Changes in Coral Reef Communities and an Associated Reef Fish Species, <Emphasis Type="Italic">Cephalopholis cruentata</Emphasis> (Lacépède), After 30 years on Curaçao (Netherlands Antilles)

Using the same methodology and identical sites, we repeat a study dating from 1973 and quantify cover of hard coral species, soft corals, sponges, hard substratum and soft substratum, and density of a commercially important reef fish species, the graysby Cephalopholis cruentata, along a depth-gradient of 3–36 m on the coral reefs of Curaçao. The objective was to determine the multi-decade change in benthic coral reef cover and structural complexity, and their effect on densities of an associated reef fish species. Total hard coral cover decreased on average from 52% in 1973 to 22% in 2003, representing a relative decline of 58%. During this time span, the cover of hard substratum increased considerably (from 11 to 58%), as did that of soft corals (from 0.1 to 2.2%), whereas the cover of sponges showed no significant change. Relative decline of hard coral cover and of reef complexity was greatest in shallow waters (near the coast), which is indicative of a combination of anthropogenic influences from shore and recent storm damage. Cover of main reef builder coral species (Agaricia spp., Siderastrea siderea, Montastrea annularis) decreased more than that of other species, and resulted in a significant decrease in reef complexity. Although density of C. cruentata was highly correlated to cover of Montastrea and Agaricia in 1973, the loss of coral cover did not show any effect on the total density of C. cruentata in 2003. However, C. cruentata showed a clear shift in density distribution from shallow water in 1973 to deep water in 2003. It can be concluded that the reefs of Curaçao have degraded considerably in the last three decades, but that this has had no major effect on the population size of one commercially important coral-associated fish species.     

Assessment of the relative contribution of asexual propagation in a population of the coral-excavating sponge Cliona delitrix from the Bahamas

Cliona delitrix is a very destructive coral-excavating sponge in Caribbean coral reef systems, particularly for Montastraea species. Little is known about how these excavating sponges propagate across coral reefs. In this study a hypothesis was tested that coral breakage caused by the bioeroding activity facilitates the asexual propagation of this sponge and in turn favors the spread of the most aggressive sponge genotypes. An allozyme analysis, involving 12 loci systems of 52 sponge individuals from a total of 13 Montastraea heads, found that no two sponges possessed identical multi-locus genotypes. Contrary to the pattern expected for fragmenting species, the incidence of clonality and asexual propagation at the population level was minimal. The lack of correlation between genetic and physical distances for the studied sponges also suggests that population maintenance appears to derive from larval dispersal, with a spatial range of dispersal larger than the average distance between the coral heads (10–10² m).     

First record of coralline demosponges in the Pleistocene: implications for reef ecology

We report the first discovery of coralline sponges from Pleistocene reef limestones of Vanuatu. Sponges of the genus Acanthochaetetes were identified from two reef terraces of Middle and Late Pleistocene age. As these sponges document cryptic habitats in modern coral reefs, they may be index fossils of cryptic habitats in the Pleistocene as well, thereby providing clues on growth conditions in fossil reefs. The small size of the discovered specimens may be attributed to the transient nature of their cryptic habitats, either due to reef growth or the occurrence of an unusual event.     

Bioerosion in Late Permian Rugosa from reefal blocks (Hawasina Complex,Oman Mountains): implications for reef degradation

Summary Rugose corals are known from allochthonous Late Permian reefal blocks of the A1 Jil and Ba’id Formation (Hawasina Complex), Oman Mountains. In contrast to many Late Permian Rugosa found elsewhere in the Tethys, they occurred in sponge reefs and contributed to reef construction. The waagenophyllid warm water coral fauna is moderately diverse comprising cerioid, thamnasterioid, and fasciculate taxa. In contrast to sponges, chaetetids, and low-growing reefbuilders, the corals secreted diagenetically stable, most probably Mg-calcitic skeletons. Borings in coral skeletons are consequently well preserved providing important data for the interpretation of reef destructive processes. Thin-section analysis revealed three taxa of infaunal borers includingEntobia Bronn 1837, uncertain thallophyte borings, and borings of unknown bioeroders. Macroborers were more important than microborers, because of the dominance of clionid sponges. Good evidence exists also for the occurrence of two types of undetermined grazers which destroyed the coral surfaces. The amount and distribution of bioerosions is variable among different coral taxa. The fasciculate coralPraewentzelella regulare Flügel 1995 was the favorate substrate. Up to 33% of the calices were bored. Dendroid and compound corals were bored subordinately. Bioerosion of these colonies does not exceed 2%. There is good evidence for substrate preference amongst the borers. Major controlling factors affecting borer distribution are believed to be variations of skeletal density and gross morphology. The borer assemblage could not limit reef accretion significantly. Factors controlling boring activity might have been quality of substrate, sedimentation rate, rapid incrustation of substrates, and competition for food with reef constructors including sponges, chaetetids, and rugose corals.     

Tiger cowrie Cypraea tigris feeds on coral-competing sponge Rhabdastrella globostellata in an Acropora dominated reef of Gulf of Mannar,India

Gulf of Mannar (GoM) in the southeast coast of India is known for its coral reefs and reef-associated biodiversity. Corals in GoM were affected to a significant extent by climate change-driven coral bleaching in 2016, and are currently recovering. After the bleaching mortality that corals suffered, the competition for space between corals and sponges is obvious in GoM. Rhabdastrella globostellata is a common marine sponge found overgrowing live coral colonies of the patch reefs in GoM at Pattinamaruthoor in March 2019. Underwater assessment of the reef revealed that 60.06% live coral cover was dominated by Acropora corals (81.91%). Among the acroporans 8.23% of colonies were found overgrown by R. globostellata. During the night dives the tiger cowrie Cypraea tigris was observed to feed on R. globostellata. From this observation the present study infers that C. tigris helps the corals fight these sponges, and concludes that tiger cowries should be protected and promoted to tackle climate change implications.     

Reef habitats and associated sessile-benthic and fish assemblages across a euphotic–mesophotic depth gradient in Isla Desecheo, Puerto Rico

Quantitative surveys of sessile benthos and fish populations associated with reef habitats across a 15–50 m depth gradient were performed by direct diver observations using rebreathers at Isla Desecheo, Puerto Rico. Statistically significant differences between depths were found for total live coral, total coral species, total benthic algae, total sponges and abiotic cover. Live coral cover was higher at the mid-shelf (20 m) and shelf-edge (25 m) stations, whereas benthic algae and sponges were the dominant sessile-benthic assemblage at mesophotic stations below 25 m. Marked shifts in the community structure of corals and benthic algae were observed across the depth gradient. A total of 119 diurnal, non-cryptic fish species were observed across the depth gradient, including 80 species distributed among 7,841 individuals counted within belt-transects. Fish species richness was positively correlated with live coral cover. However, the relationship between total fish abundance and live coral was weak. Abundance of several numerically dominant fish species varied independently from live coral cover and appeared to be more influenced by depth and/or habitat type. Statistically significant differences in the rank order of abundance of fish species at euphotic vs mesophotic stations were detected. A small assemblage of reef fishes that included the cherubfish, Centropyge argi, sunshine chromis, Chromis insolata, greenblotch parrotfish, Sparisoma atomarium, yellowcheek wrasse, Halichoeres cyanocephalus, sargassum triggerfish, Xanthichthys ringens, and the longsnout butterflyfish, Chaetodon aculeatus was most abundant or only present from stations deeper than 30 m, and thus appear to be indicator species of mesophotic habitats.     

Bdellovibrio-like parasite of cyanobacteria symbiotic in marine sponges

A bdellovibrio-like bacterium was observed infecting unicellular symbiotic cyanobacteria in two coral reef sponges, Neofibularia irata and Jaspis stellifera. The infecting bacterium, which was located between the cell wall and the cytoplasmic membrane of the cyanobacteria, was similar in size and appearance to previously described bdellovibrios. This observation is believed to extend the host range of the bdellovibrios.     

Boring by Macro-organisms in the Coral Montastrea annularis on Barbados Reefs

The fauna boring into Montastrea annularis includes sponges, bivalves, sipunculid and polychaete worms and barnacles. Sponges are most important in hard tissue destruction and account for more than 90% of the total boring in most heads. Bivalves and barnacles are locally important. Sipunculids and sabellids account for less than 4% of the total boring. The volume removed from coral samples by boring ranged from 3–60% and samples from a deeper bank reef were more highly bored than fringing reef samples. An average of 20% of the volume of bank reef corals, and 5% of the volume of fringing reef corals, was removed by boring. The distribution of individual borers is not a function of depth. The density and variety of borers and the extent of boring in coral heads is greater in older heads. The ratio of living coral surface to dead encrusted areas on colonies also influences borer density and the extent of boring.     

Growth facilitation by the octocoral Gorgonia ventalina explains spatial difference in the population size structure of the common demosponge Ircinia felix

In this study, the demography of the common demosponge Ircinia felix was examined at Tamarindo, a coral reef located in the island municipality of Culebra, Puerto Rico. A preliminary study comparing the size structure of two subpopulations within the reef, Tamarindo Norte (TN) and Tamarindo Sur (TS), indicated that sponges at TN are significantly larger than sponges at TS. This result served as a baseline for the present comparative study in which we aimed to determine whether the spatial differences in population size structure can be explained either by a difference in rates of survival, growth, or recruitment, or a combination of these. To accomplish our goal, we followed the growth, survival and recruitment of I. felix at the two localities for one year. Growth was the only demographic parameter that differed significantly between localities. Because the most obvious distinction between the study sites was the absence of the octocoral Gorgonia ventalina at TS, we hypothesized that the faster overall growth rate of sponges at TN was related to the presence of the octocoral. To test this hypothesis, we compared growth rates between sponges associated with the octocoral and those individuals not associated. We found that sponges growing near G. ventalina grew significantly faster than non-associated sponges. This result suggests that the octocoral facilitates the growth of I. felix and therefore may account, at least in part, for the spatial differences in population size structure.     

Elucidating the sponge stress response; lipids and fatty acids can facilitate survival under future climate scenarios

Ocean warming (OW) and ocean acidification (OA) are threatening coral reef ecosystems, with a bleak future forecast for reef‐building corals, which are already experiencing global declines in abundance. In contrast, many coral reef sponge species are able to tolerate climate change conditions projected for 2100. To increase our understanding of the mechanisms underpinning this tolerance, we explored the lipid and fatty acid (FA) composition of four sponge species with differing sensitivities to climate change, experimentally exposed to OW and OA levels predicted for 2100, under two CO₂ Representative Concentration Pathways. Sponges with greater concentrations of storage lipid, phospholipids, sterols and elevated concentrations of n‐3 and n‐6 long‐chain polyunsaturated FA (LC PUFA), were more resistant to OW. Such biochemical constituents likely contribute to the ability of these sponges to maintain membrane function and cell homeostasis in the face of environmental change. Our results suggest that n‐3 and n‐6 LC PUFA are important components of the sponge stress response potentially via chain elongation and the eicosanoid stress‐signalling pathways. The capacity for sponges to compositionally alter their membrane lipids in response to stress was also explored using a number of specific homeoviscous adaptation (HVA) indicators. This revealed a potential mechanism via which additional CO₂ could facilitate the resistance of phototrophic sponges to thermal stress through an increased synthesis of membrane‐stabilizing sterols. Finally, OW induced an increase in FA unsaturation in phototrophic sponges but a decrease in heterotrophic species, providing support for a difference in the thermal response pathway between the sponge host and the associated photosymbionts. Here we have shown that sponge lipids and FA are likely to be an important component of the sponge stress response and may play a role in facilitating sponge survival under future climate conditions.     

Phase shift to algal dominated communities at mesophotic depths associated with lionfish (<Emphasis Type="Italic">Pterois volitans</Emphasis>) invasion on a Bahamian coral reef

Mesophotic coral reefs (30–150 m) have been assumed to be physically and biologically connected to their shallow-water counterparts, and thus may serve as refugia for important taxonomic groups such as corals, sponges, and fish. The recent invasion of the Indo–Pacific lionfish (Pterois volitans) onto shallow reefs of the Caribbean and Bahamas has had significant, negative, effects on shallow coral reef fish populations. In the Bahamas, lionfish have extended their habitat range into mesophotic depths down to 91 m where they have reduced the diversity of several important fish guilds, including herbivores. A phase shift to an algal dominated (>50% benthic cover) community occurred simultaneously with the loss of herbivores to a depth of 61 m and caused a significant decline in corals and sponges at mesophotic depths. The effects of this invasive lionfish on mesophotic coral reefs and the subsequent changes in benthic community structure could not be explained by coral bleaching, overfishing, hurricanes, or disease independently or in combination. The significant ecological effects of the lionfish invasion into mesophotic depths of coral reefs casts doubt on whether these communities have the resilience to recover themselves or contribute to the recovery of their shallow water counterparts as refugia for key coral reef taxa.     

Taphonomy of modern deep,cold‐temperate water coral reefs

Deep‐water corals are widely distributed along the cold‐temperate northeastern Atlantic continental margin. Despite the widespread occurrence of these aphotic coral constructions in deep shelf settings, the processes of framework formation and postmortem alterations which result in different preservational styles are still poorly known. Detailed mapping surveys on probably one of the largest Lophelia reef structures were carried out on the Sula Ridge, Mid‐Norwegian Shelf in 270 to 300 m depth. Side scan sonar records and camera surveys yield information at various scales of resolution on the reef complex which is more than 9 km long and up to 45 m high. Living Lophelia colonies effectively prevent colonization by other organisms and are successful in the rejection of passing detrital material from the soft tissue. In a healthy condition the coral is able to encrust repetitively attached organisms by selectively secreted sclerenchyme layers, thus, this defensive reaction results in the thickening of the skeleton. Early postmortem alteration in Lophelia colonies is introduced by the formation of a biofilm and Dodgella (fungi) infestation. The biofilm is associated with selective Fe‐Mn precipitation on the coral skeleton. This is the zone of intense attachment of sessile invertebrates such as serpulids, brachiopods, foraminifers and encrusting bryozoans. More advanced taphonomic stages show an increasing dominance in sponges which reduce the interskeletal framework porosity significantly. In addition, boring sponges excavate the thickly calcified Lophelia skeletons, thus leading to in situ collapsing structures on the sea floor. It is the intensity of sediment trapping biofilms and sponge colonization and the amount of imported detrital particles predominantly from the pelagial zone that control the generation of a pure coral rubble facies or the preservation of collapsed but mud‐rich detrital mounds.     

A Novel Technique for the Reattachment of Large Coral Reef Sponges

Sponges are dominant components of coral reef ecosystems, often exceeding reef-building corals in abundance. Large sponges, often more than 1 m in diameter, may be hundreds to thousands of years old. When damaged or dislodged, large sponges usually die because they are unable to reattach to the reef substratum. Because suitable methods for reattaching dislodged sponges are lacking, they are typically excluded from coral reef restoration efforts. Here we present a novel technique for the reattachment of large sponges that was tested using the Caribbean Giant barrel sponge, Xestospongia muta . Transplants of X. muta were conducted at 15- and 30-m depth off Key Largo, Florida. Despite the active hurricane season of 2005, 90% of deep and 35% of shallow transplants survived, with nearly 80% reattaching to the substratum and growing after 2.3–3 years. This technique may be generally adapted for securing large sponges in coral reef restoration efforts.     

Patch reef development in the florigemma-Bank Member (Oxfordian) from the Deister Mts (NW Germany): a type example for Late Jurassic coral thrombolite thickets

Small reefal bioconstructions that developed in lagoonal settings are widespread in a few horizons of the Late Jurassic (Oxfordian) succession of the Korallenoolith Formation, exposed southwest of Hannover, Northwest Germany. Especially the florigemma-Bank Member, “sandwiched” between oolite shoal deposits, exposes a high variety of build-ups, ranging from coral thrombolite patch reefs, to biostromes and to coral meadows. The reefs show a distribution with gradual facies variations along an outcrop belt that extends about 30 km from the Wesergebirge in the NW to the Osterwald Mts in the SE.The patch reefs from the Deister Mts locality at the “Speckhals” are developed as coral-chaetetid-solenoporid-microbialite reefs and represent a reef type that was hitherto unknown so far north of its Tethyan counterparts. They are mainly built up by coral thickets that are preserved in situ up to 1.5 m in height and a few metres in diameter. They contain up to 20 coral species of different morphotypes but are chiefly composed of phaceloid Stylosmilia corallina and Goniocora socialis subordinately. The tightly branched Stylosmilia colonies are stabilized by their anastomosing growth. The coral branches are coated with microbial crusts and micro-encrusters reinforcing the coral framework. Encrusters and other biota within the thicket show a typical community replacement sequence: Lithocodium aggregatum, Koskinobullina socialis and Iberopora bodeuri are pioneer organisms, whereas the occurrence of non-rigid sponges represents the terminal growth stage. The latter are preserved in situ and seem to be characteristic so far poorly known constituents of the Late Jurassic cryptobiont reef dweller community. The distance and overall arrangement of branches seems to be the crucial factor for the manifestation of a (cryptic) habitat promoting such community replacement sequences. Widely spaced branches often lack any encrusting and/or other reef dwelling organisms, whereas tightly branched corals, as is St. corallina, stimulate such biota. Hence, such reefs are well suited for research on coelobites and community sequences of encrusting and cavity dwelling organisms.     

Consumption of coral propagules represents a significant trophic link between corals and reef fish

Mass spawning of corals provides a large seasonal pulse of high-energy prey that potentially benefits reef fish that are capable of capturing and digesting coral propagules. This study examines the range of fish species that consume coral propagules and also tests whether reef fish experience a significant increase in physiological condition when feeding on coral propagules. Thirty-six species of diurnal reef fish were seen to consume coral propagules released during mass coral spawning. Stomach content analyses of three reef fish species (Pomacentrus moluccensis, Abudefduf whitleyi, and Caesio cunning) revealed that both P. moluccensis and A. whitleyi feed almost exclusively on coral propagules during mass coral spawning. Fish feeding extensively on coral propagules also amassed considerable lipid stores, which could greatly improve the quality and survivorship of their progeny. In contrast, C. cunning consumed only very small quantities of coral propagules, and showed no detectable change in lipid stores during the course of the study. This study provides the first direct evidence that reef fish benefit from mass coral spawning, and reveals a potentially significant trophic link between scleractinian corals and reef fish. Accepted: 9 June 2000     

Wave exposure shapes reef community composition and recovery trajectories at a remote coral atoll

In a time of unprecedented ecological change, understanding natural biophysical relationships between reef resilience and physical drivers is of increasing importance. This study evaluates how wave forcing structures coral reef benthic community composition and recovery trajectories after the major 2015/2016 bleaching event in the remote Chagos Archipelago, Indian Ocean. Benthic cover and substrate rugosity were quantified from digital imagery at 23 fore reef sites around a small coral atoll (Salomon) in 2020 and compared to data from a similar survey in 2006 and opportunistic surveys in intermediate years. Cluster analysis and principal component analysis show strong separation of community composition between exposed (modelled wave exposure > 1000 J m⁻³) and sheltered sites (< 1000 J m⁻³) in 2020. This difference is driven by relatively high cover of Porites sp., other massive corals, encrusting corals, soft corals, rubble and dead table corals at sheltered sites versus high cover of pavement and sponges at exposed sites. Total coral cover and rugosity were also higher at sheltered sites. Adding data from previous years shows benthic community shifts from distinct exposure-driven assemblages and high live coral cover in 2006 towards bare pavement, dead Acropora tables and rubble after the 2015/2016 bleaching event. The subsequent recovery trajectories at sheltered and exposed sites are surprisingly parallel and lead communities towards their respective pre-bleaching communities. These results demonstrate that in the absence of human stressors, community patterns on fore reefs are strongly controlled by wave exposure, even during and after widespread coral loss from bleaching events.

     

Bacterial Diversity Associated with Cinachyra cavernosa and Haliclona pigmentifera,Cohabiting Sponges in the Coral Reef Ecosystem of Gulf of Mannar,Southeast Coast of India

Sponges are abundant, diverse and functionally important organisms of coral reef ecosystems. Sponge-associated microorganisms have been receiving greater attention because of their significant contribution to sponge biomass, biogeochemical cycles and biotechnological potentials. However, our understanding of the sponge microbiome is limited to a few species of sponges from restricted geographical locations. Here, we report for the first time the bacterial diversity of two cohabiting sponges, viz. Cinachyra cavernosa and Haliclona pigmentifera, as well as that in the ambient water from the coral reef ecosystems of the Gulf of Mannar, located along the southeast coast of India. Two hundred and fifty two clones in the 16S rRNA gene library of these sponges were grouped into eight distinct phyla, of which four belonged to the core group that are associated only with sponges. Phylogenetic analysis of the core bacteria showed close affinity to other sponge-associated bacteria from different geographical locations. γ-Proteobacteria, Chloroflexi, Planctomycetes and Deferribacter were the core groups in C. cavernosa while β and δ-Proteobacteria performed this role in H. pigmentifera. We observed greater OTU diversity for C. cavernosa (H^ǀ 2.07) compared to H. pigmentifera (H^ǀ 1.97). UniFrac analysis confirmed the difference in bacterial diversity of the two sponge species and also between the sponges and the reef water (p<0.001). The results of our study restate the existence of a host driven force in shaping the sponge microbiome.     

Larval Settlement: The Role of Surface Topography for Sessile Coral Reef Invertebrates

For sessile marine invertebrates with complex life cycles, habitat choice is directed by the larval phase. Defining which habitat-linked cues are implicated in sessile invertebrate larval settlement has largely concentrated on chemical cues which are thought to signal optimal habitat. There has been less effort establishing physical settlement cues, including the role of surface microtopography. This laboratory based study tested whether surface microtopography alone (without chemical cues) plays an important contributing role in the settlement of larvae of coral reef sessile invertebrates. We measured settlement to tiles, engineered with surface microtopography (holes) that closely matched the sizes (width) of larvae of a range of corals and sponges, in addition to surfaces with holes that were markedly larger than larvae. Larvae from two species of scleractinian corals (Acropora millepora and Ctenactis crassa) and three species of coral reef sponges (Luffariella variabilis, Carteriospongia foliascens and Ircinia sp.,) were used in experiments. L. variabilis, A. millepora and C. crassa showed markedly higher settlement to surface microtopography that closely matched their larval width. C. foliascens and Ircinia sp., showed no specificity to surface microtopography, settling just as often to microtopography as to flat surfaces. The findings of this study question the sole reliance on chemical based larval settlement cues, previously established for some coral and sponge species, and demonstrate that specific physical cues (surface complexity) can also play an important role in larval settlement of coral reef sessile invertebrates.     

Interactive effects of temperature and pCO2 on sponges: from the cradle to the grave

As atmospheric CO₂ concentrations rise, associated ocean warming (OW) and ocean acidification (OA) are predicted to cause declines in reef‐building corals globally, shifting reefs from coral‐dominated systems to those dominated by less sensitive species. Sponges are important structural and functional components of coral reef ecosystems, but despite increasing field‐based evidence that sponges may be ‘winners’ in response to environmental degradation, our understanding of how they respond to the combined effects of OW and OA is limited. To determine the tolerance of adult sponges to climate change, four abundant Great Barrier Reef species were experimentally exposed to OW and OA levels predicted for 2100, under two CO₂ Representative Concentration Pathways (RCPs). The impact of OW and OA on early life‐history stages was also assessed for one of these species to provide a more holistic view of species impacts. All species were generally unaffected by conditions predicted under RCP6.0, although environmental conditions projected under RCP8.5 caused significant adverse effects: with elevated temperature decreasing the survival of all species, increasing levels of tissue necrosis and bleaching, elevating respiration rates and decreasing photosynthetic rates. OA alone had little adverse effect, even under RCP8.5 concentrations. Importantly, the interactive effect of OW and OA varied between species with different nutritional modes, with elevated pCO₂ exacerbating temperature stress in heterotrophic species but mitigating temperature stress in phototrophic species. This antagonistic interaction was reflected by reduced mortality, necrosis and bleaching of phototrophic species in the highest OW/OA treatment. Survival and settlement success of Carteriospongia foliascens larvae were unaffected by experimental treatments, and juvenile sponges exhibited greater tolerance to OW than their adult counterparts. With elevated pCO₂ providing phototrophic species with protection from elevated temperature, across different life stages, climate change may ultimately drive a shift in the composition of sponge assemblages towards a dominance of phototrophic species.