Shrinking body size is proposed as a universal response to warming among marine ectotherms. However, in fish, body size is determined by multiple interacting factors which must be disentangled to predict how climate change will impact populations. This study investigated length variability and its drivers in commercially important demersal species across three areas within the Celtic Sea Ecoregion: the North of Ireland/Malin Sea, West of Ireland, and the Celtic Sea, over two decades (2003-2023). Mixed-effects models were used to partition length variability into its intrinsic (age, sex) and extrinsic components. Generalised additive models were used to link length variability to extrinsic factors (temperature, abundance, recruitment, fishing pressure and the North Atlantic Oscillation). Results revealed spatial heterogeneity in length-at-age and varying levels of temporal synchrony in length trends within and between species. Density-dependent mechanisms explained a significant proportion of the variability, with smaller mean sizes associated with increases in abundance and recruitment, while fishing effects were generally weak and mostly consistent with density release among survivors. Across species, length was sensitive to fluctuations in environmental variables at both regional (temperature) and broad (North Atlantic Oscillation) scales. The temperature-size rule predicts faster juvenile growth but smaller adult size under warming. Across species, temperature effects on adult size were consistently negative. However, evidence for positive juvenile responses to warming was limited in gadoids, potentially reflecting the exclusion of age-0 fish in early maturing species. These results highlight that the universality of shrinking body size under warming extends across demersal species in the Celtic Sea Ecoregion, while also underscoring the difficulty of disentangling true climate responses from population-based data in complex ecological systems.
Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesise datasets and methodologies to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy and cement production data. Emissions from land-use change (ELUC) are estimated by bookkeeping models based on land-use data. The global atmospheric CO2 growth rate (GATM) is computed from changes in concentration measured at surface stations. The global net uptake of CO2 by the ocean (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based fCO2-products. The global net uptake of CO2 by the land (SLAND) is estimated with dynamic global vegetation models. Additional lines of evidence are provided by atmospheric inversions, atmospheric oxygen measurements, ocean interior observation-based estimates, and Earth System Models. This year, we introduced corrections on the ELUC, SOCEAN and SLAND estimates. The sum of all sources and sinks results in the carbon budget imbalance (BIM), a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as ± 1σ. For the year 2024, EFOS increased by 1.1 % relative to 2023, with fossil emissions at 10.3 ± 0.5 GtC yr−1 (including the cement carbonation sink, 0.2 GtC yr−1), ELUC was 1.3 ± 0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.6 ± 0.9 GtC yr−1 (42.4 ± 3.2 GtCO2 yr−1). Also, for 2024, GATM was 7.9 ± 0.2 GtC yr−1 (3.73 ± 0.1 ppm yr−1), 2.2 GtC above the 2023 growth rate. SOCEAN was 3.4 ± 0.4 GtC yr−1 and SLAND was 1.9 ± 1.1 GtC yr−1, leaving a large negative BIM (−1.7 GtC yr−1), suggesting that the total sink or GATM is strongly overestimated in 2024. The global atmospheric CO2 concentration averaged over 2024 reached 422.8 ± 0.1 ppm. Preliminary data for 2025 suggest an increase in EFOS relative to 2024 of +1.0 % (0.2 % to 1.7 %) globally, and atmospheric CO2 concentration increasing by 2.1 ppm reaching 425.6 ppm, 53 % above the pre-industrial level (around 278 ppm in 1750). Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2024, with a near-zero overall budget imbalance, although discrepancies of up to around 1 GtC yr−1 persist for the representation of annual to decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows: (1) a persistent large uncertainty in the estimate of land-use change emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the mean ocean sink. This living data update documents changes in methods and datasets applied to this most-recent global carbon budget as well as evolving community understanding of the global carbon cycle. The data presented in this work are available at https://doi.org/10.18160/GCP-2025 (Friedlingstein et al., 2025c).
Bottom trawling affects seabed habitats, but its large-scale impacts remain poorly quantified. Assessment of trawling impacts is essential to support monitoring and achieving sustainability objectives under international conventions, sustainable development goals, and seafood certification programs. We present a Europe-wide quantitative assessment of bottom trawling impacts, accounting for regional seabed-community sensitivity drivers, across the Baltic, Atlantic, Mediterranean and Black Sea continental shelves. Using two risk-based indicators of seabed status-Relative Benthic Status determined as benthic community biomass relative to seabed fauna carrying capacity (RBStot) and RBSsen (biomass of the 10% most sensitive fauna relative to carrying capacity)-we found substantial regional and habitat differences. The Black, Baltic and Aegean-Levantine Seas showed low trawling intensity and high seabed status across habitats. In contrast, the Western Mediterranean, Ionian and Central Mediterranean and Adriatic Seas were the most severely impacted. Trawling affected the sensitive species biomass fraction more strongly than the total community biomass. RBStot was in good condition (here chosen as RBS > 75% for epifauna) for over 79% of habitat-ecoregion combinations. In contrast, RBSsen met this threshold in only 46% of these. A strong correlation emerged between the mean trawling intensity and RBStot and RBSsen, allowing the use of SAR to estimate ecosystem status. This relationship can support decisions on where, and by how much, SAR reductions are needed to achieve good environmental status in regions where no detailed assessment is available. Our approach provides a quantitative framework to balance fishery production with ecosystem sustainability, offering tools for environmental and fisheries management in Europe.
Since the invention of echosounders and sonars in the early twentieth century, the applications of active-acoustic instruments have expanded from single-frequency range detection and fisheries stock estimates to wider explorations of ecosystem dynamics using increasingly advanced tools. Echosounders are now integrated with ships, nets, probes, uncrewed and autonomous vehicles, moorings, landers, and marine mammals, to sample the oceans on ecologically relevant spatial and temporal scales. Yet the uptake of these technologies by ecologists is hindered by steep learning curves, data post-processing techniques and availability, and funding challenges, as well as persistent knowledge gaps within the field of acoustics. An interdisciplinary approach, joining expertise in sampling technology and ecology, coalesces the people, ideas, resources, and data needed to conduct priority science. Here, we present the current and anticipated applications of active-acoustic and complementary instruments deployed on a variety of platforms to conduct interdisciplinary marine ecosystem science-beyond estimates of fisheries stock biomass. We also discuss the skill development, resource and data access, and interdisciplinary collaboration necessary to address challenges to marine ecosystems and progress the priorities identified in the ICES Science Plan.
Ectoparasites that penetrate host skin can act as biological or mechanical vectors for pathogens and, in some cases, serve as reservoirs. Crustacean ectoparasites of fish are potential vectors of pathogens, which is especially relevant for obligate pathogens (e.g., Aeromonas salmonicida) with limited seawater survival. Sea lice (Lepeophtheirus salmonis), affecting Atlantic salmon, cause dermal damage and can facilitate secondary infections, resulting in economic losses. While the physical impact of sea lice is well known, their role in pathogen transmission is less clear. The gut bacterial microbiome of lice collected over four months from a salmon farm in Ireland was analysed using Illumina MiSeq and Oxford Nanopore Technologies (ONT) PromethION sequencing for comparison. Illumina and Nanopore sequencing identified 15 and 24 genera of known fish pathogens, respectively. Moreover, Nanopore data revealed up to 15 putative pathogenic species, including Tenacibaculum maritimum, T. dicentrarchi and Vibrio anguillarum, causative agents of tenacibaculosis and vibriosis. The results of this study provide a gut bacterial microbiome characterisation of L. salmonis in a commercial aquaculture setting and demonstrate the potential of sea lice to act as pathogen vectors or reservoirs. These findings have important implications for pathogen surveillance, management, and prevention strategies in salmon aquaculture.
