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This report delivers an international and multidisciplinary effort to improve the understanding of ecosystem stability, vulnerability and tipping points in each of the 12 iAtlantic study regions over the last 50 years. Drivers of temporal change were analysed across a suite of deep-sea and open-ocean time series datasets available for that region. Datasets covered ecosystem compartments ranging from bacteria and primary producers, to groundfish and benthic invertebrates, to whales, swordfish and sharks, many of which are of great conservation interest and value to the Atlantic socioeconomy. Noisy data, incomplete data, the lack of longer-term datasets, effects of larger-scale oceanographic regime shifts, and potentially confounding variables challenged all the analyses and interpretations reported here. But despite the challenges, analyses resolved interannual to multidecadal changes in ecosystem compartments in all study regions, potential tipping points were identified, and analyses helped constrain many of the drivers related to these changes.
Statistical “breakpoints” revealed large temporal shifts and potential tipping points particularly around the late 1990s and early 2000s coincident with larger scale surface, mid-water and deepwater oceanographic trends reported in iAtlantic Deliverable 1.2 from the surface of the open ocean to the abyss. Many study regions reported breakpoints or overall declines in species important to the blue economy for commercial and recreational fisheries (e.g., Atlantic halibut, monkfish, albacore and bluefin tuna), trends confounded by fisheries pressure in time and space. Steady increases in species important for marine wildlife tourism (e.g., humpback whales) were also noted and likely related to larger scale population recovery trends post- whaling. Meanwhile, remarkable stability was also observed (e.g., hydrothermal vent fauna and microbes on the mid-Atlantic ridge). More recently established time series varied too much year to year but showed strong seasonal relationships between ecosystems and drivers (e.g., net primary production, trade winds, and eddies drive seasonal trends in the epi- and mesopelagic ecosystem off Cape Verde). Relationships with sea temperature were by far the most common trend reported across the 12 Study Regions. Northward expansion of monkfish range and capelin spawning habitat around Iceland were both associated with warmer waters. Long-term ocean warming heralds in today’s new era of widespread species “tropicalisation”. Zooplankton species with warm water affinities now characterise the community off the deep and open ocean over the Scotian Slope. Widespread declines in catches of cooler water species of groundfish like Argentine hake, Argentine croaker, and codling occurred on the Brazilian Meridional Margin. Catches of cooler water species of large migratory pelagics like albacore and Atlantic bluefin tuna have also significantly declined across Brazil, the Malvinas Current, Romanche Fracture Zone, Angola to the Congo Lobe and from Walvis Ridge to South Africa and seem related to positive thermal anomalies in these regions.
While all the analyses presented in the report come with heavy caveats, our place-based approach gives managers and spatial planning authorities a better understanding of ecosystem variability and vulnerability to climate change, and provides insights into alternative states or trajectories of ecosystems in each Study Region as well as possible drivers that could push or tip ecosystems into a new state.