The 1998 bleaching event and its aftermath on a coral reef in Belize

Widespread thermal anomalies in 1997-1998, due primarily to regional effects of the El Niño-Southern Oscillation and possibly augmented by global warming, caused severe coral bleaching worldwide. Corals in all habitats along the Belizean barrier reef bleached as a result of elevated sea temperatures in the summer and fall of 1998, and in fore-reef habitats of the outer barrier reef and offshore platforms they showed signs of recovery in 1999. In contrast, coral populations on reefs in the central shelf lagoon died off catastrophically. Based on an analysis of reef cores, this was the first bleaching-induced mass coral mortality in the central lagoon in at least the last 3,000 years. Satellite data for the Channel Cay reef complex, the most intensively studied of the lagoonal reefs, revealed a prolonged period of elevated sea-surface temperatures (SSTs) in the late summer and early fall of 1998. From 18 September to 1 October 1998, anomalies around this reef averaged +2.2°C, peaking at 4.0°C above the local HotSpot threshold. In situ temperature records from a nearby site corroborated the observation that the late summer and early fall of 1998 were extraordinarily warm compared to other years. The lettuce coral, Agaricia tenuifolia, which was the dominant occupant of space on reef slopes in the central lagoon, was nearly eradicated at Channel Cay between October 1998 and January 1999. Although the loss of Ag. tenuifolia opened extensive areas of carbonate substrate for colonization, coral cover remained extremely low and coral recruitment was depressed through March 2001. High densities of the sea urchin Echinometra viridis kept the cover of fleshy and filamentous macroalgae to low levels, but the cover of an encrusting sponge, Chondrilla cf. nucula, increased. Further increases in sponge cover will impede the recovery of Ag. tenuifolia and other coral species by decreasing the availability of substrate for recruitment and growth. If coral populations are depressed on a long-term basis, the vertical accretion of skeletal carbonates at Channel Cay will slow or cease over the coming decades, a time during which global-warming scenarios predict accelerated sea-level rise.     

Seasonality,lunar periodicity of settlement and microhabitat association of juvenile humpback red snapper <Emphasis Type="Italic">Lutjanus gibbus</Emphasis> (Lutjanidae) in an Okinawan coral reef

Snappers (Lutjanidae) are one of the important fisheries resources in tropical and subtropical waters. However, there have been few studies clarifying the ecology of newly settled juvenile snappers. The aims of the present study were to clarify the seasonality and lunar periodicity of the larval settlement, and the microhabitat association of newly settled juveniles for Lutjanus gibbus in an Okinawan coral reef. Fifteen coral patches were chosen and underwater visual surveys were conducted during a 2-year period. The larval settlement of the species mainly occurred between May and October during the 2-year survey period. In terms of lunar periodicity of the settlement, the newly settled juveniles were mainly found between the last quarter moon and new moon during the main settlement season. Back calculations of settlement dates based on otolith microstructure showed that most juveniles settled during the last quarter moon and new moon. Stepwise multiple regression analyses revealed that the newly settled juveniles were mainly found on coral patches with a large number of holes on the top of the coral patch and this tendency was mainly consistent during the study period. The volume of holes at the base of coral patches had also a positive effect on the abundance of newly settled juveniles in some cases. The results of the present study suggest that larval settlement has a strong seasonal and lunar periodicity, and newly settled juveniles select coral patches with available refuge spaces.     

Diurnal and lunar patterns of larval recruitment of Brachyura into a mangrove estuary system in Ranong Province, Thailand

The present study followed the temporal recruitment pattern of brachyuran larvae in a mangrove tidal creek on the Andaman Sea coast of Ranong Province, Thailand, based on the assumption that the processes governing recruitment are important for the overall population dynamics of mangrove brachyuran crabs. Plankton net samples were taken on five occasions: on two new moon spring tides, one waxing moon neap tide, one full moon spring tide and one waning moon neap tide during October and November 1997. In addition collectors for larval crab megalopae were employed every 3 days through one dry season and one wet season (March–October 1998). Both the plankton net samples and collector samples revealed four major brachyuran groups in three families: Ocypodidae, Grapsidae and Portunidae. The grapsid group was further separated into two morphotypes which were identified as Metaplax and sesarmid species. Identified group mean numbers per cubic metre were ocypodids 3.0, sesarmids 0.8 and Metaplax 0.5, while portunid megalopae were very scarce (≪0.1 m⁻³). Further analysis of plankton net samples showed that when considering the parameters date, depth, current direction and the diel cycle, Metaplax and ocypodids distribute differently in the tidal and lunar cycle. Metaplax recruitment dominates on flood tides and on bottom layers, followed by middle and surface layers. Conversely, ocypodid abundance varied significantly with date only. Notably recruitment was not dependent on the diel cycle for either group. The collector samples of megalopae showed that recruitment of ocypodids, Metaplax and sesarmids occurred on full and new moon spring tides, while portunid megalopae preferred to settle on full moon spring tides. Since tidal currents were related to the lunar cycle megalopa groups are also cross-correlated with tidal amplitude, except for the portunid group. It is concluded that megalopae recruit in a similar manner to what has been found in other regions of the world, except that the abundance of ocypodids and Metaplax is not influenced by the diel cycle. Received: 14 February 2000 / Accepted: 24 November 2000     

Demographic plasticity in tropical reef fishes

We use age-based analyses to demonstrate consistent differences in growth, mortality, and longevity of coral reef fishes from similar habitats (exposed reef crests) 20 km apart. On outer-shelf reef crests of the northern Great Barrier Reef (GBR), size in four taxa of reef fishes (Chlorurus sordidus, Scarus frenatus, and S. niger and the acanthurid Acanthurus lineatus) was systematically and significantly smaller when compared with the same taxa on adjacent mid-shelf reef crests. Differences in size could be attributed to differences in growth between habitats (shelf positions). On outer reef crests the species examined had consistently lower size at age profiles and also reduced life spans compared with populations from mid-shelf reefs. To confirm this relationship, two of the most abundant species (C. sordidus and S. frenatus) were selected for more detailed spatial analysis of demographic patterns. Sampling adults of both taxa from reef crests on three mid- and three outer-shelf reefs revealed that most of the variation in growth was explained by shelf position, although C. sordidus also displayed differences in growth among mid-shelf reefs. We conclude that differences in body sizes across the continental shelf of the northern GBR are primarily determined by these trends in growth. Strong spatial patterns also existed in the mean ages of populations and longevity estimates for C. sordidus and S. frenatus between shelf positions. Both species on outer-shelf reefs displayed less variable cohort sizes, significantly reduced mean ages, and foreshortened longevity compared with populations on mid-shelf reefs. Furthermore, differences in these parameters were rare among replicate reefs within mid- and outer-continental-shelf positions. Age-based catch curves suggested that rates of S. frenatus natural mortality on the outer shelf were nearly twice as high as on the mid shelf. Visual surveys indicated that total scarid densities on outer-shelf reef crests are on average fourfold higher than for equivalent mid-shelf habitats. This fact, coupled with significantly reduced growth rates, reduced mean ages, and increased mortality rates, suggests that density-dependent processes may be responsible for observed differences among localities.     

Patterns of lunar settlement and early recruitment in Caribbean reef fishes at Panamá

Lunar patterns of settlement of 15 Caribbean reef fishes were assessed from daily collections of newly arrived fishes from each of two small (A=63 and B=28 m²) patch reefs at Punta de San Blas (Panamá) during two consecutive 2 yr periods (1984, 1985 and 1986, 1987). In 12 species settlement was lunar-cyclic, with a broad peak of activity around the new moon in 11 cases, and at first quarter in 1 species. However, 3 of these lunar-cyclic species displayed intermittent semilunar periodicity in settlement, with peaks around the quarter moons. One other species had a semilunar cycle of settlement with peaks at both quarter moons. Two species apparently lacked lunar settlement cycles. In some, but not all, paris of congeners: (a) monthly variation in settlement intensity was positively correlated, (b) the duration of settlement pulses in the same month consistently differed, and (c) the timing of settlement pulses in the same month often differed (although one species did not consistently arrive before the other). Recruitment of juvenile fish that survived to the end of the lunar cycle in which they settled was monitored monthly, concurrently with settlement, at a number of large sites scattered up to 2 km apart. The levels of variation in the amount of settlement and recruitment each month differed in only 2 of 17 cases, with settlement variation exceeding recruitment variation in only one of these. The intensity of recruitment was positively correlated with the intensity of settlement in 16 of 17 cases. In 15 of those 16 cases, R ² values for linear regressions of recruitment on settlement exceeded R ² values for curvilinear regressions that would indicate either increasing or decreasing recruitment success with increasing intensity of settlement. Thus it appears that variation in recruitment can be used to estimate variation in settlement, and that recruitment success may be density-independent.     

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. Spearmans 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.Communicated by O. Kinne, Oldendorf/Luhe     

Effects of the 1996 and 1998 positive sea-surface temperature anomalies on corals,coral diseases and fish in the Arabian Gulf (Dubai,UAE)

Two positive sea-surface temperature anomalies occurred in the Arabian Gulf in short sequence. Between May and August 1996 and 1998, sea-surface temperatures in the southern Arabian Gulf were elevated by 2°C above average. The consequences for coral fauna, coral diseases and coral regeneration were studied in Dubai (United Arab Emirates) between Jebel Ali and Ras Hasyan. In 1996, coral death was widespread, affecting primarily the genus Acropora. In Acropora-dominated areas, live coral cover was reduced from 90% to about 26% in 1996, while in 1998 only a reduction from 26% to 22% of the remaining coral cover occurred. In the study area, all six Acropora species suffered total mortality in 1996, thus the coral fauna was reduced from 34 species to 27. The nearest areas with surviving Acropora were 30 km to the east (Deira) and 20 km to the west (Al Jazira). Massive coral species suffered negligible mortality, and slowly increased in space cover. The Acropora overkill turned 7.9 km² (19.7% of total coral-covered area) of previously lush coral gardens into a dead framework that was increasingly bioeroded. Acropora recruitment only started in 1998, average recruit size in 1999 was 7Dž cm, and recruits were rare. Prior to the mass mortality event, coral diseases were common and seasonal (14LJ% of corals, mainly Acropora, affected in summer, in winter 7Lj%, mainly massives), after the mortality event seasonality was lost and infection remained below winter levels (6LJ%, only massives infected). In fish, overall species richness decreased from 95 to 64 species in point counts, but frequency only decreased in one species (Pseudochromis persicus). Guild structure changed inasmuch as herbivores and planktivores increased, and invertivores decreased, although differences were not statistically significant. The most abundant family, both prior to and after the coral mass mortality, was Lutjanidae. It appears that even though much of the coral was dead, the maintenance of structural complexity allowed the fish assemblage to avoid a similar catastrophic change to that experienced by the coral assemblage.     

A novel Vibrio sp. pathogen of the coral Pocillopora damicornis

A coral pathogen was isolated from the diseased tissue of Pocillopora damicornis in Zanzibar. The pathogenic bacterium, referred to as Vibrio coralyticus YB, was classified as a member of the genus Vibrio. Based on its 16S rDNA sequence, V. coralyticus is probably a new species. In controlled aquaria experiments at 26-29°C, inoculation of pure cultures of V. coralyticus YB either into the seawater or by direct contact onto the coral caused tissue lysis of P. damicornis fragments. At 29°C, lysis began as small white spots after 3-5 days, rapidly spreading so that by 2 weeks the entire tissue was destroyed, leaving only the intact bare skeleton. When an infected diseased coral was placed in direct contact with a healthy one, the healthy coral lysed in 2-4 days, further indicating that the disease was contagious. Inoculation with as few as 30 bacteria ml^-1 was sufficient to infect and lyse corals. Seawater temperature was a critical variable for the infectious process: infection and lysis occurred rapidly at 27-29°C, slowly at 26°C and was not observed at 25°C. The data suggest that the presence of V. coralyticus YB, even in low numbers, in seawater surrounding a coral reef will lead to tissue destruction of P. damicornis, when seawater temperatures rise.     

Experimental effect of cold,La Niña temperatures on the survival of reef fishes from Gorgona Island (eastern Pacific Ocean)

The eastern tropical Pacific (ETP) reefs are affected at irregular times by extremely cold temperatures that occur principally during La Niña events. The effects of these low temperatures on the survival of reef fishes were experimentally assessed by determining the critical thermal minimum (CTM) of 15 reef fish species from Gorgona Island (ETP), and comparing these CTMs with the records of temperature during past La Niña events. Among species, mean CTMs ranged from 10.8°C to 16.3°C, which were lower than the coldest temperature recorded during the last La Niña event (18°C during La Niña 1998-1999). However, the observed ranges of CTM for two species (Thalassoma lucassanum and Eucinostomus gracilis) extended above 18°C. These results suggest that most of the reef fishes we studied are physiologically tolerant to the cold temperatures encountered during La Niña, though decreases in at least two populations may be expected as a result of the mortality of less tolerant individuals. Although tolerant to cold temperatures, reef fish populations may still experience negative changes during La Niña, because other determinants in population maintenance (e.g. reproduction and recruitment) are more temperature sensitive. The effects of other cold phenomena on reef fish survival are also discussed herein.     

Oculina patagonica: a non-lessepsian scleractinian coral invading the Mediterranean Sea

The scleractinian coral Oculina patagonica De Angelis is a new immigrant from the Southwest Atlantic to the Mediterranean Sea, having established itself only recently along the Israeli coast. This species is the only scleractinian coral reported to have invaded a new region. In order to understand the swift establishment of this species along the Israeli coast, from 1994 to 1999 we studied its distribution, abundance, reproduction, recruitment, survival, and the effect of bleaching events on its population abundance. In addition, population studies of O. patagonica were performed at several localities along the eastern and western Mediterranean coasts. Highest abundance was recorded along the Spanish coast, reaching 30lj colonies per 10 m line transect in shallow water. Second in abundance was the Israeli coast, with a maximum of 10DŽ colonies per transect. O. patagonica was rare along the coast of Italy, and absent along the Mediterranean coast of France. During the study, both mortality and recruitment along the Israeli coast were very low. In contrast, recruitment along the Spanish coast was very high. Reproduction of the species was studied using gonadal histology. O. patagonica is gonochoric. Female gonads were first observed in May and male gonads in July, both reaching maturity in late August and early September. Naturally occurring azooxanthellate colonies of O. patagonica inhabiting small dark caves developed gonads and spawned in parallel to zooxanthellate colonies exposed to light. No gonads were found in zooxanthellate colonies that underwent bleaching during the reproduction season. The high incidence of bleaching events along the Israeli coast observed throughout the years of this study may explain the low recruitment of new colonies during the same period. In view of its current recruitment patterns, we expect further expansion of O. patagonica in range and abundance in the western Mediterranean, but very small expansion of the population in the eastern Mediterranean, due to repetitive annual bleaching events.     

The relationship between lunar periodicity and activity of fish-parasitic gnathiid isopods in the Caribbean

Gnathiid isopod larvae are members of the marine demersal zooplankton community and are common ectoparasites of coral reef fishes, emerging from the substratum, mostly at night and crepuscular periods to feed on fish blood. Given that the activity of many marine organisms is often linked to changes in the phase of the moon, we examined the relationship between lunar phase and activity in gnathiid isopods on Caribbean reefs. We employed two sampling methods to quantify gnathiid activity: (1) Emergence traps set on reefs over a 24 h period; and (2) live fish placed in cages on reefs and retrieved during night and dawn peaks in gnathiid activity. These were compared during discrete phases as well as a continuous metric, the lunar “angle”, and an estimate of ambient light availability (luminance). Lunar phase and angle varied in their statistical effect on gnathiid activity patterns by sampling method and/or year. Luminance had a significant but inconsistent effect on measures of gnathiid activity. Our results suggest that changes in the lunar cycle are not a strong predictor of gnathiid activity at our shallow reef study sites.     

Dynamics of larval fish assemblages over a shallow coral reef in the Florida Keys

Few time series collections have been made of the larval ichthyofauna in waters directly above shallow coral reefs. As a result, relatively little is known regarding the composition and temporal dynamics of larval fish assemblages in shallow-reef waters, particularly those near a major western boundary current. We conducted a series of nightly net tows from a small boat over a shallow reef (Pickles Reef) along the upper Florida Keys during four new moon and three third-quarter moon periods in July (two new moons), August, and September 2000. Replicate tows were made after sunset at 0–1 m and at 4–5 m depth to measure the nightly progression in community composition, differences in depth of occurrence, and abundance and diversity with lunar phase. A total of 66 families was collected over the 3-month period, with a mean (±SE) nightly density of 23.7±2.1 larvae per 100 m ³ and diversity of 24.2±0.9 taxa per tow. A total of 28.8% of the catch was composed of small, schooling fishes in the families Atherinidae, Clupeidae, and Engraulidae. Of the remaining catch, the top ten most abundant families included reef fishes as well as mangrove and oceanic taxa (in descending order): Scaridae, Blennioidei (suborder), Gobiidae, Paralichthyidae, Lutjanidae, Haemulidae, Labridae, Gerreidae (mangrove), Balistidae, and Scombridae (oceanic). These near-reef larval fish assemblages differed substantially from those collected during previous offshore collections. Taxa such as the Haemulidae were collected at a range of sizes and may remain nearshore throughout their larval period. Overall, the abundance and diversity of taxa did not differ with depth (although within-night vertical migration was evident) or with lunar phase. Temporal patterns of abundance of larval fish families clustered into distinct groups that in several cases paralleled family life-history patterns. In late July, a sharp shift in larval assemblages signaled the replacement of oceanic water with inner shelf/bay water. In general, the suite and relative abundance of taxa collected each night differed from those collected on other nights, and assemblages reflected distinct nightly events as opposed to constant or cyclical patterns. Proximity to the Florida Current likely contributes to the dynamic nature of these near-reef larval assemblages. Our results emphasize the uniqueness of near-reef larval fish assemblages and point to the need for further examination of the biophysical relationships generating event-related temporal patterns in these assemblages.     

Larval survivorship, competency periods and settlement of two brooding corals, Heliopora coerulea and Pocillopora damicornis

Larval dispersal and recruitment are important in determining adult coral distribution; however, few studies have been made of coral larval dispersal. This study examined the larval behavior, survivorship competency periods and settlement of two brooding corals, Heliopora coerulea and Pocillopora damicornis, in relation to different potential larval dispersal patterns. We also examined the lipid content of H. coerulea as a means of flotation and a source of energy. Planulae of H. coerulea were on average 3.7 mm in length, lacked zooxanthellae, and were mostly benthic, probably because of restricted movement and low lipid content (54% by dry weight). Planulae of P. damicornis were on average 1.0 mm in length, had zooxanthellae and swam actively. The competency period of H. coerulea was shorter (30 days) than that of P. damicornis (100 days). Forty percent of H. coerulea planulae crawled onto the substrata within 1 h of release, and 47% settled within 6 h. By contrast, fewer than 10% of P. damicornis planulae crawled onto the substrata within the first hour and 25% settled within 6 h of release. The planulae of H. coerulea may have a narrower dispersal range than those of P. damicornis, settling and recruiting near parent colonies. Thus, brooding corals exhibit variations in larval dispersal patterns, which are characterized by their position in the water column and competency periods.     

Elevated levels of nitrogen and phosphorus reduce fertilisation success of gametes from scleractinian reef corals

Spawned gametes were collected from colonies of Acropora longicyathus at One Tree Island and Goniastrea aspera at Magnetic Island, Great Barrier Reef, Australia, for use in fertilisation trials. Mean fertilisation rates were significantly reduced compared with controls (P<0.003), when gametes from the branching coral A. longicyathus were exposed to elevated ammonium concentrations at 1 µM and above in one cross (60-64% reduction), and at 100 µM in another cross (16% reduction). Mean fertilisation success of A. longicyathus gametes was also significantly reduced compared with controls in both crosses (P=0.000) at concentrations of 1 µM phosphate and above (35-75% reduction), and at 1 µM ammonium plus 1 µM phosphate and all higher concentrations (68-74% reduction). Similarly, the mean percentage of regular embryos that were developing normally was significantly reduced in most nutrient treatments compared with controls (P=0.000). Fertilisation trials using gametes from the brain coral G. aspera resulted in a significantly lower percentage of regular embryos (P=0.001) and a significantly higher percentage of deformed embryos (P=0.001) developing after exposure to elevated nutrient treatments compared with controls. Mean fertilisation rates for this species were only significantly reduced (P=0.034) in the 50 µM ammonium plus phosphate treatment in one cross (8% reduction), compared with the control. Therefore, ammonium and phosphate enrichment significantly impairs fertilisation success and embryo development in scleractinian reef corals.     

Panmixia in Pocillopora verrucosa from South Africa

The genetic structure of six local collections of Pocillopora verrrucosa from six coral reefs in KwaZulu-Natal, South Africa, was examined using allozyme electrophoresis. The six separate reefs lie within two different reef complexes. Twenty-two enzymes were screened on five buffer systems, but only five polymorphic loci (Gpi-1, Gdh-1, Lgg-2, Lpp-1, Est-1) could be consistently resolved. No significant differences in allelic frequencies were detected among the six sites. All local collections were genotypically diverse, with evidence of only very limited clonal replication at each site. Indeed, the ratio of observed to expected genotypic diversity (mean Go:Ge=0.64ǂ.05 SD), the ratio of observed number of genotypes to the number of individuals (mean Ng:N=0.65ǂ.04 SE), and deviations from the Hardy-Weinberg equilibrium indicate that sexual reproduction plays a major role in the maintenance of the populations. No genetic differentiation was found either within (FSR=0.026ǂ.003 SE) or between (FRT=0.000ǂ.001 SE) reef complexes. The homogeneity of the gene frequencies across the six reefs strongly supports the assumption that the KwaZulu-Natal reef complexes are highly connected by gene flow (Nem=44). The reefs in the southern and central reef complexes along the northern Maputaland coastline can therefore be considered part of a single population.     

Reproduction and recruitment of scleractinian corals in a high-latitude coral community, Amakusa, southwestern Japan

Reproduction and recruitment in high-latitude coral populations in Japan have been little studied. A comprehensive study of the reproduction and early life history was conducted on nine common scleractinian coral species in Amakusa, southwestern Japan (32°N) from 2001 to 2003 including; (1) fecundity (the proportion of colonies with mature eggs), (2) timing and synchrony of spawning, (3) initial larval settlement pattern, (4) recruitment, (5) post-settlement mortality. The fecundity was high (76.7–100%) in six of seven species examined in 2002 and 2003. Annual spawning of the seven species occurred from mid July to August in 2001–2003, when seawater temperature was at the annual maximum. Spawning was highly synchronised among conspecific colonies and species in 2002 and 2003, with five species spawning five to nine nights after the full moon and another two spawning around the new moon. Temporal patterns of larval settlement of three spawning species during the first 10 days after spawning were similar to those of other spawning species from low latitudes. The number of scleractinian recruits on settlement plates, deployed from July to October (the major recruitment period at the study site), was low (2 recruits/m²) for the three consecutive years. Post-settlement mortality of 1–1.5 month old spat of five species ranged between 88 and 100% over 3–10 months in the field, similar to the values reported for both high and low latitude species (>94–99%). Among the key stages examined, the low recruitment rate may be the most important step in limiting successful reproduction and recruitment of these high-latitude scleractinian populations. The low recruitment rate may be attributable to (1) the reduced influx of larval supply from other coral populations, which are smaller and more isolated at high-latitudes and (2) the longer precompetent larval phase of broadcast-spawning corals which results in an increased chance of larvae being dispersed away from parent populations.     

Temporal and spatial variability in coral recruitment on two Indonesian coral reefs: consistently lower recruitment to a degraded reef

Corals are the primary reef-building organisms, therefore it is key to understand their recruitment patterns for effective reef management. Coral recruitment rates and juvenile coral abundance were recorded in the Wakatobi National Marine Park, Indonesia, on two reefs (Sampela and Hoga) with different levels of environmental degradation (12.5 vs. 44 % coral cover with high and low sedimentation rates, respectively) to examine consistencies in recruitment patterns between years and seasons. Recruitment was measured on multiple panels at two sites on each reef (6–7 m depth) and cleared areas of natural reef. Although coral recruitment was twofold higher in 2008–2009 than in 2007–2008, and seasonal differences were identified, consistent significant differences in recruitment rates were found between the two reefs even though they are separated by only ~1.5 km. Recruitment rates and juvenile abundance were lower on the more degraded reef. These patterns are likely a consequence of differential pre- and post-settlement mortality as a result of the high sedimentation rates and degraded conditions and possibly reduced larval supply.     

Critical swimming speeds of late-stage coral reef fish larvae: variation within species,among species and between locations

The swimming abilities of larval fishes are important for their survival, potentially affecting their ability to avoid predators, obtain food and control dispersal patterns. Near settlement swimming abilities may also influence spatial and temporal patterns of recruitment. We examined Critical speed (U-crit) swimming ability in late stage larvae of 89 species of coral reef fishes from the Great Barrier Reef and the Caribbean. Coefficients of variation in U-crit calculated at the individual level were high (28.4%), and this was not explained by differences in size or condition factor of these same larvae. Among species U-crit ranged from 5.5 cm s⁻¹ to 100.8 cm s⁻¹ (mean=37.3 cm s⁻¹), with 95% of species able to swim faster than the average current speed around Lizard Island, suggesting that most species should be capable of influencing their spatial and temporal patterns of settlement. Inter-specific differences in swimming ability (at both the family and species levels) were significantly correlated with size and larval morphology. Correlations were found between swimming performance and propulsive area, fineness ratio and aspect ratio, and these morphological parameters may prove useful for predicting swimming ability in other taxa. Overall, the swimming speeds of larvae from the same families at the two locations were relatively similar, although the Lutjanidae and Acanthuridae from the Caribbean were significantly slower than those from the great barrier reef. Differences in swimming speed and body form among late stage larvae suggests that they will respond differently to factors influencing survival and transport during their pelagic phase, as well as habitat use following settlement.     

Extreme genetic diversity and temporal rather than spatial partitioning in a widely distributed coral reef fish

Mitochondrial control region (HVR-1) sequences were used to identify patterns of genetic structure and diversity in Naso vlamingii, a widespread coral reef fish with a long evolutionary history. We examined 113 individuals from eight locations across the Indo-Pacific Ocean. Our aims were to determine the spatial scale at which population partitioning occurred and then to evaluate the extent to which either vicariance and/or dispersal events have shaped the population structure of N. vlamingii. The analysis produced several unexpected findings. Firstly, the genetic structure of this species was temporal rather than spatial. Secondly, there was no evidence of a barrier to dispersal throughout the vast distribution range. Apparently larvae of this species traverse vicariance barriers that inhibit inter-oceanic migration of other widespread reef fish taxa. Thirdly, an unusual life history and long evolutionary history was associated with a population structure that was unique amongst coral reef fishes in terms of the magnitude and pattern of genetic diversity (haplotype diversity, h = 1.0 and nucleotide diversity π = 13.6%). In addition to these unique characteristics, there was no evidence of isolation by distance (r = 0.458, R ² = 0.210, P = 0.078) as has also been shown for some other widespread reef species. However, some reductions in gene flow were observed among and within Ocean basins [Indian–Pacific analysis of molecular variance (AMOVA), Φ _st = 0.0766, P < 0.05; West Indian–East Indian–Pacific AMOVA Φ _st = 0.079, P < 0.05]. These findings are contrasted with recent studies of coral reef fishes that imply a greater degree of spatial structuring in coral reef fish populations than would be expected from the dispersive nature of their life cycles. We conclude that increased taxon sampling of coral reef fishes for phylogeographic analysis will provide an extended view of the ecological and evolutionary processes shaping coral reef fish diversity at both ends of the life history spectrum.