Successful methods for transplanting fragments of Acropora formosa and Acropora hyacinthus

In order to establish a successful method for the transplantation of branching and tabular coral fragments, we tested the effects of orientations of attachment, seasons of transplantation, and size of fragments on survival, growth, and spawning using Acropora formosa and A. hyacinthus. Vertically attached, large-sized fragments of A. formosa showed 98–100% survival rate after 18 months. The fragments transplanted in August exhibited better survival than those transplanted in November. The larger fragments had the higher percentage of spawning. The fragments that spawned had lower growth rate, while those resorbed the oocytes carried at the time of transplantation showed higher growth rate, suggesting the trade-off between growth and reproduction. Half of the fragments spawned 1 month earlier than the donor colonies. Only the vertically attached fragments of A. hyacinthus fused to the substratum, and those transplanted in February showed 100% survival rate after 14 months, indicating that this species is well suited for transplantation.     

Skeletal development in Acropora cervicornis

Monthly linear extension and calcium carbonate accretion were measured over a year in the Caribbean staghorn coral, Acropora cervicornis. X-radiographs were made of cross sections of branches to analyze radial growth. Correlations were made between parameters of skeletal growth and four environmental parameters monitored over the same sampling periods: temperature, daylight hours, sun hours, plankton abundance. The results indicate that linear extension does not change during the year with the possible exception of April. It is suggested that temperatures outside an optimal range (ca. 26°–29°C for staghorn Acroporas) might cause a decrease in linear extension, however. Specific accretion (mg. mm^-1) does show significant variations through the year. Calcium carbonate accretion (mean specific accretion times mean linear extension, mg. tip^-1) is most strongly correlated with number of sun hours. A comparison is made between diel patterns of extension and accretion and longer term measurements. It is suggested that the accretion process is probably most influenced by some activity influenced by light. There are no annual growth bands in X-radiographs of cross-sections of the branches of A. cervicornis. This may result from secondary infilling in the skeleton.     

Cryptofaunal diversity in fringing reef rhodoliths

Coral Reefs - Rhodolith distribution, morphology, and cryptofauna have been minimally studied on fringing reefs. We present the first study to examine both rhodolith distribution and associated...     

The dissipation of wind wave energy across a fringing reef at Ipan,Guam

Field observations over a fringing reef at Ipan, Guam, during trade wind and tropical storm conditions are used to assess the transformation of sea and swell energy from the fore reef to the shoreline. Parameterizations of wave breaking and bottom friction developed for sandy beaches are found to represent the observed decay in wave energy with an increased friction coefficient. These parameterizations are incorporated into the one-dimensional energy flux balance, which is integrated across the reef to assess the effects of varying tidal range, incident wave height and reef bathymetry on the sea and swell band wave height and wave setup near the shoreline. Wave energy on the reef is strongly depth-limited and controlled by the reef submergence level. Shoreline wave energy increases with incident wave height largely due to the increase in water level from breaking wave setup. Increased tidal levels result in increased shoreline energy, since wave setup is only weakly reduced. The wave height at the shore is shown to be inversely proportional to the width of the reef flat due to dissipation.     

Spatial patterns in the distribution of damselfishes on a fringing coral reef

Damselfishes are an important element of the fauna of coral reefs. This study describes spatial patterns in the distribution of 15 species of damselfishes at Lizard Island, northern Great Barrier Reef (GBR). The aim of the work was to identify the spatial scales at which major changes in the composition and abundance of the fauna occurred. These patterns were then compared with previous studies in an attempt to determine if distributions followed general patterns at a range of localities. The assemblage found at Lizard Island was similar to that of reefs in the central GBR. The most important changes in the composition of the fauna occurred among reef zones. Shallow zones (the reef flat and crest) were dominated by herbivorous species while planktivorous and omnivorous species were most abundant in deeper zones (the reef slope). Densities of herbivorous damselfishes in shallow reef zones at Lizard Island averaged 45.5 individuals per 80 m², a value comparable to densities found in similar zones on reefs in the central and southern GBR and at one locality in the Caribbean. Comparisons of relative distributions suggested that abundant species tend to be widely distributed among zones and habitats, while rare species have restricted distributions at Lizard Island. However, computer simulation of the sampling program suggested that the ability of our study to describe the distribution patterns of rare species was limited, despite intensive sampling. Correlations between breadth of distribution and abundance may have occurred simply because rare species were less likely to be recorded within a transect. Our results suggest that it will be difficult to compare the distribution patterns of species among studies. Furthermore, the interpretation of relative patterns of distribution at a single locality in terms of ecological specialization or partitioning may first require an assessment of the ability of the sampling program to accurately record spatial patterns.     

Sexual reproduction of Acropora reef corals at Moorea, French Polynesia

Little information is available on reproductive processes among corals in isolated central Pacific reef regions, including French Polynesia. This study examined the timing and mode of sexual reproduction for Acropora reef corals at Moorea. Spawning was observed and/or inferred in 110 Acropora colonies, representing 12 species, following full moon periods in September through November 2002. Gamete release was observed and inferred in four species of Acropora between 9 and 13 nights after the full moon (nAFM) in September 2002. Twelve Acropora spp. spawned gametes between 5 and 10 nAFM in October 2002, with six species spawning 7 nAFM and four species spawning 9 nAFM. In November 2002, spawning of egg and sperm bundles was observed and inferred in 27 colonies of Acropora austera, 6 nAFM. These are the first detailed records of spawning by Acropora corals in French Polynesia.     

On the circulation in the Puerto Morelos fringing reef lagoon

For a period of 22 months beginning in September 2003, an array of four current profilers were deployed on the Puerto Morelos fringing reef lagoon, a microtidal Caribbean environment characterised by the influence of the Yucatan Current (YC) and a Trade Wind regime. The dataset includes water currents, bottom pressure, and surface waves complemented with coastal meteorological data and surface currents from an acoustic Doppler current profiler moored 12 km offshore. Normal circulation conditions consisted of a surface wave-induced flow entering the lagoon over a shallow reef flat and strong flows exiting through northern and southern channels. This wave induced flow was modulated by a low-frequency sea level change related to a geostrophic response to the YC variability offshore, with tidal and direct wind forcing playing additional minor roles. Under extended summer low-wave height conditions, together with a decrease in sea level from the intensification of the offshore current, the exchange of the lagoon with the adjacent ocean was drastically reduced. Under normal wave conditions (H _S = 0.8 ± 0.4 m, mean ± SD), water residence time was on average 3 h, whereas during Hurricane Ivan’s extreme swell (H _S = 6 m) it decreased to 0.35 h.     

CFD modelling of wave damping over a fringing reef in the Colombian Caribbean

Coral Reefs - The understanding of physical processes over submerged reefs represents an important ongoing research topic when considering wave energy dissipation and coastal protection that these...     

Benthic community composition affects O2 availability and variability in a Northern Red Sea fringing reef

Many coral reef ecosystems experience shifts in benthic community composition from scleractinian corals to algae. However, consequences of such phase shifts on O₂ availability, important for many reef organisms, are unresolved. This study therefore comparatively investigated potential in situ effects of different benthic cover by reef macroalgae and scleractinian corals on water column O₂ concentrations in a Northern Red Sea fringing reef. Findings revealed that mean daily O₂ concentrations at algae-dominated sites were significantly lower compared to coral-dominated sites. Minimum O₂ concentrations were significantly negatively correlated, while diurnal variability in O₂ concentration was significantly positively correlated, with increasing benthic cover by algae. In contrast, no correlation with coral cover was found. These results indicate that shifts from corals to benthic algae may likely affect both in situ O₂ availability and variability. This may be particularly pronounced in reef systems with low water exchange (e.g. closed lagoons) or under calm weather conditions and suggests potential O₂-mediated effects on reef organisms.     

Intra-colony variation in the growth of Acropora formosa: extension rates and skeletal structure of white (zooxanthellae-free) and brown-tipped branches

The presence or absence of zooxanthellae near the tip of Acropora formosa branches is correlated with apical skeletal structure and extension rates. White (zooxanthellae-free) tips are lightly calcified, possess thin, widely spaced skeletal elements and bear only a few, poorly developed radial corallites. Brown tips are heavily calcified, possess smaller axial corallites and larger, more numerous radial corallites. White tips exhibit a range of normally distributed extension rates. Brown tips do not extend, but radial growth and internal calcification continue. These processes progressively alter the appearance and density of brown tipped branches. In addition, the axial corallite of brown tips becomes progressively smaller and is eventually indistinguishable from adjacent radial corallites. Although brown and white tips can change from one form to the other, with a corresponding change in extension rate, it is hypothesized that in brown tips with degenerated axial corallites, a new axial corallite must develop before extension can resume. Brown tips predominate in the interior of arborescent colonies, where space for continued extension is limited. They may therefore represent a means of coordination of growth within a colony. Field and experimental evidence suggest that brown tips may develop in response to micro-environmental conditions. White, zooxanthellae-free zones are also characteristic of other branched and plate-forming species, which exhibit rapid extension in a localized region of the colony.     

Seasonal and life‐phase related differences in growth in Scarus ferrugineus on a southern Red Sea fringing reef

Temporal trends in growth of the rusty parrotfish Scarus ferrugineus were studied on a southern Red Sea fringing reef that experiences seasonal changes in environmental conditions and benthic algal resources. Length increment data from tagging and recapture were compared among periods and sexes and modelled using GROTAG, a von Bertalanffy growth model. The growth pattern of S. ferrugineus was highly seasonal with a maximum occurring between April and June and a minimum between December and March. Body condition followed the seasonal variation in growth, increasing from April to June and decreasing from December to March. The season of maximum growth coincided with high irradiation, temperature increases and peak abundance of the primary food source, the epilithic algal community. There was a decline in growth rate during summer (July to October) associated with a combination of extreme temperatures and lowered food availability. There were strong sexual size dimorphism (SSD) and life‐history traits. Terminal‐phase (TP) males achieved larger asymptotic lengths than initial‐phase individuals (IP) (L_∞ 34·55 v. 25·12 cm) with growth coefficients (K) of 0·26 and 0·38. The TPs were growing four times as fast as IPs of similar size. Three individuals changed from IP to TP while at liberty and grew eight times faster than IPs of similar size, suggesting that sex change in S. ferrugineus is accompanied by a surge in growth rate. The SSD in S. ferrugineus thus coincided with fast growth that started during sex change and continued into the TP. Faster growth during sex change suggests that the cost associated with sex change is limited.     

Effects of sediment deposition on the seaweed Sargassum on a fringing coral reef

 Coral reef degradation may involve shifts from coral to algal dominance and may be caused in part by increased sediment loads. Inshore fringing reef flats in the central Great Barrier Reef region are often subjected to periods of high sedimentation and are often dominated by macroalgae such as Sargassum. Experiments reported here examine the impacts of sediments on the recruitment, growth, survival, degeneration and vegetative regeneration of Sargassum microphyllum on a fringing coral reef flat in the central Great Barrier Reef. Comparison of three levels of sediment deposition (experimental addition, control (ambient condition) and experimental removal) showed that increased amounts of sediment significantly decreased rates of recruitment, growth, survival and vegetative regeneration, but not degeneration of S. microphyllum. In addition, the regenerative ability of S. microphyllum thalli with short, persistent erect branches (untreated) was compared with that of thalli experimentally cut back to the holdfast. This experimental damage significantly reduced regeneration. Accepted: 6 October 1997     

Increased sea level promotes coral cover on shallow reef flats in the Andaman Sea, eastern Indian Ocean

Sea level in the Indian Ocean is subject to considerable temporal and spatial variabilities. During the period 1960–2009 at Phuket, Thailand, in the NE Indian Ocean, mean sea level increased by 2.7 mm y⁻¹. Regular monitoring of coral cover on fringing reef flats at Phuket since 1979 revealed a sensitive response of this habitat to both transient sea-level depressions and sea-level elevation. Since 1987 when more frequent sampling began, coral cover was positively correlated with the mean sea level experienced over the preceding months. Changing mean sea level explained a high proportion of the observed variation in cover, with overall increasing sea levels and a lack of negative sea-level anomalies promoting cover on the outer reef flats. Concomitantly, there have been no changes in reef community structure or any apparent shifts in zonation patterns across the reef. While future benefits of continued increases in mean sea level on reef flats in the region will be constrained by the frequency and intensity of sea-level depressions associated with the Indian Ocean Dipole, and bleaching events, the overall picture for these shallow reefs is a positive one as they respond to increasing sea level and show rapid recovery from environmental disturbances.     

High herbivory despite high sediment loads on a fringing coral reef

Coral Reefs - Algal turfs are expected to increasingly dominate the benthos of coral reefs in the Anthropocene, becoming important sources of reef productivity. The sediments trapped within algal...