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Most marine organisms present an indirect lifecycle where a planktonic larval stage reaches competency before settling to the substrate and metamorphosing. Despite the critical importance of these early life history stages, little is known about how global change-related stressors, in particular ocean acidification (OA), affect marine larval settlement and metamorphosis. To date, 48 studies have investigated the effects of OA on larval settlement, focussing mostly on tropical corals (16), echinoderms (11) and fish (8). Most studies show negative effects of OA during settlement and post-settlement processes. For instance, reduced settlement is typically seen along natural pH gradients and in experimentally lowered pH treatments. This generally results in reduced settlement selectivity and metamorphosis and poorer post-settlement fitness. Carryover effects of OA exposure can also occur, with larval environmental history influencing early post-settlement performance. We conclude that OA may (1) alter larval supply for settlement by altering horizontal swimming behaviour or vertical migration; (2) directly influence settlement success through changes in the nature and distribution of suitable settlement substrates (e.g. biofilm, crustose coralline algae); and (3) mediate carryover effects at settlement by altering larval development or larval energy budgets. In contrast to fish larvae, there is little evidence for most invertebrate larvae that their perception of settlement cues is directly influenced by reduced pH. A summation of how OA affects the settlement and metamorphosis of marine invertebrates is timely, since altered settlement rates will influence the future distributions, abundances and ecology of marine benthic communities.

Successful settlement and recruitment of reef fish are influenced by spatial and temporal processes and variables on distinct scales. Moreover, they require survival at various stages in different environments for species with a complex life cycle, as in the case of most reef fish. The variability in those processes can be explained by biotic and abiotic factors that affect pre and postsettlement stages. Despite the many benefits of marine protected areas (MPAs) for fish and fisheries, the positive effects of protected areas on the reproduction, settlement, and recruitment of reef fish are still unclear. The present study reviewed the biotic and abiotic factors that influence the settlement and recruitment of reef fish, especially regarding the role of MPAs in these processes. This bibliographic review shows that the larval settlement is shaped by the interaction of biological traits (e.g., life history) and environmental factors (e.g., temperature, currents), which are determinants of the life cycle and population structure of reef fish. The main contribution of MPAs to these processes is the export of eggs and larvae to adjacent regions. However, further research is needed on the issues of settlement and recruitment in the specific context of MPAs. The absence of studies on this topic, particularly how protection affects, directly and indirectly, recruitment variability and how this is reflected in the adult population, hinders MPAs objectives and seems to be a serious shortcoming in attempts to support future populations at ecologically adequate levels.

Ocean acidification (OA) is a major threat to marine calcifying organisms. This manuscript gives an overview of the physiological effects of acidification on reef-building corals from a cellular to population scale. In addition, we present the first review of the indirect effects resulting from altered species interactions. We find that the direct effects of acidification are more consistently negative at larger spatial scales, suggesting an accumulation of sub-lethal physiological effects can result in notable changes at a population and an ecosystem level. We identify that the indirect effects of acidification also have the potential to contribute to declines in coral cover under future acidified conditions. Of particular concern for reef persistence are declines in the abundance of crustose coralline algae which can result in loss of stable substrate and settlement cues for corals, potentially compounding the direct negative effects on coral recruitment rates. In addition, an increase in the abundance of bioeroders and bioerosive capacity may compound declines in calcification and result in a shift towards net dissolution. There are significant knowledge gaps around many indirect effects, including changes in herbivory and associated coral–macroalgal interactions, and changes in habitat provision of corals to fish, invertebrates and plankton, and the impact of changes to these interactions for both individual corals and reef biodiversity as structural complexity declines. This research highlights the potential of indirect effects to contribute to alterations in reef ecosystem functions and processes. Such knowledge will be critical for scaling-up the impacts of OA from individual corals to reef ecosystems and for understanding the effects of OA on reef-dependent human societies.

Microbial biofilms are biological structures composed of surface-attached microbial communities embedded in an extracellular polymeric matrix. In aquatic environments, the microbial colonization of submerged surfaces is a complex process involving several factors, related to both environmental conditions and to the physical-chemical nature of the substrates. Several studies have addressed this issue; however, more research is still needed on microbial biofilms in marine ecosystems. After a brief report on environmental drivers of biofilm formation, this study reviews current knowledge of microbial community attached to artificial substrates, as obtained by experiments performed on several material types deployed in temperate and extreme polar marine ecosystems. Depending on the substrate, different microbial communities were found, sometimes highlighting the occurrence of species-specificity. Future research challenges and concluding remarks are also considered. Emphasis is given to future perspectives in biofilm studies and their potential applications, related to biofouling prevention (such as cell-to-cell communication by quorum sensing or improved knowledge of drivers/signals affecting biological settlement) as well as to the potential use of microbial biofilms as sentinels of environmental changes and new candidates for bioremediation purposes.

Marine biofouling, caused by the deposition and accumulation of marine organisms on submerged surfaces, represents a huge concern for the maritime industries and also contributes to environmental pollution and health concerns. The most effective way to prevent this phenomenon is the use of biocide-based coatings which have proven to cause serious damage to marine ecosystems. Several research groups have focused on the search for new environmentally friendly antifoulants, including marine and terrestrial natural products and synthetic analogues. Some of these compounds have been incorporated into marine coatings and display interesting antifouling activities caused by the interference with the biofilm-forming species as well as by the inhibition of the settlement of macroorganisms. This review highlights the proof-of-concept studies of emerging natural or synthetic antifouling compounds in coatings, from lab-made to commercial ones, performed between 2019 and 2023 and their results in the field or in in vivo laboratorial tests.

The mechanisms that link reef soundscapes to larval fish settlement behaviors are poorly understood, yet the management of threatened reef communities requires we maintain the recruitment processes that recover and sustain populations. Using a field-calibrated sound propagation model, we predicted the transmission loss in the relevant frequency band as a function of range, depth, and azimuth to estimate the spatial heterogeneity in the acoustic cuescape. The model highlighted the frequency- and depth-dependence of the sound fields fishes may encounter, and we predict these complex spatial patterns influence how sounds function as settlement cues. Both modeling and field measurements supported a non-monotonic decline in amplitude with distance from the reef. We modeled acoustic fields created by sounds at frequencies from 2 common soniferous reef-based animals (snapping shrimps and toadfish) and estimated detection spaces of these sounds for larvae of 2 reef fish species. Results demonstrated that larval depth will influence cue availability and amplitude, and these spatial patterns of detection depend on cue frequency and the larval receiver’s auditory sensitivity. Estimated spatial scales of detection coupled with field measurements suggest cue amplitudes might allow some larvae to detect reef-based sounds at a range exposing them to the predicted spatial variation in the acoustic cuescape. In an individual-based model, cues available to even the shortest modeled distances improved settlement success. Our results emphasize the need to consider the frequency- and depth-dependence of the acoustic cues larval fishes encounter to increase understanding of the role of soundscapes in larval settlement.

Our perception of reef diversity is dominated by corals, fish, and a few other groups that visibly dominate the reef surface. However, the bulk of reef biodiversity resides within the reef framework, and this cryptobiota is fundamentally important for the surface community. Sponges are abundant and conspicuous on the reef surface in productive, continental reefs, but largely vanish from surveys of the oligotrophic reefs of Oceania. However, their diversity in the cryptobiota remains poorly characterized. Here, we explore the contribution of cryptobenthic sponges to overall sponge diversity on 1750 m2 of reef habitat in Kāneʻohe Bay and Waimanalo in the island of Oʻahu, Hawaiʻi. We also assessed cryptic sponges using 15 m2 of autonomous reef monitoring structures (ARMS) deployed in this same area. We used integrative taxonomy combining morphology, COI and 28S barcoding to delineate and track species, most of which are poorly known or undescribed. We documented 186 OTUs, 150 of which are new records for the Hawaiian Islands, increasing the known sponge fauna of Kāneʻohe Bay by 3.5-fold, and that of the Hawaiian Islands by 2.5-fold. More than ¾ of the sponge OTUs were cryptobenthic. Reef sampling provided access to 31% (44 OTUs), whereas 52% (75 OTUs) were retrieved exclusively from ARMS. These results illustrate that the interstices of ARMS units provide suitable habitat for settlement of cryptobenthic sponges that would otherwise be impossible to access through traditional field surveys. Tracking species with provisional names, using integrative species delineation anchored to vouchers, images, and DNA barcodes provides a powerful approach for working with such a poorly understood fauna.

The abundance and distribution of demersal fishes rely on larvae successfully settling from the pelagic environment to a benthic habitat and their subsequent survival. With high mortality rates during this life stage, settling to a habitat that maximizes survival is critical. However, relationships between settlement choices and subsequent survival are poorly understood and may vary among species with different habitat preferences. To test this, we focused on five congeneric ( Pomacentrus ) damselfish species that are known to differ in their habitat choices and explored whether habitat associations at settlement influenced survival. Newly settled individuals were tagged and monitored daily for two weeks to estimate natural mortality rates. Morphological attributes of fish and characteristics of settlement habitats, including depth, rugosity, benthic substrata, and local fish assemblages, were used to predict mortality. We found that some species displayed stronger associations with specific benthic substrata at settlement, but contrary to expectations, these selected habitat characteristics were relatively weak predictors of survivorship. Our survival analysis revealed that the best predictors of survivorship were rugosity ( P. adelus and P . amboinensis ) and two morphological traits, body depth and ocellus size ( P. chrysurus and P. adelus ). Interestingly, we found that P. moluccensis that settled in areas of high coverage of mounding coral experienced increased mortality. Of the remaining substrata, analysis showed that instead of associating with habitat characteristics enhancing survivorship, individuals tended not to associate with habitats characteristics that increased mortality (e.g., Turbinaria and sand). This study highlights the species-specific drivers of early post-settlement mortality in coral reef fishes.

The settlement phase of crustaceans is critical and can ultimately affect their population structure. Underwater sound has been proposed as one of the most important sensory cues used by these animals during this phase because it can provide direction and habitat quality information. Here, we evaluated the effect of different acoustic signals (biological and anthropo genic) on the orientation response of different stages (megalopae and juveniles) of 4 brachyuran crabs (Cyrtograpsus angulatus, C. altimanus, Neohelice granulata, Leptuca uruguayensis) from Mar Chiquita coastal lagoon in Argentina. A binary choice chamber system was used, and different sound sources (crus ta cean, fish and motorboat signals) selected from recordings of the lagoon soundscape were reproduced. C. angulatus megalopae and juveniles responded positively towards crusta cean signals, while juveniles responded negatively towards fish sounds. N. granulata juveniles orientated negatively towards crustacean, motorboat and fish signals. C. altimanus and L. uruguayensis juveniles did not respond to fish signals. The results support the idea that invertebrates can discriminate among conspecific signals and highlight the role of sound on prey–predator relationships. The behavioral orientation response to the motorboat sound evidences a presumably negative effect of anthropogenic sound on the biological interactions of species. This information is important, given the urgent need to increase knowledge about coastal marine lagoons to enhance their protection, especially considering the role of the key species of crabs in this habitat.

Land use/land cover (LU/LC) change has significant influence on runoff and sediment characteristics of any catchment. LU/LC change studies are essential for policy planners to understand the problems and take course of action such as soil and water conservation measures for improvement. The present study is conducted for Beressa watershed using hydrological model integrated with GIS. Input data like LU/LC, weather and soil data features are required to undertake watershed simulation. The model has been calibrated and validated in SWAT-CUP. The data from 1980 to 1999 were used for calibration, while the data from 2000 to 2014 were used for validation. LU/LC analysis showed that agricultural and settlement areas have increased between 1984 and 2015, while barren, grazing land and forest area have decreased. However, the share of forest cover increased in between 1999 and 2015. SWAT model has successfully simulated and calibrated runoff and sediment yield. During calibration periods (1980–1999), the values of R 2 , NSE, RSR and PBIAS were obtained as 0.72, 0.67, 0.52 and 3.9%, respectively, whereas during the validation periods (2000–2014) the values were 0.68, 0.64, 0.56 and 7.6%, respectively. Runoff and sediment yield has significantly increased. Thus, it is concluded that the change in LU/LC significantly influenced the runoff and sediment yield.