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Climate change is imposing multiple stressors on marine life, leading to a restructuring of ecological communities as species exhibit differential sensitivities to these stressors. With the ocean warming and wind patterns shifting, processes that drive thermal variations in coastal regions, such as marine heatwaves and upwelling events, can change in frequency, timing, duration, and severity. These changes in environmental parameters can physiologically impact organisms residing in these habitats. Here, we investigate the synchrony of coral and reef fish responses to environmental disturbance in the Red Sea, including an unprecedented combination of heat stress and upwelling that led to mass coral bleaching in 2015. We developed cross-dated growth chronologies from otoliths of 156 individuals of two planktivorous damselfish species, Pomacentrus sulfureus and Amblyglyphidodon flavilatus, and from skeletal cores of 48 Porites spp. coral colonies. During and immediately after the 2015 upwelling and bleaching event, damselfishes exhibited a positive growth anomaly but corals displayed reduced growth. Yet, after 2015–2016, these patterns were reversed with damselfishes showing a decline in growth and corals rebounding to pre-disturbance growth rates. Our results reveal an asynchronous response between corals and reef fish, with corals succumbing to the direct effects of heat stress, and then quickly recovering when the heat stress subsided—at least, for those corals that survived the bleaching event. Conversely, damselfish growth temporarily benefited from the events of 2015, potentially due to the increased metabolic demand from increased temperature and increased food supply from the upwelling event, before declining over four years, possibly related to indirect effects associated with habitat degradation following coral mortality. Overall, our study highlights the increasingly complex, often asynchronous, ecological ramifications of climate extremes on the diverse species assemblages of coral reefs. [ABSTRACT FROM AUTHOR]

Rising temperatures and extreme climate events are propelling tropical species into temperate marine ecosystems, but not all species can persist. Here, we used the heatwave-driven expatriation of tropical Black Rabbitfish (Siganus fuscescens) to the temperate environments of Western Australia to assess the ecological and evolutionary mechanisms that may entail their persistence. Population genomic assays for this rabbitfish indicated little genetic differentiation between tropical residents and vagrants to temperate environments due to high migration rates, which were likely enhanced by the marine heatwave. DNA metabarcoding revealed a diverse diet for this species based on phytoplankton and algae, as well as an ability to feed on regional resources, including kelp. Irrespective of future climate scenarios, these macroalgae-consuming vagrants may self-recruit in temperate environments and further expand their geographic range by the year 2100. This expansion may compromise the health of the kelp forests that form Australia's Great Southern Reef. Overall, our study demonstrates that projected favourable climate conditions, continued large-scale genetic connectivity between populations, and diet versatility are key for tropical range-shifting fish to establish in temperate ecosystems. Laura Gajdzik et al. used population genomics, dietary DNA metabarcoding, and climate models to understand the influence of the 2010/2011 marine heatwave on the migration of rabbitfish from tropical environments into temperate environments in Western Australia. Their results reveal (i) little genetic differentiation and high migration rates between tropical residents and temperate vagrants, (ii) an overall diverse diet (including phytoplankton, local and widespread algae, and kelp), and (iii) projected suitable climate conditions for vagrants to establish in temperate marine waters. [ABSTRACT FROM AUTHOR]

Intensified coastal development is compromising the health and functioning of marine ecosystems. A key example of this is the Red Sea, a biodiversity hotspot subjected to increasing local human pressures. While some marine‐protected areas (MPAs) were placed to alleviate these stressors, it is unclear whether these MPAs are managed or enforced, thus providing limited protection. Yet, most importantly, MPAs in the Red Sea were not designed using climate considerations, likely diminishing their effectiveness against global stressors. Here, we propose to tailor the design of MPAs in the Red Sea by integrating approaches to enhance climate change mitigation and adaptation. First, including coral bleaching susceptibility could produce a more resilient network of MPAs by safeguarding reefs from different thermal regions that vary in spatiotemporal bleaching responses, reducing the risk that all protected reefs will bleach simultaneously. Second, preserving the basin‐wide genetic connectivity patterns that are assisted by mesoscale eddies could further ensure recovery of sensitive populations and maintain species potential to adapt to environmental changes. Finally, protecting mangrove forests in the northern and southern Red Sea that act as major carbon sinks could help offset greenhouse gas emissions. If implemented with multinational cooperation and concerted effort among stakeholders, our portfolio of climate‐tailored approaches may help build a network of MPAs in the Red Sea that protects more effectively its coastal resources against escalating coastal development and climate instability. Beyond the Red Sea, we anticipate this study to serve as an example of how to improve the utility of tropical MPAs as climate‐informed conservation tools. [ABSTRACT FROM AUTHOR]

The article discusses that how nutrient-supplying ocean currents modulate coral bleaching susceptibility. It mentions that incorporating nutrient-supplying ocean currents and their variability into coral bleaching forecasts will be critical for effectively guiding efforts to safeguard the reefs most likely to persist in the Anthropocene.

A core eco‐evolutionary aim is to better understand the factors driving the diversification of functions in ecosystems. Using phylogenetic, trophic, and functional information, we tested whether trophic habits (i.e. feeding guilds) affect lineage and functional diversification in two major radiations of reef fishes. Our results from wrasses (Labridae) and damselfishes (Pomacentridae) do not fully support the 'dead‐end' hypothesis that specialisation leads to reduce speciation rates because the tempo of lineage diversification did not substantially vary among guilds in both fish families. Our findings also demonstrate a tight relationship between trophic habits and functional roles held by fish in reef ecosystems, which is not associated with a variation in the tempo of functional diversification among guilds. By illustrating the pivotal importance of the generalist feeding strategy during the evolutionary history of reef fishes, our study emphasises the role of this feeding guild as a reservoir for future diversity. [ABSTRACT FROM AUTHOR]

Genetic diversity is essential for species persistence because it provides the raw material for evolution. For marine organisms, short pelagic larval duration (PLD) and small population size are characteristics generally assumed to associate with low genetic diversity. The ecological diversity of organisms may also affect genetic diversity with an expected corollary that more restricted habitat and dietary requirements could lead to a reduced genetic diversity because of pronounced genetic structuring. Here, we tested whether groups of species with narrower trophic niches displayed lower genetic diversity than those with broader niches. In order to test those predictions, we used different trophic guilds (i.e., groups of species having similar trophic habits) of coral reef damselfishes in Moorea (French Polynesia) for which we determined their genetic diversity using restriction site‐associated DNA sequencing (RADseq) and their trophic ecology with stomach contents and stable isotope data. We found that pelagic feeders‐ the guild picking zooplankton in the water column‐ exhibited the lowest genetic diversity despite having the longest PLD and the largest population size. This guild had also the lowest variation in habitat characteristics and dietary composition compared to benthic feeders (i.e., those mainly grazing on algae) and the intermediate group (i.e., those feeding on zooplankton, filamentous algae and small benthic invertebrates). Our findings highlight the association between trophic ecology and genetic diversity that should be more commonly investigated in population genetics. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the forces that influence the dynamics of communities is a key challenge to undertake in changing environments. Despite recent advances in coral reef community ecology, a more comprehensive knowledge about processes (niche‐related traits and phylogenies) driving the composition of reef fish community is needed. Here, we conducted a quantitative comparison of these processes in damselfish assemblages that belong to three distinct Indo‐Pacific coral reefs differing in taxonomic composition, morphology and degree of human disturbance. We compiled a dataset of eight categorical variables to estimate functional diversity of damselfish assemblages and a second one of stable isotope ratios to evaluate isotopic diversity, a proxy of trophic diversity. Both datasets represent the eco‐functional diversity and provide insights into niche‐related traits. Indices were then computed to grasp complementary facets of this diversity: the size of multidimensional space (richness), the partitioning of niches (divergence) and the regularity in the distribution of niches (evenness) within each space. We also tested whether functional and trophic traits displayed some evolutionary niche conservatism. We found that functional richness was influenced by the number of species and functional entities (unique combination of trait values), and that the portions of the functional spaces filled by assemblages mainly overlapped. Functional divergence and evenness indices were similarly high. For trophic diversity, the isotopic richness remained equivalent, while the two other indices were of high values and did not significantly differ. Both functional and trophic traits did not display any phylogenetic conservatism. We demonstrated consistent levels of eco‐functional diversity in Indo‐Pacific coral reef damselfishes. Each assemblage hosted species whose niches were highly differentiated and evenly distributed in eco‐functional spaces of similar sizes, albeit the extent of functional space varied with the species richness. Assemblages also tended to share similar functional attributes. The inconsistent phylogenetic structures of eco‐functional traits and the similarity in diversity indices suggest that the assemblage composition of damselfishes is mainly driven by niche‐related processes rather than by phylogenetic relatedness. Our work helps to determine which mechanisms shape coral reef fish biodiversity and more particularly assemblages issued from replicated events of ecological radiation. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

The cerato-mandibular (c-md) ligament is a synapomorphy within Pomacentridae that creates a tight link between the lower jaws and the hyoid bars. However, this morphological trait has been secondarily lost in multiple lineages during evolution. A previous study revealed that the loss of this trait acted as a release of evolutionary constraints, leading to a cascade of morphological changes such elongated buccal jaws and a slender body. Ecomorphological interpretations suggested the loss of the c-md ligament has ultimately led to a new adaptive peak in zooplanktivory through an optimization of the ram feeding mode associated with a specialization in pelagic feeding. Here, we tested these hypotheses by comparing functional and diet diversity between damselfish species with and without the c-md ligament. Although species lacking the c-md ligament presented a conserved kinematic pattern resulting from high ram and low suction performances, our results did not support an optimization of the ram feeding mode. Indeed, some species with the c-md ligament showed the same or exceeded the ram performance of species without the c-md ligament. The species with the c-md ligament had a more diverse kinematic pattern exploring the entire ram-suction functional range in damselfishes. Finally, our results did not show any diet variations associated with the loss of the c-md ligament. Our study furthers the understanding of how a morphological trait has shaped, by its presence or absence, the ecomorpho-functional diversification of Pomacentridae. [ABSTRACT FROM AUTHOR]

Conspicuous characters are often useful in species identification. Yet, identification and delineation are two different processes, and such characters do not necessarily provide the best basis on which species can be delineated. This is illustrated by the case of the Labeo with papillary lips from the Congo basin. Traditionally, species delineation in this group was based on a conspicuous trait: the shape of the dorsal fin, which shows a profound degree of differentiation. Morphometric analyses were performed on 185 specimens both with and without measurements taken on this fin. The groups obtained using these two approaches were compared with those obtained through DNA barcoding. For this, 24 sequences of the standard barcoding COI gene were obtained. Species delineations based on morphological and molecular results were in agreement when the shape of the dorsal fin was ignored. This suggested that of the five nominal species known from the Congo basin, L. altivelis, L. rosae, L. lineatus, L. weeksii and L. maleboensis, only the former three remain valid. Consequently, L. weeksii was synonymised with L. altivelis and L. maleboensis with L. lineatus. The sole Congo basin endemic is L. lineatus as L. altivelis and L. rosae also occur in more southern basins. The use of the shape of the dorsal fin in morphological studies has previously led to overestimates of species diversity in this group. This is due to the fact that L. altivelis shows a remarkable amount of geographical variation for this trait. The large amount of intra- and interspecific variation in this character was caused by differential allometric growth in different parts of the dorsal fin. [ABSTRACT FROM AUTHOR]

Humans alter ecosystems through both consumptive and non-consumptive effects. Consumptive effects occur through hunting, fishing and collecting, while non-consumptive effects occur due to the responses of wildlife to human presence. While marine conservation efforts have focused on reducing consumptive effects, managing human presence is also necessary to maintain and restore healthy ecosystems. Area closures and the tourism freeze related to the COVID-19 pandemic provided a unique natural experiment to measure the effects of decreased tourism on fish behavior in a high use no-take marine protected area (MPA) in Hawai'i. We found that when tourism shut down due to COVID restrictions in 2020, fish biomass increased and predatory species increased usage of shallow habitats, where tourists typically concentrate. When tourism resumed, fish biomass and habitat use returned to pre-pandemic levels. These displacement effects change fish community composition and biomass, which could affect key processes such as spawning, foraging and resting, and have knock-on effects that compromise ecosystem function and resilience. Managing non-consumptive uses, especially in heavily-visited MPAs, should be considered for sustainability of these ecosystems. [ABSTRACT FROM AUTHOR]

Reef-building corals typically live close to the upper limits of their thermal tolerance and even small increases in summer water temperatures can lead to bleaching and mortality. Projections of coral reef futures based on forecasts of ocean temperatures indicate that by the end of this century, corals will experience their current thermal thresholds annually, which would lead to the widespread devastation of coral reef ecosystems. Here, we use skeletal cores of long-lived Porites corals collected from 14 reefs across the northern Great Barrier Reef, the Coral Sea, and New Caledonia to evaluate changes in their sensitivity to heat stress since 1815. High-density 'stress bands'--indicative of past bleaching--first appear during a strong pre-industrial El Nin? o event in 1877 but become significantly more frequent in the late twentieth and early twenty-first centuries in accordance with rising temperatures from anthropogenic global warming. However, the proportion of cores with stress bands declines following successive bleaching events in the twenty-first century despite increasing exposure to heat stress. Our findings demonstrate an increase in the thermal tolerance of reef-building corals and offer a glimmer of hope that at least some coral species can acclimatize fast enough to keep pace with global warming. [ABSTRACT FROM AUTHOR]

Herbivore management is an important tool for resilience-based approaches to coral reef conservation, and evidence-based science is needed to enact successful management. We synthesized data from multiple monitoring programs in Hawai'i to measure herbivore biomass and benthic condition over a 10-year period preceding any major coral bleaching. We analysed data from 20 242 transects alongside data on 27 biophysical and human drivers and found herbivore biomass was highly variable throughout Hawai'i, with high values in remote locations and the lowest values near population centres. Both human and biophysical drivers explained variation in herbivore biomass, and among the human drivers both fishing and land-based pollution had negative effects on biomass. We also found evidence that herbivore functional group biomass is strongly linked to benthic condition, and that benthic condition is sensitive to changes in herbivore biomass associated with fishing. We show that when herbivore biomass is below 80% of potential biomass, benthic condition is predicted to decline. We also show that a range of management actions, including area-specific fisheries regulations and gear restrictions, can increase parrotfish biomass. Together, these results provide lines of evidence to support managing herbivores as an effective strategy for maintaining or bolstering reef resilience in a changing climate. [ABSTRACT FROM AUTHOR]

Ocean acidification poses a serious threat to marine calcifying organisms, yet experimental and field studies have found highly diverse responses among species and environments. Our understanding of the underlying drivers of differential responses to ocean acidification is currently limited by difficulties in directly observing and quantifying the mechanisms of bio‐calcification. Here, we present Raman spectroscopy techniques for characterizing the skeletal mineralogy and calcifying fluid chemistry of marine calcifying organisms such as corals, coralline algae, foraminifera, and fish (carbonate otoliths). First, our in vivo Raman technique is the ideal tool for investigating non‐classical mineralization pathways. This includes calcification by amorphous particle attachment, which has recently been controversially suggested as a mechanism by which corals resist the negative effects of ocean acidification. Second, high‐resolution ex vivo Raman mapping reveals complex banding structures in the mineralogy of marine calcifiers, and provides a tool to quantify calcification responses to environmental variability on various timescales from days to years. We describe the new insights into marine bio‐calcification that our techniques have already uncovered, and we consider the wide range of questions regarding calcifier responses to global change that can now be proposed and addressed with these new Raman spectroscopy tools. [ABSTRACT FROM AUTHOR]

Molecular-based approaches can provide timely biodiversity assessments, showing an immense potential to facilitate decision-making in marine environmental management. However, the uptake of molecular data into environmental policy remains minimal. Here, we showcase a selection of local to global scale studies applying molecular-based methodologies for environmental management at various stages of implementation. Drawing upon lessons learned from these case-studies, we provide a roadmap to facilitate applications of DNA-based methods to marine policies and to overcome the existing challenges. The main impediment identified is the need for standardized protocols to guarantee data comparison across spatial and temporal scales. Adoption of Translational Molecular Ecology – the sustained collaboration between molecular ecologists and stakeholders, will enhance consensus with regards to the objectives, methods, and outcomes of environmental management projects. Establishing a sustained dialogue among stakeholders is key to accelerating the adoption of molecular-based approaches for marine monitoring and assessment. Unlabelled Image • The adoption of DNA-based methods by marine environmental agencies remains limited. • Defining scope and possibilities ensures realistic DNA-based management applications. • Sustained dialogue among stakeholders is often critical to success. • Collaborative working will foster the uptake of DNA methods in marine policies. • Several case studies confirm the value of Translational Molecular Ecology to achieve policy impact. [ABSTRACT FROM AUTHOR]