The use of coral nubbins in coral reef ecotoxicology testing

While there is an urgent demand to establish reliable ecotoxicological assays for reef corals, there has not been yet an available source material that can supply the high number of colony replicates needed for reliable tests. In past experiments, the major obstacle to obtaining as many fragments as possible had been the damage inflicted to donor colonies by pruning. In this paper, we present the application of coral nubbins, a novel source material for coral ecotoxicology assays. Nubbins from the branching Red Sea coral Stylophora pistillata (n>450) were used for evaluating the impacts of water soluble fractions from a crude oil, an oil dispersant and dispersed oil. Coral nubbins (minute coral fragments in the size of one to several polyps) harvested from a single colony are genetically identical to each other, may be obtained in any quantity needed and whenever research activities demand their use. Several dozens of nubbins can be obtained from a single small branch in branching coral species, a procedure that has minimal impact on donor genotypes. Nubbins production is a low cost procedure and requires limited maintenance space. Results of short and long-term acute ecotoxicological tests are revealed and discussed here, indicating the advantageous use of nubbins as ubiquitous coral material for toxicology assays and physiological studies.     

Direct observations of resource sharing in coral reef fish

Summary 1. A full understanding of the community ecology of coral reef fishes must be based on an understanding of how fishes interact to share the available resources of the reef environment.2. The goal of such studies is the construction of suitable models that can be used to predict the effects of environmental changes. The validity of such predictions is a test of the adequacy of the model.3. The data on which models can be based are obtained in a combination of three approaches: (a) sampling, (b) laboratory experiments and (c) direct observation.4. Direct observations can be made by viewing from the surface, by the use of underwater chambers, by submersible vehicles, by underwater television and by diving.5. The use of diving techniques is limited by visibility, temperature and depth. Diving time can be extended by saturated diving from an underwater habitat.6. The critical areas for information about coral reef fish communities are: census, population dynamics, natural history and behavior, space sharing and food sharing.7. Complex communities can be analyzed by successively categorizing the species according to each of these aspects until the unique niche of each species is defined.8. The most pressing need in the study of coral reef fish ecology is for continuous monitoring of representative stations throughout complete seasonal cycles.

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Observations directes sur la stabilité et le partage des ressources dans les communautés de poissons habitant les récifs coralliens

Extrait La complexité structurale des récifs coralliens rend difficile le recensement des poissons qui y vivent, alors que cependant ces rassemblements extrêmement complexes offrent une excellente occasion d'étudier les mécanismes aboutissant au développement et au maintien d'une communauté animale hautement diversifiée. Au cours des operations «Tektite» et «FLARE» les auteurs ont procédé à une observation directe de populations de poissons sur de petits récifs coralliens, en utilisant des appareils «Rebreathe» et SCUBA à circuit ouvert. Une troisième station fut équipée d'un appareil de télévision sousmarin à circuit fermé, permettant d'observer une population de poissons pendant une durée prolongée; un tel dispositif ne trouble aucunement le comportement des poissons observés, mais n'est utilisable que pour des espèces d'assez grande taille et ne se cachant pas dans les anfractuoistés des récifs. La télévision permet une observation de durée illimitée et constitue le seul moyen de recenser les gran des espèces nomadiques, que l'approche d'un plongeur met en fuite. Pour les petites espèces vivant cachées, le recensement et les autres observations in situ ne peuvent être effectués, pendant un temps suffisant, qu'à partir d'un habitacle sousmarin. Ainsi peuvent être rassemblées des données permettant la discrimination entre espèces transitantes, visiteuses ou résidentes; l'évaluation du taux de remplacement; la situation des abris et des terrains de chasse; la stabilité des groupes et essaims; les cycles d'activité; la diversité des réactions interspécifiques aboutissant à l'organisation et à la stabilité des communautés. L'observation n'entraînant aucune destruction peut être poursuivie pendant une longue durée.

     

Metapopulation theory, its use and misuse

Baguette (2004) has criticized the use of patch-occupancy metapopulation models in conservation. I discuss the relative strengths and weaknesses of different types of metapopulation models, taking for granted that there is a need to develop both general theory and predictive models. I conclude that the classical metapopulation theory is most appropriate for species living in highly fragmented landscapes. For these situations, the patch-occupancy metapopulation models provide a modelling approach that has been helpful also for conservation.     

Volcaniclastic events in coral reef and seagrass environments: evidence for disturbance and recovery (Middle Miocene, Styrian Basin, Austria)

Volcanic disturbances and ecosystem recovery at sites of neritic carbonate production are rarely documented, neither in the recent nor past geological record. Herein, we present a Middle Miocene (ca 14.5 Ma) shallow-marine carbonate record from the Styrian Basin (Austria) that shows recurrent breakdowns of the carbonate producers (i.e., coralline red algae and zooxanthellate corals) in response to ashfalls from nearby volcanic island sources. These volcanic events are preserved as distinct marl layers with idiomorphic biotite crystals and volcaniclasts that mantle the former seafloor topography. The pyroclastic sediments suffocated the carbonate producers in coral reef and seagrass environments. A subsequent turbid, eutrophic phase caused by the redistribution, suspension, and dissolution of volcaniclastics is characterized by the spreading of suspension-feeding biota, coralline algae, and the larger benthic foraminifer Planostegina. During this stage, rapidly consolidated pyroclastic deposits acted as hard grounds for attached-living bivalves. The fact that the facies below and above the studied ashbeds are almost identical suggests that volcaniclastic events had no long-lasting effects on the structure of the carbonate-producing benthic communities. Although Miocene shallow-water carbonate systems of the circum-Mediterranean region are well known and situated in one of the geodynamically most active regions worldwide, this study is the first that exams the impact of volcanic sedimentation events on shallow marine ecosystems.     

Preliminary observations of spawning behavior of white-streaked grouper (Epinephelus ongus) in an Okinawan coral reef

Epinephelus ongus forms spawning aggregations at specific reef sites at Okinawa. The aim of the present study was to describe the spawning behavior of E. ongus based upon underwater video imagery. Epinephelus ongus spawning is usually paired with courting males and females rushing upwards towards the surface during the spawning ascent, with a subsequent release of eggs at the apex of the ascent. In two of four spawning events we observed, however, the ascending pair was joined by additional males. Fish eggs collected at the site were identified as those of E. ongus and confirmed that this species spawns mainly at night during a slack tide. This study is the first documentation of E. ongus spawning behavior in the field.     

Microhabitat use of juvenile coral reef fish in Palau

While relationships between adult fish density and structural habitat features are well established, relatively little is known about the habitat associations of juvenile reef fish. In a reserve system in Palau, we quantified microhabitat association with juvenile reef fish community structure, and determined the influence of foraging space, predator size and confamilial attraction on juvenile and adult pomacentrid abundance. Habitat structure and juvenile reef fish communities differed significantly among microhabitats with one exception: no difference was found between foliose and consolidated rubble microhabitats. Overall, pomacentrids characterised the juvenile community structure of each microhabitat. The abundance of early juvenile pomacentrids is simultaneously determined by microhabitat structure and predator size, with little evidence for settlement selection near adults. The results also suggest that the influence of habitat structure become weaker with ontogeny which in part, drives large predators to negatively influence the abundance of adult pomacentrids. The results have important implications on management, specifically in prioritizing areas for protection, and in modeling the impacts of habitat loss on reef fish communities.     

Assessing the accuracy of acoustic seabed classification for mapping coral reef environments in South Florida (Broward County, USA)

The Atlantic coast of Broward County, Florida (USA) is paralleled by a series of progressively deeper, shore-parallel coral reef communities. Two of these reef systems are drowned early Holocene coral reefs of 5 ky and 7 ky uncorrected radiocarbon age. Despite the case of access to these reefs, and their major contribution to the local economy, accurate benthic habitat maps of the area are not available. Ecological studies have shown that different benthic communities (i.e. communities composed of different biological taxa) exist along several spatial gradients on all reefs. Since these studies are limited by time and spatial extent, acoustic surveys with the QTCView V bottom classification system based on a 50 kHz transducer were used as an alternative method of producing habitat maps. From the acoustic data of a 3.1 km(2) survey area, spatial prediction maps were created for the area. These were compared with habitat maps interpreted from in situ data and Laser Airborne Depth Sounder (LADS) bathymetry, in order to ground-truth the remotely sensed data. An error matrix was used to quantitatively determine the accuracy of the acoustically derived spatial prediction model against the maps derived from the in situ and LADS data sets. Confusion analysis of 100 random points showed that the system was able to distinguish areas of reef from areas of rubble and sand with an overall accuracy of 61%. When asked to detect more subtle spatial differences, for example, those between distinct reef communities, the classification was only about 40% accurate. We discuss to what degree a synthesis of acoustic and in situ techniques can provide accurate habitat maps in coral reef environments, and conclude that acoustic methods were able to reflect the spatial extent and composition of at least three different biological communities.     

Suspended sediment impairs habitat choice and chemosensory discrimination in two coral reef fishes

Increasing sediment onto coral reefs has been identified as a major source of habitat degradation, and yet little is known about how it affects reef fishes. In this study, we tested the hypothesis that sediment-enriched water impairs the ability of larval damselfish to find suitable settlement sites. At three different experimental concentrations of suspended sediment (45, 90, and 180 mg l⁻¹), pre-settlement individuals of two species (Pomacentrus amboinensis and P. moluccensis) were not able to select their preferred habitat. In a clear water environment (no suspended sediment), both species exhibit a strong preference for live coral over partially dead and dead coral, choosing live coral 70 and 80% of the time, respectively. However, when exposed to suspended sediment, no habitat choice was observed, with individuals of both species settling on live coral, partially dead, and dead coral, at the same frequency. To determine a potential mechanism underlying these results, we tested chemosensory discrimination in sediment-enriched water. We demonstrated that sediment disrupts the ability of this species to respond to chemical cues from different substrata. That is, individuals of P. moluccensis prefer live coral to dead coral in clear water, but in sediment-enriched water, chemical cues from live and dead coral were not distinguished. These results suggest that increasing suspended sediment in coral reef environments may reduce settlement success or survival of coral reef fishes. A sediment-induced disruption of habitat choice may compound the effects of habitat loss on coral reefs.     

Capturing the cornerstones of coral reef resilience: linking theory to practice

Coral reefs can undergo unexpected and dramatic changes in community composition, so called phase shifts. This can have profound consequences for ecosystem services upon which human welfare depends. Understanding of this behavior is in many aspects still in its infancy. Resilience has been argued to provide insurance against unforeseen ecosystem responses in the face of environmental change, and has become a prime goal for the management of coral reefs. However, diverse definitions of resilience can be found in the literature, making its meaning ambiguous. Several studies have used the term as a theoretical framework and concern regarding its practical applicability has been raised. Consequently, operationalizing theory to make resilience observable is an important task, particularly for policy makers and managers dealing with pressing environmental problems. Ultimately this requires some type of empirical assessments, something that has proven difficult due to the multidimensional nature of the concept. Biodiversity, spatial heterogeneity, and connectivity have been proposed as cornerstones of resilience as they may provide insurance against ecological uncertainty. The aim of this article is to provide an overview of the divergent uses of the concept and to propose empirical indicators of the cornerstones of coral reef resilience. These indicators include functional group approaches, the ratios of “good” and “bad” colonizers of space, measurements of spatial heterogeneity, and estimates of potential space availability against grazing capacity. The essence of these operational indicators of resilience is to use them as predictive tools to recognize vulnerability before disturbance occurs that may lead to abrupt phase shifts. Moving toward operationalizing resilience theory is imperative to the successful management of coral reefs in an increasingly disturbed and human-dominated environment. Communicating by Ecology Editor Professor Peter Mumby Order of authors 2–3 is alphabetic     

Relative gut lengths of coral reef butterflyfishes (Pisces: Chaetodontidae)

Variation in gut length of closely related animals is known to generally be a good predictor of dietary habits. We examined gut length in 28 species of butterflyfishes (Chaetodontidae), which encompass a wide range of dietary types (planktivores, omnivores, and corallivores). We found general dietary patterns to be a good predictor of relative gut length, although we found high variation among groups and covariance with body size. The longest gut lengths are found in species that exclusively feed on the living tissue of corals, while the shortest gut length is found in a planktivorous species. Although we tried to control for phylogeny, corallivory has arisen multiple times in this family, confounding our analyses. The butterflyfishes, a speciose family with a wide range of dietary habits, may nonetheless provide an ideal system for future work studying gut physiology associated with specialization and foraging behaviors.     

The effects of suspended sediment on coral reef fish assemblages and feeding guilds of north-west Australia

Coral Reefs - Understanding environmental drivers of fish assemblage composition is fundamental to designing useful management plans for anthropogenic activities. This study investigated the...     

Environmentally controlled succession in a late Pleistocene coral reef (Sinai, Egypt)

The concept of ecological succession has been frequently applied in the study of ancient reefs. Whereas Paleozoic and Mesozoic reefs are commonly thought to reveal an autogenic primary—climax zonation, patterns in Neogene and Quaternary reefs are much more diverse. Here, we describe a well-preserved late Pleistocene coral reef from Dahab on Sinai Peninsula (Egypt), which shows a distinct zonation that resembles an ecological succession. In contrast to classical examples of ecological successions, species composition, paleoenvironmental conditions, and coral biodiversity of the Dahab reef indicate an allogenic, sea-level controlled community change, from marginal marine to reef slope and back reef. A review of the literature confirms that autogenic, short-term successions are virtually absent in Quaternary reefs. We predict that long generation times of corals make it unlikely that classical autogenic successions develop in reefs at all, unless environmental conditions are unusually stable.     

Spatial and temporal patterns of scleractinian coral, soft coral, and zoanthid disease on a remote, near-pristine coral reef (Palmyra Atoll, central Pacific)

There is an urgent need for accurate baselines of coral disease prevalence across our oceans in order for sudden or unnatural changes to be recognized. Palmyra Atoll allows us to study disease dynamics under near-pristine, functionally intact conditions. We examined disease prevalence among all known species of scleractinian coral, soft coral and zoanthid (Palythoa) at a variety of coral reef habitats at Palmyra over a 2 yr period. In 2008, overall disease prevalence across the atoll was low (0.33%), but higher on the shallower backreef (0.88%) and reef terrace (0.80%) than on the deeper forereef (0.09%). Scleractinian coral disease prevalence was higher (0.30%) than were soft coral and zoanthid disease (0.03% combined). Growth anomalies (GAs) were the most commonly encountered lesions, with scleractinian species in the genera Astreopora (2.12%), Acropora (1.30%), and Montipora (0.98%) showing the highest prevalence atoll-wide. Discoloration necrosis (DN) was most prevalent in the zoanthid Palythoa tuberculosa (1.18%), although the soft coral Sinulana and Montipora also had a prevalence of 0.44 and 0.01%, respectively. Overall disease prevalence within permanently marked transects increased from 0.65% in 2008 to 0.79% in 2009. Palythoa DN contributed most to this increased prevalence, which coincided with rising temperatures during the 2009 El Ni?o. GAs on the majority of susceptible genera at Palmyra increased in number over time, and led to tissue death. Host distribution and environmental factors (e.g., temperature) appear to be important for determining spatiotemporal patterns of disease at Palmyra. More sophisticated analyses are required to tease apart the likely inter-correlated proximate drivers of disease occurrence on remote, near-pristine reefs.     

Record of natural and anthropogenic changes in reef environments (Barbados West Indies) using laser ablation ICP-MS and sclerochronology on coral cores

Coral growth rate can be affected by environmental parameters such as seawater temperature, depth, and light intensity. The natural reef environment is also disturbed by human influences such as anthropogenic pollutants, which in Barbados are released close to the reefs. Here we describe a relatively new method of assessing the history of pollution and explain how these effects have influenced the coral communities off the west coast of Barbados. We evaluate the relative impact of both anthropogenic pollutants and natural stresses. Sclerochronology documents framework and skeletal growth rate and records pollution history (recorded as reduced growth) for a suite of sampled Montastraea annularis coral cores. X-radiography shows annual growth band patterns of the corals extending back over several decades and indicates significantly lower growth rate in polluted sites. Results using laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on the whole sample (aragonite, organic matter, trapped particulate matter, etc.), have shown contrasting concentrations of the trace elements (Cu, Sn, Zn, and Pb) between corals at different locations and within a single coral. Deepwater corals 7 km apart, record different levels of Pb and Sn, suggesting that a current transported the metal pollution in the water. In addition, the 1995 hurricanes are associated with anomalous values for Sn and Cu from most sites. These are believed to result from dispersion of nearshore polluted water. We compared the concentrations of trace elements in the coral growth of particular years to those in the relevant contemporaneous seawater. Mean values for the concentration factor in the coral, relative to the water, ranged from 10 for Cu and Ni to 2.4 and 0.7 for Cd and Zn, respectively. Although the uncertainties are large (60–80%), the coral record enabled us to demonstrate the possibility of calculating a history of seawater pollution for these elements from the 1940s to 1997. Our values were much higher than those obtained from analysis of carefully cleaned coral aragonite; they demonstrate the incorporation of more contamination including that from particulate material as well as dissolved metals.     

Community structure,social organization and ecological requirements of coral reef fish (Pomacentridae)

In the Gulf of Aqaba (Red Sea), 25 species of damselfish (Pomacentridae) which form typical interspecific communities were studied. Several species are typical for different depth zones, others are ubiquitous. Damselfish are variously specialized in feeding (herbivore, omnivore, plankton-carnivore); habitat (bottom-dwelling, midwater); home-and-shelter site (selective or unselective). Environmental factors and social structures were found to be interlinked. Species with the same social structure are similarly specialized ecologically. A hypothetical flow diagram shows the effects of abiotic and biotic factors on group size, available food, and social structure. Damselfish are extremely flexible to environmental change, showing intraspecific modification of group structure, feeding habits, reproductive strategy etc. Experimental results suggest a strong selection against redundant males. This research is considered a pilot study for future field work, aimed at a prediction of environmental influences on behaviour.Supported by the Deutsche Forschungsgemeinschaft, Bad Godesberg, and the Max-Planck-Institut für Verhaltensphysiologie, Seewiesen.     

Spatio-temporal variability in fish recruitment to a coral reef (Moorea,French Polynesia)

Spatial and temporal patterns of recruitment of juvenile coral reef fishes were studied on the reefs of the high island of Moorea (Society Archipelago, French Polynesia) during the wet season (October 1988 to April 1989). Two size-classes of fishes (new-recruits and juveniles) were censused by visual counts within 24 quadrats along a transect across the lagoon. Correspondence analysis was used to calculate the hypothetical movements of the two size classes. Spatial variability was far more important than temporal variability; six main spatial communities were revealed, which could result from differences among habitats. Temporal variability in recuitment occurred only at nearshore stations; stations on the outer fringing reef and inner barrier reef displayed stable recruitment patterns.     

Histological observations in the Hawaiian reef coral, Porites compressa, affected by Porites bleaching with tissue loss

The scleractinian finger coral Porites compressa is affected by the coral disease Porites bleaching with tissue loss (PBTL). This disease initially manifests as bleaching of the coenenchyme (tissue between polyps) while the polyps remain brown with eventual tissue loss and subsequent algal overgrowth of the bare skeleton. Histopathological investigation showed a loss of symbiont and melanin-containing granular cells which was more pronounced in the coenenchyme than the polyps. Cell counts confirmed a 65% reduction in symbiont density. Tissue loss was due to tissue fragmentation and necrosis in affected areas. In addition, a reduction in putative bacterial aggregate densities was found in diseased samples but no potential pathogens were observed.     

The effect of territorial damselfish (family Pomacentridae) on the space use and behaviour of the coral reef fish, Halichoeres bivittatus (Bloch, 1791) (family Labridae)

Most demersal species of damselfish (family Pomacentridae) are territorial herbivores that aggressively chase other fishes away from their nests. This study investigates whether the aggressive territorial damselfish, Stegastes leucostictus, modifies behaviours and home range area use in a less aggressive, non-territorial species, the slippery dick wrasse, Halichoeres bivittatus (family Labridae). Damselfishes and wrasses are ubiquitous and abundant members of coral reef fish assemblages around the world; hence, this study has broader implications beyond the two Caribbean species chosen for this study. A manipulative field experiment consisted of transplanting one or three S. leucostictus into artificial shelters positioned within adult or adjacent to juvenile H. bivittatus home ranges. The introduction of damselfish had little effect on the size of home range areas of juvenile or adult wrasses, but had a significant effect on the location of their home ranges. The damselfish also affected adult microhabitat use but did not affect use by juveniles. In addition, there was an increase in damselfish-wrasse interactions that resulted in a significant reduction in the amount of time adult wrasses could spend foraging or in a foraging assemblage. It was concluded that aggressive interactions with territorial damselfish affect individual H. bivittatus space use and may consequently affect the spatial distribution of H. bivittatus populations.