Coral Recruitment Patterns Research Articles

Reef location and season, but not recruitment substrate contour and composition, affect coral recruitment patterns

Most studies have quantified coral recruitment using recruitment tiles temporarily deployed on reefs. However, the wide range of tile types used in different studies potentially influences recruitment patterns thereby hindering accurate comparisons among reef areas. We examined the effect of different tile types with different surface structure and composition on spatial (reef locations) and temporal (season) patterns of coral recruitment in the northwestern Philippines. Dead coral skeleton, terracotta, and fibre-cement tiles were deployed and retrieved quarterly over a 15-month period. In contrast to previous studies, patterns of standardized density and composition of recruits were consistent among tile types. Recruits varied spatially and were highest in Caniogan reef, followed by Cory reef and Lucero reef, suggesting that coral recruitment in the Bolinao-Anda Reef Complex (BARC) is influenced by reef location and existing coral cover. Highest recruitment was also found during the peak coral spawning season. The results of this study contrast with some previous reports which indicate that coral recruitment patterns are strongly influenced by recruitment substrate types. Our study suggests that once sufficient biological conditioning of the tile surfaces has occurred, the microbial and algal community present on the different tile surfaces are similarly conducive to larval settlement of some coral taxa.

In situ Estimation of Coral Recruitment Patterns From Shallow to Mesophotic Reefs Using an Optimized Fluorescence Imaging System

Coral recruitment represents a key element for coral reef persistence and resilience in the face of environmental disturbances. Studying coral recruitment patterns is fundamental for assessing reef health and implementing appropriate management strategies in an era of climate change. The FluorIS system has been developed to acquire high resolution, wide field-of-view (FOV) in situ images of coral recruits fluorescence and has proven successful in shallow reef environments. However, up to now, its applicability to mesophotic coral ecosystems remains unknown due to the complexity of the system and the limited time available when working at mesophotic depth. In this study we optimized the FluorIS system by utilizing a single infrared-converted camera instead of the bulkier regular dual-camera system, substantially reducing the system complexity and significantly decreasing the acquisition time to an average of 10 s for a set of 3 images. Moreover, the speed-FluorIS system is much more economical, decreasing the cost of the full set-up by roughly 40% compared to the original dual-camera system. We tested the utility of the speed-FluorIS by surveying coral recruits across shallow and mesophotic reefs of the Red Sea (Gulf of Eilat) and Bermuda, two of the most northerly reefs in the world with markedly different substrate and topography, and demonstrate that the modified system enables fast imaging of fluorescence to study coral recruitment patterns over a broader range of depths and reef topographies than previous fluorescence methods. Our single-camera system represents a valuable, non-invasive and rapid underwater tool which will help standardize surveys and long-term monitoring of coral recruits, contributing to our understanding of these vital and delicate early life stages of corals.

Spatial and Temporal Variation of Scleractinian Coral Recruitment in Balok Coastal Waters and Bidong Island, Malaysia

Understanding coral recruitment is important as increasing of regional decline of coral reef worldwide. This study aimed to investigate the spatial and temporal coral recruitment patterns around reef sites in Balok coastal waters and Bidong Island, Malaysia. Recruitment density was determined by quantifying number of coral recruits settled on the terra-cotta tiles and artificial reef settlement plates. In Balok coastal waters, a total of 159 coral recruits were counted with 0.09 ± 0.03 n/m2 mean recruitment density per plate, while in Bidong Island, a total of 319 coral recruits were counted with 0.19 ± 0.02 n/m2 mean recruitment density per plate. Coral recruits were dominated by genus Pocillopora followed by Stylopora and Seriatopora in Bidong. Meanwhile in Balok, genus Platygyra was dominant coral recruits followed by Porites and Fungia. Additionally, minor spawning event was predicted in Balok coastal waters in September due to increase number of Platygyra coral. Recruitment density varied significantly between locations, types of settlement plates and plate’s orientation at both study areas. Current findings highlighted the significant use of artificial reef plates to increase the chances of larval settlement. This research also provides important information in assessing coral resilience towards different environmental conditions between coastal and sheltered reef areas.

Coral larval recruitment in north-western Australia predicted by regional and local conditions

Understanding ecological processes that shape contemporary and future communities facilitates knowledge-based environmental management. In marine ecosystems, one of the most important processes is the supply of new recruits into a population. Here, we investigated spatiotemporal variability in coral recruitment at 15 reefs throughout the Dampier Archipelago, north-western Australia between 2015 and 2017 and identified the best environmental predictors for coral recruitment patterns over this period. Large differences in recruitment were observed among years with the average density of recruits increasing by 375% from 0.017 recruits cm−2 in 2015 to 0.059 recruits cm−2 in 2017. Despite differences in recruitment among years, the rank order of coral recruit density among reefs remained similar among years, suggesting that spatial variation in recruitment within the Dampier Archipelago is partly deterministic and predictable. The density of coral recruits was best explained by percent cover of live corals at both local (within 5 m) and meso-scales (within 15 km), water turbidity and an oceanographic model that predicted larval dispersal. The highest density of coral recruits (~0.13 recruits cm−2 or 37 recruits per tile) occurred on reefs within sub-regions (15 km) with greater than 35% coral cover, low to moderate turbidity (KD490 < 0.2) and moderate to high modelled predictions of larval dispersal. Our results demonstrate that broad-scale larval dispersal models, when combined with local metrics of percent hard coral cover and water turbidity, can reliably predict the relative abundance of coral recruits over large geographical areas and thus can identify hotspots of recruit abundance and potential recovery following environmental disturbances; information that is essential for effective management of coral reefs.

Depth-related patterns in coral recruitment across a shallow to mesophotic gradient

There is currently very limited information around the spatial patterns of coral recruitment at mesophotic depths globally. This study investigated depth-related differences in coral recruitment patterns from shallow (~ 3 m) to mesophotic depths (~ 40 m) in the Indian Ocean. A new method is described for assessing coral recruitment, which allows for the improved study of recruitment patterns on deep reefs globally, as the method does not require SCUBA diving. This method allows for comparisons with other studies as there appears to be no influence on the density, composition, or settlement orientation of recruits relative to the most commonly used methods. Using this method, we investigated coral recruitment at Ningaloo Reef, Western Australia, finding the abundance of coral recruits varied significantly with depth and was highest at 25 m. The size of coral recruits changed significantly with depth, with larger recruits observed in shallower areas (3 and 8 m) than in deep areas. Distinct changes in settlement densities on tile surfaces occurred with increasing depth, with a shift to upper tile surfaces between 8 and 25 m, where the proportion of recruits increased from 10.72 to 87.69%, respectively. Overall counts of recruits were low, with minimal recruitment at the deepest sites and moderate but significant correlations between recruit numbers and hard coral cover were observed. This suggests that variations in larval supply, potentially coupled with larval behaviour and local-scale influences, limit exchange of larvae between depths and locations. This is consistent with genetic studies that show limited exchange between shallow and mesophotic reefs and points to a limited potential for mesophotic reefs to act as a source of larvae for impacted shallow reefs.

Coral recruitment patterns in the Florida Keys.

This study examines scleractinian zooxanthellate coral recruitment patterns in the Florida Keys to determine if differences in density or community composition exist between regions. From July to September 2002, nine patch reefs, three in each of the upper, middle and lower Keys, were surveyed for coral recruits (colonies <5 cm in diameter) using randomly placed quadrats and transects. Coral recruits were enumerated, measured, and identified to genus. Fourteen genera of corals were observed across all sites and ranged from five to 13 per site. Densities ranged from 6.29 +/- 1.92 (mean +/- SE) to 39.08 +/- 4.53 recruits m(-2), and there were significant site and regional differences in recruit densities. The density of recruits in the upper Keys was significantly lower than in the middle and lower Keys. In addition, the upper Keys were less diverse and had a different recruit size-frequency distribution. The majority of recruits were non-massive scleractinian species that contribute relatively little to overall reef-building processes, a finding that is similar to previous studies. Fewer recruits of massive species were found in the upper Keys compared to the middle and lower Keys. The recruitment patterns of the reefs in the upper Keys could potentially hinder their ability to recover from stress and disturbances.

Patterns of scleractinian coral recruitment at Lord Howe Island, an isolated subtropical reef off eastern Australia

Changing oceanic conditions, particularly ocean warming and altered currents, can affect the reproductive success of corals. Improving the knowledge of coral reproductive processes at the marginal range limits of coral reefs is important for understanding the ecology of subtropical coral communities and the potential for coral species to expand their ranges in higher latitudes in the future. The extent of live coral cover around subtropical Lord Howe Island (LHI; 31°33′S, 159°05′E) approximately 600 km off the east coast of Australia, has been relatively stable over the last several decades; however, shifts in dominant species in the adult coral community have been reported. To examine the potential influences of recent altered currents and shifts in dominant scleractinian taxa within this community, this study examined spatial and seasonal variation of coral larval settlement at different habitats within the LHI reef lagoon. The study also assessed whether the assemblage of scleractinian corals settling at LHI has changed between 1990–1991 and 2011–2012. Mean densities of coral settlement in 2011–2012 (230 spat m−2 yr−1) were consistent with those reported in 1990–1991 and in other regions. However, changes in taxonomic composition were apparent with increases in the proportion of Acroporidae spat at some sites. Settlement of all taxa was highest over summer months, whereas during winter only one coral spat (Pocilloporidae) was detected. Coral settlement was highest and most taxonomically diverse at sites closest to the reef crest, where mortality of settled spat was also greatest. Rates of settlement were high compared with juvenile densities; hence, post-settlement mortality is also likely to be high. Post-settlement processes, influenced by local environmental conditions, are likely to be very important in structuring the adult coral communities within the LHI reef lagoon.

Characterizing the ecological trade‐offs throughout the early ontogeny of coral recruitment

Abstract Drivers of recruitment in sessile marine organisms are often poorly understood, due to the rapidly changing requirements experienced during early ontogeny. The complex suite of physical, biological, and ecological interactions beginning at larval settlement involves a series of trade‐offs that influence recruitment success. For example, while cryptic settlement within complex microhabitats is a commonly observed phenomenon in sessile marine organisms, it is unclear whether trade‐offs between competition in cryptic refuges and predation on exposed surfaces leads to higher recruitment.To explore the trade‐offs during the early ontogeny of scleractinian corals, we combined field observations with laboratory and field experiments to develop a mechanistic understanding of coral recruitment success. Multiple experiments conducted over 15 months in Palau (Micronesia) allowed a mechanistic approach to study the individual factors involved in recruitment: settlement behavior, growth, competition, and predation, as functions of microhabitat and ontogeny. We finally developed and tested a predictive recruitment model with the broader aim of testing whether our empirical insights explained patterns of coral recruitment and quantifying the relative importance of each trade‐off.Coral settlement was higher in crevices than exposed microhabitats, but post‐settlement bottlenecks differed markedly in the presence (uncaged) and absence (caged) of predators. Incidental predation by herbivores on exposed surfaces at early post‐settlement (&lt;3 mm) stages and targeted predation by corallivores at late post‐settlement (3–10 mm) stages exceeded competition in crevices as major drivers of mortality. In contrast, when fish were excluded, competition with macroalgae and heterotrophic invertebrates intensified mortality, particularly in crevices. As a result, post‐settlement trade‐offs were reversed, and recruitment was more than twofold higher on exposed surfaces than crevices. Once post‐settlement bottlenecks were overcome, survival was higher on exposed surfaces regardless of fish exclusion. However, maximum recruitment occurred in crevices of uncaged treatments, being ninefold higher than caged treatments. Overall, we characterize recruitment success throughout the earliest life‐history stages of corals and uncover some intriguing trade‐offs between growth, competition and predation, highlighting how these change and even reverse during ontogeny and under alternate disturbance regimes.

Spatio-temporal patterns of coral recruitment at Vamizi Island, Quirimbas Archipelago, Mozambique

Spatial and temporal patterns of recruitment of reef corals were assessed for the first time in Mozambique by deploying settlement plates at various spatio-temporal scales between October 2012 and October 2013. The abundance of juvenile corals (5−50 mm in diameter) was assessed along transects. Settlement of acroporids was highly seasonal, with 97% of spat settling between July and October 2013. Pocilloporids settled throughout the year, peaking slightly between October 2012 and January 2013. The annual mean larval settlement of up to 1 135 spat m−2 was comparable to that on other East African reefs, but was dominated by acroporids, which constituted over 80% of all spat, whereas pocilloporids settle in higher densities in Kenya and South Africa. The peak settlement season also differed from other African locations. A greater proportion of variance in settlement rates occurred at the spatial scale of kilometres (between sites) and centimetres (between settlement plates) than at the scale of metres (between subsites), implying that most patchiness occurs at those scales. The peak in acroporid settlement coincided with the period of multispecific spawning, with settlement occurring as early as nine days after a spawning event. As no similar spawning events have been reported for other reefs in the area, our results suggest that these spawning events strongly influence overall annual settlement rates and promote high levels of self-seeding at Vamizi. There was no relationship between settlement of larvae to settlement plates and juvenile density on adjacent reefs, suggesting either variable levels of early post-settlement mortality or high interannual variability in settlement.

SCLERACTINIAN CORAL RECRUITMENT DENSITY IN COASTAL WATER OF BALOK, PAHANG, MALAYSIA

Study on scleractinian coral recruitment is important in understanding the mechanisms that regulate their population and the resilience of coral reef communities to disturbance. This study aims to investigate temporal recruitment density of scleractinian coral at selected remote area in Balok, Pahang. Two types of settlement plates, which are terra-cotta tiles and artificial reef, were deployed at three stations to determine the recruitment density. The retrieval of the settlement plate was done at every three months interval started from March to September 2014. A total of 159 coral recruits were counted with mean recruitment densities on both terracotta tiles was 1.52 ± 0.65 and artificial reef plate was 4.37 ± 1.84 respectively. Recruitment was dominated by Platygyra (36%) followed by Porites (32%), Fungia (17%), Turbinaria (7%), Acropora (2%), Stylopora (2%), Montipora (1%), Leptoria (1%), Favites (1%) and Echinophyllia (1%). Kruskal - Wallis ANOVA test shown that recruitment densities varied significantly with plate’s orientation (p &lt; 0.05), but not with sampling stations, type of substrates and month retrieval. Artificial reef plate has better recruitment densities compared to terra-cotta tiles. Coral spat settlement and recruitment patterns were consistent with adult coral distributions. The percentage cover of adult coral varied within the three stations. A total of 33 coral genera from 13 families were recorded during coral video transect survey with Station 3 showed the highest H’ (2.35). Meanwhile, Station 2 showed higher EH’ indexes with 0.82. Therefore, results of this study is important because coral recruitment pattern reflect its adult coral population, and if it closely monitored and harvested sustainably, the survival of parent population could be increased for successful breeding.

Long-term changes in coral communities under stress from sediment

Chronic disturbances of coral reefs are usually caused by a complex combination of several stresses that are increasingly driving coral reef degradation on both a regional and global scale. This study is aimed at assessing the long-term changes of coral communities (2004–2010) by integrated investigation on sedimentation rates, coral community structures and coral recruitment patterns at the study sites in the Western Gulf of Thailand. Sedimentation rates at the study sites during the study periods had means ranging from 29.49 to 59.53mgcm−2d−1. The coral community structures of the study sites did not change much during the study periods, with means of live coral cover 20.47–27.87%. The dominant corals were Porites lutea, Favites abdita, Pavona decussata and Goniopora columna. However, the composition and density of juvenile corals at both study sites were much changed during the study periods. The dominant juvenile corals were P. lutea, Favia spp., Favites spp. and Pocillopora damicornis. The densities of juvenile corals were relatively low and they suffered high mortality rates because of high sediment deposition and macroalgal overgrowth. Coral recovery is a difficult task that will require an ecosystem approach involving several management strategies and measures which include appropriate coastal development, the enhancement of coastal wetlands and effective fishery management.

The Influence of Extreme Climate Events on Models of Coral Colony Recruitment and Survival in the Caribbean

Knowledge of coral recruitment patterns helps us understand how reefs react following major disturbances and provides us with an early warning system for predicting future reef health problems. We have reconstructed and interpreted historical and modern-day recruitment patterns, using growth modeling, in order to understand how hurricanes, storms and bleaching events have influenced coral recruitment in the Caribbean. The results indicate that regional hurricane events negatively impact coral recruitment patterns in the Caribbean, from the south in Tobago to more northerly areas in Belize and Jamaica. However, despite multiple large-scale disturbances, corals are still recruiting to marginal reef systems, and to the Mesoamerican Barrier reef off the coast of Belize. While recruitment and initial growth since the Caribbean-wide bleaching event of 2005 has been successful for Colpophylia natans at the sites studied in North Jamaica, medium and large sized colonies of this species have decreased in numbers since the bleaching event at most sites, except where the rugosity is highest, at Dairy Bull reef.

Hurricanes and coral bleaching linked to changes in coral recruitment in Tobago

Knowledge of coral recruitment patterns helps us understand how reefs react following major disturbances and provides us with an early warning system for predicting future reef health problems. We have reconstructed and interpreted historical and modern-day recruitment patterns, using a combination of growth modelling and in situ recruitment experiments, in order to understand how hurricanes, storms and bleaching events have influenced coral recruitment on the Caribbean coastline of Tobago. Whilst Tobago does not lie within the main hurricane belt results indicate that regional hurricane events negatively impact coral recruitment patterns in the Southern Caribbean. In years following hurricanes, tropical storms and bleaching events, coral recruitment was reduced when compared to normal years ( p = 0.016). Following Hurricane Ivan in 2004 and the 2005–2006 bleaching event, coral recruitment was markedly limited with only 2% ( n = 6) of colonies estimated to have recruited during 2006 and 2007. Our experimental results indicate that despite multiple large-scale disturbances corals are still recruiting on Tobago’s marginal reef systems, albeit in low numbers.

Coral recruitment patterns in high-latitude coral communities in southwestern Shikoku, Japan

造礁サンゴの群集構造と動態に重要な役割を果たしている幼生加入について，四国南西海域の高緯度造礁サンゴ群集で周年にわたる季節変動を調査した。2007年と2008年に，本海域内の須ノ川，西泊，桜浜の3地点で，設置期間を2ヶ月とする定着板の設置と回収を繰り返した。造礁サンゴ幼生の定着は，5月から9月に設置した定着板で観察された。定着量のピークは，2007年は7-9月，2008年は6-8月で，それぞれ定着板1セットあたり1.7個と2.1個であった。種類別では，ハナヤサイサンゴ科が72.1％で最も多く，次いでハマサンゴ科が12.6％，ミドリイシ科が6.0％であった。これは，本海域の造礁サンゴ群集ではミドリイシ属が優占することと一致しなかった。幼生の定着パターンは種類によって異なっていた。ハナヤサイサンゴ科では，定着は5-7月から9-11月までのおよそ半年にわたったが，本海域での幼生放出期に当たる期間前半で多かった。ハマサンゴ科も同様の期間で定着がみられたが，季節変動は不明瞭であった。ミドリイシ科の定着は，本海域でのミドリイシ科の産卵時期である7月から8月の短期間に集中した。本海域での造礁サンゴの幼生加入は，サンゴ礁域に比べて少なくハナヤサイサンゴ科の割合が高いという，高緯度造礁サンゴ群集に特有の特徴が見られた。

Influence of dead coral substrate morphology on patterns of juvenile coral distribution

This study examines the abundances of three morphological categories of juvenile corals (massive, branching and encrusting) on two different types of natural substratum, dead massive and dead branching corals. The overall results show that the morphological characteristics of dead coral substratum have a significant influence on the coral recruitment patterns with respect to the morphology of the recruits: juvenile corals of massive and branching types were more abundant on substrates of corresponding morphology. The results obtained from this study suggest that dead coral might attract coral larvae that are morphologically similar. On the other hand, it may be the result of post-settlement mortality. Whatever the mechanism shaping the patterns is, it seems that the physical morphology of the dead coral substrate has a significant influence on the coral recruit assemblage. Hence, we suggest that substrate morphology can be an important qualitative factor for coral settlement and a possible determinant of community structure.

Coral recruitment patterns at Sodwana Bay, South Africa

Recruitment is widely acknowledged as one of the most important processes in the maintenance of coral reef systems, particularly in their recovery and replenishment following disturbances. In this study variation in coral recruitment was monitored for 3 years at Sodwana Bay, South Africa, located in the Greater St Lucia Wetland Park (GSLWP), a world heritage site. Due to the latitude (27–28°S) and physical conditions, this area is considered marginal for coral reef growth. Recruitment of corals to ceramic tiles peaked between March and May each year, with broadcast spawners dominating plates in March and brooders more abundant in May. Pocilloporid corals were the most abundant during all periods except March 2001, when acroporids comprised 72% of the total number of spat. Total recruitment was the highest during this period, with a mean of 13.2 ± 15.73 (mean ± SD) corals tile−1. Recruitment rates varied widely between and within different reefs monitored. Patterns of variation were inconsistent between seasons, but some reefs had persistently low rates of settlement.

Coral recruitment: a spatio-temporal analysis along the coastline of Eilat, northern Red Sea

Recruitment rates of stony corals to artificial substrates were monitored for 2 years at 20 sites along the coast of Eilat, northern Red Sea, to compare with those recorded at other coral reef locations and to assess variation in recruitment at several spatial scales. Coral recruitment was low compared to that observed on the Great Barrier Reef in Australia, but was similar to levels reported from other high-latitude reef locations. Pocilloporids were the most abundant coral recruits in all seasons. Recruitment was twofold higher during the first year than during the second year of study. There was considerable spatial variability, with the largest proportion of variance, apart from the error term, attributable to differences between sites, at a scale of 102 m. Spearman’s ranked correlation showed consistency in spatial patterns of recruitment of pocilloporid corals between years, but not of acroporid corals. During spring, when only the brooding pocilloporid coral Stylophora pistillata reproduces at this locality, most coral recruitment occurred at central and southern sites adjacent to well-developed coral reefs. During summer, recruitment patterns varied significantly between years, with wide variation in the recruitment of broadcasting acroporid corals at northern sites located distant from coral reefs. Settlement was low at all sites during autumn and winter. This work is the first detailed analysis of coral recruitment patterns in the Red Sea, and contributes to the understanding of the spatial and temporal scales of variation in this important reef process.

Spatio-temporal variation in coral recruitment at different scales on Heron Reef, southern Great Barrier Reef

Recruitment of scleractinian corals on settlement plates at Heron Island, Great Barrier Reef, was examined over four years (September 1991–September 1995) to quantify spatio-temporal patterns at different scales and to assess post settlement mortality. Recruitment was dominated by pocilloporid corals which accounted for 80.1% of the 8627 spat counted, whereas non-isoporan acroporids represented only 16.4%. Poritids, faviids and isoporan acroporids rarely recruited to the plates (3.5%), despite their obvious abundance as adults on the reef. Recruitment patterns on the plates indicate strong space-time interactions as evidenced by patchy recruitment of both pocilloporid and acroporid spat. Interactions were found between space (on the scale of 102 m, i.e. sites within zones, and 101 m, i.e. racks within sites) and time (on the scale of years) for pocilloporids and between space (on the scale of 103 m, i.e. zones, and 102 m) and time (on the scale of years) for acroporids. Post-recruitment mortality of acroporid spat in the period 3–10 months after their major spawning was dependent on their initial recruitment density, but pocilloporid mortality was either independent of initial recruitment density or, more likely, obscured by additional recruitment of pocilloporids to plates between late February and September. High rates of recruitment and growth by other sessile organisms, particularly bryozoans and oysters, appear to result in increased post-recruitment mortality and limit recruitment of scleractinian corals on settlement plates. The work reinforces an emerging picture that coral recruitment patterns are determined by mechanisms that manifest over a large range of spatial scales.

Coral recruitment in Moorea, French Polynesia:the importance of patch type and temporal variation

Coral recruitment to artifi ial substrata (ceramic tiles) was measured in shallow back-reef (1–2 m depth) and deeper fore-reef (8–10 m depth) habitats on the island of Moorea, French Polynesia. Recruitment to three patch types within each of those habitats was measured at 4 month intervals for 3 years. Recruitment rates did not differ between fore-reef and back-reef habitats nor between sites within a habitat when data for the 3 years of the study were combined. There was a strong effect of patch type within the back-reef habitat on patterns of coral recruitment. In the shallow back-reef habitat, recruitment was 2–6 times higher to tiles inside territories of the damselfish, Stegastes nigricans (Lacepede), than to tiles in patches characterized by heavy grazing (crustosealgal dominated) or high cover of fleshy algae (especially Turbinaria ornata (Turner) J. Agardh). This pattern was not seen on the fore-reef where other species of damselfish were present. Temporal patterns of coral recruitment in Moorea were characterized by large inter-annual variability, as well as seasonal variability. Mean recruitment rates ranged between < 1 and 16 recruits/tile (tile surface area was 486 cm 2) over the course of the study. A total of 2801 recruits were found on 939 tiles in 3 years. Highest recruitment rates occurred in the December to April period, which corresponds to the period of warmest water temperatures. Recruits in the family Pocilloporidae were found year-round, with a seasonal peak in the December to April period, and accounted for 63% of total recruitment over 3 years. Recruitment of acroporids followed the same pattern, but contributed only 5% to total recruitment. Poritids were also found year-round, but in highest relative proportion in the August–December period; recruitment of poritids accounted for 26% of the total over 3 years. Recruitment was highest in the first year of the study, with a large increase in recruitment immediately preceding a major coral bleaching event.

Patterns of coral recruitment at the Gneering Shoals, southeast Queensland, Australia

Recruitment patterns of scleractinian corals were investigated at the Gneering Shoals, a coral-dominated rocky-reef south of the Great Barrier Reef, in subtropical Queensland. The density of recruits (mean of 0.8 to 6.3 recruits per tile (15 cm × 15 cm) pair from 4 sites) was the lowest ever recorded from six regions in tropical or subtropical eastern Australia that have been studied using directly comparable methods. Recruitment in summer was dominated by recruits from the Family Acroporidae, while corals from the Family Pocilloporidae recruited throughout the year. Recruits of massive corals andTurbinaria sp., which dominate the established coral communities, were absent. Possible explanations for the low recruitment rate in the region, include the depth of most sites (> 10m), competition for space with fouling organisms, and isolation, that is the failure of the south flowing East Australian Current to supply tropical larvae regularly from the Great Barrier Reef, 250 km to the north. The low coral recruitment rate at Gneering Shoals indicates that this region is unlikely to act as a “stepping-stone” for dispersal of tropical corals to more southern regions, which are more directly influenced by the East Australian Current.