Article

Global biogeography of coral recruitment: tropical decline and subtropical increase

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Abstract

Despite widespread climate-driven r ductions of coral cover on tropical reefs, little attention has been paid to the possibility that changes in the geographic distribution of coral recruitment could facilitate beneficial responses to the changing climate through latitudinal range shifts. To address this possibility, we compiled a global database of normalized densities of coral recruits on settlement tiles (corals m −2 ) deployed from 1974 to 2012, and used the data therein to test for latitudinal range shifts in the distribution of coral recruits. In total, 92 studies provided 1253 records of coral recruitment, with 77% originating from settlement tiles immersed for 3−24 mo, herein defined as long-immersion tiles (LITs); the limited temporal and geographic coverage of data from short-immersion tiles (SITs; deployed for <3 mo) made them less suitable for the present purpose. The results from LITs show declines in coral recruitment, on a global scale (i.e. 82% from 1974 to 2012) and throughout the tropics (85% reduction at <20°latitude), and increases in the sub-tropics (78% increase at >20°latitude). These trends indicate that a global decline in coral recruitment has occurred since 1974, and the persistent reduction in the densities of recruits in equatorial latitudes, coupled with increased densities in sub-tropical latitudes, suggests that coral recruitment may be shifting poleward.

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... Patterns of coral recruitment are, however, increasingly altered by global environmental changes, threatening the resilience capacities of coral reefs (Hughes et al. 2019, Price et al. 2019, Edmunds & Riegl 2020, Guerrini et al. 2020. A recent synthesis has pointed out the global decline in coral recruitment since 1974, with decreasing rates in equatorial reefs but increasing densities at sub-tropical latitudes reflecting a poleward expansion in coral reef distribution (Price et al. 2019). ...
... Patterns of coral recruitment are, however, increasingly altered by global environmental changes, threatening the resilience capacities of coral reefs (Hughes et al. 2019, Price et al. 2019, Edmunds & Riegl 2020, Guerrini et al. 2020. A recent synthesis has pointed out the global decline in coral recruitment since 1974, with decreasing rates in equatorial reefs but increasing densities at sub-tropical latitudes reflecting a poleward expansion in coral reef distribution (Price et al. 2019). Declining recruitment rates may also be associated with shifts in recruit assemblage compositions, as recently recorded on the Australian Great Barrier Reef (GBR) following thermally induced coral bleaching events (Hughes et al. 2019). ...
... The overall mean coral recruitment rate of 34.9 re cruits per tile recorded in our study, corresponding to 1220.9 recruits m −2 , was quite high compared to most Western Pacific reefs such as the GBR (Table 1), a region known for its high recruitment rates (Price et al. 2019), with up to 4590 recruits m −2 reported in 1995−1997 (Hughes et al. 1999) before recent de clines (Hughes et al. 2019). Furthermore, the peak mean values of 388.1 recruits per tile we recorded at some stations in 2014, corresponding to 13 572.8 ...
Article
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Recruitment processes largely drive spatial distributions, dynamics, and recovery potential of marine communities. Determining scales of variation in recruitment rates and composition can help in understanding population replenishment mechanisms, while identifying recruitment hotspots is crucial for improving conservation strategies, particularly for threatened marine ecosystems such as coral reefs. We examined the spatial and interannual variability (2012-2014) of coral recruitment at multiple scales within and among reef habitats (14 stations) in the southwestern lagoon of New Caledonia. Recruit assemblages were characterized by high recruitment rates compared to other regions (overall mean of 34.9 recruits per 11 × 11 × 1 cm settlement tile, corresponding to 1220.9 recruits m ⁻² ) and strong dominance of Acroporidae. We found a marked spatial heterogeneity among habitats but also exceptionally high interannual variation (100-fold), with extreme recruitment peaks (up to 13572.8 recruits m ⁻² , with a maximum of 811 recruits on a single tile) recorded in 2014 at some fringing and mid-shelf reefs, the highest records ever reported to date. These encouraging results contrast with other reefs where recent declines in coral recruitment rates have been documented with major concerns for their resilience capacities. However, the marked spatio-temporal variability of coral recruitment complicates conservation strategies, as it makes it difficult to identify ‘recruitment hotspots’ as priority sites to protect for their potential capacity to boost the replenishment of local populations.
... The causes and implications of this gradient have been extensively studied (Veron 1995;Bellwood and Hughes 2001), but recent analyses of this gradient have focused on the high rates of coral mortality in the western Atlantic vs. the Indo-Pacific (Roff and Mumby 2012). Coral recruitment is thought to contribute to this discrepancy (Hughes and Tanner 2000;Arnold et al. 2010), in part because historically it has been lower in the western Atlantic than in the Indo-Pacific, where large numbers of mass-spawning acroporids are common on settlement tiles (Doropoulos et al. 2016a,b;Price et al. 2019). The demographic implications of reduced recruitment are intensified by the bottleneck preventing recruits from becoming adults (Chong-Seng et al. 2014;Doropoulos et al. 2016a), notably in the Caribbean (Arnold et al. 2010). ...
... Results from settlement tiles deployed in Mo'orea, French Polynesia, and St. John, U.S. Virgin Islands from 2005 to 2019 were used to test two hypotheses: (1) among-year variation in recruitment is a weak predictor of long-term variation in the density of recruits, and (2) annual variation in recruitment is associated with changes in seawater temperature. The rationale for these hypotheses was provided by the inferred capacity for severe bleaching to disrupt the stock-recruitment relationships in corals (Burt and Bauman 2019;Hughes et al. 2019;Price et al. 2019), and the vulnerability of coral recruitment to climate change (Price et al. 2019). Correctly quantifying these relationships is important to the broader objective of accurately projecting coral community structure into a future perturbed by anthropogenic effects. ...
... Results from settlement tiles deployed in Mo'orea, French Polynesia, and St. John, U.S. Virgin Islands from 2005 to 2019 were used to test two hypotheses: (1) among-year variation in recruitment is a weak predictor of long-term variation in the density of recruits, and (2) annual variation in recruitment is associated with changes in seawater temperature. The rationale for these hypotheses was provided by the inferred capacity for severe bleaching to disrupt the stock-recruitment relationships in corals (Burt and Bauman 2019;Hughes et al. 2019;Price et al. 2019), and the vulnerability of coral recruitment to climate change (Price et al. 2019). Correctly quantifying these relationships is important to the broader objective of accurately projecting coral community structure into a future perturbed by anthropogenic effects. ...
Article
The supply of propagules mediates recruitment and population dynamics, thereby driving community resilience following disturbances. These relationships are of interest on tropical reefs, where coral populations have drastically declined in abundance and sexual recruitment is the only means by which they will recover. To better understand the causes and implications of variation in this vital rate (i.e., recruitment), coral recruitment was measured in Mo'orea, French Polynesia, and St. John, U.S. Virgin Islands, using settlement tiles deployed from 2005 to 2019. The results were used to test two hypotheses: (1) annual variation in recruitment is a weak predictor of long‐term variation in recruitment, but (2) it is associated with seawater temperature. Coral recruitment varied over space and time, so that differences in recruitment between consecutive years were uninformative of long‐term trends. Recruitment varied among years in an apparently chaotic manner, but the variation reflected linear and quadratic associations with mean annual temperature and the daily variation in temperature. These associations are consistent with theory addressing the mechanisms by which temperature affects coral larvae and recruitment. Comprehension of these mechanisms is required to accurately interpret evidence of coral recruitment collapse, and to elucidate the conditions favoring recovery of coral communities through recruitment.
... Numerous studies on coral recruitment have been carried out in tropical areas where large coral reef developments are found (Wallace 1985, Hughes et al. 1999, Ritson-Williams et al. 2009, Elmer et al. 2016, Price et al. 2019). However, little attention has been paid to coral recruitment in high latitudes (>28°N and >28°S) (Baird and Thompson 2018). ...
... The recruitment rate of P. panamensis in BLA is lower compared to that reported for other scleractinian corals at extreme latitudes in both the northern and southern hemispheres (25°S, 25°N) in the Tropical Atlantic (76 ind m À2 y À1 ) and central (770 ind m À2 y À1 ), eastern (140 ind m À2 y À1 ), and western (334 ind m À2 yr À1 ) Indo-Pacific regions (Price et al. 2019). Historically, the highest recruitment rates have been reported in tropical areas, which have optimal environmental characteristics for sexual reproduction and coral development (Glynn et al. 1991, Ritson-Williams et al. 2009). ...
... Historically, the highest recruitment rates have been reported in tropical areas, which have optimal environmental characteristics for sexual reproduction and coral development (Glynn et al. 1991, Ritson-Williams et al. 2009). However, after 1980, a negative trend was detected in the coral recruitment rate in low latitudes (<25°), and by 2000, the recruitment rate in the tropics had decreased by 82% (Price et al. 2019) while coral recruitment in high latitudes (>25°) had increased (Nozawa et al. 2006, Kenyon 2008, Cabral-Tena et al. 2018, Price et al. 2019). This downward trend in coral recruitment observed in tropical areas may be related to reductions in coral cover and abundance due to changes in oceanographic conditions and anthropogenic impacts over recent decades (Price et al. 2019). ...
Article
The aim of this study is to explore if sexual reproduction is present in scleractinian corals at the northern limit of their distribution (28.980 N, 113.470 W) in a zone subject to upwelling and seasonal variations in sea surface temperature, and sampling was performed from August 2018 to October 2019. We placed 42 terracotta recruitment tiles in Baha de los ngeles, Baja California. Coral cover was estimated, and the height, major diameter, and minor diameter of coral colonies were measured. Astrangia haimei and Porites panamensis recruits were identified on the recruitment tiles, constituting the first quantitative record for the northeastern tropical Pacific. Recruitment of P. panamensis was higher (Llave: 63.09 114 ind m2 y1, Rasito: 3.21 7 ind m2 y1), while A. haimei recruitment at the same sites was 3.85 8 and 1.93 6 ind m2 y1, respectively. Recruitment differences between locations were attributed to coral cover (the abundance of Porites panamensis is 15-fold greater in Llave than in Rasito) and colony size (P. panamensis Llave: 10.53 5.93 cm, Rasito: 4 0.63 cm). Both SST and Chl-a concentrations were also highly correlated with coral recruitment, with higher recruitment rates observed in the warmer seasons when high nutrient concentrations were also present. In contrast to other sites in the eastern tropical Pacific, the highest rate of recruitment was reported at this study (high-latitude coral community), which, according with the positive high latitude trend reported by other studies, is likely due to climate change.
... Demographic studies conducted in marginal or degraded locations have indicated that current levels of recruitment will be insufficient to compensate for reductions in adult survivorship necessary to ensure population persistence for many groups of organisms (Bak and Meesters 1999;Chui and Ang Jr 2017;Guerrini et al. 2020;Hughes and Tanner 2000). Decline in adult survivorship can be particularly destabilizing when it occurs to structure-forming species such as reef-building corals which have experienced quantitative declines in recruitment globally; a synthesis of standardized data from 1974 until 2012 suggests that coral recruitment has been reduced by over 80% across the tropics (Price et al. 2019). The recent reduction of coral recruitment may be driven either by decline in settlement rate or reduction in survivorship of new settlers (e.g., via declines of available adult brood stock) (Hughes et al. 2019). ...
... The recent reduction of coral recruitment may be driven either by decline in settlement rate or reduction in survivorship of new settlers (e.g., via declines of available adult brood stock) (Hughes et al. 2019). While estimates of settlement are available (Bak and Engel 1979;Price et al. 2019), we currently lack a quantitative description of the entire coral recruitment process, specifically the pattern and rate of demographic transition from juvenile to adult. ...
... Studies of the earliest life stages of corals are particularly difficult in natural settings due to the challenge of detecting recently settled individuals and tracking them consistently through time (Vermeij and Sandin 2008). As a result, the demographics of early life stages have been limited largely to artificial substrata located in situ (Guerrini et al. 2020;Price et al. 2019) or in experimental settings (Harrington et al. 2004;Ritson-Williams et al. 2016), and usually over limited spatial and temporal scales. From such studies, it can be concluded that settling corals generally require 1 to 2 years to reach the juvenile stage, with the term 'juvenile' referring to young colonies with a maximum diameter greater than 1 cm, but less than 5 cm (Bak and Engel 1979;Doropoulos et al. 2015). ...
Article
Full-text available
For many organisms, early life stages experience significantly higher rates of mortality relative to adults. However, tracking early life stage individuals through time in natural settings is difficult, limiting our understanding of the duration of these ‘mortality bottlenecks’, and the time required for survivorship to match that of adults. Here, we track a cohort of juvenile corals (1–5 cm maximum diameter) from 12 taxa at a remote atoll in the Central Pacific from 2013 to 2017 and describe patterns of annual survivorship. Of the 537 juveniles initially detected, 219 (41%) were alive 4 years later, 163 (30%) died via complete loss of live tissue from the skeleton, and the remaining 155 (29%) died via dislodgement. The differing mortality patterns suggest that habitat characteristics, as well as species-specific features, may influence early life stage survival. Across most taxa, survival fit a logistic model, reaching > 90% annual survival within 4 years. These data suggest that mortality bottlenecks characteristic of ‘recruitment’ extend up to 5 years after individuals can be visually detected. Ultimately, replenishment of adult coral populations via sexual reproduction is needed to maintain both coral cover and genetic diversity. This study provides key insights into the dynamics and time scales that characterize these critical early life stages.
... Recruitment dynamics play a critical role in structuring and maintaining diversity in communities and in the resilience of populations to disturbances (Warner and Chesson 1985;Caley et al. 1996;Wright 2002). This is especially evident for sessile organisms, such as plants and benthic invertebrates, because their recruitment success is essential to the recovery of adult populations following disturbance events, and variation in recruitment success can drive adult population abundance and spatial distributions (Gaines and Roughgarden 1985;Crawley 2000;Price et al. 2019). The role of recruitment success in community dynamics is particularly striking on Caribbean reefs, where scleractinian coral populations have declined due to local human stressors (e.g., overfishing, pollution, poor water quality) and increasing global climatic events (e.g., bleaching and hurricanes). ...
... The role of recruitment success in community dynamics is particularly striking on Caribbean reefs, where scleractinian coral populations have declined due to local human stressors (e.g., overfishing, pollution, poor water quality) and increasing global climatic events (e.g., bleaching and hurricanes). Those stresses have impacted critical ecological processes such as survivorship, growth, reproduction, settlement, and recruitment (Goreau et al. 1998;Gardner et al. 2005;McWilliams et al. 2005;Price et al. 2019). However, just as the decline in scleractinians is an inevitable consequence of failed recruitment, successful recruitment has been essential to the increased prevalence of other taxa such as sponges and octocorals (Norström et al. 2009;Ruzicka et al. 2013;Lenz et al. 2015;Edmunds and Lasker 2016;Sánchez et al. 2019). ...
Article
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Algal cover has increased and scleractinian coral cover has steadily declined over the past 40 years on Caribbean coral reefs, while octocoral abundance has increased at sites where abundances have been monitored. The effects of algal cover on recruitment may be a key component in these patterns, as upright octocoral recruits may escape competition with algae by growing above the ubiquitous algal turfs. We used laboratory and field recruitment experiments to examine impacts of algal turf on recruitment of the common, upright, and zooxanthellate Caribbean octocoral Plexaura homomalla. Laboratory recruitment rate was significantly higher in lower turf cover treatments. The survival of recruits in the field was significantly reduced by increased turf cover; for every 1% increase in turf cover, polyps died 1.3% faster. In a model parameterized by the observed field survival, polyps exposed to 100% turf cover had a 2% survival rate over 51 days, while polyps exposed to no turf cover had a 32% survival rate over the same time. We found that high densities of turf algae can significantly inhibit recruitment of octocorals. Experimentally obtained octocoral survival rates were higher than those published for Caribbean octocorals. The factors that influence recruitment are critical in understanding the dynamics of octocorals on Caribbean reefs as continuing declines in scleractinian cover may lead to more octocoral-dominated communities.
... • Increases in mean sea surface temperatures and marine heatwaves has led to worldwide coral bleaching events (Brown, 1997;Burke et al., 2011). • In addition to severe mortality, bleaching events may lead to poleward range shifts in coral recruits and dominance of stress-tolerant species (Loya et al., 2001;Price et al., 2019). ...
... These conditions drive biophysical feedbacks, where physical controls on light and temperature can induce coral genetic expression and competitive selection for thermal tolerance ( Barshis et al., 2013;Putnam et al., 2017). Corals may expand their home range under climate change (Yamano et al., 2011;Price et al., 2019), though SLR is expected to limit coral growth, particularly in turbid reefs (Morgan et al., 2020). Research comparing geospatial shifts in corals, seagrasses, and mangroves is critically needed, in order to predict novel interactions between these ecosystems. ...
Article
Full-text available
Mangroves, seagrasses, and coral reefs interact in tropical regions throughout the world. These ecosystems exhibit strong synergies, as the health of each ecosystem supports the functioning of adjacent habitats. We present a global spatial analysis of mangrove, seagrass, and reef communities, identifying regions where these habitats co-occur. While only an estimated 18% of interaction zones are covered by protected areas, boundaries between mangroves, seagrasses, and reefs represent areas of high conservation efficiency, where benefits of conservation amplify synergistically as land-sea ecosystems are jointly managed. We discuss four types of conservation efficiencies in these coastal ecosystems: 1) increased resistance to disturbance through inter-ecosystem feedbacks, 2) high biodiversity within small geographic areas, 3) habitat portfolio effects giving rise to climate refugia, and 4) synergistic ecosystem services, where building one ecosystem service inherently increases others. Given these synergistic benefits, global campaigns to expand marine and terrestrial protection should focus on the tightly connective interface between mangroves, seagrasses, and reefs, in order to more efficiently build resilience within and between these habitats.
... Multiple positive and negative factors can influence coral recovery and community dynamics (Pearson 1981, Knowlton 2001, Sato et al. 2018. Coral larval recruitment is a crucial ecological process that affects the structure and maintenance of reef communities (Price 2010, Ritson-Williams et al. 2010, Price et al. 2019.Therefore, the successful settlement and recruitment of larvae to the optimal substrata is a vital step in the process of population recovering from a decimated coral reef (Pearson 1981, Polidoro and Carpenter 2013, Kayal et al. 2018. It is well documented that corals have an array of life history and larval strategies, hinting there maybe species-specific habitat selection for successful recruitment. ...
... Suitable settlement substrata and post-settlement survival are the vital steps in the life cycle of reef corals, and thus is a key bottleneck for the recovery of the damaged coral populations. In our experiment, high rates of settlement related to high rates of post-settlement survival, which was consistent with the results found by (Price 2010, Ritson-Williams et al. 2010, Price et al. 2019. Especially, each treatment had high larvae settlement and metamorphosis and post-settlement survival when CCA was present regardless of the algae tissue is living or not. ...
Article
Full-text available
Selection of a permanent attachment site of coral larvae can be a critical determinant of recruitment success affecting the structure of coral communities and underpins the ability of coral reef ecosystems to recover from disturbance. Settlement specificity of a threatened coral in Sanya reefs, Acropora millepora , was tested by measuring the larval metamorphosis preferences and post-settlement survival in response to crustose coralline algae (CCA) species Hydrolithon reinboldii and other substrata. In the no-choice experiments, the larvae of A. millepora had similar rates of total metamorphosis with the presence of CCA regardless of the algae tissue being alive or not, and settlement success induced by CCA was higher than by other substrata (tile or glass). In the paired-choice experiments, when CCA was in presence, the coral larvae preferred the surface of the dish and the side of living CCA. In the absence of CCA, total larvae metamorphosis was lower than in the treatments where CCA was present. New recruits of A. millepora had approximately 68% mean survival on all the settlement substrata after 2 weeks maintained in aquaria with flow-through seawater similar to the coral larval sampling site, but with no coral spat survival in the treatments where CCA was absent. However, there were statistical differences between the larvae survival of dead CCA and glass chips treatment and the others where CCA was present. Our results were consistent with the conclusion that some CCA species could facilitate coral larval settlement and post-settlement survivorship, highlighting the importance of substrata selection success for facilitating coral recruitment in the threatened coral reefs.
... Recruitment dynamics play a critical role in structuring and maintaining diversity in communities, and in the resilience of populations to disturbances (Warner and Chesson, 1985;Caley et al., 1996;Wright, 2002). This is especially evident for sessile organisms, such as plants and benthic invertebrates, where variation in recruitment success is essential to recovery from disturbance and impacts adult population dynamics and spatial distributions and (Gaines and Roughgarden, 1985;McGuinness, 1996;Crawley, 2000;Price et al., 2019). On Caribbean coral reefs the abundance of scleractinian corals has been decreasing for decades as a consequence of reduced recruitment in concert with bleaching events, hurricanes, and disease outbreaks (Goreau et al., 1998;Gardner et al., 2005;McWilliams et al., 2005;Price et al., 2019). ...
... This is especially evident for sessile organisms, such as plants and benthic invertebrates, where variation in recruitment success is essential to recovery from disturbance and impacts adult population dynamics and spatial distributions and (Gaines and Roughgarden, 1985;McGuinness, 1996;Crawley, 2000;Price et al., 2019). On Caribbean coral reefs the abundance of scleractinian corals has been decreasing for decades as a consequence of reduced recruitment in concert with bleaching events, hurricanes, and disease outbreaks (Goreau et al., 1998;Gardner et al., 2005;McWilliams et al., 2005;Price et al., 2019). Just as the decline in scleractinians is an inevitable consequence of failed recruitment, successful recruitment must have been essential to the increased prevalence of other taxa such as sponges and octocorals (Norström et al., 2009;Ruzicka et al., 2013;Lenz et al., 2015;Edmunds and Lasker, 2016;Sánchez et al., 2019). ...
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Algal cover has increased and scleractinian coral cover has steadily declined over the past 40 years on Caribbean coral reefs. In contrast, octocoral abundance has increased at those sites where octocoral abundances have been monitored. The effects of algal cover on recruitment may be a key component in these patterns, as upright octocoral recruits have the potential to escape competition with algae by growing above the ubiquitous algal turfs. However, the impacts of algal turf on octocorals have not been tested. We used laboratory and field recruitment experiments to examine impacts of algal turf on settlement and then survival of newly-settled octocorals. Tiles were preconditioned on a Caribbean reef, allowing algae to settle and grow. Tiles were then partitioned into three treatments: lightly scrubbed (0% turf cover), left alone (19% turf cover), or kept for 15 days in a sea table without fish or large invertebrate herbivores (50% turf cover). Planulae of the common Caribbean octocoral Plexaura homomalla were allowed to settle and metamorphose on the tiles for six days. Tiles were then deployed onto a reef and survival of those recruits was monitored for seven weeks. Settlers that recruited to the tiles after deployment to the reef were also monitored. Laboratory recruitment rate was significantly higher in lower turf cover treatments. Field survival was significantly reduced by increased turf cover; for every 1% increase in turf cover, polyps died 1.3% faster. In a model parameterized by the observed field survival, polyps exposed to 100% turf cover had a 2% survival rate over 51 days, while polyps exposed to no turf cover had a 32% survival rate over the same time. Synthesis . We found that high densities of turf algae can significantly inhibit recruitment of octocorals. Octocoral survival rates were similar to those published for scleractinians, but field settlement rates were much higher, which likely contributes to the higher resilience of octocorals to disturbances. The factors that influence recruitment are critical in understanding the dynamics of octocorals on Caribbean reefs as continuing declines in scleractinian cover may lead to more octocoral-dominated communities in the Caribbean.
... Moreover, resilience differs among the different species with respect to their response to environmental changes (e.g., light and temperature; Kahng et al., 2019), reflecting the different adaptation potential and physiological features of each species. Both abiotic (i.e., light, temperature, and currents) and biotic (i.e., nutrients and algal blooms) variation correlates with the different coral cover and composition along both latitudinal and depth gradients (Connell et al., 2010;Hughes et al., 2018;Price et al., 2019;Tamir et al., 2019). ...
... The potential for corals to flourish under changing conditions and/or to replenish affected sites along depth gradients is gaining increasing interest Price et al., 2019). Vertical zonation in coral community structure is accompanied by special adaptations (e.g., morphology, physiology, and skeleton structure) in response to a varying environmental regimes, including changes in light quality (intensity and spectrum) and angular distribution (Kahng et al., 2019). ...
Article
Most studies to date on the various life-history aspects of scleractinian corals (e.g. reproduction, connectivity, and physiology) have focused on their innate habitats. However, comprehensive data on the ability of both shallow and mesophotic corals to contend in the coming decades with the different environmental conditions they may encounter due to new habitats or environmental changes (e.g. eutrophication), are scarce. Long-term cross-transplantation experiments assessing the potential responses and acclimatization ability of corals are thus needed in order to expand our knowledge. Here we examined the survivorship and changes in the photobiological acclimatization of corals following their cross-transplantation between two different depths (5–10 m and 45 m) and two sites characterized by different abiotic conditions (i.e. light, nutrient, and sedimentation regime). This year-long in-situ experiment was performed on five depth-generalist coral species. Depth of origin and the species’ particular morphology were found to be the strongest predictors of survivorship. Physiological responses occurred mainly among those corals that had been translocated from deep-to-shallow water, and were expressed in a significant reduction in chlorophyll-a concentration and algal density, as well as changes in photosynthetic parameters (e.g. minimal/maximal saturating points, Ek and Em, and rETRmax). Our findings contribute to the existing knowledge on the ability of species-specific coral responses to contend with dramatic changes in their environment. The findings presented here contribute to assessment of the physiological and ecological consequences for corals of the long-term environmental changes that result from extreme environmental events.
... Paleontological records seem to empirically support the possibility of equatorial decline (Kiessling, Simpson, Beck, Mewis, & Pandolfi, 2012) and poleward expansion (Veron, 1992) of reef corals. Furthermore, and despite a global decline in coral recruitment since 1974 (Price et al., 2019), the persistent reduction in the densities of recruits in equatorial latitudes coupled with increased densities in sub-tropical latitudes suggest that coral recruitment may also be shifting poleward (Price et al., 2019). In this context, high latitude areas are hypothesized to constitute refuge habitats for endangered tropical taxa as climate changes (Beger, Sommer, Harrison, Smith, & Pandolfi, 2014), especially in areas with strong poleward currents that encourage dispersion like the Kuroshio region (Kumagai et al., 2018). ...
... Paleontological records seem to empirically support the possibility of equatorial decline (Kiessling, Simpson, Beck, Mewis, & Pandolfi, 2012) and poleward expansion (Veron, 1992) of reef corals. Furthermore, and despite a global decline in coral recruitment since 1974 (Price et al., 2019), the persistent reduction in the densities of recruits in equatorial latitudes coupled with increased densities in sub-tropical latitudes suggest that coral recruitment may also be shifting poleward (Price et al., 2019). In this context, high latitude areas are hypothesized to constitute refuge habitats for endangered tropical taxa as climate changes (Beger, Sommer, Harrison, Smith, & Pandolfi, 2014), especially in areas with strong poleward currents that encourage dispersion like the Kuroshio region (Kumagai et al., 2018). ...
Article
In line with contemporary changes in oceanic conditions, reef communities could be declining at the equator and expanding polewards, having previously happened in the past. Yet, some tropical organisms are now decimated at their distributional cores and observed beyond their inferred range limits. However, it remains unclear if this is happening at the community scale, especially due to the challenges of collecting quantitative and comparable data across latitudes. Here, we propose that monitoring sentinel plots via photogrammetry could help to assess abiding changes in benthic communities and trajectories of reef-building populations across the Kuroshio region. We think that as oceans are becoming warmer, accretive reef communities may shift their distribution northwards which may be primarily due to a change in the relative biomass-abundance of resident taxa. Consistent trends among latitudes will resolve the possibility of contraction or expansion of accretive reef communities, providing further insight into the variety of responses and dynamics observed across latitudes in the context of the Anthropocene.
... Tropicalization, a process by which species formerly restricted to tropical waters expand their ranges and become resident in temperate waters is a global phenomenon that follows the warming of the world's oceans (Vergés et al., 2014;Hyndes et al., 2016). This phenomenon is exemplified by global changes in coral distributions, in which coral recruitment is shifting poleward at the same time it is declining in equatorial regions (Price et al., 2019). ...
... Also, anthropogenic influences such as coral mining, use of explosives for fishing and anchoring activities have destroyed reefs greatly at many places in the world (Burke and Maidens, 2004;Bruno and Selig, 2007). Due to global warming and climate change, considerably corals in tropical environment are declining and shifting towards subtropical regions (Price and Al, 2019). ...
Article
Since past three decades, coral reefs of the world are degrading at large scales due to climate change and through combination of anthropogenic and natural disturbances. Coral reefs in the 21 islands of Gulf of Mannar Marine Biosphere Reserve, Southeast coast of Tamil Nadu, India are also greatly damaged by frequent bleaching events, destructive fishing, invasive algal assemblage, sedimentation, diseases, and destructive waves and currents. To facilitate the restoration of these habitats, an extensive artificial restoration of corals has been implemented as a counter measurement. This conservation practice will help to increases the live coral covers, rebuild the destroyed coral reefs, and protect the reef biodiversity. The present study underwater experiments were revealed that profuse growths of transplanted corals are dependent on coral species and the study sites. There was significant differences in seasonal growth rate at northern side of Hare Island (p = 0.03), where the maximum mean Acropora coral growth rate around 11.75 cm was observed during summer from initial mean growth 7.65 cm. Similarly, significant variation in growth rate was observed during monsoon between naturally recruited and transplanted corals (p =0.02), where naturally recruited coral colonies, and transplanted coral colonies were displayed the maximum mean growth rates as 11.5 cm, and 7.5 cm respectively in two months,. Significance seasonal influence on growth rates of transplanted coral was observed (p = 0.01). Relatively, Acropora corals have showed faster growth rates and also resistance to environmental influences such as algal invasion, sedimentation, turbidity, and bleaching events.
... In line with the relative lack of understanding about processes occurring in mesophotic reefs (i.e. > 30 m) in general (Turner et al. 2017), the vast majority of work on coral recruitment using settlement tiles has been conducted at shallow depths < 10 m (74% of studies), followed by studies occurring at 10-20 m depth (21%), with few occurring at > 20 m depth (4%) (Price et al. 2019). Moreover, no previous study has investigated coral settlement interactions at depths > 24 m. ...
Article
Depth gradients are known to drive patterns of adult and juvenile coral distribution, but the influence on early successional communities and subsequent interactions with coral larvae settlement are poorly understood. We studied how early successional communities changed across a 40 m depth gradient to test whether patterns of coral larvae settlement could be explained by changes in preferred settlement substrates. Light decreased 83-fold from 3 to 40 m, and coral settlement orientation switched from tile undersides at 3 and 8 m to tile topsides at 25 and 40 m as expected. Regardless of the reduction in light, community composition on the topsides of settlement tiles did not change across depths, being dominated by turf algae (49%), crustose coralline algae (CCA; 29%), and biofilmed tile (12%). In contrast, settlement tile undersides were dominated by coralline and fleshy algae at 3 m, transitioning to ascidians and bryozoans at 8 m and 25 m, and biofilmed tile (80%) at 40 m. Following multiple regression analysis from an initial 21 bio-physical variables (R2 = 0.34), the optimal reduced model for predicting coral settlement included just five variables and explained most of the variability (R2 = 0.29). CCA contributed an R2 of 0.14 to the model and was positively correlated with Acroporidae settlement, biofilmed tile contributed an R2 of 0.09 to the model and was negatively correlated with Acroporidae settlement, while the other predictors explained nominal model variance. As assessed using electivity indices, Acroporidae switched settlement preference from CCA at shallower depths to biofilmed tile in deeper environments. In addition to the influence of light on larval settlement behaviour as described in previous research, our results show that CCA also provide an important facilitator of coral settlement behaviour across depth gradients. However, as in shallow reefs environments, further work is required to elucidate whether changes occurring at a finer taxonomic resolution within the CCA community can help to further explain switches in coral larval settlement behaviour in light-limited environments.
... The vast heat transport associated with the Kuroshio elevates surface temperatures in the ECS and facilitates a significant coral larval flux along the Ryukyu Islands, enabling Japan to host some of the northernmost known coral reefs (Yamano et al., 2011(Yamano et al., , 2012. and present (e.g., Iryu, 2006;Price et al., 2019;Yamano et al., 2011). In particular, the Last Glacial Maximum (LGM) and subsequent recovery therefrom may serve as a useful case study for this purpose. ...
Article
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The Kuroshio Current is a major hydrographical feature of the modern East China Sea, but it has been suggested that its flow was diverted to the east of the Ryukyu Arc at the Last Glacial Maximum. Shoaling of the Yonaguni Depression has also been proposed as a cause of Kuroshio Current diversion which, while unlikely to have been significant at the Last Glacial Maximum, may have been an important consideration further back in time. Using an ensemble of high‐resolution ocean simulations with climatic boundary conditions emulating those of the Last Glacial Maximum, we present the first regional state estimates of the glacial East China Sea which are both physically consistent and compatible with sea surface temperature proxy compilations. We find that while the Kuroshio Current transport in the East China Sea is slightly reduced at the Last Glacial Maximum, its path is relatively unchanged, with limited sensitivity to glacioeustatic sea level change, glacial‐interglacial changes in climate, and tectonic shoaling of the Yonaguni Depression. Simulations with the best model‐proxy agreement predict only limited contraction of the reef front at the Last Glacial Maximum, and strong surface currents associated with the glacial Kuroshio may have maintained or even improved long‐distance coral larval dispersal along the Ryukyu Arc, suggesting that conditions may have enabled coral reefs in this region to remain widespread throughout the last glacial. Further field studies investigating whether this is genuinely the case will provide insights into how the coral reef front responds to long‐term environmental change.
... An increase in habitat suitability in relation to SST is confirmed, for example, by increasing growth rate of massive Porites along a latitudinal gradient in Western Australia (Cooper, O'Leary, & Lough, 2012) and by previous model studies (Couce et al., 2013;Descombes et al., 2015). This trend is also confirmed by a decline in coral recruitment in tropical waters accompanied by an increase in subtropical waters becoming warmer (Price et al., 2019). However, large-scale bleaching events that occurred in the GBR and in the Caribbean over the last decades (Berkelmans & Oliver, 1998;Eakin et al., 2010;Hughes, Anderson, et al., 2018;Hughes et al., 2017;McWilliams, Côté, Gill, Sutherland, & Watkinson, 2005) indicate that temperature is not the only factor responsible for coral bleaching. ...
Article
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Coral reefs are threatened by global and local stressors. Yet, reefs appear to respond differently to different environmental stressors. Using a global dataset of coral reef occurrence as a proxy for the long-term adaptation of corals to environmental conditions in combination with global environmental data, we show here how global (warming: sea surface temperature, SST, acidification: aragonite saturation state, Ωarag ) and local (eutrophication: nitrate concentration, [ NO 3 - ] , and phosphate concentration, [ PO 4 3 - ] ) stressors influence coral reef habitat suitability. We analyse the relative distance of coral communities to their regional environmental optima. In addition, we calculate the expected change of coral reef habitat suitability across the tropics in relation to an increase of 0.1°C in temperature, an increase of 0.02 μmol L-1 in nitrate, an increase of 0.01 μmol L-1 in phosphate, and a decrease of 0.04 in Ωarag . Our findings reveal that only 6% of the reefs worldwide will be unaffected by local and global stressors and can thus act as temporary refugia. Local stressors, driven by nutrient increase, will affect 22% of the reefs worldwide, whereas global stressors will affect 11% of these reefs. The remaining 61% of the reefs will be simultaneously affected by local and global stressors. Appropriate wastewater treatments can mitigate local eutrophication and could increase areas of temporary refugia to 28%, allowing us to "buy time", while international agreements are found to abate global stressors.
... This is notably true for coral reefs, as many corals have extended life spans that may mask slowly developing degradation trends for decades and more before their footprints are seen in adult populations. A recent meta-analysis (Price et al. 2019) indicated an increase in coral recruitment rates in sub-tropical reefs, when compared with tropical reefs. In contrast, using the IUI site as a paragon for other coral reefs, this study on early recruitment (1-month-old coral recruits) suggests a yet unnoticed trend of biodiversity dwindling, that we link with a reduced recruitment (within and overall taxa), and a presumable footprint impairing future reef resilience. ...
Article
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The status of coral reefs is often portrayed by parameters (e.g., coverage, bleaching, diseases, nutrients and rugosity) assigned to adult populations. Yet, coral recruitment is essential for sustaining coral populations, especially in the aftermath of major disturbances. Studying earliest coral recruitment at species level can reveal declines in the recovery potential and resilience of coral populations and communities, even if adult abundance and coral cover is sustained. Rates of coral recruitment were quantified once a month for 4 yrs from tiles and stones (Eilat, Red Sea), revealing a dramatic discrepancy in coral species recruited (n = 15) compared to adult-species currently on site (n = 55), with 1–2 dominant species accounting for ≥ 80% of recruits. The low rates and limited diversity of settling corals recorded in this study appear unlikely to sustain contemporary coral assemblages, so unless there are marked changes in the settlement dynamics, we would expect to see inevitable declines in the abundance and diversity of reef corals at these locations.
... The collapse of coral reefs that has occurred since the 1970s has largely been attributed to climate change, which has caused the coral cover to significantly decline by approximately 50-80% worldwide (Gardner et al., 2003;Bruno and Selig, 2007;Silverstein et al., 2015;Hughes et al., 2018). Biogeographical evidence showed that the global coral recruitment has declined by 85% throughout the tropics, but has increased by 78% in the sub-tropics (Price et al., 2019). Several studies have suggested that in some areas, such as eastern Australia (Booth et al., 2007;Figueira and Booth, 2010), Japan (Yamano et al., 2011), the western Mediterranean (Serrano et al., 2013), and the northern part of the South China Sea (SCS) (Tkachenko and Soong, 2017;Qin et al., 2019aQin et al., , 2019bYu et al., 2019), sub-tropical coral reefs may be potential zones of refuge for tropical coral resisting the oceans' increasing temperatures (Beger et al., 2014). ...
Article
Regional acclimatisation and microbial interactions significantly influence the resilience of reef-building corals facing anthropogenic climate change, allowing them to adapt to environmental stresses. However, the connections between community structure and microbial interactions of the endemic coral microbiome and holobiont acclimatisation remain unclear. Herein, we used generation sequencing of internal transcribed spacer (ITS2) and 16S rRNA genes to investigate the microbiome composition (Symbiodiniaceae and bacteria) and associated potential interactions of endemic dominant coral holobionts (Pocillopora verrucosa and Turbinaria peltata) in the South China Sea (SCS). We found that shifts in Symbiodiniaceae and bacterial communities of P. verrucosa were associated with latitudinal gradient and climate zone changes, respectively. The C1 sub-clade consistently dominated the Symbiodiniaceae community in T. peltata; yet, the bacterial community structure was spatially heterogeneous. The relative abundance of the core microbiome among P. verrucosa holobionts was reduced in the biogeographical transition zone, while bacterial taxa associated with anthropogenic activity (Escherichia coli and Sphingomonas) were identified in the core microbiomes. Symbiodiniaceae and bacteria potentially interact in microbial co-occurrence networks. Further, increased bacterial, and Symbiodiniaceae α-diversity was associated with increased and decreased network complexity, respectively. Hence, Symbiodiniaceae and bacteria demonstrated different flexibility in latitudinal or climatic environmental regimes, which correlated with holobiont acclimatisation. Core microbiome analysis has indicated that the function of core bacterial microbiota might have changed in distinct environmental regimes, implying potential human activity in the coral habitats. Increased bacterial α diversity may lead to a decline in the stability of coral-microorganism symbioses, whereas rare Symbiodiniaceae may help to retain symbioses. Cladocopium, γ-proteobacteria, while α-proteobacteria may have been the primary drivers in the Symbiodiniaceae-bacterial interactions (SBIs). Our study highlights the association between microbiome shift in distinct environmental regimes and holobiont acclimatisation, while providing insights into the impact of SBIs on holobiont health and acclimatisation during climate change.
... Corals are stenothermic and extremely sensitive to temperature changes (Carricart-Ganivet, 2004). Thus, rising sea surface temperatures (SST) threatens the survival of coral reefs worldwide, especially in lowlatitude reefs (Price et al., 2019). Although the SST in relatively highlatitude areas (20-30°N) has also increased, this increment not only haven't exceeded the coral upper temperature limit (32°C), but also has alleviated the low temperature pressure during the winter (Schleyer et al., 2008). ...
Article
With the rapid degradation of coral reefs due to global warming and anthropogenic impacts, relatively high-latitude areas, such as the northern South China Sea (SCS), are likely to become refuges for tropical coral species. Here we investigated the genetic features and adaptability of one dominant scleractinian coral species, Turbinaria peltata, in the northern SCS. A total of 81 samples from 5 sites were studied to explore potential mechanisms of adaptability to environmental stress as a result of climate change. Ten microsatellite markers developed in this study, one nuclear gene (internal transcribed spacer, ITS), and one mitochondrial gene (mitochondrial cytochrome oxidase subunit I gene, mtDNA COI) were used. Our results indicated that the genetic diversity of T. peltata in the northern SCS is low (Ar=1.403–2.011, Ho=0.105–0.248, He=0.187–0.421) with the lowest in Dongfang population (DF) (Ar=1.403, Ho=0.22, He=0.187). These results indicate that T. peltata has insufficient genetic adaptability and may unable to handle increasingly complex global changes. A significantly moderate genetic differentiation was observed among T. peltata populations (ΦST=0.167), in addition to a high genetic differentiation between DF and other populations (FST=0.272–0.536>0.25). The DF population near a fishing port was exposed to severe anthropogenic environmental stress, which may drive the extraordinarily high genetic differentiation between DF and other populations. Furthermore, the Mantel test results showed that the genetic differentiation of the other four populations was strongly correlated with the average sea surface temperature (SST) (R²=0.82, Mantel test P<0.05) and geographical distance (R²=0.57, Mantel test P<0.05). Our results suggest that the genetic structure of T. peltata in the relatively high-latitude of the SCS was significantly affected by average SST, geographical isolation, and anthropogenic activities. These findings provide a theoretical foundation for the protection of relatively high-latitude coral reefs.
... Low incidence of mortality observed following coral bleaching at the Revillagigedo Archipelago supports this theory. If favourable temperature conditions in the Revillagigedo Archipelago are maintained, there could be opportunity for it to serve as a safe haven for ex situ tropical species that migrate polewards as conditions in equatorial latitudes become unfavourable [77,78]. However, it is recognised that the long-term effectiveness of refugia is uncertain and will be determined by spatially complex ocean warming trends in the ETP and the effect of a warming ocean on the dynamics of El Niño events. ...
Article
Coral reef refugia are habitats which possess physical, biological and ecological characteristics that make them likely to be relatively resilient to future climate change. Identification of refugia locations will be important to ensure suitable marine conservation planning is undertaken to protect sites where coral ecosystems will be better preserved now and in the future. This paper presents (1) a review of current knowledge of the oceanographic conditions and coral community in the Revillagigedo Archipelago Large Scale Marine Protected Area, (2) the first assessment of the potential for the Revillagigedo Archipelago to act as a climate refugia site for corals and coral reefs in the eastern tropical Pacific, and (3) consequent management and learning opportunities, to inform reef conservation both locally and globally. Through utilising published literature, remote and in situ environmental data, and field observations it was found that the Revillagigedo area exhibits a combination of distinctive characteristics in the coral community and in oceanographic processes which support conditions of refugia. The potential for refugia is further enhanced due to the absence of significant secondary anthropogenic stressors. This leads to a recommendation to establish the Revillagigedo as a globally significant 'sentinel site' where, through long-term monitoring of oceanographic conditions and of the coral and associated ecosystems, the effects of climate change can be quantified, and the effectiveness of specific refugia attributes established. This information may then be used to underpin the recognition of potential coral refugia elsewhere, and to guide MPA designation and management decisions to enhance their effectiveness.
... Corals may adapt to environmental changes through altering their phenology, behaviour, physiology, or even their own genetics or their association with symbiont genotypes, but whether these adaptive mechanisms are effective depends on a number of factors such as the rates of the environmental change, the amount of genetic variation available and the life-history of the coral, and the diversity of the habitat (Hughes, 2012). For those species that cannot adapt to the environmental change, migration through larval dispersal to other areas is the only strategy to avoid extinction (Greenstein and Pandolfi, 2008;Hughes, 2012;Nakabayashi et al., 2019;Price et al., 2019;Denis et al., 2020). However, little is known about how environmental changes may affect subtropical coral communities, and how they respond to the potential invasion of tropical species (Beger et al., 2014;Kavousi and Keppel, 2018). ...
Article
We surveyed 41 sites to provide an updated baseline of Hong Kong coral communities. Five community types were identified, among them the most common one inhabited oceanic waters and dominated by both massive and upward-plating corals. The 41 sites had 2.1–⁠79% coral cover; among them 21 in the eastern waters had >40% coral cover. Corals in several sites showed signs of external bioerosion or bleaching-induced damage. Sites in the southern waters had low coral cover. Both coral cover and generic richness correlated negatively with several water quality parameters including total inorganic nitrogen concentration and turbidity, indicating the development of Hong Kong's coral communities is constrained by water quality parameters. Management actions are proposed to reduce bioerosion, and to monitor sites affected by bleaching.
... Climate change, especially global warming, has been considered one of the main contemporary forces driving adaptive changes in wildlife (Walther et al., 2002;Parmesan and Yohe, 2003;Richardson, 2008;Daufresne et al., 2009;Dyderski et al., 2018;Price et al., 2019). Organisms must provide mechanisms that allow them not to exceed their thermal limits in extreme edge environments (Marshall et al., 2010;Fusi et al., 2015;Munguia et al., 2017). ...
Article
Fiddler crab males present a hypertrophied claw, which is used for sexual and aggressive displays, fights with competitors, and has been proposed as an important thermoregulatory organ for heat control. Two claw morphologies can be observed within fiddler crab populations: brachychelous claws (unregenerated) and leptochelous claws (regenerated). The leptochelous morphotype presents less muscle mass and longer fingers, resulting in a less advantageous weapon in fights. Considering their slender shape, we hypothesized that the leptochelous morphotype would present lower thermal inertia and be more efficient at body heat dissipation. We evaluated the role of the fiddler crabs' claw shape as a heat sink and how this influences their distribution between unshaded and shaded microhabitats. We tested in the field whether the proportion of adult male Leptuca uruguayensis with leptochelous claws was higher in unshaded microhabitats than shaded ones. In the laboratory, we tested if heat transfer between the body and claw is higher in leptochelous males than in brachychelous males. Spontaneous waving behaviour and active time above the surface were compared between both morphotypes in the field during the hottest period of the day. Leptuca uruguayensis with regenerated claws comprised more than 60% of the sampled male population of unshaded microhabitats compared to 18% in shaded microhabitats. Leptochelous males showed a mean heat transfer between body to claw 35% higher than that observed for brachychelous males. During the hottest period of the day, brachychelous males waved approximately 28% more than leptochelous males. Moreover, brachychelous males spent less time under the sediment surface since the surface temperature increased, while activity of leptochelous males was not associated with a temperature increase. Therefore, regenerated claws may be advantageous for the establishment of L. uruguayensis males in warmer and unshaded microhabitats because they are more efficient for heat loss and allow crabs to cool down, spending less time waving. Our study shows the relevant context of winners and losers in the face of climate change and highlights the importance of morphological variations in thermoregulatory structures for the occupation of thermal niches.
... Nutrient enrichment has been shown to increase the susceptibility of coral reefs to bleaching (Wiedenmann et al. 2013), increase the severity of coral diseases (Bruno et al. 2003) and increase the vulnerability of coral reefs to ocean acidification (Silbiger et al. 2018). Furthermore, the poleward movement (Price et al. 2019), potential thermal evolution/adaptation (Speers et al. 2016;Donner 2009) and species-specific responses of corals (Fabricius et al. 2011) are not accounted for in our projections. All these additional climate change-induced stressors and the confounding effect of local stressors impact local and national economies (Hoegh-Guldberg et al. 2018). ...
... Even moderate climate change will lead to rising sea surface temperatures and a fundamental and irreversible ecological transformation of the world's oceans including increased extinction rates and shifting of species distribution ranges (Hoegh-Guldberg & Bruno 2010;Pachauri et al. 2014;Jones & Cheung 2015;Price et al. 2019;IPCC 2021). The loss in species richness may occur abruptly (Tisos et al. 2020), will impact marine ecosystem functioning, and will have noticeable consequences for humanity (Hoegh-Guldberg & Bruno 2010;Cardinale et al. 2012;Doney et al. 2012;Hughes et al. 2017;Magnan et al. 2021). ...
Article
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Global warming threatens the viability of tropical coral reefs and associated marine calcifiers, including symbiont‐bearing larger benthic foraminifera (LBF). The impacts of current climate change on LBF are debated because they were particularly diverse and abundant during past warm periods. Studies on the responses of selected LBF species to changing environmental conditions reveal varying results. Based on a comprehensive review of the scientific literature on LBF species occurrences, we applied species distribution modeling using Maxent to estimate present‐day and future species richness patterns on a global scale for the time periods 2040‐2050 and 2090‐2100. For our future projections we focus on Representative Concentration Pathway 6.0 from the Intergovernmental Panel on Climate Change, which projects mean surface temperature changes of +2.2 °C by the year 2100. Our results suggest that species richness in the Central Indo‐Pacific is two to three times higher than in the Bahamian ecoregion, which we have identified as the present‐day center of LBF diversity in the Atlantic. Our future predictions project a dramatic temperature‐driven decline in low‐latitude species richness and an increasing widening bimodal latitudinal pattern of species diversity. While the central Indo‐Pacific, now the stronghold of LBF diversity, is expected to be most pushed outside of the currently realized niches of most species, refugia may be largely preserved in the Atlantic. LBF species will face large‐scale non‐analogous climatic conditions compared to currently realized climate space in the near future, as reflected in the extensive areas of extrapolation, particularly in the Indo‐Pacific. Our study supports hypotheses that species richness and biogeographical patterns of LBF will fundamentally change under future climate conditions, possibly initiating a faunal turnover by the late 21st century.
... Climate change is considered to be one of the main factors driving recent shifts in the phenology, behaviour, abundance and distribution of various organisms (McCarty, 2001;Parmesan and Yohe, 2003;Parmesan, 2006;Poloczanska et al., 2016;Dyderski et al., 2018;Price et al., 2019). Species can develop four general responses to climate change: dispersal, acclimatization, adaptation or extinction (Holt, 1990;Peterson et al., 2001). ...
Article
Rising temperatures due to climate change are expected to drive shifts in species composition, phenological patterns and the productivity of mangrove trees. During early life history stages, such as dispersal and settlement, temperature may affect the survival of propagules and, consequently, drive the distribution of mangrove species. The aim of this work was to evaluate whether low water and air temperatures experienced by propagules during the dispersal and settlement stages, respectively, limit the latitudinal distribution of the white mangrove Laguncularia racemosa. Based on the distribution range of L. racemosa, we investigated four water and air temperatures: 10, 15, 20 and 25 °C. First, we evaluated the effect of seawater temperature on the buoyancy time of propagules. Then we tested the effect of seawater temperature and buoyancy time (24, 48, 72 and 96 h) on the germination rate of L. racemosa. Finally, we evaluated the effect of air temperature (10, 15, 20 and 25 °C) on the germination of propagules during the stranded stage. The propagules in higher water temperatures (20 and 25 °C) submerged faster than in lower temperatures (10 and 15 °C). The percentage germination of propagules in water temperatures of 20 and 15 °C was higher than those in 25 and 10 °C. However, the percentage germination was greater than 70%, regardless of the water temperature or buoyancy time tested. Furthermore, the percentage germination of propagules in air temperatures of 25 and 20 °C was higher (above 70%) than in air temperatures of 15 and 10 °C (below 50%). Lower water temperature increased the dispersal time of propagules, but it was not crucial to the germination rate of L. racemosa, regardless of the buoyancy time of propagules. In contrast, a lower air temperature reduced the germination of propagules during the stranded stage. Therefore, water temperature is not a limiting factor for the success of L. racemosa during the dispersal stage, however, we found that the mangrove tree is highly sensitive to air temperature during its stranded stage. We hypothesized that the increased buoyancy time of propagules during lower temperatures is an adaptive advantage, which allows L. racemosa to be transported to warmer areas or to tolerate cold temperatures for longer periods before settlement.
... These data were then scattered in many databases, and one of the tasks of the workshop was to favour the creation of a comprehensive database. We initiated the analysis of this rich information during the workshop and continued it after, which led us to find that coral recruitment had been progressively shifting from the equator polewards in the two hemispheres since the 1980s (Price et al., 2019). I think this is a major discovery at a time when coral reefs are under threat in tropical waters. ...
Article
In this Food for Thought, I use my experience of writing scientific publications to stress some aspects of the process that were especially significant for me, and from which I try to derive some general suggestions. These aspects include strong interactions (co-evolution) between paper writing and some of my research directions; the pleasure of writing with co-authors; writing as a tool of scientific creativity; long scientific quests through several publications; the importance of writing books, if possible starting early in the career; being published, reaching readers, and contributing to the advancement of knowledge; and giving in to the pleasure of writing. I explain that I often seized unexpected opportunities that led me to develop ideas and write publications that influenced the course of my career, but I do not necessarily suggest that anyone proceed as I did. My motivation was the enjoyment of exploring new topics, and I wholeheartedly recommend that everyone give in to the pleasure of writing.
... If the projected increase in water temperatures that is expected to occur within the next 50 years outpaces the thermal tolerance and adaptation potential of local species, as has been suggested for shallow-water coral reefs (Donner et al. 2005), local extinctions and shifts in latitudinal or bathymetric range would be expected (Morato et al. 2020). The capacity for coral populations to shift their range (i.e., move poleward) are dependent on larval dispersion and availability of suitable habitat (Price et al. 2019). However, the evidence that L. pertusa colonies within a region have disparate physiological (Kurman et al. 2017) and genetic expression (Glazier et al. 2020) responses to stress, and that different populations behave quite differently under similar conditions (Georgian et al. 2016b), coupled with the apparent flexibility in the L. pertusa microbiome (Meistertzheim et al. 2016) suggest that this species may be able to adapt at the same pace as the predicted environmental conditions. ...
Article
Seawater temperature is one of the main variables that determines cold-water coral distribution worldwide. As part of an initiative to explore new areas of deep-sea habitats along the Southeast United States (SEUS) continental margin, a series of expeditions were carried out as part of the Deep-Sea Exploration to Advance Research on Corals/Canyons/Cold seeps (DEEP SEARCH) project. During these explorations, a cold-water coral reef complex composed mainly of Lophelia pertusa was located off the coast of South Carolina at 650–850 m depth. In this geographic area the species normally has a thermal tolerance between 6 and 12 °C with the capacity to form extensive calcium carbonate structures, thus creating complex habitat for a variety of associated species. Owing to the paucity of these structures and the unusual environmental conditions of this geographic area, with regular arrival of warm surface waters from the Gulf Stream, the main aim of this study was to understand the physiological response of L. pertusa to the variation in extreme temperature events in this region. Short-term experiments simulated the rate of temperature increase from the ambient temperature (8 °C) to the environmental maximum (14 °C) (heat-wave treatment). We found that temperature had a significant effect on the metabolic functions through an increase in respiration (0.108 to 0.247 µmol O2 g−1DW h−1) and excretion rates (0.002 to 0.011 µmol NH3 g−1DW h−1) at 14 °C. Oxygen to Nitrogen ratios (O:N) also showed an effect of temperature where corals switched from lipid-dominated toward a mix of lipid-protein and protein-dominated catabolism. To further characterize the metabolic response, feeding assays (capture rate of Artemia) were performed at the same temperature range with an overall three-fold decrease in capture rates under 14 °C compared to ambient temperature, thus increasing the probability of temperature-induced metabolic stress. Our results suggest that temperature variations affect the metabolic response of cold-water corals, particularly along the SEUS continental margin. Since the incursion of warm surface water to deeper zones is predicted to increase in frequency and duration due to climate change, L. pertusa may be implicated negatively, followed by ecological consequences for the survival and functionality for the ecosystem it supports.
... Global warming caused by increased burning of fossil fuels has shifted the poleward range limits of organisms around the word (Parmesan and Yohe, 2003;Parmesan, 2006;Hickling et al., 2006;Chen et al., 2011;Dyderski et al., 2018;Price et al., 2019). Increased temperatures have allowed several species to expand their range limits to deeper waters, higher altitudes and higher latitudes (Walther et al., 2009;Parmesan and Yohe, 2003;Chen et al., 2011;He and Silliman, 2019). ...
Article
Temperature increase due to climate change has caused shifts in the range distribution of several organisms globally. In coastal intertidal environments most organisms have an amphibious life cycle and their poleward range limits may be delimited by their thermal tolerance during the pelagic larval stages. Fiddler crabs are key species in intertidal environments and their early larval stages occur in coastal waters. We evaluated the mean and monthly minimum sea surface temperature (SST) gradient over the South American coast and compared it to the minimum and maximum critical thermal limits (CTmin and CTmax) of the first larval stage of eight fiddler crab species to assess whether temperature delimits their distributional ranges. We found a clinal decrease in mean SST of 0.28 °C per latitudinal degree along the distribution of fiddler crabs in South America. Cold tolerance differed among the larvae of fiddler crab species, which corresponds to the latitudinal temperature gradient observed in their poleward range limits. Thus, our results suggest that cold water temperature can define the poleward range limits of South American fiddler crabs. The CTmax cannot explain the northern poleward range limits of the fiddler crabs. Fiddler crabs showed a similar tolerance to high temperatures (mean 40.5 °C) regardless of species (except Leptuca uruguayensis) and these are higher than environmental temperatures observed in South America. We also observed an increase in mean SST of 0.9 °C in the last 37 years. This increase in water temperature may explain the recent poleward range expansion of one South American fiddler crab species, Leptuca cumulanta. Therefore, we showed that differential thermal responses at the early larval stage have consequences on the geographic range limits of the fiddler crab species. Our findings allow us to hypothesize that fiddler crabs’ poleward range limits may expand to higher latitudes in the future due to global warming.
... Coral restoration has historically sought to return coral to previously denuded or impacted areas of reefs. This focus on working only in historical ranges fails to take into account that species and entire ecosystems are shifting their ranges in response to climate change [5,6], a pattern which has also been documented in corals [7,8]. However, some projects have moved species for other reasons like offsetting degradation as was the case at Port Everglades in Florida, USA where managers sought to move corals in order to save them from dredging [9], unfortunately with little success [10]. ...
Article
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Assisted migration is becoming a hot topic in view of the growing impacts of climate change on ecosystems. One area where assisted migration and its cousin ecosystem pushing could have increasing importance is in coral restoration, but marine scientists’ opinions on the ethics and feasibility of assisted migration and ecosystem pushing in coral conservation has not been assessed. Surveys and interviews were conducted with coral research practitioners to determine the field’s receptibility to such techniques. Thematic network analysis revealed that support for ecosystem pushing was mixed. Several management guidelines followed from the analysis. A grounded theory statement on ecosystem pushing was produced that serves as a starting point for managers to consider the complexity and implications of the action.
... larvae was lower in the temperate region compared with the subtropics. With abiotic barriers limiting the dispersal and survival of coral larvae at higher latitudes this pattern is to be expected (Nakabayashi et al. 2019), despite the conflicting evidence of recent warminginduced increases in the densities of settling larvae at higher latitudes (Price et al. 2019). Intriguingly, though, we report that the survival of coral larvae following successful settlement appeared highest in the temperate region. ...
Article
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Predicting the viability of species exposed to increasing climatic stress requires an appreciation for the mechanisms underpinning the success or failure of marginal populations. Rather than traditional metrics of long‐term population performance, here we illustrate that short‐term (i.e. transient) demographic characteristics, including measures of resistance, recovery and compensation, are fundamental in the poleward range expansion of hard corals, facilitating the establishment of coral populations at higher latitudes. Through the annual census of subtropical and temperate Acropora spp. colonies in Japan between 2017 and 2019, we show how enhanced transient amplification (i.e. short‐term increases in population growth following disturbance) supports the persistence of coral assemblages within more variable high‐latitude environments. The transient dynamics of both the subtropical and temperate assemblages were strongly influenced by their corresponding recruitment patterns. However, we demonstrate that variation in colony survival and fragmentation patterns between the two assemblages determines their relative capacities for transient amplification. This latitudinal variation in the transient dynamics of Acropora spp. assemblages emphasizes that coral populations can possess the demographic plasticity necessary for exploiting more variable, marginal conditions.
... This exposes whole ecosystems to conditions outside long-term baselines that result in severe stress and mortality across key species such as coral and kelp (Hughes et al., 2003;Wernberg et al., 2016;Smale, 2020). For these ecosystems to persist into the future, key habitat-forming species will either need to adapt, acclimatize or shift geographic range (Parmesan and Yohe, 2003;Burrows et al., 2011;Blois et al., 2013;Price et al., 2019). Adaptation arises when variation in fitness has a genetic basis and adaptive alleles can be selected for by local conditions over generations (Ellegren and Sheldon, 2008). ...
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Strong population-by-habitat interactions across environmental gradients arise from genetic adaptation or acclimatization and represents phenotypic variation required for populations to respond to changing environmental conditions. As such, patterns of adaptation and acclimatization of reef-building corals are integral to predictions of the future of coral reefs under climate warming. The common brooding coral, Pocillopora damicornis , exhibits extensive differences in host genetic and microbial symbiont community composition between depth habitats at Heron Island in the southern Great Barrier Reef, Australia. An 18-month reciprocal field transplant experiment was undertaken to examine the environmental and genetic drivers behind variation in survival, weight gain, heat tolerance and algal symbiont community between the reef flat and slope habitats. We observed population-by-habitat interactions for in situ partial mortality and weight gain, where trait-related fitness of natives was greater than transplants in most cases, consistent with local adaptation. On average, flat colonies transplanted to the slope had a relatively low partial mortality but minimal weight gain, whereas slope colonies transplanted to the flat had relatively high partial mortality and average weight gain. Experimental heat tolerance was always higher in colonies sourced from the flat, but increased when slope colonies were transplanted to the flat, providing evidence of acclimatization in these colonies. The performance of certain slope to flat transplants may have been driven by each colony’s algal symbiont (Symbiodiniaceae) community, and flat variants were observed in a small number of slope colonies that either had a fixed flat composition before transplantation or shuffled after transplantation. Host genotypes of previously identified genetic outlier loci could not predict survival following transplantation, possibly because of low sample size and/or polygenic basis to the traits examined. Local environmental conditions and Symbiodiniaceae composition may provide insight into the adaptive potential to changing environmental conditions.
... The transformation of reefs from coral to algal domination will dramatically impact their carbon cycle by changing rates of photosynthesis, respiration, and calcification (Roth et al., 2021). Range shifts of corals have also been attributed to warming, suggesting that climate change may expand habitat suitable for coral growth (Kumagai et al., 2018;Price et al., 2019;Yamano et al., 2011). ...
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The Earth’s climate is strongly affected by the partitioning of carbon between its mobile reservoirs, primarily between the atmosphere and the ocean. The distribution between the reservoirs is being massively perturbed by human activities, primarily due to fossil fuel emissions, with a range of consequences, including ocean warming and acidification, sea-level rise and coastal erosion, and changes in ocean productivity. These changes directly impact valuable habitats in many coastal regions and threaten the important services the habitats provide to mankind. Among the most productive and diverse systems are coral reefs and vegetated habitats, including saltmarshes, seagrass meadows, and mangroves. Coral reefs are particularly vulnerable to ocean warming and acidification. Vegetated habitats are receiving heightened attention for their ability to sequester carbon, but they are being impacted by land-use change, sea-level rise, and climate change. Overall, coasts play an important, but poorly quantified, role in the global cycling of carbon. Carbon reservoirs on land and in the ocean are connected through the so-called land–ocean aquatic continuum, which includes rivers, estuaries, and the coastal ocean. Terrestrial carbon from soils and rocks enters this continuum via inland water networks and is subject to transformations and exchanges with the atmosphere and sediments during its journey along the aquatic continuum. The expansive permafrost regions, comprised of ground on land and in the seabed that has been frozen for many years, are of increasing concern because they store vast amounts of carbon that is being mobilized due to warming. Quantitative estimates of these transformations and exchanges are relatively uncertain, in large part because the systems are diverse and the fluxes are highly variable in space and time, making observation at the necessary spatial and temporal coverage challenging. But despite their uncertainty, existing estimates point to an important role of these systems in global carbon cycling.
... Corals inhabiting higher latitudes face marginal conditions, yield less calcareous accretion due to low temperatures and low aragonite saturation, resulting in lower growth rates (Kleypas et al., 1999;Veron et al., 2015). Increases in temperature may remove some of these physiological limitations (McIlroy et al., 2019) and positively affect expanding species by promoting establishment in subtropical and temperate locations (Price et al., 2019). Dispersal potential, tolerance to environmental gradients such as the resilience to cold stress (Higuchi et al., 2020) and competitive ability are additional key features for overcoming biogeographic barriers (Keith et al., 2015;Sommer et al., 2014). ...
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Communities inhabiting biogeographic transition zones are shifting in composition as a result of progressive warming and heatwaves. In the marine environment, corals are expanding onto higher latitude reefs historically dominated by temperate kelp forests, initiating a shift towards warm‐affinity coral dominated states. Although these coral expansions are a global phenomenon, the mechanisms that are underpinning the expansion process remain poorly understood, which limits the projections of the rate and extent of ecosystem reconfiguration. Here, we investigated the interaction between the kelp Ecklonia radiata and the high latitude scleractinian coral Plesiastrea versipora in several of Western Australia’s temperate reefs, where coral colony abundance has increased by 50% in recent years. Combining field surveys with field and laboratory experiments, we test the importance of physical (abrasion and light reduction) and chemical (allelopathic effects) effects of kelp canopies on coral tissue cover, photosynthetic parameters, and calcification rates. In the field, kelp cover had a negative effect on coral density that was overwhelming in comparison to other dominant macroalgal taxa. Abrasion by kelp whiplash was the predominant mechanism by which kelp exerted a negative effect on P. versipora fitness, scraping up to 80% of live coenosarc from experimental colonies. In contrast, canopies had no effects on P. versipora photochemical efficiency and laboratory incubations showed that there were no allelochemical effects from kelp on P. versipora. We conclude that E. radiata inhibits P. versipora establishment and development through abrasion, and the survey data confirmed that recent climate‐driven kelp loss released corals from this effect, facilitating their expansion on high‐latitude reefs in Western Australia. This shows how competitive interactions actively shield against species expansion in biogeographic transition zones and suggests a continued decline of kelp canopies will increase the permeability of temperate reefs to warm affinity species such as scleractinian corals.
... Other than the association between recruitment and K d490 that emerged from tiles retrieved in January/February and August/September (which reversed between times), recruitment on the August/September tiles was associated with features differing from those associated with recruitment on January/February tiles. The reasons for these differences are unclear, but it is noteworthy that additional information on the causes of variable recruitment only came to light through analyses of the results generated through biannual deployment of tiles that is uncommon in coral biology (e.g., Price et al. 2019). Indeed, pooling of the present recruitment results between samplings within a year, and testing for associations with temperature produced evidence of curvilinear relationships with the mean and variation in temperature that differed between depths (Edmunds 2021). ...
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Measurements of coral recruitment can improve understanding of coral population dynamics, but in short duration studies high variance impedes interpretation of this vital rate. Here, coral recruitment in Moorea, French Polynesia, was measured over 13 yr and tested for associations with environmental conditions. Recruitment of spawning pocilloporid corals was recorded using settlement tiles immersed for ~ 6 months at 10 m and 17 m depth, biannually, and the environment was quantified through seawater clarity (Kd490), surface and bottom flow speeds, coral cover, and temperature. Using GAMs, most of the variation (63–74%) in recruitment was explained using depth and three predictors. Recruitment was high in January/February following a year of low seawater clarity (high Kd490), and in August/September following a year of high clarity. Recruitment in January/February was elevated by high coral cover, and by high surface flow during larval dispersal; recruitment was low in August/September following high temperature during gametogenesis. These effects reveal the extent to which early life stages of corals are exposed to annually variable environmental conditions that have differential consequences depending on the phenology of reproduction and recruitment. The temporal mosaic defining interactions between reproduction, recruitment, and environmental conditions create opportunities for acclimatization to affect where and when coral recruitment is successful.
... The poleward expansion of corals occurs during the larval periods and depends on ocean currents and habitat suitability 53 . Recent evidences point to a decline in coral recruitment in tropical regions and an increase in extratropical regions 54 , demonstrating the potential for distribution shift. Contrary to terrestrial species, range expansions are more likely and occur faster in marine species, which tend to have longer dispersal periods in the water column and higher sensitivity to temperature change 16 . ...
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Global climate change is a major threat to reefs by increasing the frequency and severity of coral bleaching events over time, reducing coral cover and diversity. Ocean warming may cause shifts in coral communities by increasing temperatures above coral’s upper thermal limits in tropical regions, and by making extratropical regions (marginal reefs) more suitable and potential refugia. We used Bayesian models to project coral occurrence, cover and bleaching probabilities in Southwestern Atlantic and predicted how these probabilities will change under a high-emission scenario (RCP8.5). By overlapping these projections, we categorized areas that combine high probabilities of coral occurrence, cover and bleaching as vulnerability-hotspots. Current coral occurrence and cover probabilities were higher in the tropics (1°S–20°S) but both will decrease and shift to new suitable extratropical reefs (20°S–27°S; tropicalization) with ocean warming. Over 90% of the area present low and mild vulnerability, while the vulnerability-hotspots represent ~ 3% under current and future scenarios, but include the most biodiverse reef complex in South Atlantic (13°S–18°S; Abrolhos Bank). As bleaching probabilities increase with warming, the least vulnerable areas that could act as potential refugia are predicted to reduce by 50%. Predicting potential refugia and highly vulnerable areas can inform conservation actions to face climate change.
... Worldwide, the pole-ward shift of species has been reported for many taxa belonging to different trophic levels and functional groups (Jones & Cheung, 2015). These include sessile and benthic species such as seaweeds and seagrasses (Hyndes et al., 2016;Wernberg et al., 2011), echinoderms, mollusks (Mulders & Wernberg, 2020), hermatypic corals (Price et al., 2019), and highly mobile fauna such as fish (Hastings et al., 2020;Vergés, Tomas, et al., 2014). However, changes in the composition of foundation species will have the greatest consequences for the functioning of the ecosystems (Vergés et al., 2019). ...
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Abstract Temperate reefs are increasingly affected by the direct and indirect effects of climate change. At many of their warm range edges, cool‐water kelps are decreasing, while seaweeds with warm‐water affinities are increasing. These habitat‐forming species provide different ecological functions, and shifts to warm‐affinity seaweeds are expected to modify the structure of associated communities. Predicting the nature of such shifts at the ecosystem level is, however, challenging, as they often occur gradually over large geographical areas. Here, we take advantage of a climatic transition zone, where cool‐affinity (kelp) and warm‐affinity (Sargassum) seaweed forests occur adjacently under similar environmental conditions, to test whether these seaweed habitats support different associated seaweed, invertebrate, coral, and fish assemblages. We found clear differences in associated seaweed assemblages between habitats characterized by kelp and Sargassum abundance, with kelp having higher biomass and seaweed diversity and more cool‐affinity species than Sargassum habitats. The multivariate invertebrate and fish assemblages were not different between habitats, despite a higher diversity of fish species in the Sargassum habitat. No pattern in temperature affinity of the invertebrate or fish assemblages in each habitat was found, and few fish species were exclusive to one habitat or the other. These findings suggest that, as ocean warming continues to replace kelps with Sargassum, the abundance and diversity of associated seaweeds could decrease, whereas fish could increase. Nevertheless, the more tropicalized seaweed habitats may provide a degree of functional redundancy to associated fauna in temperate seaweed habitats.
... When we think about the effects that climate change will have on the survival of different species, we often think about macroscopic and eukaryotic examples, such as the decline in polar bear populations due to the decrease in sea ice area (Stirling et al., 1999). Or, another example is the increased bleaching of coral reefs -a result of temperatures ≥ 1 • C warmer than the usual for the summer -and their observed diminishment in tropical regions concomitant with their "retreat" to the subtropics (Price et al., 2019). And yet another example is the global decline in amphibian populations, due to infection by a fungus that appears to thrive in warmer conditions (Cohen et al., 2019). ...
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Circadian clocks are phylogenetically widespread biological oscillators that allow organisms to entrain to environmental cycles and use their steady-state phase relationship to anticipate predictable daily phenomena – such as the light-dark transitions of a day – and prepare accordingly. Present from cyanobacteria to mammals, circadian clocks are evolutionarily ancient and are thought to increase the fitness of the organisms that possess them by allowing for better resource usage and/or proper internal temporal order. Here, we review literature with respect to the ecology and evolution of circadian clocks, with a special focus on cyanobacteria as model organisms. We first discuss what can be inferred about future clock evolution in response to climate change, based on data from latitudinal clines and domestication. We then address our current understanding of the role that circadian clocks might be contributing to the adaptive fitness of cyanobacteria at the present time. Lastly, we discuss what is currently known about the oldest known circadian clock, and the early Earth conditions that could have led to its evolution.
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Climate warming is driving a global redistribution of marine life as species shift their distribution to accommodate temperature changes. This is often analysed at the ocean surface, but a global analysis of temperature vertical migration provides a new perspective of the challenges and opportunities for marine life under future warming.
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After centuries of human-mediated disturbances, Caribbean reef communities are vastly different from those described in the 1950s. Many are functionally dominated by macroalgae, but this community state represents only one of several possibilities into which present-day coral reefs can transition. Octocorals have always been abundant on Caribbean reefs, but increases in their abundance over the last few decades suggest that arborescent octocorals have the potential to expand their populations on reefs that hitherto had been dominated by scleractinians. Here we show that octocoral-dominated communities at three sites on the fringing reefs of St. John, US Virgin Islands, were resilient to the effects of two Category 5 hurricanes in 2017. We describe the dynamics of octocoral communities over five years at three sites on shallow reefs (~9-m depth), and test for the effects of Hurricanes Irma and Maria. The hurricanes depressed the densities of juvenile and adult octocoral colonies as much as 47%. However, there were only weak effects on species richness and the relative abundances of the octocoral species. The hurricanes did not alter patterns of spatial variability in octocoral community structure that existed among sites prior to the storms. The density of octocoral recruits (individuals ≤ 5 cm high) was reduced in the year following the hurricanes, mainly due to a decline in abundance of recruits <0.5 cm, but returned to pre-storm densities in 2019. Persistently high octocoral recruitment provides a mechanism supporting ecological resilience of these communities. Continuing environmental degradation is a threat to all tropical marine communities, but the reefs of St. John illustrate how “octocoral forests” can persist as the structurally dominant community on Caribbean reefs.
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This chapter focuses on the degradation and destruction of coral reefs, seagrass meadows, and mangrove forests throughout the tropics as an expanding database permits a global assessment of the extent of their degradation and destruction. Coral reef degradation has resulted in changes in community structure of many organisms, especially fish, as well as the abundance of many species, leading to changes in trophic pathways and food web functioning. Like seagrasses, the global area of mangrove forests is uncertain making a definite assessment of long‐term losses of mangroves difficult. Large‐scale erosion has been the main cause of mangrove loss in the Mekong delta. Some mangrove forests have experienced episodes of massive mortality due to hydrological modifications coupled to climatic changes. Degradation of mangrove forests often leads to habitat fragmentation, having serious consequences for ecosystem functioning and the capacity of mangrove to provide ecosystem services, such as preventing shoreline erosion and facilitating shoreline protection.
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Backcasting involves the design of a desirable future that is not simply predicted with forecasts being, instead, proactively aimed at with effective action. So far, all initiatives towards sustainability failed, probably due to lack of investments in the acquisition of knowledge on the structure and the function of natural systems (i.e. biodiversity and ecosystem functioning), and to the reliance on models and estimates based on incomplete data.
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Globally, species are migrating in an attempt to track optimal isotherms as climate change increasingly warms existing habitats. Stony corals are severely threatened by anthropogenic warming, which has resulted in repeated mass bleaching and mortality events. Since corals are sessile as adults and with a relatively old age of sexual maturity, they are slow to latitudinally migrate, but corals may also migrate vertically to deeper, cooler reefs. Herein we describe vertical migration of the Mediterranean coral Oculina patagonica from less than 10 m depth to > 30 m. We suggest that this range shift is a response to rapidly warming sea surface temperatures on the Israeli Mediterranean coastline. In contrast to the vast latitudinal distance required to track temperature change, this species has migrated deeper where summer water temperatures are up to 2 °C cooler. Comparisons of physiology, morphology, trophic position, symbiont type, and photochemistry between deep and shallow conspecifics revealed only a few depth-specific differences. At this study site, shallow colonies typically inhabit low light environments (caves, crevices) and have a facultative relationship with photosymbionts. We suggest that this existing phenotype aided colonization of the mesophotic zone. This observation highlights the potential for other marine species to vertically migrate.
Article
Modern-day Indo-Pacific coral reefs are characterized by rapid recovery driven by pulses of coral recruitment, but Caribbean reefs exhibit low rates of recruitment and poor recovery following a wide range of disturbance events. The contrasting evolutionary history of coral taxa offers key insight into biogeographic patterns of coral resilience. Following the closure of the Isthmus of Panama approximately 2.8 million years ago, widespread extinction of Caribbean corals led to an evolutionary bottleneck that favored large and long-lived species with a relatively high reliance on asexual versus sexual reproduction. In contrast, adaptive radiation led to the evolution of superrecruiting tabular, digitate, and corymbose corals that drive the rapid recovery of modern-day Indo-Pacific reefs following disturbance. The dominance of branching growth forms and evolutionary absence of superrecruiting growth forms throughout the entire evolutionary history of the Caribbean (approximately 38 million years ago to present) may explain the exceptionally high recruitment rates on modern-day Indo-Pacific reefs and low historical recruitment on Caribbean reefs. The evolutionary history of the Caribbean coral reef-building taxa implies that, even with a reversal of ecosystem state, widespread recovery of Caribbean reefs may be limited.
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The Caribbean is facing major threats due to climate change that will continue to cause environmental, economic, and social damage. Compounding these problems are the stressors associated with economic development in the region. The U.S. Virgin Islands are particularly threatened by the complex problems these two issues present as the pressures of increasing tourism threaten vital natural resources, making sustainable economic diversification necessary. As the U.S. Virgin Islands creates economic development and climate adaptation plans, it is also important to understand how local stakeholders are included in the planning process. Research on community engagement can help reveal whether planning is being done equitably. To analyze these problems, this study examined news discourse around the issues of climate change, economic development, and community engagement. By understanding discourse in local media, this study aims to evaluate the construction of knowledge regarding these issues and demonstrate areas of deficiency that should be addressed. This study took quantitative and qualitative approaches to analyze how these issues were discussed in relation to one another and examined these trends in the context of existing policies and challenges being faced by the territory. This study concludes by providing valuable insights for decision-makers to craft strategies informed by the media presentation and associated public perceptions of these issues.
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Climate change is driving ecosystem change across the biosphere on an unprecedented scale. Large biogeographic shifts are underway as habitats move their ranges towards the poles in an attempt to remain in zones that adhere to organisms’ preferred temperature ranges. These new areas of shifting climatic ranges, or refugia, represent important opportunities for the future survival of countless species in a warming world. However, many species may have colonisation rates too slow to keep up with climate change. This may be due to barriers to dispersal, long time periods in reproductive cycles, survival and viability of offspring, geographic isolation of suitable new habitats, stochasticity and other environmental factors. Ecosystem pushing proposes to propagate species into refugia using restoration techniques with the aim of supporting species survival and ecosystem conservation. This paper proposes ecosystem pushing as a new management intervention for the field of coral reef restoration. Management considerations will need to include geographic models of refugia projections to ascertain appropriate locations for restoration work. Other important considerations would include assessing the risks of losing one ecosystem type for another, invasive species and disease introductions, issues of intervention scale and time constraints, and levels of stakeholder engagement with local communities.
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Climate change can potentially impact coral reefs through several key mechanisms, in particular increasing sea surface temperatures, ocean acidification, increasing storminess, and sea level rise. This chapter focuses on the impact of rising sea temperatures on coral reef ecosystems, particularly the effect of mass bleaching of the corals themselves. Bleaching is due to a whitening of the corals following the expulsion of the algae that provide most of the coral's color, and is often considered as a response to increasing sea temperatures. Following major global scale bleaching events in 1982–83, 1987–88, 1994–95, 1997–98, and 2014–17, and regional events in 2002 (Great Barrier Reef; Great Barrier Reef) and 2005 (Caribbean), the link between climate change and large-scale bleaching of corals is now undeniable. While bleaching may offer an opportunity for corals to acquire different species of algae that may be more temperature tolerant, prolonged bleaching can result in the death of the corals, with significant consequences for reef-associated species. The coral reef structure provides refuge to many species; however, once corals die, their skeletons are eroded and the reef structure begins to collapse. Research suggests that a loss of reef structure may result in declines in the abundance, diversity, and productivity of reef fish. In addition, reef fish may be affected by the more direct impacts of climate change, with recent studies observing effects of increased temperature on physiology and behavior. While corals may have a natural ability to adapt to such changes, more frequent and severe bleaching events combined with the impacts of other human activities, such as fishing, pollution, and tourism, make coral reefs among the most vulnerable of the world's ecosystems under current scenarios of future climate change.
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Peyssonnelid algal crusts (PAC) have rapidly spread on coral reefs throughout the Caribbean since 2010 and have become dominant space holders in multiple locations. In 2019, PAC covered 31–86% of the shallow reefs (< 6-m depth) at two sites in St. John, US Virgin Islands, but within halos around aggregates of the echinoid, Diadema antillarum, PAC was absent and small corals were common. To test the hypothesis that the density of small corals is greater in Diadema halos versus on adjacent substrata, and that this effect is accentuated by high coverage of PAC, the shallow reefs of St. John were surveyed in July/August 2019 and January 2020. Densities of small corals (pooled among taxa) in Diadema halos were equal to, or greater than, densities on adjacent substrata, and were highest in Diadema halos adjacent to areas with high coverage of PAC. Where the cover of PAC was ≥ ~ 10%, the mean (± SE) density of small corals was 23.3 ± 2.1 colonies m⁻² in Diadema halos, but was 67% lower at 7.5 ± 1.2 colonies m⁻² on adjacent substrata; where the cover of PAC was < ~10%, densities of small corals were nearly identical in Diadema halos (9.1 ± 0.9 colonies m⁻²) and on adjacent substrata (9.0 ± 1.1 colonies m⁻²). Similar results were obtained when the analyses were repeated for the common corals, Porites spp., Siderastrea radians, and S. siderea. As Diadema halos remained in the same location for at least 6 months, they may function as refuges for coral recruitment in locations where PAC is becoming spatially dominant.
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The coral reef crisis has resulted in many reefs stabilizing in a low coral cover state, and this condition is exemplified by the fringing reefs of St. John, US Virgin Islands, where coral cover has remained low for decades. To evaluate the demographic features maintaining this condition, a decade of coral abundance was examined in three domains: recruits, small colonies (≤ 40-mm diameter), and cover. While cover was stable from 2007 to 2016, other aspects of coral community structure changed in taxonomically unique ways differing among domains. Most changes occurred gradually, although the warm year of 2010 was associated with perturbations in growth, mortality, and density that differed among domains and taxa, and summed to a weak signal distinguishing communities before and after ~ 2011/2012. As a result, coral community structure was taxonomically shuffled within each domain, while low cover was maintained. These low coral cover communities may be characterized by functional redundancy among taxa and a weakening of interactions among them that traditionally have supported emergent properties like community calcification. With persistent failure of recruitment to augment coral cover, some corals may already occur at such low abundances that they cannot perform the ecological services with which they were once associated.
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In coral reef conservation and management, the prevailing metric of reef health is percent coral cover, a measurement commonly used with the assumption that each unit of live coral tissue has equivalent ecological value. Here we show that the reproductive output of a coral population is not proportional to the cover of coral present. Instead, when compared to declining populations nearby, high cover coral populations produced up to four times more larvae per square centimeter of tissue, resulting in up to 200 times higher larval production per square meter of reef. Importantly, corals that produced more larvae did not produce smaller larvae, as predicted by resource allocation theory. Instead, higher fecundity corresponded to higher energetic lipid reserves in higher cover coral populations. In the wake of unprecedented global coral bleaching, our findings suggest that the largest reductions in coral reproduction may occur when corals are lost from previously healthy populations.
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The future of coral reefs under increasing CO2 depends on their capacity to recover from disturbances. To predict the recovery potential of coral communities that are fully acclimatized to elevated CO2, we compared the relative success of coral recruitment and later life stages at two volcanic CO2 seeps and adjacent control sites in Papua New Guinea. Our field experiments showed that the effects of ocean acidification (OA) on coral recruitment rates were up to an order of magnitude greater than the effects on the survival and growth of established corals. Settlement rates, recruit and juvenile densities were best predicted by the presence of crustose coralline algae, as opposed to the direct effects of seawater CO2. Offspring from high CO2 acclimatized parents had similarly impaired settlement rates as offspring from control parents. For most coral taxa, field data showed no evidence of cumulative and compounding detrimental effects of high CO2 on successive life stages, and three taxa showed improved adult performance at high CO2 that compensated for their low recruitment rates. Our data suggest that severely declining capacity for reefs to recover, due to altered settlement substrata and reduced coral recruitment, is likely to become a dominant mechanism of how OA will alter coral reefs. © 2017 The Author(s) Published by the Royal Society. All rights reserved.
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In theMediterrean Sea the population features of demersal resources fluctuate over spatial and temporal scales due to the variability of abiotic and biotic factors as well as to human activities. The two shrimps Parapenaeus longirostris and Aristaeomorpha foliacea are among the most important deep-sea demersal resources in the North-Western Ionian Sea. Their changes in terms of density, biomass andmedian length induced by anthropogenic and environmental variables (fishing effort, sea surface temperature, precipitations, Winter North Atlantic Oscillation (NAO) and Annual MediterraneanOscillation (MO) indices) were investigated. Biological data were collected during trawl surveys carried out from 1995 to 2006 as part of the international program MEDITS (International Bottom Trawl Survey in the Mediterranean). Generalized AdditiveModels were used to evaluate the spatio-temporal variation of both species, together with the possible nonlinear effects of biotic and abiotic factors. Density and biomass were assumed to be distributed according to a member of the Tweedie family in order to account for zero-inflation in the relative data. Spacetime interaction was consideredwithin a non-separablemodel with smooth spatio-temporal component based on tensor product splines. The results show significant spatio-temporal and depth effects in the three population parameters of these resources. Winter NAO index significantly influenced the density, biomass and length of P. longirostris. Sea surface temperature significantly influenced the size of this species and the three population features of A. foliacea. The size of this shrimp resulted also influenced negatively by fishing effort and positively by the MO index.
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Theory suggests that density-associated processes can modulate community resilience following declines in population size. Here, we demonstrate densityassociated processes in two scleractinian populations on the outer reef of Moorea, French Polynesia, that are rapidly increasing in size following the effects of two catastrophic disturbances. Between 2006 and 2010, predation by the corallivorous crown-of-thorns sea star reduced coral cover by 93 %; in 2010, the dead coral skeletons were removed by a cyclone, and in 2011 and 2012, high coral recruitment initiated population recovery. Coral recruitment was associated with coral cover, but the relationship differed between two coral genera that are almost exclusively broadcast spawners in Moorea. Acroporids recruited at low densities, and the density of recruits was positively associated with cover of Acropora, whereas pocilloporids recruited at high densities, and densities of their recruits were negatively associated with cover of Pocillopora. Together, our results suggest that associations between adult cover and density of both juveniles and recruits can mediate rapid coral community recovery after large disturbances. The difference between taxa in sign of the relationships between recruit density and coral cover indicate that they reflect contrasting mechanisms with the potential to mediate temporal shifts in taxonomic composition of coral communities.
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A single ecosystem can exhibit great biogeographic and environmental variability. While a given ecological driver might have a strong impact in one region, it does not necessarily hold that its importance will extend elsewhere. Coral reefs provide a striking example in that coral communities have low resilience in the Atlantic and remarkable resilience in parts of the species-rich Pacific. Recent experimental evidence from the Atlantic finds that fishing of large herbivorous fish can be a strong driver of coral resilience. Here, we repeat the Atlantic experiment in the highly resilient forereef of Moorea (French Polynesia), which has repeatedly recovered from disturbances. A combination of cages, parrotfish deterrents (FDs), and controls allowed us to simulate the consequences of fishing large herbivores on algal assemblages, coral recruitment, and the demographic rates of coral juveniles. We find that the impacts of removing large herbivorous reef fish vary with early coral ontogeny. Reduced herbivore access led to a modest macroalgal bloom and reduction in coral recruitment. However, larger juvenile corals (>1 cm diameter) survived better and grew faster under these conditions because of a reduction in corallivory. To determine the net impact of losing larger herbivorous fish, we combined experimental results with estimated demographic parameters in an individual-based model. Simulating coral recovery trajectories for 5 years, we find that protecting larger reef fish led to better recovery in 66-99% of simulations, depending on underlying assumptions (with the more credible assumptions being associated with greater likelihood of net positive impacts). While we find that fishing effects are detrimental to corals in both the Atlantic and Pacific systems studied, the nature of the interactions varied markedly. In the identical previously-published study in the Atlantic, macroalgae exhibited a rapid bloom and caused a sufficiently large reduction in coral recruitment to force a predicted ecosystem shift to an alternative attractor. The commensurate macroalgal bloom in Moorea was weak yet the corals were two orders of magnitude more sensitive to its presence. We do not suggest that a reduction in recruitment in Moorea will lead to alternative attractors but the long-term risks of a reduction in recovery rate are cause for concern as rates of coral mortality are projected to increase. The emerging picture is that Pacific reefs are less likely to experience macroalgal blooms but are surprisingly sensitive to such blooms if they occur.This article is protected by copyright. All rights reserved.
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Dominance shifts in ecosystems can occur rapidly, resulting in alternative stable states. While some coral reef ecosystems shift and recover relatively quickly, others recover slowly or not at all over periods of centuries. We explore the role of large (fishing-susceptible) parrotfish in triggering algal phase shifts as alternative attractors that may lock reefs into coral-depleted alternative stable states. We designed an experiment to modestly reduce herbivory only from large parrotfish in the immediate vicinity of experimental coral settlement nursery habitats. We used vertical pegs ('parrotfish deterrents' or PDs) around coral settlement plates on 2 Belizean fore reefs. Time-lapse videos and a year's accumulation of bite-marks on plates confirmed that only herbivory from large parrotfish declined significantly due to PDs. Patches of macroalgae developed around PDs reducing coral recruitment in this treatment only. Two dominant reef-dwelling coral genera (Porites and Agaricia) recruited to our settlement plates. The fast-growing, high-light requiring, reef-building coral Porites was more negatively affected by phase shifts; this coral failed to recruit at and above mid-levels of algal abundance. We illustrate the direct roles ecological processes such as herbivory from large parrotfish play in regulating algal abundance, which in turn reduces the recruitment potential of reefs and thus the ecosystem's capacity to recover. Combining our empirical results with an individually-based ecological simulation model, we determined that these processes cascade to drive alternative states and create a 'hysteresis' effect delaying or preventing recovery of the coral reef ecosystem.
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An analysis of present-day global depth distributions of reef-building corals and underlying environmental drivers contradicts a commonly held belief that ocean warming will promote tropical coral expansion into temperate latitudes. Using a global data set of a major group of reef corals, we found that corals were confined to shallower depths at higher latitudes (up to 0.6 meters of predicted shallowing per additional degree of latitude). Latitudinal attenuation of the most important driver of this phenomenon-the dose of photosynthetically available radiation over winter-would severely constrain latitudinal coral range extension in response to ocean warming. Latitudinal gradients in species richness for the group also suggest that higher winter irradiance at depth in low latitudes allowed a deep-water fauna that was not viable at higher latitudes. Copyright © 2015, American Association for the Advancement of Science.
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Rising temperatures caused by climatic warming may cause poleward range shifts and/or expansions in species distribution. Tropical reef corals (hereafter corals) are some of the world's most important species, being not only primary producers, but also habitat-forming species, and thus fundamental ecosystem modification is expected according to changes in their distribution. Although most studies of climate change effects on corals have focused on temperature-induced coral bleaching in tropical areas, poleward range shifts and/or expansions may also occur in temperate areas. We show the first large-scale evidence of the poleward range expansion of modern corals, based on 80 years of national records from the temperate areas of Japan, where century-long measurements of in situ sea-surface temperatures have shown statistically significant rises. Four major coral species categories, including two key species for reef formation in tropical areas, showed poleward range expansions since the 1930s, whereas no species demonstrated southward range shrinkage or local extinction. The speed of these expansions reached up to 14 km/year, which is far greater than that for other species. Our results, in combination with recent findings suggesting range expansions of tropical coral-reef associated organisms, strongly suggest that rapid, fundamental modifications of temperate coastal ecosystems could be in progress.
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Knowledge of the degree to which corals undergo physiological acclimatization or genetic adaptation in response to changes in their thermal environment is crucial to the success of coral reef conservation strategies. The potential of corals to acclimatize to temperatures exceeding historical thermal regimes was investigated by reciprocal transplantation of Acropora millepora colonies between the warm central and cool southern regions of the Great Barrier Reef (GBR) for a duration of 14 months. Colony fragments retained at native sites remained healthy, whereas transplanted fragments, although healthy over initial months when temperatures remained within native thermal regimes, subsequently bleached and suffered mortality during seasonal temperature extremes. Corals hosting Symbiodinium D transplanted to the southern GBR bleached in winter and the majority suffered whole (40%; n=20 colonies) or partial (50%) mortality at temperatures 1.1 degrees C below their 15-year native minimum. In contrast, corals hosting Symbiodinium C2 transplanted to the central GBR bleached in summer and suffered whole (50%; n=10 colonies) or partial (42%) mortality at temperatures 2.5 degrees C above their 15-year native maximum. During summer bleaching, the dominant Symbiodinium type changed from C2 to D within corals transplanted to the central GBR. Corals transplanted to the cooler, southern GBR grew 74-80% slower than corals at their native site, and only 50% of surviving colonies reproduced, at least partially because of cold water bleaching of transplants. Despite the absence of any visual signs of stress, corals transplanted to the warmer, central GBR grew 52-59% more slowly than corals at their native site before the summer bleaching (i.e., from autumn to spring). Allocation of energy to initial acclimatization or reproduction may explain this pattern, as the majority (65%) of transplants reproduced one month earlier than portions of the same colonies retained at the southern native site. All parameters investigated (bleaching, mortality, Symbiodinium type fidelity, reproductive timing) demonstrated strong interactions between genotype and environment, indicating that the acclimatization potential of A. millepora populations may be limited by adaptation of the holobiont to native thermal regimes.
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Staghorn coral (Acropora cervicornis) and elkhorn coral (Acropora palmata), are important reef builders in the Caribbean. In the early to middle Holocene (10000-6000 years ago), when sea temperatures were warmer than today, Acropora-dominated reefs were common along the east coast of Florida as far north as Palm Beach County. The fossil record shows that the northern limits of these two cold-sensitive species subsequently contracted to Biscayne Bay, south of Miami, apparently as a result of climatic cooling. This response of the Acropora species to climate provides a context for interpreting recent shifts in their geographic distribution. Despite recent disease-induced mass mortalities throughout the Caribbean and western Atlantic, the two species are now re-expanding their ranges northward along the Florida Peninsula and into the northern Gulf of Mexico, coincident with increasing sea temperatures. In the face of continued global warming, the northernmost limit of this range expansion will ultimately be determined by a combination of temperature and other physical constraints.
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The recruitment of juvenile corals and post-settlement mortality are important processes for coral population dynamics and reef community ecology. I monitored juvenile coral recruitment and survival on a severely disturbed reef in Bermuda from 1981 to 1989 and on adjacent healthy reefs from 1986 to 1990. Porites astreoides was the dominant recruiting species at all sites, due to the release of brooded planulae that may settle rapidly. The dominant corals on Bermuda's reef, Diploria spp., were poor recruiters, perhaps due to the broadcast mode of reproduction of these species. However, Diploria spp. have lower juvenile mortality rates compared to P. astreoides, which may explain their abundance on Bermuda's reefs. Brooding corals, primarily agariciids, were the dominant recruits on Atlantic reefs compared to high recruitment rates by spawning acroporids in the Pacific, which may be the result of different environmental conditions and/or evolutionary trends in the two oceans. The latter group also suffered high post-settlement mortality compared to brooding coralsin both the Atlantic and the Pacific. Massive corals in both oceans had generally low recruitment rates, related to their spawning mode of reproduction, and low rates of post-settlement mortality. The dominant role of long-lived massive corals on the Atlantic and Pacific reefs can be understood in terms of their life-history strategy in comparison to the relatively short-lived Pacific acroporids and Atlantic agariciids that rely on different strategies to maintain their populations.
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Using results from four coupled global carbon cycle-climate models combined with in situ observations, we estimate the effects of future global warming and ocean acidification on potential habitats for tropical/subtropical and temperate coral communities in the seas around Japan. The suitability of coral habitats is classified on the basis of the currently observed regional ranges for temperature and saturation states with regard to aragonite (Ωarag). We find that, under the "business as usual" SRES A2 scenario, coral habitats are projected to expand northward by several hundred kilometers by the end of this century. At the same time, coral habitats are projected to become sandwiched between regions where the frequency of coral bleaching will increase, and regions where Ωarag will become too low to support sufficiently high calcification rates. As a result, the habitat suitable for tropical/subtropical corals around Japan may be reduced by half by the 2020s to 2030s, and is projected to disappear by the 2030s to 2040s. The habitat suitable for the temperate coral communities is also projected to decrease, although at a less pronounced rate, due to the higher tolerance of temperate corals for low Ωarag. Our study has two important caveats: first, it does not consider the potential adaptation of the coral communities, which would permit them to colonize habitats that are outside their current range. Second, it also does not consider whether or not coral communities can migrate quickly enough to actually occupy newly emerging habitats. As such, our results serve as a baseline for the assessment of the future evolution of coral habitats, but the consideration of important biological and ecological factors and feedbacks will be required to make more accurate projections.
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Coral mortality has increased in recent decades, making coral recruitment more important than ever in sustaining coral reef ecosystems and contributing to their resilience. This review summarizes existing information on ecological factors affecting scleractinian coral recruitment. Successful recruitment requires the survival of coral offspring through sequential life history stages. Larval availability, successful settlement, and post-settlement survival and growth are all necessary for the addition of new coral individuals to a reef and ultimately maintenance or recovery of coral reef ecosystems. As environmental conditions continue to become more hostile to corals on a global scale, further research on fertilization ecology, connectivity, larval condition, positive and negative cues infl uencing substrate selection, and post-settlement ecology will be critical to our ability to manage these diverse ecosystems for recovery. A better understanding of the ecological factors infl uencing coral recruitment is fundamental to coral reef ecology and management.