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PubMed2026

Ocean warming enhances iron use efficiencies of marine ammonia-oxidizing archaea.

Ammonia-oxidizing archaea (AOA) are among the most abundant microorganisms in the ocean, playing a fundamental role in the marine nitrogen cycle. Although temperature and trace metal availability each individually influence the growth and activity of marine AOA, there is only a very limited understanding of the interactive effects of these two major factors on AOA in the rapidly changing ocean. Here, we show that the iron requirements of the model marine AOA species Nitrosopumilus maritimus SCM1 are highly sensitive to temperature changes. A 5 °C increase in growth temperature reduced SCM1 iron requirements by >80%, and was associated with a substantial increase in iron use efficiencies (IUE, mol C fixed/h/mol cellular Fe) under iron-limited and warming conditions. A thermally enhanced IUE enables SCM1 to more efficiently utilize scarce available iron supplies to support its growth. Whole-cell proteomic analysis revealed that iron limitation decreased expression of a ferredoxin and increased expression of a copper-dependent plastocyanin that became more pronounced with warming, suggesting coordinated electron transport response regulation under combined iron and temperature stress. The global impacts of these temperature-dependent changes to AOA iron demands were assessed using sensitivity experiments with a state-of-the-art biogeochemical model. Simulations showed that impacts on nitrification were concentrated at higher latitudes, but the alterations to ammonia concentrations were redistributed toward lower latitudes by mode and intermediate water transport. These findings reveal a previously unrecognized mechanism by which ocean warming may alleviate iron limitation of AOA, enhance their ecological competitiveness, and reshape ocean nitrogen cycling throughout marine ecosystems.

Iron↗

PubMed2026

Coral color morphs exhibit distinct microbial and proteomic profiles linked to stress and immune mechanisms in a changing ocean.

BACKGROUND: Coral phenotypic plasticity facilitates acclimation and adaptation to environmental variability. Coral species often display a variety of color morphs, yet key biological and ecological implications of such phenotypic variation remain underexplored. Here, we present the first proteomic and untargeted lipidomic and metabolomic survey to explore the biological characteristics and potential ecological significance of different color morphs (pink and brown) of healthy Pocillopora verrucosa sampled along a latitudinal gradient. RESULTS: Our multi-omic approach elucidated distinct mechanisms associated with these dominant color morphs. We discovered bacterial indicators specific to each morph: putative pathogens such as Salmonella, Escherichia-Shigella, and carotenoid-producing Gemmatimonas were notably associated with the pink morph, whereas the brown morph was associated with potentially beneficial bacteria, such as Lysobacter, Acinetobacter, and Endozoicomonas. Despite these microbiome differences, the lipidome and metabolome of P. verrucosa were surprisingly homogeneous across colors and locations, suggesting similar metabolic performances during summer conditions. Key polar and apolar lipid classes, such as fatty acids, glycerophosphocholines, and retinoids, were prevalent. Notably, our proteomic analysis revealed morph-specific expressions, with pink morphs exhibiting enhanced levels of GFP-like proteins, Ankyrin, and the enzyme pullulanase, suggesting novel putative protective roles. In contrast, the brown morphs showed a higher abundance of heat shock proteins, indicating putative differential stress response capabilities. CONCLUSION: This comprehensive study provides the first proteomic survey of P. verrucosa and identifies key physiological pathways and trade-offs linked to color morphs, which can further contribute to enhancing our understanding of coral resilience in the face of climate change. SIGNIFICANCE STATEMENT: Understanding the phenotypic plasticity of corals is crucial for uncovering mechanisms of resilience in warming oceans, yet the biological significance of coral color morphs still needs to be explored. Using an innovative multi-omic approach (proteomics, lipidomics, and metabolomics), we provide the first comprehensive analysis of differences between pink and brown morphs of Pocillopora verrucosa. Our data reveal key taxa, potentially pathogenic or beneficial, associated with each morph, and suggest different strategies for each color morph to cope with heat stress, either expressing proteins involved in UV protection and heterotrophic activity or enhanced levels of heat stress resilience and DNA repair. These findings offer insights into the phenotypic plasticity of coral color morphs and their differential responses to climate change. Video Abstract.

Anthozoa↗

PubMed2026

Lifestyle Differentiation Among Marine Denitrifying Microorganisms.

Microorganisms carrying out denitrification in marine anoxic zones drive bioavailable nitrogen loss. Sequencing datasets have demonstrated the modularity of denitrification, with most populations having the genetic capability for only a subset of the pathway (NO3-➔NO2-➔NO➔N2O➔N2). Although previous work provided ecological explanations for this diversity among the functional modules, large trait variations exist within each functional module, and this within-module diversity and its biogeochemical implications remain unexplored. Here, we combine genomic data and modeling to explore how metabolic "lifestyle" strategies influence denitrifier community structure. We build a comprehensive genomic database of marine denitrifiers, and identify lifestyle differentiation among denitrifier functional groups. We then extend a mathematical ecosystem model by resolving two microbial functional types for each module representing a metabolic trade-off: a copiotroph, optimized for fast growth, and an oligotroph, optimized for high nutrient affinity. In the model, as the supply of organic matter relative to nitrate increases, the degree of copiotrophy among the community increases and then decreases. This suggests that oligotrophs are associated with either organic-matter- or nitrate-limiting conditions, whereas copiotrophic lifestyles are associated with an intermediate regime. Our model further associates NO2- reducers with oligotrophy and NO3- reducers with copiotrophy, particularly those producing greenhouse gas nitrous oxide (N2O), linking N2O production to substrate-replete conditions, which is consistent with our genome-based lifestyle estimates. Results provide insight into denitrifier ecological niches and thus the biogeochemical conditions that are associated with the production of intermediates, such as N2O, improving our understanding of how nitrogen cycling will change in a warming ocean.

Marine denitrifiers↗

PubMed2026

Sugar kelp (Saccharina latissima) population genetics map onto geographic distance and oceanographic features across coastal Maine.

Sugar kelp (Saccharina latissima; order Laminariales) plays a vital role in kelp forest ecosystems, as well as an expanding kelp aquaculture industry, in the Gulf of Maine, United States. However, ocean warming is eroding the resilience of Maine's kelp forests and may be compromising their local genetic diversity, with impacts on population structure and gene flow. Here, we used genome-wide single nucleotide polymorphism (SNP) data to assess the genetic diversity, structure, and connectivity of S. latissima populations at 11 outer coastal sites spanning the historical range of kelp forests in Maine. Our analyses identified moderate genetic diversity and limited inbreeding within sites (average heterozygosity: 0.27). Further, they revealed that three clusters comprising four genetically distinct populations exist across the study region. Population structure was strongly associated with geographic distance and oceanographic features, as supported by principal coordinate analysis, FST calculations, Bayesian clustering, and spore dispersal modeling. Lastly, our outlier analysis identified genes potentially under selection. Thus, our findings highlight distinct, genetically unique kelp populations along Maine's coast and emphasize the need for regional management strategies that support both ecosystem resilience and sustainable aquaculture under climate change.

Gulf of Maine↗

PubMed2026

Symbiotic interactions and climate change implications of the octocoral microbiome.

Octocorals are vital components of tropical, temperate, and cold-water benthic marine ecosystems. Their associated microbiomes, comprising microeukaryotes, prokaryotes, and viruses, are increasingly recognised as central to host health, nutrient cycling, and chemical defence. Metagenomics and amplicon sequencing have uncovered taxonomic and functional complexity within these microbial communities, revealing patterns of host specificity and health status, along with seasonality and geographic structuring. However, anthropogenic stressors, particularly those associated with global climate change, exert intense pressure on coral-dominated ecosystems, leading to complex and poorly understood local and regional patterns of octocoral expansion and mortality. Microbial interactions may be a main driver of these contrasting outcomes by mediating the ecological resilience of octocorals to environmental stress. We synthesise the current state of research on the diversity, organisation, and function of the octocoral microbiome, and identify critical knowledge gaps on octocoral holobionts relative to scleractinian corals. Our meta-analysis of 79 publicly available bacterial genomes from octocorals reveals group-specific specialisation in denitrification and nitrate assimilation, along with widespread capacities for essential amino acid, cofactor, and vitamin production, suggesting important contributions to nutrient cycling in the holobiont. While sampling efforts between cultured and uncultured lineages are even, our genomic survey reveals strong sampling bias toward the Atlantic Ocean, temperate gorgonians, and healthy host states, whereas bacterial genomes representing the pathobiome, tropical and/or deep-sea regions, and other octocoral taxa remain underrepresented. Accordingly, we propose future research directions to advance understanding of octocoral microbiome ecology and its role in the resilience of tropical, temperate and cold-water coral reefs.

Endozoicomonadaceae↗

PubMed2026

Fine-Scale Population Genomics Reveals Genetic Differentiation in the Brooding Amphipod Cheirimedon femoratus Across the South Shetland Islands, Antarctica.

Antarctic marine ecosystems are sensitive to environmental change, and impacts on processes such as population connectivity will play a fundamental role in future population dynamics and persistence, affecting short-term demography and long-term evolution. We investigated the population genomics of the common benthic brooding Antarctic amphipod Cheirimedon femoratus (Pfeffer, 1888), using 8837 high-quality single-nucleotide polymorphisms (SNPs) from 87 individuals collected at 4 sites in the South Shetland Islands, separated by up to 200 km: Deception Island, King George Island, Livingston Island, and Snow Island. While Admixture, F ST, principal component analysis (PCA), and demographic (Ne) analyses revealed a generally weak population genetic structure, Livingston Island emerged as a distinct population, especially compared to King George Island. All populations showed a heterozygote deficit with positive inbreeding coefficients (F IS), particularly high in the Snow Island population (~0.55). Tajima's D test suggested overall neutral evolution, although slight variation was observed among sites. Despite the limited dispersal potential of this brooding species, the observed connectivity may be maintained through passive dispersal, likely via floating macroalgae or ice-rafted debris, facilitated by prevailing regional ocean currents. This may enhance the population resilience of Antarctic benthic communities under environmental change, including regional warming and shifts in ocean circulation, compared to more isolated populations. Our findings underscore the complex interplay between passive connectivity and fine-scale differentiation in shaping Antarctic benthic invertebrate diversity.

Amphipoda↗

PubMed1975

Ecological comparative analysis of parasite fauna of Rutilus rutilus L. and Coregonus albula L. from waters of the European part of the Arctic Ocean Province.

The differences between the parasite fauna of Rutilus rutilus L. and Coregonus albula L. are caused by the fact that the former host is more warm-requiring and the conditions in waters of the Arctic Ocean Province of the Circumpolar Subregion are less favourable to it. On the other hand, C. Albula, which is a northern species, lives here under optimal conditions. R. rutilus is bentophytophagous and C. albula planktophagous species, which results in the differences in species composition of their parasites. Also differences in the growth and seasonal and annual changes of their parasite fauna have been observed.

Animals↗

PubMed2026

Minimizing decompression and warming during deep seawater collection increases abundance and activity of autochthonous bacteria and archaea.

The deep ocean hosts autochthonous pressure-adapted microorganisms that are unique to this environment, as well as allochthonous pressure-sensitive members transported from shallow depths by vertical advection and particle-sinking. However, conventional sampling instruments decompress and warm deep-sea samples during retrieval, potentially altering microbial properties when studied ex situ. Here, we assess this potential sampling bias by comparing seawater microbial communities collected with or without measures aimed at minimizing pressure and temperature effects. When compared to samples collected under pressurized conditions, conventional sampling (using Niskin bottles) was found to affect prokaryotic cells retrieved by reducing their total numbers, diminishing protein synthesis activity (>10%), and also causing overall shifts in the community composition. The most significant compositional change was a >20% decrease in metagenomic archaeal representation (TACK-group/Thaumarchaeota/Nitrososphaerota). Deep-sea bacterial groups had mixed responses to preserving pressure during retrieval, with some groups exhibiting higher representation when samples were maintained pressurized (e.g. members of the family Pelagibacteraceae, unclassified Thiotricales, Thioglobaceae, and Chitinophagaceae), whereas others increased their representation when decompressed (e.g. Burkholderiaceae, Comamonadaceae, and Oxalobacteraceae). This study reveals the existence of bias introduced by the complete decompression of samples retrieved with traditional instrumentation, as well as a decrease in overall bacterial activity when samples are completely decompressed during retrieval. Additionally, incubations lasting for >24 h were shown to transform the original prokaryotic community composition. Precautions addressing these effects are necessary to enhance the reliability of ex situ measurements and improve our understanding of deep-sea microbial ecology and biogeochemistry.

Seawater↗

PubMed1992

Switches in fish myosin genes induced by environment temperature in muscle of the carp.

Fish are cold blooded animals and their muscle function is expected to be greatly affected by environmental temperature. Species that live in the Antarctic ocean have evolved a different contractile system to fish that live in the tropical waters. In the case of Antarctic fish they have a higher specific myofibrillar ATPase activity but 'the trade off' seems to be a lower thermal stability. They are thus capable of a greater muscle power output at low temperatures but the lower thermal stability means they are restricted to living at temperatures below +4 degrees C. Some species, however, experience a wide range of seasonal variations in temperature. We found that these species adapt by changing their myofibrillar apparatus so that they have a higher specific ATPase which physiological studies indicate is due to a different type of myosin crossbridge for low temperature swimming. This is reversible and they develop a contractile system with a greater thermal stability and a commensurate loss of ATPase activity when their environment warms up again. There were several possibilities by which this may be achieved including expression of different isoform genes or the post- translational processing of existing proteins. To elucidate the mechanism we made a carp genomic library and screened this for myosin heavy chain gene using mammalian cDNA sequences under moderate stringency conditions. The clones were restriction mapped which resulted in 28 non overlapping sequences. This indicated that the carp had a reasonably large family of myosin heavy chain genes that is about twice the size of that in mammals. Rather fortuitously the first sequence to be identified was from the gene that is predominantly expressed in white muscle at warm temperatures. This was done by extracting the RNA from red and white muscle of fish acclimated to different 25 degrees C, 18 degrees C or 8 degrees C and carrying out Northern analysis using the gene fragment as the probe. The time course for the expression of this gene when carp maintained at a low temperature were acclimated to a warm temperature was slightly in advance of the change in myofibrillar ATPase which suggested that this strategy for adaptation is regulated at the transcriptional level. Hence these species of fish can adapt to seasonal changes in temperature by expressing different myosin heavy chain isoform genes and rebuilding their myofibrils for either warm or cold temperature swimming. At the present time we are characterising the 5' regulatory (promoter) sequence of this gene to see how a temperature switch may operate.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗