Brain Coral Research Articles

Long-term effects of competition on coral growth and sweeper tentacle development

Outcomes of competition between corals vary temporally and spatially, and depend in part on the agonistic mechanism involved. Competition may impact coral growth, reproduction and energy reserves, however few experimental studies have quantified these effects. We conducted a 1 yr laboratory experiment on competition between 2 massive corals, Platygyra daedalea and Favites complanata. Colonies of P. daedalea developed sweeper tentacles and extensively damaged the F. complanata colonies, causing them to loose ca. 55% of their soft tissue and eventually killing 30% of F. complanata colonies. Skeletal accretion rate varied widely among corals within each treatment, and correlated negatively with the percent tissue damaged on competing colonies of F. complanata. On isolated control colonies, sweeper tentacles developed randomly throughout the year, and then reverted back to feeding tentacles. They appeared to serve as probes to detect the approach of com- petitors. Development of sweeper tentacles is a powerful aggressive/defensive mechanism that may enable brain corals to dominate some reef areas in the Indo-Pacific region.

Record of Little Ice Age sea surface temperatures at Bermuda using a growth‐dependent calibration of coral Sr/Ca

Strontium to calcium ratios (Sr/Ca) are reported for a massive brain coral Diploria labyrinthiformis collected from the south shore of Bermuda and are strongly correlated with both sea surface temperature (SST) and mean annual skeletal growth rate. High Sr/Ca ratios correspond with cold SSTs and slow skeletal growth rate and vice versa. We provide a quantitative calibration of Sr/Ca to extension rate and SST along the axis of maximum growth and derive a growth‐dependent Sr/Ca–SST calibration equation to reconstruct western subtropical North Atlantic SSTs for the past 223 years. When the influence of growth rate is excluded from the calibration, Sr/Ca ratios yield SSTs that are too cold during cool anomalies and too warm during warm anomalies. Toward the end of the Little Ice Age (∼1850), SST changes derived using a calibration that is not growth‐dependent are exaggerated by a factor of 2 relative to those from the growth‐corrected model that yields SSTs ∼1.5°C cooler than today. Our results indicate that incorporation of growth rate effects into coral Sr/Ca calibrations may improve the accuracy of SSTs derived from living and fossil corals.

Development of a sublethal test to determine the effects of copper and lead on scleractinian coral larvae.

A new sublethal toxicity test was developed in this study to measure the effect of copper and lead on the motility of coral larvae. Larval motility was significantly affected by copper and lead doses immediately after dosing. The copper EC50 values for motility of Goniastrea aspera brain coral larvae (12 h, 21 microg/L; 24 h, 16 microg/L; 48 h, 22 microg/L) were much lower than the copper LC50 values for G. aspera larval survival (6 h, 260 microg/L, and 24 h, 121 microg/L, for 5-day-old larvae and 6 h, 248 microg/L, and 24 h, 136.64 microg/L, for 6-day-old larvae) during the early part of the experiments. However, at later times, the LC50 values (48 h, 40 microg/L, for 5-day-old larvae and 48- h, 87 microg/L, for 6-day-old larvae) were similar to the EC50 values for larval motility. The lead 72-h EC50 value for G. aspera larval motility (2900 microg/L) was much lower than the lead 72-h LC50 value for larval survival (9890 microg/L). The results show that larval motility can be a useful parameter to measure in order to determine the sublethal effects of trace metals on coral larvae.

How brain corals record climate: an integration of skeletal structure, growth and chemistry of Diploria labyrinthiformis from Bermuda

The aragonite skeleton of massive reef-building corals contains a record of the oceanic environment in which they grow. However, reading of the record requires understanding of how it is archived, a process complicated by the elaborate skeletal construction and seasonal growth patterns that characterize many species. In this study, we assess the utility of the massive brain coral Diploria labyrinthiformis as an archive of sea surface temperature (SST) variability in the western North Atlantic. In situ staining of live colonies combined with microscale analysis of skeletal chemistry indi- cate that D. labyrinthiformis grows throughout the year on Bermuda and records the full annual cycle of SST variability. However, skeleton accreted during the summer is overlain (thickened) by skeleton accreted during the subsequent fall and winter. As a result, conventional coarse sampling for δ 18 O enables seasonal δ 18 O cycles to be resolved but these do not capture the full amplitude of the annual SST cycle. Our data show that the shallow gradient of the δ 18 O-SST regression equation derived for D. labyrinthiformis (-0.113‰ oC -1 ) relative to the expected -0.22‰ oC -1 for marine skeletons results from dampening of the summertime peak in δ 18 O. In contrast, skeleton accreted during the winter is not thickened and wintertime δ 18 O captures the interannual wintertime SST variability at this site. Using SIMS ion microprobe to analyse strontium to calcium ratios (Sr/Ca), we avoided the thickening deposits and were able to resolve the full amplitude of the annual Sr/Ca cycle. The Sr/Ca-SST relationship obtained for D. labyrinthiformis (-0.0843 mmol/mol oC -1 ) corresponds to that derived from fast-growing tropical reef corals. X-ray intensity ratios, used as a proxy for skeletal density, reveal the expected seasonal changes associated with growth banding as well as variability on inter- annual and decadal timescales. These variations are well correlated with wintertime SST variability in the subtropical gyre and may be a valuable proxy thermometer for the North Atlantic.

Sweeper tentacles of the brain coral Platygyra daedalea: induced development and effects on competitors

Benthic marine organisms utilize an array of defensive and aggressive mechanisms that affect competition for space on hard marine substrata. The sweeper tentacles of stony corals are inducible aggressive organs used during competition, but they also may serve a pre-emptive defen- sive function. About half of the colonies of the brain coral Platygyra daedalea at Eilat, northern Red Sea, possess sweeper tentacles, many of which are not directed toward neighboring corals. These randomly oriented sweeper tentacles may be produced in order to detect the settlement or advance of corals occurring at >5 cm distance from the colony. Of coral colonies <5 cm distant from P. daedalea, about 43% exhibit tissue damage facing the interaction area. Adjacent corals with the most damage belong to the genera Favites and Leptastrea, while colonies of Millepora and congeneric Platygyra exhibit significantly less damage. Tissue damage of neighboring coral colonies decreases significantly with increasing distance from P. daedalea. The presence of sweeper tentacles on brain corals correlates significantly with colony diameter, but not with the number of neighboring colonies. The aggressive reach of P. daedalea in Eilat is 5.3 ± 3.0 cm, longer than previously reported for mem- bers of this genus. Under laboratory conditions, sweeper tentacles develop on P. daedalea colonies about 30 d following initial contact with colonies of the common massive coral F. complanata, and at approximately 50 d they reach a maximum length of about 6.5 cm, 10 × longer than feeding tentacles. Sweeper tentacles cause increasing tissue damage to F. complanata colonies over 2 mo. During mor- phogenesis, their tip-to-stalk ratio and ectoderm thickness doubles, indicating acrosphere develop- ment, but maximal width of the tentacle stalk does not change. Sweeper tentacles appear to be a common agonistic mechanism among stony corals, and may serve also as a defensive mechanism that allows the persistence of some species in crowded reef habitats.

Microscale Titania Shapes Grown Within Swollen PDMS

ABSTRACTA variety of titania microstructures have been synthesized using a swollen polymer matrix of polydimethylsiloxane (PDMS). The shapes and structures grown to date include spheres, ‘bowls’, ‘nets’ and ‘brain coral’ matrices. The PDMS polymer network can be swollen by one of a variety of organic solvents. These solvents create internal voids or spaces within the PDMS, of particular volume. These spaces can then be filled with metal alkoxide liquid. The metal alkoxide is then polymerized to form metal oxides, in a shape templated by the swollen PDMS polymer. The resultant product is a composite of metal oxide within a polymer. Some of the shapes can be removed mechanically or chemically. Methods of characterization include scanning electron microscopy (SEM) and optical microscopy. Potential applications of the shaped titania include catalysts, fillers, capsules, and chemical separators. The synthesis and characterization of these compounds will be discussed.

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.

Brain Coral of the Caribbean Sea

Brain Coral of the Caribbean Sea

Measurement of solar‐stimulated fluorescence in natural waters

The oceanic Fraunhofer line discriminator (OFLD), designed to measure the solar ‐stimulated inelastic scattering in the ocean, has been deployed in various types of water in Florida Bay and the Dry Tortugas to measure Fraunhofer lines and oxygen‐absorption lines near 689 nm in the solar spectrum. The line‐filling principle and previous work enable us to partition the measured light into elastic, Raman scattering, and fluorescence components. We show that in optically deep, oligotrophic water, where chlorophyll a (Chl a) concentration is as low as 0.1 mg m−3, fluorescence near 689 nm was still measurable by the OFLD. In moderately eutrophic shallow waters, where Chl a concentration ranges from 0.2 to 0.8 mg m−3, the fluorescence from either Chl a or dissolved organic matter in the water column was found to be a negligible component of the total light field due to the additional light reflected from the bottom. We also include measurements of the solar ‐stimulated fluorescence for benthic surfaces, such as brain coral, and have found these to be saturated under normal solar illumination.

Rapid-Wasting Disease: Pathogen or Predator?

Researchers have raised concern about the sudden emergence of coral diseases and the contagious nature of many of these diseases ([1][1]). A new “disease” was recently identified on star coral ( Montastraea annularis species complex) and brain coral ( Colpophyllia natans ) from reefs of Bonaire

Effects of chemically dispersed oil on the brain coral, Diploria strigosa

The frequency of oil spills in tropical seas may threaten coral reef survival and some of the past research has indicated that oil alone as well as oil dispersed with chemical dispersants is toxic to corals. These experiments were probably realistic of intertidal reef zones and sheltered shallow reef areas. However, few experiments have incorporated analytical chemistry necessary to relate reported biological effects to actual oil spill concentrations and exposure times. This paper outlines some new results with emphasis on a 3 year programme carried out in Bermuda using a flow-through laboratory dosing system, comparative laboratory and field experiments, real time measurements of oil concentrations, and non-destructive bioassays to allow repetitive data collection from the same specimens. Suggestions for future research programmes are given in light of these results. In addition to research on the effects of oil and chemically dispersed oil on other coral species and associated organisms in the coral reef, the relative sensitivity of the various ecosystems comprising the tropical coastal zone (mangroves, seagrasses and reef) must also be addressed. It is hoped that such advances will ensure that overall oil spill clean-up decisions will give due consideration to the individual physical and biological characteristics of each of these tropical environments.

Effects of crude oil and chemical dispersant on photosynthesis in the brain coral Diploria strigosa

An eight-hour exposure of Diploria strigosa (Dana) to a mixture of Arabian Light crude oil (19 ppm) and the chemical dispersant “Corexit 9527” (1 ppm) in a flowing seawater system reduced photosynthesis by symbiotic zooxanthellae by 85%, while either oil or dispersant alone had no effect. The greatest effect of crude oil plus dispersant occurred in the incorporation of photosynthetic products into lipids. Synthesis of was esters and triglycerides, the major storage lipids, was particularly affected. Total carbon fixation was restored within 3–5 h after treatment, and lipid synthesis was restored within 5–24 h after exposure.

A 200 year record of carbon‐13 and carbon‐14 variations in a Bermuda coral

A 200 year old brain coral, captured in Bermuda in 1976 was slabbed and x‐rayed. Using the annual growth bands sequential, dated samples were taken over the entire growth period of the coral and analyzed for Δ14C, δ13C and δ18O. During the past 80 years atmospheric variations in Δ14C and δ13C due to human effects, such as release of bomb C‐14 and dilution of both C‐14 and C‐13 by fossil fuel burning, are closely tracked by the coral. Prior to 1900 divergences between the coral and tree Δ14C and δ13C can be related to world‐wide changes in plant production and possibly oceanic upwelling rates.

Multiple conducting systems and the control of behaviour in the brain coral Meandrina meandrites (L.)

Extracellular suction electrode recordings from tentacles of Meandrina provide evidence for three conducting systems. One system may be the colonial nerve net. It is through-conducting and occasionally gives multiple responses to mechanical and electrical stimulation. The other two systems are also normally through-conducting but they conduct very slowly and are termed slow systems. One slow system (SSo) is in the oral disk and the other (SSc) is in the tissue covering the thecal ridges (coenosarc). SSo pulses travel throughout the interconnected oral disk regions of the colony but also enter the SSc. SSc pulses travel over the entire coenosarc but cannot enter the SSo. Both slow systems are present in the tentacles. Repetitive stimulation of the SSo evokes oral disk expansion and tentacle extension, seemingly identical to the expansion that normally occurs at night when the colony shows tentacular feeding. Repetitive stimulation of the SSc also evokes slight tentacle extension but more noticeably causes the coenosarc to become turgid. Many colonies show coenosarc expansion during the day and this may alter the exposure of symbiotic zooxanthellae to sunlight. The SSo and SSc are spontaneously active and both show a marked increase in pulse frequency when exposed to dissolved food substances. The level of activity in each system may also be modified by changes in light intensity and the SSc and SSo may thus control respectively diurnal and nocturnal expansion of different parts of the colony. The colonial nerve net appears to coordinate fast and slow contractions. Intense light can increase the level of spon­taneous activity in the nerve net.

Coral diseases in Bermuda

WE report here diseases of reef corals that seem to be associated with bacterial infection. On reefs around Bermuda, where our field work was carried out in the summer of 1973, the most commonly affected species are the brain corals Diploria labyrintheformis and D. strigosa (Fig. 1). We believe that this is the first unequivocal report of a coral disease and our observations suggest that diseases may be important agents of coral death. (There are some indications that others have seen diseased corals1,2.)

LIGHT TRANSMISSION AND SPECTRAL DISTRIBUTION THROUGH EPI- AND ENDOZOIC ALGAL LAYERS IN THE BRAIN CORAL,FAVIA

Two species of algae were living symbiotically with a hard brain coral, Fa@ia, harvested in the environs of the Flinders Island Group on the Great Barrier Reef in Australia. One of the algae has the microscopic appearance and pigment corn position of dinoflagellates (Halldal, 1968, Jeffrey and Haxo, 1968) and it contrib utes the dark brown color to the coral tissues which form a surface layer over the colony. This alga resembles Symbiodiniuni microadriaticum Freudenthal. Green algae lived inside the spherical coral forming another colored layer (Jeffrey, 1968) , and there was an intermediate pale green (nearly white) layer between these brown and green layers. The green algae seemed to be of mixed genera and species, most of them probably belonging to Ostreobiuni Reineckei Bornet within the order Siphonales. The present paper describes the in vivo absorption spectra of these algal layers as well as the spectral distribution. EXPERIMENTAL METHODS The samples of Favia pallida DaIla were harvested in the environs of the Flinders Island Group, and were kept in running sea-water aquaria on the open deck of the research vessel. The spectral data presented in this paper were observed for the sample which was 12 cm in diameter and 8.5 cm in thickness

PIGMENT COMPOSITION OF SIPHONALES ALGAE IN THE BRAIN CORAL FAVIA

1. The photosynthetic pigments of the green subsurface layer (Ostreobium) of The pigments found were chlorophylls a and b, α- and β-carotene, siphonein, traces the brain coral Favia were studied by two-dimensional paper chromatography. of siphonaxanthin and neoxanthin, and an unknown yellow-orange xanthophyll.2. The pigment composition of Ostreobium closely resembled that of two members of the Siphonales, Halimeda and Codium. Therefore, this alga may be appropriately grouped within the Siphonales.3. The three algae, Halimeda, Codium, and Ostreobium contained a high proportion of chlorophyll b, from two-thirds to three-quarters that of chlorophyll a.