Coastal benthic ecosystems are shaped by the combined effects of climate change and anthropogenic pressures. Ocean warming, acidification, and deoxygenation interact with eutrophication, pollution, bottom trawling, and coastal development, altering biodiversity, habitat structure, and functioning from shallow coasts to continental margins. Benthic communities, comprising infaunal and epifaunal taxa, regulate key processes including nutrient cycling, sediment dynamics, and carbon burial, thereby underpinning benthic-pelagic coupling and biogeochemical dynamics. Rising temperatures and marine heatwaves drive widespread losses of habitat-forming species, while ocean acidification constrains calcification. Warming, acidification, hypoxia, eutrophication, and pollution increasingly simplify assemblages, and alter trophic pathways and performance. Interactions among stressors can amplify organismal sensitivity and push ecosystems towards ecological thresholds. However, many knowledge gaps remain. Recent methodological advances, including environmental DNA metabarcoding, automated imaging, trait-based analyses, and multi-stressor experiments, are improving the detection of ecosystem changes at large and our mechanistic understanding of ecosystem responses to ongoing change. By summarizing the various stressors that benthic habitats and taxa face, their interactions and potential outlooks, this review provides a concise synthesis of current understanding and identifies key knowledge gaps for future research and management under accelerating climate change.
Perforated semicircular submerged breakwaters can attenuate incident waves while allowing water exchange, making them suitable for coastal protection and marine infrastructure. Their hydraulic performance is often assessed using physical models based on Froude similarity, for which Reynolds similarity cannot be preserved. Extrapolating wave loads from reduced models to prototype conditions may therefore introduce bias. To quantify this effect, a validated numerical wave flume was used to examine six geometric scale ratios (λ L = 1, 5, 10, 15, 25, and 35), four perforation rates (ϵ = 0–15%), and five wave conditions. Validation used measurements from physical model experiments and field pressures obtained at prototype scale. Comparisons considered horizontal force coefficients, free surface elevations, velocity fields, and vorticity fields. Smaller models increasingly overestimated the shoreward peak force. At λ L = 35 and ϵ = 10%, the mean model to prototype ratio of the shoreward peak force coefficient reached 1.23. The differences between model and prototype responses were mainly associated with changes in wave transmission, reverse flow, and vortical motion over and behind the structure as scale decreased. These findings improve the interpretation of reduced model results and support more reliable prototype extrapolation of wave loads on perforated submerged structures.
Bradley Arrington, Lindsay Dade, Deborah J. Gochfeld, Julie Beth Olson, Raphael Ritson-Williams, Erin Hollander, Tyler Burton Smith, Marilyn E. Brandt
Caribbean coral reefs have declined severely under cumulative stressors including hurricanes, thermal anomalies, disease outbreaks, and local anthropogenic impacts. In early 2019, stony coral tissue loss disease (SCTLD) emerged in the northern U.S. Virgin Islands (USVI), followed later that year by anomalously high temperatures and mass bleaching across the territory, providing an opportunity to assess the resilience of recruitment to acute disturbance. This study quantified recruitment at three shallow reef sites (7–14 m) in St. Thomas from 2019–2022 and compared results with pre-disturbance data (2015–2017). Recruitment tiles (15 × 15 cm) were deployed across eight time periods and photographed to determine recruit density and taxonomic identity. Bleaching and disease prevalence were calculated from coral health assessments along six 10-m transects as part of the Territorial Coral Reef Monitoring Program. All recruits observed were Agaricia spp. Recruitment rates in 2019 and 2020, following these disturbances, declined by an order of magnitude relative to pre-disturbance surveys. Because the six environmental predictors vary to differing degrees among versus within sites, their correlations with recruitment were decomposed into between-site and within-site components. Coral cover and Agaricia spp. abundance varied predominantly among sites (86.9% and 51.9% of variance between sites, respectively); their apparent positive associations with recruitment reflected differences among three site means rather than temporal variation within sites, and neither persisted once site means were removed. In contrast, Degree Heating Weeks (DHW) and combined bleaching and paling prevalence varied almost entirely within sites (8.7% and 1.3% between-site variance), and both showed marginal negative within-site relationships with recruitment (DHW: r = -0.43, p = 0.054; bleaching/paling: r = -0.41, p = 0.064). Thermal stress was therefore the only environmental variable with a detectable within-site signal, consistent with the temporal concordance between the 2019 disturbance and recruitment collapse. By 2021–2022, recruitment rebounded toward pre-disturbance levels at most sites, indicating recovery of recruitment potential within approximately two years. These findings demonstrate the sensitivity of Agaricia spp. recruitment to disturbance and underscore monitoring recruitment as a key indicator of reef resilience, as continued thermal stress and persistent disease threaten the natural recovery capacity of Caribbean reefs.
Coastal upwelling is a key dynamical process along the southeastern coast of China, regulating regional circulation, biogeochemical cycling, and marine ecosystem dynamics. While previous studies have provided valuable insights into the mechanisms and variability of this coastal upwelling, its future evolution and underlying physical drivers under climate change remain unclear. Here, we investigate projected changes in coastal upwelling along the southeastern coast of China during 2006–2100 using a high-resolution (0.1°) coupled-model realization under the Representative Concentration Pathway 8.5 scenario. During 2006–2100, the area-weighted mean oceanic vertical velocity at 30 m increases at 0.755 m day -1 century -1, while the upwelling area increases at 1.822 × 10³ km² century -1. The trend in the total upwelling volume transport is approximately 0.27 Sv century -1. Enhanced Ekman transport makes the largest contribution (0.26 Sv century -1), accompanied by a geostrophic-transport trend of 0.07 Sv century -1. Marine heatwave (MHW) metrics based on local linear detrended SST are generally lower at the selected coastal sites than at offshore sites, with an 18.3% reduction in MHW days, a 33.2% reduction in mean annual duration, and a 2.4% reduction in mean cumulative intensity. These coastal–offshore contrasts are to some extent consistent with a potential moderating influence of upwelling on MHWs, though rigorous attribution and mechanistic analyses of this effect remain open for dedicated future investigations. This study can advance our understanding of ocean dynamics along the southeastern coast of China under future climate change.
