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1.
Sven Zea 《Marine Ecology》2011,32(2):162-173
The Caribbean sponge Cliona delitrix is among the strongest reef space competitors; it is able to overpower entire coral heads by undermining coral polyps. It has become abundant in reefs exposed to organic pollution, such as San Andrés Island, Colombia, SW Caribbean. Forty‐four sponge‐colonized coral colonies were followed‐up for 13 months to establish the circumstances and the speed at which this sponge advances laterally into live coral tissue and the coral tissue retreats. Cliona delitrix presence and abundance was recorded at seven stations to interpret current reef space and coral species colonization trends. The spread of C. delitrix on a coral colony was preceded by a band of dead coral a few millimeters to several centimeters wide. However, the sponge was directly responsible for coral death only when live coral tissue was within about 2 cm distance; coral death became sponge advance‐independent at greater distances, being indirectly dependent on other conditions that tend to accelerate its retreat. Cliona delitrix advanced fastest into recently killed clean coral calices; however, sponge spread slowed down when these became colonized by algae. The lateral advance of C. delitrix was slower than other Cliona spp. encrusting excavating sponges, probably owing to the greater depth of its excavation into the substratum. Cliona delitrix prefers elevated portions of massive corals, apparently settling on recently dead areas. It currently inhabits 6–9% of colonies in reefs bordering San Andrés. It was found more frequently in Siderastrea siderea (the most abundant local massive coral), which is apparently more susceptible to tissue mortality than other corals. Current massive coral mortality caused by C. delitrix could initially change the relative proportions of coral species and in the long‐term favor foliose and branching corals.  相似文献   

2.
Excavating sponges often compete with reef‐building corals. To study sponge–coral interactions, we devised a design of hybrid cores that allows sponges and corals to be arranged side by side with similar size and shape, mimicking the situation of neighbouring organisms. Compared to earlier methods that attached sponge cores onto coral surfaces, hybrid cores provide an opportunity to study organism interactions under conditions more equal to the interacting partners. The use of hybrid cores was demonstrated for the excavating sponge Cliona orientalis and the massive coral Porites, which commonly interact on the Great Barrier Reef. Cliona orientalis and massive Porites were cut into half‐moon shaped explants and combined as hybrid cores under replicate conditions. After 90 days in an aquarium setting, positive growth of Cl. orientalis along with net bioerosion were observed in sponge control cores that combined Cl. orientalis with blank substrate. However, when Cl. orientalis and massive Porites were in contact in interaction cores, the sponge displayed negative growth and undetectable bioerosion, and was slightly overgrown by the coral. Cliona orientalis may have developed tissue extension beneath the living coral tissue, but growth and net calcification rates of massive Porites were apparently not affected by Cl. orientalis when comparing the interaction cores to coral control cores that combined massive Porites with blank substrate. Overall, the present work demonstrated that hybrid cores can be used to generate conditions suitable for studying sponge–coral interactions in the laboratory, which can also be applied in the field.  相似文献   

3.
On Caribbean reefs, the excavating sponge Cliona tenuis opportunistically colonized dead skeletons of the elkhorn coral Acropora palmata after its massive die‐off in the 1980s. Further C. tenuis population increase occurred by colonization of other coral species, causing coral tissue death through undermining of live tissue and lateral growth. To follow up on a previous (2001) characterization of the abundance and size structure of C. tenuis at Islas del Rosario (Colombia), these factors were again estimated in 2014, along with its substratum utilization. The fate of sponge individuals colonizing massive coral colonies marked in 2001–2004 was also followed. By 2014 C. tenuis was still disproportionally occupying dead A. palmata branches, but its abundance and density, and the cover of other benthic elements, had not significantly changed over the 13‐year period, suggesting that a stasis has been reached. Cliona tenuis was thus initially favored in the 1980s, but substratum monopolization did not occur. From 2001 to 2014, small individuals increased in number and very large ones decreased, suggesting not only that new recruitment is occurring, but also that larger sponges are shrinking or fragmenting. Marked sponges continued killing corals over the first few years, but over longer times they retreated or died, allowing corals to resume upward growth. However, it could not be ascertained whether the sponge retreat was age‐related or the result of some environmental effect. The apparent preference for recently dead clean coral by larvae of C. tenuis and its current dynamics of recruitment, growth, fragmentation and mortality have stabilized its space occupation at Islas del Rosario.  相似文献   

4.
Recent studies suggest a future increase in sponge bioerosion as an outcome of coral reef decline around the world. However, the factors that shape boring sponge assemblages in coral reefs are not currently well understood. This work presents the results of a 17‐month assessment of the presence and species richness of boring sponges in fragments collected from living corals, dead coral reef matrix and coral rubble from Punta de Mita and Isabel Island, two coral reefs from the central coast of the Mexican Pacific Ocean. Both localities have a high cover of dead corals generated by past El Niño Southern Oscillation events, but Punta de Mita was also highly exposed to anthropogenic impacts. Additionally, environmental factors (water transparency, water movement, temperature, sediment deposition, SST, and chlorophyll concentration) were assessed to test the hypothesis that environmental conditions which are potentially harmful for corals can enhance sponge bioerosion. Isabel Island and Punta de Mita showed a similar species richness (13 and 11 species, respectively) but boring sponge presence in both live and dead corals was higher at Isabel Island (57.6%) than at Punta de Mita (35.7%). The same result was obtained when each type of substrate was analysed separately: dead coral reef matrix (81.3% versus 55.5%), coral rubble (47.7% versus 20.0%) and living corals (43.7% versus 31.7%). A principal components analysis showed a higher environmental heterogeneity at Punta de Mita, as well as important environmental differences between Punta de Mita and Isabel Island, due to sediment deposition (2.0 versus 0.2 kg·m?2·d?1) and water movement (24.5% versus 20.5% plaster dissolution day?1), that were also negatively correlated with boring sponge presence (r = ?0.7). By analysing the boring sponge assemblage, we found that environmental settings, together with habitat availability (i.e., dead coral substrate) differentiated assemblage structure at both localities. Major structural differences were largely due to species such as Cliona vermifera, Cliona tropicalis and Aka cryptica. In conclusion, factors such as habitat availability favored the presence of boring sponges but some environmental factors such as abrasion resulting from moving sediment acted restrictively, and exerted a major role in structuring boring sponge assemblages in the Mexican Pacific.  相似文献   

5.
Bioeroding sponges belong to the most dominant bioeroders, significantly contributing to the erosion of coral reefs. Some species are tolerant or even benefit from environmental conditions such as ocean warming, acidification, and eutrophication. In consequence, increases in sponge bioerosion have been observed on some coral reefs over the last decades. The Abrolhos Bank is the largest coral reef system in the South Atlantic. It has been affected by sedimentation, eutrophication, overfishing, and climate change, mainly affecting coastal reefs, and at lesser intensity outer ones as well. This study aimed to describe spatial and temporal patterns in bioeroding sponge distribution in carbonate substrates in the Abrolhos Bank. Photo‐quadrats were used to compare bioeroding sponge abundance between two shallow reefs: a coastal, Pedra de Leste (PL), and an outer reef, Parcel dos Abrolhos (PAB). Each individual was delimitated over the substrate by determining the sponge surface through a line connecting the outermost papillae. The study was conducted over 6 years in 2008–2009 and 2013–2016. Four species of bioeroding sponges were identified: Cliona carteri Ridley, 1881, C. delitrix Pang, 1973, C. cf. schmidtii Ridley, 1881, and Siphonodictyon coralliphagum Rützler, 1971. The distribution and abundance of species varied between the inner and outer reefs and across the years, and displayed certain selectivity for the calcareous substrates recorded. Crustose coralline algae (CCA) were the main substrate excavated by the most abundant bioeroding species, C. carteri, and represented 70% of the substrate types occupied by this sponge (CCA, coral overgrown by CCA and plain coral). The highest abundance of bioeroding sponges observed in photo‐quadrats was 21.3 individuals/m2 at the outer reefs (PAB) in 2014. The abundances or areal extents of bioeroding sponges were up to 10 times greater on the outer reefs than on the coastal ones, where sedimentation is higher and more strongly influenced by siliciclastic material. Moreover, a higher herbivorous fish biomass has been reported on outer reefs which could also influence the higher abundance of bioeroding sponges in outer reefs. During the study period of 6 years, an increase in bioeroding sponge abundance was observed at the outer reefs (PAB), with the sea surface temperature increase. As CCA have an important role in reefal cementation and carbonate production in the Abrolhos reefs, a bioerosion impact might be expected, in particular, on the outer reefs.  相似文献   

6.
Bioerosion is a natural process in coral reefs. It is fundamental to the health of these ecosystems. In the Eastern Tropical Pacific (ETP) coral reefs, the most important bioeroders are sponges, bivalves, sea urchins and the fish Arothron meleagris. In the 1980s, El Niño caused high coral mortality and an increase in macroalgal growth. As a result, greater sea urchin bioerosion occurred. This weakened the reef framework. Considering the high vulnerability of the ETP coral reefs, the goal of this study was to determine the current bioerosion impact of the sea urchin Diadema mexicanum along the western coasts of Mexico, El Salvador, Costa Rica and Panamá. The balance between coral bioaccretion and sea urchin bioerosion was also calculated. Between 2009 and 2010, in 12 coral reefs localities, D. mexicanum density, bottom cover and rugosity were quantified along band transects. The daily bioerosion rate was obtained from the amount of carbonates evacuated by sea urchins per unit time. The rate of coral accretion was calculated by multiplying the coral growth rate of the dominant genus by the density of their skeleton and by their specific coral cover. The localities were dissimilar (R = 0.765, P < 0.001) in terms of live coral cover, crustose calcareous algae, turf cover, rugosity index, and density and size of D. mexicanum. At all sites, with the exception of Bahía Culebra (Costa Rica), coral bioerosion was less than coral bioaccretion. Diadema mexicanum plays a dominant role in the balance of carbonates in the ETP, but this depends on reef condition (protection, overfishing, eutrophication) and so the impacts can be either positive or negative.  相似文献   

7.
Eastern Pacific reefs are mostly made up of interlocking coral branches of Pocillopora, which are easily broken by physical forces associated with heavy swells and winds. In this study we investigated the potential of these coral fragments to enable propagation of boring sponges. For this, we quantified the frequency of occurrence and diversity of boring sponges in fragments of corals recently trapped among the branches of live colonies, and later tested the hypothesis that these sponges colonize new branches of corals. Nearly 80% of the coral colonies investigated had coral fragments among their branches, and 69% of these coral fragments contained boring sponges (11 species), some of these sponges in reproduction (23% of them carried oocytes). To test whether sponges inhabiting coral fragments could colonize new branching corals we transplanted them to healthy branches, and to branches whose living tissue was mechanically eliminated to simulate damage produced by grazing and death after bleaching and other causes of coral tissue mortality. All the transplanted coral fragments cemented to each new colony by means of calcification, and of the three sponge species tested (Cliona vermifera, Cliona tropicalis and Thoosa mismalolli) only C. vermifera was able to colonize both new living branches (26.9%) and cleaned branches (65.5%). The apparent capability of C. vermifera to colonize by direct contact may be another key ability of this species to maintain high frequency of occurrence in Pacific coral reefs. However, although C. tropicalis and T. mismalolli were not able to colonize new coral substrata by direct contact, coral fragments have the potential to contribute to local persistence of these sponges and to their dispersal, both by asexual (fragments) and sexual means (transport of sexual products). The present findings may partly explain the current increase of excavating sponges on deteriorating reefs with a large availability of dead branching corals.  相似文献   

8.
Some sponges of the genus Cliona (Porifera, Hadromerida, Clionidae) simultaneously excavate and encrust calcareous substratum, competing aggressively for illuminated space with corals and other organisms. To interpret current trends of reef space occupation, the patterns of distribution and size of three Caribbean species were examined at San Andrés Island and Islas del Rosario in Colombia. While Cliona aprica was ubiquitous, C. caribbaea (= C. langae) preferred deep and protected reef zones, and C. tenuis shallow and wave‐exposed settings. In contrast to the effect on other excavating sponges, chronic exposure to raw sewage did not significantly increase the abundance of the studied sponges. Substratum occupation/availability ratios showed a positive tendency of the sponges toward certain coral skeletons, and a negative or neutral tendency toward calcareous rock, indicating that establishment may be easier on clean, recently dead coral than on older, heavily incrusted substratum. High relief generally limits sponge size to that of the illuminated portions of the substratum. A generally lower proportion of small individuals than of larger ones indicates currently low recruitment rates and low subsequent mortality. Successful events of higher recruitment seem to have occurred for C. tenuis. These are related to the massive acroporid coral die‐off in the early 1980s and to asexual dispersion during storms, resulting in a current 10% substratum cover. Reefs with high coral mortality were and/or are thus more susceptible to colonization and subsequent space occupation by these sponges, although relief may prevent space monopolization.  相似文献   

9.
Although bioerosion is among the most destructive forces on coral reefs, indirect effects influencing the bioerosion dynamics are understudied. Here, I assess the hypothesis that coral reef grazers indirectly facilitate proliferation of bioeroding sponges by removing epibiotic fleshy seaweeds from the Great Barrier Reef. This study quantifies the degree of spatial correlation between the distribution of bioeroding sponges and the distribution of grazing pressure, as evidenced by the abundance of seaweed and parrotfish bite marks. While the sponge tissue area was negatively correlated with seaweed coverage, the number of parrotfish bite marks was associated with less algae and more sponge tissue. Several factors derived from grazing on seaweeds may facilitate sponge growth: increases in the availability of light may favor primary production by symbiotic zooxanthellae and thereby increase growth of bioeroding sponges; on the other hand, sponge settlement may be facilitated on grazed substrates. All these factors are likely related, and contribute to an increasing erosion of coral reefs. Similar processes have recently been described in Mediterranean ecosystems, suggesting that the interactions I document here, could be widespread.  相似文献   

10.
Sponges are one of the principal agents of bioerosion and sediment production in coral reefs. They generate small carbonate chips that can be found in the sediments, and we investigated whether these could provide a means for assessment of bioerosion applicable to reef monitoring. We tested this hypothesis on samples from 12 Mexican coral reefs distributed along the Pacific coast, where boring sponges were particularly abundant, and quantified the amount of chips in samples of superficial sediment in three grain‐size fractions: fine (<44 μm), medium (44–210 μm) and coarse (>210 μm). The grain‐size distribution varied among reefs, with the majority of the sediment of most reefs being composed of coarse sands, and the medium and fine fractions dominating only at La Entrega and Playa Blanca. All the reefs presented clear evidence of bioerosion by sponges, with the characteristic chips present in the sediment, although at most sites the percentage of chips was very low (from 1% to 3% of the total sediment). Only at La Entrega and Playa Blanca did they constitute a significant fraction of the total sediment (18% and 16%, respectively). While not statistically significant, there was an interesting trend between sponge chips versus sponge abundance that suggests that quantification of the chips in the sediment could be used as a proxy for sponge erosion of the entire community, which cannot be estimated in by laboratory experiments. However, while this methodology could provide an integrated approach to monitor sponge bioerosion, more studies are necessary due to the influence of environmental factors on the transport and deposition of these chips.  相似文献   

11.
Coral reefs are increasingly threatened by anthropogenic disturbances and consequently coral cover and complexity are declining globally. However, bioeroding sponges, which are the principal agents of internal bioerosion on many coral reefs, are increasing in abundance on some degraded reefs, tipping them towards net carbonate erosion. The aim of this study was to identify the environmental factors that drive the erosion rates of the common Indonesian bioeroding sponge Spheciospongia cf. vagabunda . Sponge explants were attached to limestone blocks and deployed across seven sites characterized by different environmental conditions in the UNESCO Wakatobi Biosphere Reserve in Indonesia. Average bioerosion rates were 12.0 kg m?2 sponge tissue year?1 (±0.87 SE ), and were negatively correlated with depth of settled sediment (r  = ?.717, p  < .01) and showed weak positive correlation with water movement (r  = .485, p  = .012). Our results suggest that although bioeroding sponges may generally benefit from coral reef degradation, bioerosion rates may be reduced on reefs that are impacted by high sedimentation, which is a common regional stressor in the South‐East Asian Indo‐Pacific.  相似文献   

12.
This study applied the loss after combustion (LAC) method and the acid decalcification (ADC) method to quantify different components of an excavating sponge. Samples of dried coral skeleton of Favia sp. invaded by the Indo‐Pacific excavating sponge Cliona orientalis Thiele, 1900 were used. The sponge tissue penetrated the 12‐mm‐thick samples to approximately 10 mm. The average proportional weight of organic matter, siliceous spicules, calcareous substrate and salts in the entire samples was found to be respectively 2.5%, 4.4%, 90.5% and 2.5% of dry weight applying the LAC method, and 2.9%, 5.9%, 89.0% and 2.3% of dry weight applying the ADC method. Respective volumetric proportions of the organic matter, spicules, substrate and salts were then calculated to be 6.4%, 5.5%, 85.2% and 3.0% of volume with the LAC method, and 7.4%, 7.2%, 82.7% and 2.7% of volume with the ADC method. The LAC method showed low variability of data and is simple and fast and therefore is recommended. The ADC method generated very similar results to the LAC method. However, due to the handling involved in the ADC method, more than half of the spicules may be lost and the method is therefore not recommended unless careful data corrections are considered. In addition, the buoyant weight method was used to quantify actual substrate weight in the fresh sponge‐substrate samples. This method was found to be at least 97% effective, revealing that buoyant weights can potentially be used to quantify bioerosion rates of excavating sponges. To our knowledge, this is the first study to systemically quantify organic and inorganic components of an excavating sponge and its calcareous substrate, providing improved standard methods for future studies.  相似文献   

13.
Abstract Sponge bioerosion is a result of tissue expansion of endolithic sponges in calcium carbonate substrates. The efficiency of erosion by the sponges can be affected by substrate features, which are thus also likely to influence the way in which the sponge will grow. A field experiment was conducted, in which sponge tissue was grafted to biogenic blocks cut from the corals Goniopora tenuidens, massive Porites sp., Astreopora listeri, Favites halicora, Favia pallida, Goniastrea retiformis and Cyphastrea serailia, and the clam Tridacna squamosa, to investigate colonisation capabilities and growth patterns of Cliona orientalis Thiele, 1900 after 9 months of the experiment. C. orientalis is not substrate‐specific. It invaded > 90 % of the different substrate blocks and penetrated them to varying depths, but usually only down to slightly more than 1 cm. Lateral penetration clearly exceeded depth penetration. Enlargement of surface area versus restricted depth penetration benefits the symbiotic zooxanthellae located in the sponge's surface. Structural irregularities and barriers such as coral dissepiments temporarily deflected the direction of tissue growth and created characteristic tissue patch patterns in different substrates. Tissue growth may be more pronounced in substrates of higher density and lower pore volume, but evidence was only slight. Protection against predation is better in denser materials, which may stimulate the sponge's tissue growth especially in shallower substrate depth. In more porous substrates, favoured by grazers and corallivores, relatively more tissue was located in deeper layers.  相似文献   

14.
Sponges are sessile organisms capable of colonizing diverse substrata. In the Caribbean, coral reefs have suffered a drastic decline, and branching corals of the genus Acropora have been widely decimated. On dead coral skeletons and around surviving tissue the settling of sessile organisms can be observed, sponges being common. In order to investigate whether or not sponges have a preference for a particular species of coral, or for specific microhabitats of the colonies, we evaluated species composition, cover, richness and diversity of sponges colonizing the dead parts of still live colonies of the branching corals Acropora palmata and Acropora cervicornis in five locations of the Tayrona National Natural Park in the Colombian Caribbean. Ten colonies of Ac. palmata were quantified in each of the five locations, and eight Ac. cervicornis colonies in each of two locations. Quantification was carried out using video taken within 0.625‐m2 photoquadrats. Seventeen sponge species were found, 13 of them associated with Ac. palmata and seven with Ac. cervicornis. Desmapsamma anchorata, Clathria venosa and Scopalina rutzleri were found to be common to all Ac. palmata locations, while De. anchorata occurred in the two Ac. cervicornis locations. On Ac. palmata, encrusting sponges dominated, while on Ac. cervicornis branched and lobed sponges predominated. Significant differences in sponge cover were not found among locations but were observed in the sponge species present. On Ac. palmata the species with highest cover were D. anchorata and Cla. venosa, while on Ac. cervicornis it was De. anchorata. The richness and diversity of sponges were low for both coral species, and their varying distribution can be attributed to the differences in available substrate for attachment, given coral colony morphology; for Ac. palmata, sponges predominated on the underside of the branches, semi‐cryptic areas and colony bases, whereas for Ac. cervicornis, they were located over the entire area of the cylindrical branches. Surviving colonies of Ac. palmata and Ac. cervicornis that are still erect offer additional microhabitats for reef sponges, some of which can be found directly interacting with live coral tissue, further threatening their recovery.  相似文献   

15.
By the consumption of algae, parrotfishes open space for young coral settlement and growth, thus playing a central role on the maintenance of coral reefs. However, juvenile parrotfish ecology is often overlooked due to the difficulty discerning species during this phase. Herein, we present the first attempt to investigate changes in habitat use and diet that happen to juveniles of the Redeye parrotfish Sparisoma axillare, focusing on four zones within an algal‐dominated reef: the macroalgal beds, back reef, reef flat, and fore reef. Smaller S. axillare juveniles (<5 cm) preferred to inhabit the macroalgal beds and the reef flat, whereas juveniles larger than 5 cm were more abundant in the back and fore reefs due to distinct post‐settlement habitat conditions. Aggressive interactions with the territorial damselfish Stegastes fuscus were the primary driving factor of juvenile distribution and feeding rates. Attack rates increased with juvenile size and the lowest bite rates were observed in zones with higher densities of territorial damselfish. In previous studies, the persistence of parrotfish recruits in habitats dominated by damselfish was reduced, but newly settled parrotfish occurred more densely within the damselfish domain by behaving as a cryptic reef fish. As these juveniles grew, their bite rates increased, a change associated with a shift from cryptic to roving behavior. Feeding preferences were determined by substrate cover, where juveniles fed on available food sources in each habitat. Juveniles relied on jointed calcareous algae in habitats dominated by these algae, a pattern not observed for thick leathery algae. Filamentous algae were the preferred food for smaller fish; for individuals greater than 10 cm, a higher ingestion of sand was observed. Most studies evaluating the functional role of parrotfish do not consider species feeding preferences. However, the potential for a species to turn an impacted reef back to a coral‐dominated phase is influenced by their food selection, which is dependent on the algal species composition.  相似文献   

16.
Tissue degradation and resulting mortality are major threats to coral reefs around the world. Information on interactions of the major environmental factors that mediate tissue loss and mortality in coral reefs is of great importance. It is essential to understand the prevailing reef health conditions and to develop appropriate management actions. In the present study, a series of benthic surveys conducted in the Lakshadweep Islands revealed the interaction of major biological factors in causing tissue loss and mortality. Hierarchical regression analysis revealed interactions of various environmental scenarios. Tissue loss was prevalent in islands with high cover of massive corals (m = 20.91) and low in islands dominated by branching corals (m = 0.61). Hierarchical regression analysis revealed black band disease (β = .59; p < .001) and algal interactions (β = .48; p < .001) to be major factors responsible for coral mortality caused by tissue loss in the region.  相似文献   

17.
Spongivory by Parrotfish in Florida Mangrove and Reef Habitats   总被引：7，自引：0，他引：7  
Abstract. Although parrotfish are generally reported to be herbivorous, increasing evidence suggests that some Caribbean species feed on sponges. After observing grazing scars on the barrel sponge, Xestospongia muta , 40 sponges were videotaped on three reefs for >0.5 h to determine the frequency of parrotfish bites on this species. A total of 10 h of video recording captured 45 bites on normally coloured X. muta and 527 bites on four bleached X. muta by the parrotfish Sparisoma aurofrenarum, Scarus croicensis and Scarus taeniopterus. The viscera gut and liver of 55 parrotfish collected from mangrove and reef habitats were digested in nitric acid and analysed for spicule content. The parrotfish collected in the mangroves mostly Scarus guacamaia and Sparisoma chrysopterum had significantly higher masses of spicules in their viscera than did parrotfish collected on the reef Sparisoma aurofrenatum, Sparisoma viride, Sparisoma chrysopterum, Scarus vetula, Scarus coelestinus and Scarus taeniopterus . The spicules of Geodia gibhrrosa, a chemically undefended sponge that is common in the mangroves but rare in exposed locations on the reef, were abundant in the viscera of parrotfish collected in the mangroves. These results provide further evidence that fish predation has an important effect on the distribution and abundance of Caribbean sponges.  相似文献   

18.
Abstract. Bioeroding sponges are highly specialised to live in and to erode various natural and man-made calcareous substrates. They encounter very different substrate features. Previous field observations suggest that damage caused by sponge bioerosion may vary with substrate density and architecture. This study aims to experimentally investigate influences of structurally different calcareous substrates on bioerosion activities of Cliona orientalis Thiele, 1900 , an important eroder of inshore Great Barrier Reef calcium carbonate. Blocks were made of the corals Goniopora tenuidens , massive Porites sp., Astreopora listeri, Favites halicora, Favia pallida, Goniastrea retiformis and Cyphastrea serailia , and of the clam Tridacna squamosa . They were grafted with C. orientalis tissue and re-examined after 9 months. Block weight loss, increase of pore volume and differences in breaking stability were measured as indicators of sponge erosion.Erosion caused by C. orientalis differed between substrates and was significantly more pronounced in denser materials with lower pore volume and in coral blocks with more structural barriers. Coral substrates with imperforate thecae and thicker dissepiment walls were more strongly eroded than those with perforate thecae and thinner dissepiments. At similar growth rates, more material has to be removed in denser material with more barriers compared to more porous substrates. Existing pores will be occupied, resulting in lower erosion rates. Erosion capabilities of the sponge could best be detected by the blocks' loss in dry weight, but the sponges also significantly reduced block breaking stability. Change in pore volume was not found to be a reliable parameter to investigate sponge erosion.  相似文献   

19.
In situ video observations of echinoids interacting with deep-sea coral are common in the deep-sea, but paradoxically the deep-sea literature is devoid of reports of bioerosion by extant echinoids. Here we present evidence of contemporary bioerosion of cold-water coral by four species of deep-sea echinoids, Gracilechinus elegans, Gracilechinus alexandri, Cidaris cidaris, and Araeosoma fenestratum, showing that they actively predate on the living framework of reef building corals, Lophelia pertusa and Madrepora oculata, in the NE Atlantic. Echinoid specimens were collected in six canyons located in the Bay of Biscay, France and two canyons on the north side of the Porcupine Bank and Goban Spur, Ireland. A total of 44 live specimens from the four taxa (9 of G. elegans, 4 of G. alexandri, 21 of C. cidaris and 10 of A. fenestratum) showed recent ingestion of the coral infrastructure. Upon dissection, live coral skeleton was observed encased in a thick mucus layer within the gastrointestinal tract of G. elegans and G. alexandri while both live and dead coral fragments were found in C. cidaris and A. fenestratum. Echinoid bioerosion limits the growth of shallow-water reefs. Our observations suggest that echinoids may also play an important role in the ecology of deep-water coral reefs.  相似文献   

20.
Abstract. Using an in situ observational approach, the food preferences among hard corals were examined for the two obligate coral‐feeding butterflyfishes Chaetodon austriacus and C. trifascialis in the Northern Red Sea, Gulf of Aqaba, Egypt. Chaetodon austriacus is a generalist coral feeder that feeds mainly on three genera of abundant hard corals (Acropora, Porites and Pocillopora). In contrast, C. trifascialis is a specialist coral feeder on Acropora spp. and Pocillopora verrucosa. In general, C. austriacus had a lower feeding rate than C. trifascialis (both species in the Northern Red Sea reefs had high feeding rates compared with other reefs). Ivlev's electivity index was calculated for the two species. This index shows that C. austriacus prefers Montipora and Pocillopora, and avoids Lobophyllia and Favites. On the other hand, C. trifascialis prefers Acropora valida and avoids Porites solida. Thus, the feeding preference and avoidance of these chaetodontids depend on both biting rate and food availability in the environment rather than on biting rate alone.  相似文献   

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