Extremely high but localized pulses of coral recruitment in the southwestern lagoon of New Caledonia and implications for conservation (original) (raw)
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Marine Pollution Bulletin, 2010
We investigated the spatial distribution of adult and juvenile coral assemblages in the southwestern lagoon of New Caledonia, from disturbed fringing reefs within bays, to oceanic barrier reefs. Generic richness, abundance, and percent cover were highly variable at this scale, but no clear cross-shelf gradient was found. Rather, community composition was more related to reef biotopes. Correlations and canonical correspondence analyses revealed that composition and abundance of coral assemblages were related to substrate types (cover of turf algae and cover of encrusting coralline algae), but not to water quality or metal concentrations in sediments. We found a strong relationship between juvenile and adult distribution for all dominant genera, which suggests that recruitment processes are also a major factor structuring these populations. The densities of juveniles and their proportion in the coral assemblages were relatively low, which implies that replenishment capacities and potential for recovery are probably limited for these reefs.
Compiled abundances of juvenile corals revealed no change over time in the Pacific, but a decline in the Caribbean. Using these analyses as a rationale, we explored recruitment and post-settlement success in determining coral cover using studies in the Caribbean (St John, Bonaire) and Pacific (Moorea, Okinawa). Juvenile corals, coral recruits, and coral cover have been censused in these locations for years, and the ratio of juvenile (J) to recruiting (R) corals was used to measure post-settlement success. In St John and Bonaire, coral cover was stable but different between studies, with the CSIRO PUBLISHING Journal compilation Ó CSIRO 2015 www.publish.csiro.au/journals/mfr ratio of the density of juveniles to density of recruits (J : R) ,0.10; in Moorea, declines in coral cover were followed by recovery that was related to the density of juvenile corals 3 years before, with J : R ,0.40; and in Okinawa, a decline in coral cover in 1998 was followed by a slow recovery with J/R ,0.01. Coral cover was associated positively with juvenile corals in St John, and in Okinawa, the density of juvenile corals was associated positively with recruits the year before. J : R varied among studies, and standardised densities of juvenile corals declined in the Caribbean, but increased in the Pacific. These results suggest that differences in the post-settlement success may drive variation in coral community structure. B Marine and Freshwater Research P. J. Edmunds et al. D Marine and Freshwater Research P. J. Edmunds et al.
Marine Ecology Progress Series, 2013
We compared relationships among distribution patterns of recruits, juveniles and adults of 3 different coral families with distinct life history traits at multiple spatial scales in an insular, fragmented reef system characterized by recurrent disturbances to better understand recruitment and maintenance processes of reef corals. The goal of our study was to detect at what scale most abundance variation occurred, and if this was consistent among life cycle stages and life histories. Results demonstrate a very high spatial variability of recruitment rates at the re gional, insular and local hierarchical levels, with some locations displaying much higher recruitment rates than others, in 2 successive seasons. Juvenile and adult abundances were less variable, and most of the variation occurred at a local level for these life cycle stages. Recruit assemblage composition differed from juvenile and adult ones, which were much more similar. Moreover, abundance variation of recruits was unrelated to variation of juveniles and adults, but juvenile abundance was significantly correlated with adult abundance across all levels. These results have important implications for conservation planning, showing that some locations have better recovery abilities, and revealing the paramount importance of events occurring during the first weeks and months after settlement on the distribution of adults at regional, island and local levels, thus confirming the significance of local processes in shaping coral assemblages distribution and maintenance.
Recruitment Drives Spatial Variation in Recovery Rates of Resilient Coral Reefs
Scientific reports, 2018
Tropical reefs often undergo acute disturbances that result in landscape-scale loss of coral. Due to increasing threats to coral reefs from climate change and anthropogenic perturbations, it is critical to understand mechanisms that drive recovery of these ecosystems. We explored this issue on the fore reef of Moorea, French Polynesia, following a crown-of-thorns seastar outbreak and cyclone that dramatically reduced cover of coral. During the five-years following the disturbances, the rate of re-establishment of coral cover differed systematically around the triangular-shaped island; coral cover returned most rapidly at sites where the least amount of live coral remained after the disturbances. Although sites differed greatly in the rate of return of coral, all showed at least some evidence of re-assembly to their pre-disturbance community structure in terms of relative abundance of coral taxa and other benthic space holders. The primary driver of spatial variation in recovery was ...
Landscape-scale variation in coral recruitment in Moorea, French Polynesia
Marine Ecology Progress Series, 2010
In this study, we describe spatio-temporal variation in coral recruitment in the back reef of Moorea, French Polynesia, and explore the extent to which it is associated with community structure, seawater temperature, and wave regimes. Recruitment was assessed with settlement tiles deployed at 10 sites on the north, southeast, and southwest shores and sampled every 5 to 7 mo from 2005 to 2007. Temperature and waves were measured using thermistors and pressure sensors, and community structure was assessed using in situ surveys. Mean recruitment varied from 0 to 6 recruits tile-1 (510 cm 2) and was generally greater in the second compared to the first year of the study. Recruitment varied among sites, and this variation was similar between years but differed among sampling periods: acroporids were common on the southwest shore between January and September, but rare from September to January; poritids were common on the north shore between September and January, but rare on the southwest shore from January to September; and pocilloporids were found all year, but at slightly elevated densities between January and September. The mean daily seawater temperature, and the daily range, varied among sites, but neither was closely related to coral recruitment, and both were of biologically small magnitudes. The coral community structure also varied among sites, but likewise, was not associated with coral recruitment. In contrast, outer reef wave energy exposure, which likely played an important role in driving cross-reef transport of seawater into the lagoon, differed between shores and seasons in a pattern consistent with the variation in coral recruitment in the back reef. We hypothesize that coral recruitment in the back reef of Moorea is influenced by the interaction of seasonal variation in wave exposure, family-level differences in coral reproductive timing, and the spatial distribution of adult corals.
Bulletin of Marine Science -Miami-
Reef restoration is becoming increasingly popular as tropical coral reefs through the world are subject to increasing levels of anthropogenic and natural damage. This study examined recruitment rates of scleractinian and milleporan corals in three different reef systems and assessed the potential for rapid natural reef recovery based on coral recruitment rates. Scleractinian summer recruitment at sites in the Commonwealth of the Northern Mariana Islands, Western Pacific Ocean ranged from 0 to 112 spat m−2; mean annual recruitment in Fiji, South Pacific Ocean and the U.S. Virgin Islands, Caribbean Sea varied from 51-1812 spat m−2 and 89-180 spat m−2, respectively. In the Caribbean no acroporids recruited to the plates and there were few spat from other broadcast spawning species. However, the hydrocoral Millepora, an uncommon recruit in the Pacific studies, was common in the Caribbean study. Some reef systems receive a large natural supply of planulae and coral cover will likely retu...
PLOS ONE, 2019
Coral recruitment refers to the processes allowing maintenance and renewal of coral communities. Recruitment success is therefore indispensable for coral reef recovery after disturbances. Recruitment processes are governed by a variety of factors occurring at all spatial and temporal scales, from centimetres to hundreds of kilometres. In the present context of rising disturbances, it is thus of major importance to better understand the relative importance of different scales in this variation, and when possible, the factors associated with these scales. Multiscale spatio-temporal variability of scleractinian coral recruitment was investigated at two of the Mascarene Islands: Reunion and Rodrigues. Recruitment rates and taxonomic composition were examined during three consecutive six-month periods from regional to micro-local scales (i.e. from hundreds of kilometres to few centimetres) and between two protection levels (no-take zones and general protection zones). Very low recruitment rates were observed. Rodrigues displayed lower recruitment rates than Reunion. Recruit assemblage was dominated by Pocilloporidae (77.9%), followed by Acroporidae (9.9%) and Poritidae (5.2%). No protection effect was identified on coral recruitment, despite differences in recruitment rates among sites within islands. Recruits were patchily distributed within sites but no aggregative effect was detected, i.e. the preferentially colonised tiles were not spatially grouped. Recruits settled mainly on the sides of the tiles, especially at Rodrigues, which could be attributed to the high concentration of suspended matter. The variability of recruitment patterns at various spatial scales emphasises the importance of micro-to macro-local variations of the environment in the dynamics and maintenance of coral populations. High temporal variability was also detected, between seasons and years, which may be related to the early 2016 bleaching event at Rodrigues. The low recruitment rates and the absence of protection effect raise questions about the potential for recovery from disturbances of coral reefs in the Mascarene Islands.
Global biogeography of coral recruitment: tropical decline and subtropical increase
Marine Ecology Progress Series, 2019
Despite widespread climate-driven reductions 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% origi nating 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 de clines in coral recruitment, on a global scale (i.e. 82% from 1974 to 2012) and throughout the tropics (85% reduction at < 20°latitude), and in creases 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 subtropical latitudes, suggests that coral recruitment may be shifting poleward.
Density-dependent recruitment mediates coral population dynamics on a coral reef.
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.
Predicting Coral Recruitment in Palau’s Complex Reef Archipelago
PLoS ONE, 2012
Reproduction and recruitment are key processes that replenish marine populations. Here we use the Palau archipelago, in the western Pacific Ocean, as a case study to examine scales of connectivity and to determine whether an oceanographic model, incorporating the complex reef architecture, is a useful predictor of coral recruitment. We tested the hypothesis that the reefs with the highest retention also had the highest densities of juvenile coral density from 80 field sites. Field comparisons showed a significant correlation between the densities of juvenile Acropora colonies and total larval recruitment derived from the model (i.e., calculated as the sum of the densities of larvae that self-seeded and recruited from the other reefs in the archipelago). Long-distance larval imports may be too infrequent to sustain coral populations, but are critical for recovery in times of extreme local stress.