Some of the longest and most comprehensive marine ecosystem monitoring programs were established in the Gulf of Alaska following the environmental disaster of the Exxon Valdez oil spill over 30 years ago. These monitoring programs have been successful in assessing recovery from oil spill impacts, and their continuation decades later has now provided an unparalleled assessment of ecosystem responses to another newly emerging global threat, marine heatwaves. The 2014–2016 northeast Pacific marine heatwave (PMH) in the Gulf of Alaska was the longest lasting heatwave globally over the past decade, with some cooling, but also continued warm conditions through 2019. Our analysis of 187 time series from primary production to commercial fisheries and nearshore intertidal to offshore oceanic domains demonstrate abrupt changes across trophic levels, with many responses persisting up to at least 5 years after the onset of the heatwave. Furthermore, our suite of metrics showed novel community-level groupings relative to at least a decade prior to the heatwave. Given anticipated increases in marine heatwaves under current climate projections, it remains uncertain when or if the Gulf of Alaska ecosystem will return to a pre-PMH state.

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Evidence for regulation of animal populations by negative density dependence is ubiquitous across the animal realm, and yet the dynamics of carrying capacity (K) are often overlooked. K acts as a threshold below which population size tends to increase and above which it tends to decrease. Documenting changes in this threshold is particularly important to population viability analysis (PVA). We reconstructed the population sizes of five longlived seabird species in Alaska, USA, and analyzed their population dynamics from the past four decades: Black-legged (Rissa tridactyla) and Red-legged Kittiwakes (R. brevirostris), Common (Uria aalge) and Thick-billed Murres (U. lomvia) and Tufted Puffins (Fratercula cirrhata). We evaluated a set of models that allowed for either density independence or density dependence, with or without a time trend in K. The best approximating models indicated that these seabird populations behaved in a negative density-dependent fashion. K increased significantly for murres, and remained relatively stable for Red-legged Kittiwakes. It decreased significantly (N 40%) for Black-legged Kittiwakes and Tufted Puffins, particularly in the Gulf of Alaska, following the 1989 Exxon Valdez oil spill. Although we have less confidence in the puffin data, our PVA suggests that, in the next 100 years, Tufted Puffins may become extirpated from the few colonies that are monitored in the Gulf of Alaska. Negative density dependence can help to prevent population crashes, but time lags and serial correlation in rates of change could suppress the recovery of contracted populations. Therefore, estimating the magnitude of population fluctuations around a changing carrying capacity is essential to managing and conserving declining populations.

Kasatochi Island, home to a rich community of largely marine-dependent fauna, erupted with little warning on 7-8 August 2008 and buried the island under up to 30 m of tephra. We visited the island during the summer of 2009 to examine the effects of the eruption on local wildlife. The abundance of sea lions and many seabird species in 2009 was comparable to pre-eruption estimates, suggesting that adult mortality was low for these species. In contrast, shorebirds and passerines formerly breeding on the island were not observed in 2009 and probably perished in the eruption. The largest direct effect of the eruption to individual animals was probably mortality of chicks, with an estimated total 20,000-40,000 young birds lost. Indirect effects on wildlife consisted of loss of foraging habitat for species that relied on former terrestrial, intertidal, or nearshore-subtidal habitat and the near-total destruction of all former nesting habitats for most species. Although several species attempted to breed in 2009, all except Steller's sea lions failed due to lack of suitable breeding sites. The recovery of wildlife at Kasatochi will depend on erosion of the tephra layer blanketing the island to re-expose former breeding habitat.

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