About 62,000 dead or dying common murres (Uria aalge), the trophically dominant fish-eating seabird of the North Pacific, washed ashore between summer 2015 and spring 2016 on beaches from California to Alaska. Most birds were severely emaciated and, so far, no evidence for anything other than starvation was found to explain this mass mortality. Threequarters of murres were found in the Gulf of Alaska and the remainder along the West Coast. Studies show that only a fraction of birds that die at sea typically wash ashore, and we estimate that total mortality approached 1 million birds. About two-thirds of murres killed were adults, a substantial blow to breeding populations. Additionally, 22 complete reproductive failures were observed at multiple colonies region-wide during (2015) and after (2016-2017) the mass mortality event. Die-offs and breeding failures occur sporadically in murres, but the magnitude, duration and spatial extent of this die-off, associated with multi-colony and multi-year reproductive failures, is unprecedented and astonishing. These events cooccurred with the most powerful marine heatwave on record that persisted through 2014-2016 and created an enormous volume of ocean water (the "Blob") from California to Alaska with temperatures that exceeded average by 2-3 standard deviations. Other studies PLOS ONE | https://doi.org/10.1371/journal.pone.0226087 January 15, 2020 1 / 32 OPEN ACCESS Citation: Piatt JF, Parrish JK, Renner HM, Schoen SK, Jones TT, Arimitsu ML, et al. (2020) Extreme mortality and reproductive failure of common murres resulting from the northeast Pacific marine heatwave of 2014-2016. PLoS ONE 15(1):indicate that this prolonged heatwave reduced phytoplankton biomass and restructured zooplankton communities in favor of lower-calorie species, while it simultaneously increased metabolically driven food demands of ectothermic forage fish. In response, forage fish quality and quantity diminished. Similarly, large ectothermic groundfish were thought to have increased their demand for forage fish, resulting in greater top-predator demands for diminished forage fish resources. We hypothesize that these bottom-up and top-down forces created an "ectothermic vise" on forage species leading to their system-wide scarcity and resulting in mass mortality of murres and many other fish, bird and mammal species in the region during 2014-2017.

Eighty-one Californian sea lions (Zalophus californianus) with signs of domoic acid toxicity stranded along the coast of California in 1998 when there were blooms of the domoic acid-producing alga Pseudonitzschia australis off-shore. In 2000, a further 184 sea lions stranded with similar clinical signs, but the strandings occurred both during detectable algal blooms and after the blooms had subsided. The clinical signs in these 265 Californian sea lions included seizures, ataxia, head weaving, decreased responsiveness to stimuli and scratching behaviour. Affected animals had high haematocrits, and eosinophil counts, and high activities of serum creatine kinase. They were treated supportively by using fluid therapy, diazepam, lorazepam and phenobarbitone. Fifty-five of the 81 sea lions (68 per cent) affected in 1998 and 81 of the 184 (44 per cent) affected in 2000 died despite the treatment. Three of the 23 sea lions which survived in 1998 were tracked with satellite and radiotransmitters; they travelled as far south as San Miguel Island, California, and survived for at least three months. Eleven of the 129 animals which were released stranded within four months of being released.

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We characterized the genome of a highly divergent gyrovirus (GyV8) in the spleen and uropygial gland tissues of a diseased northern fulmar (Fulmarus glacialis), a pelagic bird beached in San Francisco, California. No other exogenous viral sequences could be identified using viral metagenomics. The small circular DNA genome shared no significant nucleotide sequence identity, and only 38–42 % amino acid sequence identity in VP1, with any of the previously identified gyroviruses. GyV8 is the first member of the third major phylogenetic clade of this viral genus and the first gyrovirus detected in an avian species other than chicken.

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