Mechanistic responses of coccolithophores to exposure to the marine pollutant atrazine.

More precise accounting of marine carbon emission efficiency: Based on input-output analysis and considering marine carbon sinks

Integrating physics-based modeling and deep learning for high-resolution vertical chlorophyll-a predictions in the ocean.

Relative contribution of dark carbon fixation to total carbon uptake along a latitudinal transect in the Seychelles-Chagos thermocline ridge, western Indian ocean.

Preliminary evaluation of ferrous sulphate toxicity on larvae of the sea urchin Paracentrotus lividus: implications for ocean iron fertilization.

The evolution of Earth's marine carbonate factory

Fisheries carbon sinks–ecosystem services–human well-being nexus: A systematic map

Optimizing pH for acetate production in saline photo-assisted microbial electrosynthesis: Roles of EPS and metabolic regulation.

Expert views on the governance of marine sedimentary carbon for climate change mitigation.

ABSTRACT Australia stands at a critical juncture in its climate transition, aiming for net-zero emissions by 2050 with an interim target of a 62–70% reduction below 2005 levels by 2035. As of 2024, onshore renewable sources supplied approximately 39% of Australia's electricity, predominantly from solar and onshore wind. Marine-based solutions, offshore wind, blue carbon ecosystems and emerging marine carbon dioxide removal technologies, offer significant, underutilised potential to meet these goals while supporting economic prosperity and environmental resilience. Offshore wind can provide reliable, high-capacity renewable energy near key demand centres, complementing existing solar and onshore wind, and create opportunities for producing critical energy transition minerals and green fuels. Blue carbon habitats, including mangroves, seagrasses and saltmarshes, are effective natural carbon sinks with additional biodiversity and coastal protection benefits. Realising these opportunities demands coordinated national action, investment in infrastructure, regulatory frameworks, scientific research and workforce development. The National Marine Science Committee (NMSC) is well positioned to lead cross-sector integration. Key dependencies include governance coordination, robust monitoring and verification systems, and meaningful community engagement, particularly with Indigenous groups. Australia's ocean is no longer just a climate victim but a critical climate solution, capable of strengthening regional economies and global leadership.

Brown algal cell walls are complex matrices composed primarily of alginate, cellulose, and fucoidan. Their depolymerization is important in marine carbon cycling. Although numerous algal polysaccharide-degrading enzymes have been characterized, most studies focus on breaking down single, purified polysaccharides, leaving the degradation mechanisms of native cell walls containing mixed polysaccharides poorly understood. Here we report the integrated modular enzymes involved in brown algal cell wall polysaccharides (BACWPs) degradation. Using the marine flavobacterium Aquimarina sp. 2-A2 as a model, we isolated a bifunctional enzyme, CelAly, which integrates a glycoside hydrolase family 5 cellulase domain and a polysaccharide lyase family 31 alginate lyase domain within a single polypeptide, enabling the degradation of cellulose and alginate in brown algal cell walls. In vivo relevance of CelAly was confirmed by upregulation of its gene during growth on algal biomass. CelAly also contains three distinctive substrate-binding modules (B1, B2, UKD) that support its multimodular functionality; among these, UKD is notable for its dual substrate-binding capability. CelAly's modular architecture and interdomain flexibility may facilitate coordinated degradation of BACWPs. Bioinformatic analyses and biochemical validation revealed three additional types of such modular enzymes from marine microbes. CelAly and related modular enzymes are strongly associated with marine environments and exhibit conserved modular strategy for substrate recognition and catabolism. Thus, these enzyme architectures represent a previously unrecognized strategy specialised for BACWPs decomposition. This study elucidates the unique structural and functional adaptations of the integrated multimodular enzymes and highlights their ecological prevalence among marine bacteria, providing insights into natural biomass decomposition.

Deciphering the composition and bioavailability of dissolved organic matter in rivers discharging into a temperate eutrophic bay.

Differential impacts of ocean acidification and alkalinization on shell microstructure and molecular responses in Mytilus edulis.

Kinetic insights into measurable marine carbon dioxide removal via carbonation of electrolytically alkalinized seawater

Seagrass meadows, though covering a small percentage of the ocean floor, play a critical role in marine carbon sequestration. However, the mechanisms behind this role remain uncertain due to challenges in mapping seagrass extent and flux, accounting for spatial variation in carbon storage, and incorporating site-specific histories. This study investigates the effects of short-term (≤10years) seagrass loss on sediment carbon stocks within a large seagrass meadow in the Great Barrier Reef region. Using remote sensing data to construct a seagrass recovery timeline, combined with field sampling and assessments of ecological factors, we found higher sediment organic carbon in areas where seagrass coverage was retained throughout the study period. Carbon stock and sediment accumulation varied with Recovery stage and were influenced by ecological factors and the length of seagrass absence. Minimal differences in sedimentary carbon stocks were observed between retained areas and those recovering within 3-8years, suggesting limited disturbance impacts on carbon storage when recovery occurs within this timeframe. However, significant differences in carbon stocks were observed between persistent meadow areas and sites where no seagrass recovery had occurred for ≥10years. The study meadow contained an estimated 39,779Mg C (to 1m), with spatial variation linked to seagrass loss and recovery history, as well as ecological and environmental factors. Our findings offer context to the permanence of seagrass Blue Carbon during meadow loss and suggest sedimentary carbon stocks can largely persist in similar systems experiencing cycles of seagrass loss and recovery that occur over 3-to-8-year timeframes.

The record of environmental and climatic change through the late Norian stage in paleoequatorial settings has so far received limited attention. Here we present new geochemical and sedimentological data to investigate the depositional and environmental changes through the late Norian into the earliest Rhaetian in the marine carbonate Milaha and Ghalilah Formation exposed in Wadi Milaha, Ras Al-Khaimah, UAE. The upper part of the Milaha Formation studied in Wadi Milaha, comprises sediments deposited in a shallow marine environment, with some evidence of high-energy shoal deposition. Restricted conditions are present in the basal and middle part of the Asfal member of the Ghalilah formation, followed by high diversity faunal content, indicating the development of open marine conditions in the late Norian-early Rhaetian. Development of the restricted conditions upwards suggests changes in the relative sea level. Our results show that the succession is comprised of regressive-transgressive cycles, which include minor depositional cycles influenced by changes in clastic input. Sedimentological and elemental data indicate fluctuations in clastic input throughout the sedimentary succession studied. The increase in siliciclastic input coincides with a major regressive sea level cycle during the middle-late Norian. Our results suggest that the increased coarse terrigenous input is likely due to enhanced weathering and an associated warming episode during the late Norian. Very low correlation of δ 13 C carb and δ 18 O indicates little diagenetic influence on the isotopic record. The δ 13 C carb records an overall negative trend during the middle-late Norian with small-scale fluctuations of −2.8‰ magnitude and coincides with increased clastic input. A small positive excursion in δ 13 C carb is recorded at the Norian-Rhaetian boundary. The observed variations in sedimentary succession, relative sea level, and bulk carbonate carbon isotopic record are similar to those of other Tethyan sections. This comprehensive and comparably high-resolution record very likely indicates far-reaching or global ecological changes during the middle-late Norian. • Study area occupied a paleo-equatorial position during the mid-late Norian • Sedimentological investigations allowed the interpretation of sea level cycles • Enhanced siliciclastic input suggest intensification of hydrological cycle • Comparison of the carbon isotope trends suggests ecological changes in late Norian

Coccolithophores play a dual role in the marine carbon cycle, serving as CO2 sinks through photosynthesis while simultaneously emitting CO2 via calcification, resulting in uncertainty regarding their net carbon sequestration potential. In addition, their calcite coccoliths (CaCO3) can increase the carbon export efficiency by functioning as ballasts for organic matter. Although biogeochemically significant, the molecular mechanisms governing calcification and associated metabolic adaptations in coccolithophores remain poorly characterized, impeding accurate predictions of their responses to climate change. Through comparative multiomics analyses of calcified (RCC1266) and noncalcified (PML B92/11) Gephyrocapsa huxleyi strains, as well as chemically induced decalcified and recalcified states, we screened several ion transport genes, which potentially facilitate Ca2+ and HCO3 - uptake/transport coupled with H+ extrusion during calcification in the calcified strain, along with their associated proteins, including signal molecules and chaperones. Furthermore, an energy-intensive process was observed in calcifying cells, and this process was principally sustained by enhanced photosynthetic efficiency, supplemented by glucose accumulation as an energy reserve and COX6B translational upregulation, providing nocturnal energy. Notably, calcifying cells employed an energy conservation strategy characterized by transcriptional downregulation yet translational maintenance of photosynthesis and carbon metabolism genes while simultaneously upregulating protein biosynthesis and trafficking pathways to probably meet calcification demands, a process potentially facilitated by increased glutamine biosynthesis. Through multiomic technology, our findings provide insights into the molecular adaptations in the calcified coccolithophorid cells, revealing critical physiological trade-offs, carbon metabolism, and energy allocation that can inform predictions of their acclimation capacity under changing oceanic conditions.

The oceanic uptake of anthropogenic CO 2 has resulted in ocean acidification (OA). Macroalgae farming has the potential to mitigate OA by removing CO 2 from the surface water via photosynthesis. However, continuous in-situ observations of marine carbonate chemistry related to macroalgae farming remain limited, leaving its effectiveness in addressing OA uncertain. To address these knowledge gaps, this study examined a 2-acre Saccharina latissima , sugar kelp, farm located at Point Judith, Rhode Island, as a case study to assess the potential of sugar kelp aquaculture in mitigating local OA. Over the full growing season from December 2022 to May 2023, high-temporal-resolution (every 30–60 minutes) measurements of surface temperature, salinity, dissolved oxygen and pH were taken inside and outside the kelp farm. The results demonstrate that sugar kelp farming does not significantly impact the carbonate system, thus providing negligible OA mitigation locally. Specifically, a temporary, local-scale CO 2 reduction and higher pH occurred during very early kelp growth in early February, but was reversed by a higher surface CO 2 , exaggerating OA, starting in mid-February. Over the entire observation period, kelp growth resulted in a 5.1 ± 11.6 μatm increase of p CO 2 per week compared to the control site in the surface, a signal which is small compared to the substantial natural variability. However, the minimal p CO 2 difference at the kelp farm may be reflective of the relatively small cultivation area (2 acres) or depressed growth of phytoplankton, resulting from nutrient competition between the kelp and in-situ phytoplankton. This study underscores the need for future sustained observations to evaluate the impact of seaweed cultivation on OA mitigation and the carbon cycle at the ecosystem scale.

Sedimentary record of black carbon in Daya Bay: Temporal evolution and source apportionment over the past 140years.

Abstract Ocean alkalinity enhancement (OAE) is a promising marine carbon dioxide removal (CDR) option, but its net climate benefit and wider environmental implications depend strongly on where, and how it is implemented and on decarbonized energy and material supply chains. We develop a prospective, site-specific, life cycle assessment (pLCA) that couples a field trials’ validated high-resolution ocean biogeochemical model with LCA for five OAE pathways deployed via wastewater outfalls in Halifax Harbor, Canada: three on magnesium hydroxide (two from serpentinite, via ammonium sulfate (AS) and HCl leaching (HCl), one from bischofite brine (BIS)) and two on sodium hydroxide (from industrial-grade sodium chloride (NaOHs) and seawater desalination brine hydroxide (NaOHb)). Using the functional unit of removing and permanently storing 1 t of atmospheric CO₂, we compare present-day conditions with a 2050 scenario and quantify eighteen ReCiPe 2016 midpoint impacts. Present-day results show little to no net climate benefit: net climate effects range from −0.09 to +0.71 t CO2-equivalent (CO2e) per t CO₂ removed, with fossil electricity and heat supply dominating the impact. By 2050, all pathways are net removers with uptake efficiencies of 81–95% as energy supply decarbonizes. BIS performs best in sixteen of eighteen impact categories, whereas NaOHs and AS are consistently worst across most categories. As energy decarbonizes, burdens shift from fossil fuel combustion to materials, metals, and related mining (especially copper), chemicals, and biofuels production for feedstock transport. The analysis shows that robust OAE assessment requires site-specific CO₂ uptake efficiencies, prospective supply-chain representation, and multi-criteria evaluation rather than focusing only on net CO₂ removal, because climate-attractive pathways can carry substantial burdens in (eco)toxicity, resource depletion, or other impact categories. The proposed coupling of a regional ocean model with pLCA provides a transferable template to evaluate OAE and other marine CDR options in CDR portfolios.