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Oceanographic changes are occurring more rapidly in recent decades, with new implications for ocean ecosystems and adjacent human communities. It is important to bring attention to these changes while they are unfolding rather than after they have occurred. Here we report on a rapid shift toward colder, fresher water in the deep Gulf of Maine that, as of mid-June 2024, has persisted for at least six months. The shift likely represents an influx of Labrador Slope Water and resembles conditions that predated a major warming shift that occurred in 2011–2012. Deep-water oceanographic conditions in the Gulf of Maine have a strong influence on ecosystem dynamics, including the prey of critically endangered North Atlantic right whales, the seasonal and disease dynamics of American lobster, and the distribution and abundance of kelp forest communities, among others. Oceanographic surprises have an important role in this system, and monitoring how this shift unfolds, oceanographically and ecologically, will give new insights into how oceanographic signals can inform our understanding of ecosystem responses. 

Greenhouse gas emissions are warming the ocean with profound consequences at all levels of organization, from organismal rates to ecosystem processes. The proximate driver is an interplay between anthropogenic warming (the trend) and natural fluctuations in local temperature. These two properties cause anomalously warm events such as marine heatwaves to occur with increasing frequency and magnitude. Because warming and variance are not uniform, there is a large degree of geographic variation in temporal temperature variability. We review the underappreciated interaction between trend and variance in the ocean and how it modulates ecological responses to ocean warming. For example, organisms in more thermally variable environments are often more acclimatized and/or adapted to temperature extremes and are thus less sensitive to anthropogenic heatwaves. Considering both trend and variability highlights the importance of processes like legacy effects and extinction debt that influence the rate of community transformation. 

Abstract Fish contribute to the export of carbon out of the euphotic zone. They ingest organic carbon fixed by phytoplankton, store it in their tissues for their lifetime, and contribute to long‐term sequestration by producing sinking fecal pellets, respiring at depth, or via their own sinking carcasses. While the flux of carbon through fish is small relative to the export flux by plankton, humans have a direct influence on fish communities and thus on the magnitude of carbon storage and flux. We use a size spectrum model to examine the combined effect of fishing and trophic dynamics on the total carbon stored as biomass of a simulated community of fish. By sampling 10,500 possible fishing strategies that randomize fishing mortality and size‐selectivity, we consider optimal strategies that balance several UN Sustainable Development Goals addressing (1) food security, (2) climate action, and (3) marine conservation. The model shows that fishery management strategies that preferentially conserve large species increase overall carbon stored in the fish community. This study presents a perspective for considering carbon storage and sequestration in fisheries management alongside alternative objectives such as food production and biodiversity conservation. Our study focused on the state (total carbon in the living community). Incorporating rate processes like fecal pellet flux, vertical migration, and natural mortality would build toward a more holistic carbon approach to fisheries management. 

Compared with terrestrial ecosystems, marine ecosystems have a higher proportion of heterotrophic biomass. Building from this observation, we define the North Atlantic biome as the region where the large, lipid-rich copepod Calanus finmarchicus is the dominant mesozooplankton species. This species is superbly adapted to take advantage of the intense pulse of productivity associated with the North Atlantic spring bloom. Most of the characteristic North Atlantic species, including cod, herring, and right whales, rely on C. finmarchicus either directly or indirectly. The notion of a biome rests inherently on an assumption of stability, yet conditions in the North Atlantic are anything but stable. Humans have reduced the abundance of many fish and whales (though some recovery is underway). Humans are also introducing physical and chemical trends associated with global climate change. Thus, the future of the North Atlantic depends on the biome's newest species, Homo sapiens.