Marco Fusi

Understanding how marine invertebrates respond to multiple environmental stressors is essential for predicting the impacts of global change on ocean biodiversity. While numerous experimental studies have investigated individual stressors, the combined effects of ocean acidification (OA), warming (OW), cooling (OC), deoxygenation (OD), hypersalinity (HES), and hyposalinity (HIS) remain poorly quantified. We conducted a systematic review and meta-analysis of 215 experimental studies, synthesizing 8,872 biological responses across ten marine invertebrate phyla and five life history stages. Our results reveal that responses to global change drivers are highly variable and frequently non-additive, with synergistic and antagonistic interactions depending on stressor combinations, taxa, and life stages. Notably, OA and OW were the most studied drivers, highlighting a strong publication bias that limits broader ecological generalizations. While some combined drivers, such as OW × OA, consistently induced synergistic effects, others (e.g., OW × HES) displayed antagonistic interactions, suggesting the presence of adaptive mechanisms including cross-protection. This review contribute to highlight two fundamental research gaps. Firstly the need to consistenly adopt a multistressors approach in assessing species tolerance. Secondly and more importantly, the overwhelming reliance on fixed exposure regimes, rather than fluctuating or dynamic treatments is needed to better reflect natural environmental variability. Our synthesis provides a robust empirical foundation for evaluating how multiple drivers jointly affect marine invertebrates and generates mechanistic hypotheses for future testing. To improve ecological forecasting and conservation strategies, future research should prioritize underrepresented stressor combinations, early life stages, and integrative approaches that link physiological, behavioral, and molecular responses. Such efforts will enhance our understanding of tolerance mechanisms and resilience across biological scales, ultimately supporting more accurate predictions of marine biodiversity responses in a rapidly changing ocean.

Microbial communities in mangrove sediments are critical for carbon and nutrient cycling; yet despite their importance, responses to eutrophication—a pervasive global threat to coastal ecosystems—remain poorly understood. Here, we tested whether nutrient enrichment restructures mangrove sediment bacterial communities more strongly in the subsurface than at the sediment surface. We assessed bacterial community responses to an in-situ slow-release NPK (Osmocote®) enrichment experiment in a temperate mangrove (Avicennia marina subsp. australasica) forest in Aotearoa New Zealand. Using 16S rRNA gene sequencing, we compared surface (0–2 cm) and subsurface (5–7 cm) community diversity and functional potential, 4.5 months after enrichment. Differences in porewater nutrient concentrations between ambient and enriched plots were subtle and spatially heterogeneous; however, bacterial communities exhibited significant shifts relative to controls. Community shifts in subsurface samples were stronger compared to the surface, with enrichment reducing diversity and altering community composition to Proteobacteria and Bacteroidota favoured communities. Conversely, taxa from Desulfobacterota, Chloroflexi, and Nitrospirota were more abundant in controls. Similarly, shifts in inferred functional potential in the surface remained limited, while the subsurface showed strong, selective changes: a proportional decline of sulphur-cycling and hydrogen-oxidizing taxa and a relative increase of heterotrophic guilds. Community assembly was more deterministic in subsurface compared to surface sediments, and under nutrient addition subsurface assembly shifted, mainly through reduced dispersal limitation, to more closely resemble the surface communities. These results underscore the need to better understand and integrate microbial responses at relevant spatial scales into predictions of ecosystem resilience under increasing anthropogenic pressures.

The sediments in mangrove forests play an important role in the global carbon cycle due to high inputs of organic matter (OM) and low decomposition rates, making them highly efficient at sequestering carbon. The balance between OM sequestration and decomposition in these systems is influenced by a complex interplay of environmental factors. However, there is a large amount of uncertainty surrounding decomposition rates from mangrove forests, particularly at regional scales. We used standardized decomposition assays of a labile and recalcitrant substrate in 30 estuaries, spanning a gradient in human land use intensity, to identify dominant drivers of OM decomposition in temperate mangrove forests. Our results reveal that, while labile OM decomposition is strongly driven by eutrophication, recalcitrant OM decomposition is primarily influenced by increases in the minimum sediment temperature. Furthermore, we demonstrate that nutrient enrichment from human land use, in combination with increased sediment temperature, synergistically accelerates the decomposition of labile OM, thereby threatening the carbon sequestration potential of these ecosystems. This suggests that coastal eutrophication can exacerbate the effects of warming on decomposition, leading to heightened vulnerability of carbon storage and potential feedbacks between local and global stressors.

Two bacteria, UG2_1T and UG2_2, were isolated from the gill tissues of the mangrove fiddler crab Cranuca inversa collected on the east coast of the Red Sea (Thuwal, Saudi Arabia). The cells are Gram-negative, rod-shaped, orange-pigmented, motile by gliding with no flagella, strictly aerobic, and grow at 20–37 °C (optimum, 28–35 °C), at pH 5.0–9.0 (optimum, pH 6.0–7.0), and with 1–11 % (w/v) NaCl (optimum, 2–4 %). They were positive for oxidase and catalase activity. Phylogenetic analysis based on 16S rRNA gene sequences indicated that isolates UG2_1T and UG2_2 belong to the genus Mangrovimonas, showing the highest similarity to Mangrovimonas spongiae HN-E26T (99.4 %). Phylogenomic analysis based on the whole genomes, independently using 49 and 120 concatenated genes, showed that strains UG2_1T and UG2_2 formed a monophyletic lineage in a different cluster from other type strain species within the genus Mangrovimonas. The genome sizes were 3.08 and 3.07 Mbp for UG2_1T and UG2_2, respectively, with a G+C content of 33.8 mol% for both strains. Values of average nucleotide identity and digital DNA–DNA hybridization between the strains and closely related species were 91.0 and 43.5 %, respectively. Chemotaxonomic analysis indicated that both strains had iso-C15 : 0 and iso-C15 : 1 G as dominant fatty acids, and the primary respiratory quinone was identified as MK-6. The major polar lipids comprised phosphatidylethanolamine, one unidentified glycolipid, one unidentified phospholipid, two unidentified aminolipids, and four unidentified lipids. Based on phylogenetic, phylogenomic, genome relatedness, phenotypic, and chemotaxonomical data, the two isolates represent a novel species within the genus Mangrovimonas, with the proposed name Mangrovimonas cancribranchiae sp. nov., and the type strain UG2_1T (=KCTC 102158T=DSM 117025T).

Background: The transition from water to air is a key event in the evolution of many marine organisms to access new food sources, escape water hypoxia, and exploit the higher and temperature-independent oxygen concentration of air. Despite the importance of microorganisms in host adaptation, their contribution to overcoming the challenges posed by the lifestyle changes from water to land is not well understood. To address this, we examined how microbial association with a key multifunctional organ, the gill, is involved in the intertidal adaptation of fiddler crabs, a dual-breathing organism. Results: Electron microscopy revealed a rod-shaped bacterial layer tightly connected to the gill lamellae of the five crab species sampled across a latitudinal gradient from the central Red Sea to the southern Indian Ocean. The gill bacterial community diversity assessed with 16S rRNA gene amplicon sequencing was consistently low across crab species, and the same actinobacterial group, namely Ilumatobacter, was dominant regardless of the geographic location of the host. Using metagenomics and metatranscriptomics, we detected that these members of actinobacteria are potentially able to convert ammonia to amino acids and may help eliminate toxic sulphur compounds and carbon monoxide to which crabs are constantly exposed. Conclusions: These results indicate that bacteria selected on gills can play a role in the adaptation of animals in dynamic intertidal ecosystems. Hence, this relationship is likely to be important in the ecological and evolutionary processes of the transition from water to air and deserves further attention, including the ontogenetic onset of this association.

Oxygen availability is a pivotal factor for ecosystem functioning and the resistance of organisms to the effect of climate change in aquatic habitats. Although extensive work has been done to assess the effect of oxygen on marine and freshwater biota, many studies have not captured the ecological importance of oxygen variations. Overlooking the fluctuating nature of oxygen may cause potential biases in the design and implementation of management policies for aquatic habitats. Conceptual perspectives on the dynamic nature of oxygen fluctuations have been raised in the scientific community in order to enhance the understanding of the effect of oxygen on the physiology and the ecology of aquatic species as well as the biogeochemical functioning of their ecosystems. A growing number of empirical work has been outlining a novel conceptual framework that considers the magnitude of oxygen fluctuation as a key variable that explains adaptation to stress conditions. Oxygen in productive aquatic habitats shows large fluctuations at the diel scale, exposing aquatic species to conditions ranging from extreme supersaturation to anoxia. Recent research has indicated that such a fluctuation tunes the physiological plasticity of the animal in response to thermal stresses. In this paper, we provide compelling evidence based on current research that the fluctuating oxygen landscape, here defined as “oxyscape”, has an important role in aquatic animal physiology and adaptation as well as the ecosystem biogeochemistry. We propose that the oxyscape should be considered in the modelling and managing policies of aquatic ecosystems.

Salt marshes occur globally across climatic and coastal settings, providing key linkages between terrestrial and marine ecosystems. However, salt marsh science lacks a unifying conceptual framework; consequently, historically well‐studied locations have been used as normative benchmarks. To allow for more effective comparisons across the diversity of salt marshes, we developed an integrative salt marsh conceptual framework. We review ecosystem‐relevant drivers from global to local spatial scales, integrate these multi‐scale settings into a framework, and provide guidance on applying the framework using specific variables on 11 global examples. Overall, this framework allows for appropriate comparison of study sites by accounting for global, coastal, inter‐, and intra‐system spatial settings unique to each salt marsh. We anticipate that incorporating this framework into salt marsh science will provide a mechanism to critically evaluate research questions and a foundation for effective quantitative studies that deepen our understanding of salt marsh function across spatial scales.