John B. Lewis

PROCESSES OF ORGANIC PRODUCTION ON CORAL REEFS

1. The first quantitative studies of production on coral reefs were those of Sargent & Austin who showed that productivity on reefs was considerably higher than in surrounding waters. This high production occurred in spite of nutrient limitation and low productivity of offshore waters. Their conclusions have since been confirmed by numerous other workers in both the Atlantic and the Pacific.

The settlement behaviour of planulae larvae of the hermatypic coral Favia fragum (Esper)

Experiments on the settlement behaviour of planulae larvae of the reef coral Favia fragum (Esper) are described. The larvae are positively phototaxic upon release but reverse this and become attracted to dark surfaces, corners, crevices, and the undersides of objects on the bottom. Clean glass surfaces were preferred to surfaces covered with biological slime but there was no preference for rough against smooth surfaces. There was clear evidence of gregarious settlement behaviour, the planulae being able to recognize both adult colonies and previously settled juveniles. A distinction was made between crawling and swimming larvae, and the consequences of their differences in behaviour on the spatial distribution of Favia on reef are discussed. Settlement behaviour of Favia is similar in many respects to that of the Pacific reef coral Pocillopora damicornis (Dana) but is distinguished by gregarious settlement and by a preference for clean surfaces over surfaces covered with biological slime.

ENVIRONMENTAL AND TISSUE TEMPERATURES OF SOME TROPICAL INTERTIDAL MARINE ANIMALS

1. Body temperatures of three common intertidal animals were measured with fine wire thermocouples.2. Body temperatures were observed to be considerably above ambient air temperatures on a hot sunny day.3. The difference between body temperatures and ambient air temperatures was less marked on a cloudy day.4. Evaporative cooling was apparently the mechanism for lowering body temperatures. This process was most effective in the gastropod, Nerita.5. A relationship between ability to regulate body temperature by evaporation and intertidal zonation is suggested.

The ecology of Millepora

Attention is drawn to the lack of quantitative ecological information on the calcareous hydrozoan Millepora. In spite of their abundance and geological importance on reefs, little attention has been paid to the millepores compared to the dominant corals. The literature on distribution and abundance on reefs is reviewed and attention is drawn to sources of bias in reported estimates of Millepora abundance. Millepora is shown to have many of the same parasites and predators as scleractinians. The sparse data on growth and production are reviewed and compared with that of corals. The physiological and ecological responses of Millepora to storms and other disturbances appear to be similar to those of the scleractinans but the millepores have escaped attack by the starfish Acanthaster and appear to be immune to the common diseases of corals. The morphological similarities and ecological differences between millepores and scleractinians are discussed in terms of life-history strategies.

The Acropora inheritance: A reinterpretation of the development of fringing reefs in Barbados, West Indies

The discovery of the widespread occurrence of the remains of the reef coral Acropora palmata within the fabric of the fringing reefs on the west coast of Barbados requires a new interpretation of their Holocene development. Radiocarbon dating of the A. palmata framework suggests that reef construction by this species began as early as 2,300 years B.P. A. palmata probably flourished in Barbados into the present century but has now declined. The present fringing reefs are characterized by a core and base of A. palmata upon which subsequent colonization took place, especially by Montastrea annularis, Porites porites and coralline algae.

Spherical growth in the Caribbean coral Siderastrea radians (Pallas) and its survival in disturbed habitats

Siderastrea radians (Pallas) is a common West Indian reef coral that displays wide morphological variation. The hypothesis that a spherical form of free living colonies of S. radians has advantages for survival was examined in Barbados. Colonies were sampled from tide pools and from random quadrats at four reef flat sites subjected to strong wave action. Survival was found to be a positive function of colony size measured as living surface area and was correlated with stage of development toward a spherical shape. The combination of spherical shape and larger size confer a selective advantage on free living colonies in disturbed habitats.

Abundance, distribution and partial mortality of the massive coral Siderastrea siderea on degrading coral reefs at Barbados, West Indies

The abundance, distribution and partial mortality (amount of tissue loss) of colonies of the long-lived massive coral Siderastrea siderea were examined on seven fringing reefs along a eutrophication gradient at Barbados, West Indies. Size-frequency distributions are strongly skewed towards small colonies and spatial distributions of colonies are aggregated or clumped on all reefs. Partial mortality of damaged colonies, as measured by the percent of dead surface area and number of separated live tissue patches, is substantial and varies significantly between reefs. Partial mortality is positively correlated with colony size (diameter). There is no apparent gradient in partial mortality among the seven reefs when the amount of tissue loss is corrected for colony size and thus no correspondence in amount of coral surface damage with the reported eutrophication gradient.

Comparative respiration of some tropical intertidal gastropods

Abstract The rate of oxygen uptake of three species of tropical intertidal gastropods, Nerita tessellata Gmelid., N. Versicolor Gmelin and N. Peloronta L., have been investigated under different environmental conditions. In all species the rates increased from 30 to 37°C, were depressed at 20 °C and were not size-dependent at that temperature. The rates of oxygen uptake varied between individuals collected from different habitats and were greater in areas of higher mean maximum daily temperatures, lower rainfall and lower wind speeds than in areas with the reverse conditions. A decrease in oxygen uptake was shown to occur with an increase of exposure time of the animals on the shore and in the laboratory. Rates were higher in two species collected at the time of high tide than those collected at the same level after exposure to low tides.

Ecological energetics of the tropical sea urchin Diadema antillarum Philippi in Barbados, West Indies

Abstract The common tropical sea urchin Diadema antillarum Philippi is the dominant herbivore on fringing coral reefs in Barbados, West Indies. The biological importance of Diadema as an agent of energy transfer was evaluated from energy budgets constructed for the population and for individuals of 10 size groups. Monthly energy budgets for urchins of various size groups balance within 1 kcal except for urchins of the largest size group examined. Approximately 20% of the monthly net benthic primary production of the fringing coral reef is consumed by Diadema . This percentage is considerably larger than the 7% reported for the consumption of benthic algal production by a population of the temperate water sea urchin, Strongylocentrotus droebachiensis , feeding in kelp beds but is lower than the 47% reported for the consumption of sea grass by the tropical urchin Lytechinus variegatus . Higher rates of secondary production of Diadema compared to that of Strongylocentrotus may be in part due to higher net and gross growth efficiencies exhibited by Diadema . It is apparent that Diadema is more efficient at converting its algal food resources into urchin biomass than is Strongylocentrotus of similar size. In comparison to Strongylocentrotus and Lytechinus, Diadema releases as much energy to the benthos in the form of fecal pellet detritus as do the other two species. The production of fecal pellet detritus is the most important pathway of energy transfer on the fringing coral reef. Fecal pellet detritus contributes approximately 26 kcal m −2 month −1 to the benthic community. This amount is equivalent to 7·4% of the monthly net primary production of the benthic algae or approximately 37% of the caloric intake of the urchin population. In addition fecal pellet detritus produced by Diadema contains about 10 times the caloric content of surface sediments found to the north and south of the fringing reef and approximately 1·7 times the caloric content of sediments within the reef. The utilization of this energy-rich fecal pellet detritus by other reef organisms is discussed briefly.

The importance of light and food upon the early growth of the reef coral favia fragum (esper)

Abstract Planulae larvae of the reef coral Favia fragum (Esper) were allowed to settle and metamorphose to juveniles on glass microscope slides. The growth of the juveniles under conditions of light and darkness, with and without food, was measured for a period of about three months. Only those juveniles which were given food and incubated under a daily programme of 12 hours light continued to grow throughout the whole period of the experiment. Juveniles deprived of either light or food did not increase in size after the first week, but continued to survive for periods of up to three months with tissue atrophy.