AtlantECO-KER-AM-3

Climate-induced distribution changes are particularly challenging for fisheries targeting fish populations shared between exclusive economic zones (EEZs) and the high seas, known as straddling stocks. Here, we combine multiple datasets and ecosystem modeling to identify the presence of straddling stocks worldwide and consider the management implications of climate change–driven shifts. We identify 347 straddling stocks across 67 species, including both highly migratory and less mobile species. Our results suggest that regardless of the climate change scenario, at least 37% and 54% of stocks are projected to shift between EEZs and the high seas, by 2030 and 2050, respectively. More stocks are expected to shift toward the high seas, and highly migratory stocks are projected to shift across Regional Fisheries Management Organizations (RFMOs). Coastal states and RFMOs require to revise governance frameworks to support sustainable and equitable adaptation to shifting stocks. Developing such strategies requires cooperation between management bodies within EEZs and the high seas.

The contribution of the ocean biological carbon pump to the export of organic carbon at depth has predominantly been assessed by considering sinking particulate matter and vertically migrating organisms. Despite growing recognition of the importance of dynamical pathways that export carbon through upper-ocean mixing and advection, observation-based estimates of their global impact are still lacking. Here, we quantify the values and uncertainties of the export driven by the physical injection pump (PIP) and its interannual variability by leveraging a 4D data-driven time series (1997-2018) of particulate organic carbon concentration (POC) and ocean circulation, as well as 3D fields of climatological dissolved organic carbon (DOC). Vertical diffusion dominates our POC export estimates, but remains the most uncertain process. Assuming maximal diffusivity estimates that are consistent with observations, POC and DOC export amount to 0.37 Pg C yr−1 and 0.48 Pg C yr−1, respectively. The contribution from entrainment and advection is strongly modulated by the POC annual cycle, revealing the critical coupling between biological production and upper-layer mixing in driving the net annual export. Observed interannual signals correlate with a linear combination of El Niño–Southern Oscillation and Southern Annular Mode indices, suggesting that the PIP is connected to intermediate- and mode-water formation dynamics in the Southern Ocean.

The physical environment both above and below the ocean surface has changed dramatically during the last century. Changes in the marine environment induced by increased release of greenhouse gases and direct exploitation of resources include increased ocean temperature, decreased salinity and pH, and removal of apex predators. The risk of ecological regime shifts occurring has similarly increased. A variety of methodologies to identify regime shifts have already been used in the North Sea, which has become an important case study for the analysis of regime shifts in a semi-enclosed waterbody. The North Sea is regarded as a case study in part due to the operation of the continuous plankton recorder, which has provided detailed abundance records of phyto- and zooplankton for over 60 years. Here, we propose a new methodology to calculate regime shift likelihood for every month between 1958 and 2020. This unique model produces a single time series of regime shift likelihood, using sequential abundance data of more than 300 plankton species. We show the model's ability to identify when regime shifts occurred in the past by comparing it to previous less automated methodologies. We have validated the model for use in the North Sea by estimating how often false positives and false negatives are generated. Results from the model indicate evidence for three periods of high regime shift likelihood in various parts of the North Sea: between 1962 and 1972, between 1989 and 1999, and from 2002 until 2015. We show that these periods are consistent with previous estimates of North Sea regime shifts, and discuss possible applications of the model's output of a single time series.

This work combines ecological and macroeconomic approaches to assess the economic costs of climate change impacts on Net Primary Production in the Atlantic Ocean by 2050. The novelty of this study lies in introducing ecological limits in the fishery sector of the Computable General Equilibrium model used for macroeconomic assessment. To control socio-economic and climate uncertainties, we include projections from three CMIP6 climate models under two Shared Socioeconomic Pathways. Our results suggest a substantial economic loss by 2050 in Western African regions higher than 1% of Gross Domestic Product in most of the scenarios. This is the consequence of the impact on Net Primary Production and the strong increase in global fishery prices, which will affect the future economic structure. Economic losses and increases in fish prices are strongly amplified when biophysical constraints on fishery expansion are introduced in the macroeconomic model.

Southern Ocean phytoplankton have unique traits that allow them to survive extreme environmental conditions of low iron, light, and temperature. These traits are not well represented in Earth System Models and may lead to misrepresentation of the bloom seasonal cycle in this critical oceanic region. This has implications for understanding the role of the biological carbon pump in driving ocean carbon uptake and storage. We conduct a sensitivity analysis using a 1D model in the Subantarctic Zone to identify (a) the most sensitive parameters for improving representation of the seasonal cycle and its mechanisms and (b) the impact of these changes on carbon export. Lowering the phytoplankton iron quota or increasing zooplankton iron stoichiometry and both improve the seasonal cycle timing and amplitude, aligning chlorophyll and carbon seasonal cycle. However, the resulting increases in bloom amplitude translates into minimal change in carbon export due to enhanced cycling through the dissolved organic carbon pool.

Ocean biogeochemical models underpin projections of future marine ecosystem change, including anticipated shifts in the biological carbon pump (BCP) and broader biogeochemical cycles. However, their outputs remain highly sensitive to model complexity and parameterisation choices. Here, we evaluate five configurations of the Pelagic Interaction Scheme for Carbon and Ecosystem Studies (PISCES) to quantify intramodel variability in net primary productivity (NPP), carbon export (Cexp), and export efficiency (e-ratio) over the 21st century under the high emissions RCP8.5 scenario. The tested PISCES configurations differed from the standard model through distinct modifications to phytoplankton growth processes, but are forced by identical physical variables, representing an ensemble opportunity. All configurations resolve NPP and Cexp within the range of remote-sensing variability. The more complex Quota-based configurations produce 15–21 (10–18) Pg C yr−1 more NPP than the simpler Monod-quota models in the reference (future) period, but this increase, driven by elevated small phytoplankton biomass, does not enhance Cexp, yielding lower e-ratios (0.14–0.17) than in the Monod-quota configurations (∼0.25). The introduction of a picophytoplankton functional type (PFT) emerges as one of the most influential parameterisation choices. It drives opposing future NPP responses between 30–60° N/S, an increase in the Monod-quota configurations versus a decline in the Quota-based ones, as well as contrasting latitudinal trends in Cexp within the same region. Other parameterisations, such as a low-iron scheme, an added diazotroph PFT, and explicit manganese cycling, exert more modest, regionally confined effects under high emissions scenarios, influencing NPP and Cexp primarily at biome scales rather than driving large-scale divergence in model behaviour.