GEOMAR 海洋研究赫尔姆霍茨中心基尔

Bottom trawl fishing effort in the Balearic Islands has decreased considerably in recent decades due to a progressive fleet reduction and the implementation, since 2020, of the effort regime under the multiannual plan for demersal fisheries in the western Mediterranean (WestMed-MAP). By 2024, this regime had reduced the average annual fishing days by 40% compared to the 2015–2017 baseline period. Concurrently, seawater temperature is increasing. We used the Ecosim model to explore the long-term effects of several WestMed-MAP and climate change scenarios on key demersal resources and vulnerable fish species in the Balearic Islands. Management effects were stock-dependent. Some stocks (deep-water rose shrimp, mullets and rays) reached biomass and catch levels comparable to those expected at maximum sustainable yield (MSY) under fishing effort levels prior to the WestMed-MAP, or following its early (2022) implementation. Conversely, hake and red shrimp would not recover to MSY biomass levels, even under 2024 effort reductions coupled with selectivity improvements. Deep-water rose shrimp was the only species positively affected by global warming, whereas Norway lobster was negatively impacted by warming, only recovers under a no fishing scenario. All successful scenarios required over 5 years to achieve full potential recovery. These results call for a re-evaluation of WestMed-MAP fishing effort reductions implemented in the Balearic Islands, highlighting the need for a regional downscaling that considers specific fishing strategies and the initial state of local stocks, as well as the time lag required to detect expected management effects.

Abstract Many large igneous provinces (LIPs) comprise once contiguous magmatic products that are now fragmented across multiple tectonic plates. Emplacement of these voluminous magmatic products is commonly coeval with, or shortly followed by, fragmentation into constituent domains. However, the Kerguelen LIP, predominantly within the southern Indian Ocean, rifted after an unusually protracted c. 45 Myr interval post‐emplacement. To investigate this protracted post‐emplacement rifting, a recent voyage by the RV Investigator sampled the conjugate margins of the Kerguelen Plateau, William's Ridge (WR) and Broken Ridge (BR) for the first time. Dredged volcanic rocks were characterized using petrographic, geochemical (major and trace element, Sr‐Nd‐Pb‐Hf isotopes) and geochronological (40Ar/39Ar) techniques. Here, we focus on the sampled 82–67 Ma tholeiitic volcanic rocks. The observed geochemical data in conjunction with rare earth element inversion modeling of these Late Cretaceous volcanic rocks reflect plume–ridge interaction with variable assimilation (≤10%) of continental crust. We propose that the Kerguelen plume transported melt to the WR–BR margin during episodes of extension. Extension and magmatism were localized along the rheologically weak margins of the WR microcontinent. The combination of these mechanically weak boundaries and earlier extensional events facilitated a final ridge jump into the WR–BR margin at c. 44 Ma. We demonstrate a pre‐existing history of extension in the Late Cretaceous prior to complete fragmentation in the Eocene, resolving the apparent protracted interval between emplacement and separation of the Kerguelen LIP.

Ocean knowledge is crucial for shaping policies that enable sustainable development, adaptation, and well-being at all levels, as everyone—either directly or indirectly—depends on the ocean, which today faces escalating threats from climate change, pollution, and biodiversity loss, pushing us beyond critical planetary boundaries. Ocean indicators are crucial for translating ocean science and data into practical metrics, guidance, and tools informing on the state and health of the ocean that can be directly applied by policymakers, practitioners, and the public. Despite their critical importance, ocean indicators trail behind those for continental areas, limiting effective monitoring and policy integration. Developing reliable, comparable, and regularly updated ocean indicators, backed by a unified international framework, is essential for delivering coherent, actionable insights that can guide global goals and protect the ocean's future. This paper establishes a scientific foundation for ocean indicators through international and multidisciplinary collaboration, presenting defined criteria and a set of pilot indicators for the ocean’s physical, biogeochemical, biodiversity, and ecosystem aspects. The proposed framework offers a solid foundation for generating indicators that not only track the ocean state but also provide outputs for application in informing policy and decision-making.

Silicate weathering regulates Earth’s long-term climate by removing atmospheric CO2. Understanding changes in weathering regimes and rates is key to predicting climate response time scales. We investigated the reactivity of the North American source-to-sink system and the chemical weathering regime during the Paleocene−Eocene Thermal Maximum (PETM). We measured the detrital lithium isotope composition (δ7Li) in a deep-marine sediment core from the Gulf of Mexico, tracking changes in the formation of clay minerals, alongside neodymium isotopes (εNd), to constrain sediment provenance. We find a buffered negative δ7Li excursion during the PETM body, likely reflecting the mixing of neoformed and reworked clays from continental floodplains, followed by a stronger negative δ7Li excursion during the recovery phase. This pattern aligns with the continental Bighorn Basin (Wyoming, USA) δ7Li record, indicating rapid propagation of enhanced weathering and erosion fluxes in response to the PETM, which would have contributed to efficient CO2 drawdown.

Offshore relatively fresh groundwater (ORFG; <10 grams per liter) represents an underexplored frontier in addressing global freshwater scarcity, yet its origin, persistence, and vulnerability remain poorly constrained. Here, we reveal a vast climate-driven freshwater reservoir beneath the Pearl River estuary and adjacent shelf. Integrating hydrochemical profiling, isotopic tracing, and groundwater dating, we demonstrate that this ORFG is a relic of ancient meteoric recharge, emplaced during Late Pleistocene sea-level lowstands and preserved beneath the seafloor for tens of millennia. Secular equilibrium in offshore 226 Ra/ 230 Th activity ratios, consistent 14 C ages of 6 to 10 thousand years in onshore groundwater, and pronounced onshore-offshore contrasts in salinity and δ 18 O collectively confirm its fossil nature rather than slowly circulating modern groundwater. Numerical modeling further constrains the timescale of natural degradation, underscoring the system’s resilience. These findings establish ORFG as not only as a long-lived archive of paleohydrological cycles but also as a potential strategic freshwater reserve, with substantial implications for coastal water security in a changing climate.