Abstract.

Using histological analysis, the reproductive pattern of Mussismilia hispida, a zooxanthellate coral species endemic to the Brazilian coast, was verified. Fragments from two tagged colonies and ten haphazardly chosen colonies were collected monthly, from April 1989 to March 1990, at Praia da Tartaruga, Buzios, Rio de Janeiro state. The results showed that M. hispida is a sequential hermaphroditic species with a broadcast-spawning mode of reproduction. Small immature oocytes were first observed in April 1989 while early spermatic cysts were found in December 1989. After entering the mesoglea, the largest oocytes increase in size by incorporating the smallest ones into their cytoplasm. Mature oocytes and spermaries occurred concomitantly on the same fertile mesenteries during summer, and disappeared from some samples between February 1990 and March 1990 (late summer/early autumn). Gonad maturation occurred with increasing seawater temperature, suggesting seasonal synchrony in the reproductive cycle. Not all oocytes reached their full development, and some were resorbed after a short period of degeneration. No zooxanthellae were found in pre-spawn oocytes, which characteristically had a large amount of vitelline material and a peripheral germ vesicle.

Population connectivity for most marine species is dictated by dispersal during the pelagic larval stage. Although reef fish larvae are known to display behavioral adaptations that influence settlement site selection, little is known about the development of behavioral preferences throughout the larval phase. Whether larvae are attracted to the same sensory cues throughout their larval phase, or exhibit distinct ontogenetic shifts in sensory preference is unknown. Here, we demonstrate an ontogenetic shift in olfactory cue preferences for two species of anemonefish, a process that could aid in understanding both patterns of dispersal and settlement. Aquarium-bred naïve Amphiprion percula and A. melanopus larvae were tested for olfactory preference of relevant reef-associated chemical cues throughout the 11-day pelagic larval stage. Age posthatching had a significant effect on the preference for olfactory cues from host anemones and live corals for both species. Preferences of olfactory cues from tropical plants of A. percula, increased by approximately ninefold between hatching and settlement, with A. percula larvae showing a fivefold increase in preference for the olfactory cue produced by the grass species. Larval age had no effect on the olfactory preference for untreated seawater over the swamp-based tree Melaleuca nervosa, which was always avoided compared with blank seawater. These results indicate that reef fish larvae are capable of utilizing olfactory cues early in the larval stage and may be predisposed to disperse away from reefs, with innate olfactory preferences drawing newly hatched larvae into the pelagic environment. Toward the end of the larval phase, larvae become attracted to the olfactory cues of appropriate habitats, which may assist them in identification of and navigation toward suitable settlement sites.

On reefs around Australia, coral mass spawning typically occurs during the austral spring (October/November) on the east coast, and during autumn (March/April) on the west coast. However, to investigate the incidence of a secondary spawning event in spring on the west coast, the reproductive state of corals was assessed on two reefs. The results indicated that of the 29 species of Acropora investigated, multiple colonies of 11 species spawned in late spring or in early summer, in contrast to previous reports of spawning during autumn. Additionally, of four species that were followed through time at one reef, two spawned in both spring and autumn, however, individual colonies had only one gametogenic cycle. Within a single site, conspecific colonies were reproductively isolated and may not interbreed, potentially representing the initial stage of sympatric speciation in these populations.

Changes in the size-structure of populations of the mushroom coral Fungia fungites were quantified at two reefs during four annual surveys. Exposure to disturbance was predicted to affect the size and frequency of life history stages of polyps at each reef and their variability through time. The Mainland reef experienced frequent and intense disturbances, primarily as exposure to cyclones and substantial sedimentation, which were comparatively absent from the East Lewis reef. Disturbance to the Mainland reef was evident in the smaller size of polyps, and the many parent polyps, asexual buds, and polyp skeletons, which were all absent from the East Lewis reef. Over three years, the number and area cover of polyps at the Mainland reef decreased to 9% and 3% of their initial values respectively, compared with 73% and 36% at East Lewis. The size-structure of polyps at East Lewis remained comparatively stable; whereas, the abundance of all life history stages at the Mainland reef had high but variable rates of decline each year. Changes in the size-structure of polyps at the Mainland reef indicated it was exposed to levels of disturbance that it had not experienced, and would not recover from, for many years.

Larval transport between Johnston Atoll and the Hawaiian Archipelago was examined using computer simulation and high-resolution ocean current data. The effects of pelagic larval duration and spawning seasonality on long-distance transport and local retention were examined using a Lagrangian, individual-based approach. Retention around Johnston Atoll appeared to be low, and there appeared to be seasonal effects on both retention and dispersal. Potential larval transport corridors between Johnston Atoll and the Hawaiian Archipelago were charted. One corridor connects Johnston Atoll with the middle portion of the Hawaiian Archipelago in the vicinity of French Frigate Shoals. Another corridor connects Johnston Atoll with the lower inhabited islands in the vicinity of Kauai. Transport appears to be related to the subtropical countercurrent and the Hawaiian Lee countercurrent, both located to the west of the archipelago and flowing to the east. A new analytical tool, termed CONREC–IRC is presented for the quantification of spatial patterns.

The spectral reflectance of coral is inherently related to the amounts of photosynthetic pigments present in the zooxanthellae. There are no studies, however, showing that the suite of major photosynthetic pigments can be predicted from optical reflectance spectra. In this study, we measured cm-scale in vivo and in situ spectral reflectance for several colonies of the massive corals Porites lobata and Porites lutea, two colonies of the branching coral Porites compressa, and one colony of the encrusting coral Montipora flabellata in Kaneohe Bay, Oahu, Hawaii. For each reflectance spectrum, we collected a tissue sample and utilized high-performance liquid chromatography to quantify six major photosynthetic pigments, located in the zooxanthellae. We used multivariate multiple regression analysis with cross-validation to build and test an empirical linear model for predicting pigment concentrations from optical reflectance spectra. The model accurately predicted concentrations of chlorophyll a, chlorophyll c₂, peridinin, diadinoxanthin, diatoxanthin and β-carotene, with correlation coefficients of 0.997, 0.941, 0.995, 0.996, 0.980 and 0.984, respectively. The relationship between predicted and actual concentrations was 1:1 for each pigment, except chlorophyll c₂. This simple empirical model demonstrates the potential for routine, rapid, non-invasive monitoring of coral-zooxanthellae status, and ultimately for remote sensing of reef biogeochemical processes.

The obligate coral-dwelling gobiid genus Gobiodon inhabits Acropora corals and has developed various physiological, morphological and ethological adaptations towards this life habit. While the advantages of this coral-fish association are well documented for Gobiodon, possible fitness-increasing factors for the host coral are unknown. This study examines the influence of coral-dwelling gobies on the feeding behaviour of obligate corallivorous butterflyfishes. In an aquarium experiment using video observation, the corallivorous butterflyfish Chaetodon austriacus fed significantly less on corals inhabited by two Gobiodon species compared to unoccupied coral colonies of similar size. The more agonistic species G. histrio, which mostly displayed directed movements towards butterflyfishes, decreased butterflyfish bite rate by 62–98 % compared to uninhabited colonies. For Gobiodon sp. 3, which mostly displayed undirected movements in response to visits by C. austriacus, bite rate reduction was 64–68 %. The scale-less skin of Gobiodon spp. is covered by mucus that is toxic and multi-functional by reducing predation as well as affecting parasite attachment. A choice flume experiment suggests that the highly diluted skin mucus of Gobiodon spp. also functions as a corallivore repellent. This study demonstrates that Gobiodon spp. exhibit resource defence against coral-feeding butterflyfishes and also that coral colonies without resident Gobiodon suffer higher predation rates. Although the genus Gobiodon is probably a facultative corallivore, this study shows that by reducing predation on inhabited colonies by other fishes, these obligate coral-dwellers either compensate for their own fitness-decreasing impact on host colonies or live in a mutualistic association with them.

An integrating sphere was used to estimate the fraction of the incident quantum flux absorbed by a coral colony placed within it. This method allows one to examine the in vivo light absorption of intact coral colonies. We used this method to study effects of colony morphology, size, and photoacclimation status on the light harvesting efficiency by the zooxanthellae. Light absorption per unit of coral surface area decreased with increase in colony size, with a clear effect of different coral morphologies. In branched colonies, shading among branches reduced the absorbed light per unit area and per zooxanthellae. Photoacclimation to low light resulted in increased cellular chlorophyll concentrations in the zooxanthellae. In shade acclimated colonies, areal chlorophyll concentrations increased significantly, leading to more overlap among the optical cross-sections of pigments within cells and mutual shading among cells. These “package effects” showed up as a decrease in the in vivo, chlorophyll-a specific, spectral average, effective optical cross-section, a*. An integrating sphere is a useful tool for collecting optical information on corals.

Patterns of abundance, age structure and recruitment of coral trout (Plectropomus leopardus) and snapper (Lutjanus carponotatus) were described in different environments, which varied in benthic cover, in a 12-yr study at One Tree Island. It was hypothesized that both taxa would show strong preferences to different environments and benthic cover and that patterns would be consistent through time. Plectropomus leopardus were abundant on the reef slope and seaward edge of the lagoon, where live coral cover was high, and recruitment was generally low, in all environments. The population was sustained by a trickle of recruits, and total abundance varied little after 10 to 25 yr of protection in a no-take area, suggesting P. leopardus had reached an environment-related carrying capacity. Protogynous P. leopardus recruited to shallow environments at sites with 20% or more hard live coral and age data indicated the abundance of fish on the reef slope was from redistribution. Most recruits of gonochoristic L. carponotatus (<150 mm Standard length, SL) were found in the lagoonal environments, and adults were rare on the reef slope. Abundance of recruit L. carponotatus and P. leopardus did not correlate with percent cover of live and soft coral within environments. Recruits of L. carponotatus were usually rare in all lagoonal environments, but in 2003, many recruits (80 to 120 mm SL) were found in lagoonal environments with low and high hard live coral cover. A substantial proportion of the population (age max 18 yr) was from strong recruitment events. In 2003 and 2004, total abundance of L. carponotatus was supported by 1 year class 51.7 and 41% respectively. The utilization of environments and types of substrata varied among taxa and in some cases among life-history stages. There was also temporal variation in the importance of some environments (e.g. Lagoon Centre).

One hundred and fifteen species of fishes (14 oceanic, plus 101 shore and nearshore species) are known from Clipperton Island, a small, remote coral atoll in the tropical eastern Pacific (TEP). This fish fauna includes only ∼ 14% of the region's shallow-water species, and also is depauperate relative to the fish faunas of other isolated tropical islands. The island's isolation, small size, reduced habitat diversity, and oceanic environment contribute to this paucity of species.

Fifty-two species at Clipperton can be identified as TEP; these include 37 widespread species, six species shared only with the Revillagigedo Islands [the nearest (950 km) offshore shoals], and eight endemic to Clipperton. Endemics species apparently have a mix of west and east Pacific origins. Sixty-three species are transpacific; they include three new records (of Naso surgeonfishes) that maybe vagrants recruited > 4,000 km from Oceania.

Clipperton is situated at the juncture between the TEP and Oceania. Its fish fauna contains about equal numbers of TEP and transpacific species. This faunal structure reflects the relative influence of surface currents from Oceania and the TEP. Although most of Clipperton's transpacific shorefishes are widespread in eastern Oceania, the Clipperton fauna has specific affinities to the fauna of the Line Islands, which are located within the main eastbound current from Oceania. Clipperton may therefore be a major stepping stone for dispersal between Oceania and the remainder of the TEP. About 50% of the non-oceanic, tropical transpacific fishes occur there, and at least 75 % of those species apparently have resident populations at the island.