses km-1) occurred infrequently (n = 5), with an unprecedented sequence from 2014-2019. Event characteristics, including encounter rate (carcasses km-1), duration, and spatial extent, were positively related to prior-year averaged sea surface temperature anomaly, with event magnitude (product of encounter rate, extent, and duration) displaying a step-like transition, increasing 5-fold between +0°C and +1°C above baseline (1981-2010) temperatures. Mortality events occurred more frequently following MHWs, and a common sequence of mortality events (at 1-6 and 10-16 mo after heatwave onset) was observed in the California Current large marine ecosystem following 3 prolonged MHW events. Following the second wave of mortality at 10-16 mo after MHW onset, a consistent 16 mo period of depressed carcass encounter rates ensued. Given continued global warming, our results point to more frequent large-scale mortality events and the potential for a new lower carrying capacity for marine birds in the Northeast Pacific.

KEY WORDS: Extreme events · Marine heatwaves · Citizen science · Seabird wrecks · North Pacific

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Cite this article as: Jones T, Parrish JK, Lindsey J, Wright C and others (2024) Marine bird mass mortality events as an indicator of the impacts of ocean warming. Mar Ecol Prog Ser 737:161-181.

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