Federal Maritime and Hydrographic Agency of Germany

Long-term time series of dissolved oxygen (DO) measurements from the upper 500 m of the eastern tropical North Atlantic (ETNA), collected over a period of up to 15 years at three different mooring sites, reveal recurring extreme low-oxygen events lasting for several weeks. Similarly, observations from 15 individual meridional ship sections between 6 and 12° N along 23° W show DO concentrations far below 60 µmol kg−1 in the upper 200 m – significantly lower than the climatological values in this depth range (>80 µmol kg−1). Two-third of these low-oxygen events could be related with high-baroclinic-mode vorticies (HBVs) with their cores located well below the mixed layer. Despite the energetic equatorial circulation and the expected dominance of wave-like structures in the near-equatorial region, these HBVs persist as relatively long-lived and coherent features. Based on moored and shipboard observations from the ETNA, and supported by an eddy-resolving ocean-biogeochemistry model, we characterize their dynamics and DO distribution. Observed water mass properties and model analyses suggest that most HBVs originate from the eastern boundary and can persist for more than six months. As they propagate westward into regions of higher potential vorticity (PV), anticyclonic HBVs with low-PV cores remain more effectively isolated and have longer lifespans compared to cyclonic HBVs with high-PV core. The vertical structure of the dominant anticyclonic HBVs corresponds to baroclinic modes 4–10, with associated Rossby radii ranging from 34 to 13 km, respectively. This is consistent with observed eddy sizes and is well below the corresponding 1st baroclinic Rossby radius of deformation (>100 km). Since none of the observed HBVs exhibit a surface signature, a substantial portion of the near-equatorial eddy field may remain undetected by satellites, yet still exert significant influence on local ocean ecosystems and biogeochemical cycles.

Storm surges in the German Bight are among the North Sea's most severe coastal hazards. Assessing their future frequency and intensity is essential for evaluating coastal risk under changing climate conditions. We apply a statistical storm surge model for the German Bight to a CMIP6 multi-model ensemble under three emission scenarios (SSP2-4.5, SSP3-7.0, SSP5-8.5). Across all SSP scenarios, potential storm surge situations are projected to become significantly more frequent in winter by the end of the century. This increase is driven by stronger and more frequent westerly and northwesterly winds, likely linked to storm track shifts and more frequent positive North Atlantic Oscillation phases. In contrast, summer surge frequency is projected to decrease. These seasonal trends intensify under higher-emission scenarios. In combination with local sea-level rise projections, we find both moderate and severe present-day storm surge thresholds being exceeded up to six times more often by 2100, especially under high-emission scenarios. Notably, sea-level rise is found as the dominant factor behind these increasing occurrences of extreme water levels.

The offshore wind energy sector is experiencing rapid and large-scale expansion in Europe, driven by increasingly ambitious renewable energy targets that position it as a central component of global climate mitigation efforts. The increasing number of offshore wind projects in the North Sea requires comprehensive regulations to monitor and minimize the impacts on the marine environment during construction, operation and decommissioning. This policy brief aims to summarize current regulations for chemical emissions in the North Sea area by reviewing available national documents and websites for guidance in Belgium, Denmark, France, Germany, the Netherlands, and Norway in combination with information received from respective authorities. Based on the collected information, the policy brief will give recommendations for potential harmonization to increase the protection of the environment and facilitate procedures. The comparative analysis of national and transnational regulations for chemical emissions from offshore wind farms in North Sea bordering countries revealed that these are incomplete and differ between countries in terms of their specifications and level of detail. For example, specific rules for the application of galvanic anodes including the ban of zinc-based anodes are only available in Germany while several but not all countries prohibit the use of antifouling or other toxic paints. Incompleteness and differences may also be related to a lack of information on substances and their environmental effects. To achieve harmonization and more efficient protection of the marine environment, more data and minimum requirements on a regional level will be necessary, while at the same time, innovation may not be hampered and design and techniques should be further optimized and adapted based on latest available information.

Development in the sea has long been thought to be a nutritional gamble that disproportionately ends in starvation. Here, we unexpectedly show that components of plastids are incorporated into sea urchin eggs and that these, in turn, benefit developmental fitness. We find chromoplast-derived carotenoid crystals and chromoplast-specific metabolites inside of sea urchin eggs. The light-dependent activity of these chromoplast components influence the subsequent abundance of phytohormones that, in turn, regulate the use of energetic lipids that promote development and survival. Offspring that benefit from these chromoplast components are predicted to disperse further, over larger geographic areas, and use a wider range of currents, including those that cross ocean basins. Data presented here challenge the long-held assumption that components of non-metazoan organelles are unable to enter the germline and be passed between generations. We hypothesize that sea urchins manipulate plastids solely for their self-interest by a process that we term ‘machioplasty,’ with the result of this process being a novel and adaptive form of maternal provisioning. SIGNIFICANCE Making a fertilizable egg is a complex and carefully regulated process. One long-held assumption is that any component of non-animal organelles are unable to cross the evolutionary valley between non-reproductive and reproductive cells. Here, we unexpectedly show that components of plastids are incorporated into sea urchin eggs and that these, in turn, benefit developmental fitness. Offspring benefit from these plastid components by developing more quickly into larvae and having higher survival due to ability to use phytohormones that influence energetic lipids. This allows offspring to use a wider range of ocean currents, including those that cross entire basins. This challenge the long-held assumption that components of non-metazoan organelles are unable to be passed between generations. ### Competing Interest Statement The authors have declared no competing interest.

The Wadden Sea stretches along the coasts of the Netherlands, Germany, and Denmark in Western Europe. As the world’s largest coherent channel-shoal environment and as a UNESCO world heritage site, managing economic and political interests is complex. All stakeholders require a common understanding through shared, public databases and tools, e.g., to comply with the strict national park legislation. Although digital twins of the European oceans are emerging, current solutions still lack spatial resolution and neglect changes in coastal morphology. Here, we present a hydrographic dataset of the Wadden Sea covering the period of 2015 to 2022 with annually updated topography, and we outline a framework for the transition of digital twins toward the coastal oceans. A coupled numerical modeling approach was used to derive tides, currents, waves, salinity, temperature, and suspended sediments in 20-minute intervals. All data were published in an open-access governmental repository as files and web services with FAIR metadata documentation.