Coral Rubble Research Articles

Status of benthic cover in Carbin Reef, Sagay Marine Reserve, Western Visayas, the Philippines

This study determined the status of Carbin Reef benthic cover, Sagay Marine Reserve, Negros Occidental. The underwater benthic assessment was conducted on March 2019 by laying eight 50-meter transect lines at the depths of 6 meters (crest) and 12 meters (slope). Photo-quadrat method was used in obtaining still benthic images for every 1-m across eight 50-meter transect lines. A total of 400 still images were acquired and analyzed using Coral Point Count with Excel Extension (CPCe). The sedimentation rate was also determined by deploying sediment collectors. Results showed that Carbin Reef is characterized by 26.09% live coral cover and 43.25% abiotic structure such as rocks, sand, and coral rubbles. Fifty-five (55) coral species belonging to thirty-three (33) genera were identified, dominated by Porites, Fungia, and Goniastrea. Throughout the area, Porites lobata was the most dominant coral species. The overall hard coral cover seemed to have decreased since 2014. Further analysis showed the prevalence of bleached corals and diseases such as white syndrome, and white band disease. Similarly, two signs of compromised health including sediment damage and competition overgrowth were also present. The sedimentation rate per day was below the maximum tolerable levels by most corals during dry season. Overall, this study presents the first extensive study of coral diversity in Carbin Reef–characterized by a moderately diverse area and considered as a moderately stressed habitat.

Impacts of coastal armouring on rubble mobile cryptofauna at shallow coral reefs in Okinawa, Japan

Shoreline armouring has progressively affected the coastal landscapes of countries all over the world, and armouring construction will increase in coming years as a consequence of climate change. Armouring has the potential to affect coastal environments and induce changes in the abundance and diversity of marine communities, and its effects might by increased by wide adoption. Moreover, compared with temperate locations, the effects of armouring have been less studied in tropical and subtropical areas. Okinawa Island, the largest and most populated island of the Ryukyu Archipelago in southern Japan, has been affected by numerous civil and military engineering works. After decades of development, less than 40% of its coastline remains natural, and yet impacts from armouring on local marine communities have been overlooked until recent years. The aim of this research was to evaluate effects of near-shore armouring on the surrounding environment by comparing diversity and abundance of coral rubble mobile cryptofauna benthic communities between armoured and control sites. Across six different geographic locations, coral rubble was sampled in front of subtidal breakwaters and at nearby control sites. Armoured sites were associated with lower cryptofauna abundances and reduced richness and diversity at higher taxonomic levels (phylum and class). Reduction in spatial complexity could be a plausible reason for the observed patterns. Impacts could be mitigated by combining technical innovations, habitat restoration, and use of natural spaces as buffers for coastal protection. Since less than half of Okinawa Island’s coastline remains in a natural state, environmental conservation should be prioritized.

A Comparison of Size, Shape, and Fractal Diversity Between Coral Rubble Sampled From Natural and Artificial Coastlines Around Okinawa Island, Japan

Substrate surface area and fractal complexity have been reported to influence the abundance and diversity of mobile cryptic animal communities. Surfaces with higher fractal dimensions not only offer additional space for colonization, but bias space availability toward smaller size ranges, increasing the number of available niches. Conversely, smaller surface areas tend to be associated with a decrease in abundances while reduced fractal complexities may support less diversity in the benthic community. In this study, we compared morphological parameters between rubble sampled from rubble mounds accumulated at the seaward side of artificial breakwaters and rubble sampled from a nearby location with no breakwaters (=control site). The purpose of this work was to establish a methodology for comparing the surface area and fractal complexity of coral rubble fragments using easily available equipment that could be efficiently utilized during field work. Rubble fragments were individually weighed and photographed in controlled light conditions. Each photograph was then analyzed using ImageJ software. Rubble pieces from each photograph went through segmentation, the separation of sample outlines from the picture background, before being measured and analyzed for surface area, width, and length (size estimators), and circularity, aspect ratio, roundness, solidity, and Feret properties (shape estimators). Surface fractal complexity was also measured, using the box counting method on segmented rubble surfaces. We observed lowered surface areas, weight, and fractal complexity for rubble fragments sampled at the breakwater. We demonstrate how this method could be used to compare coral rubble from a variety of environmental conditions, thus becoming a useful aid in environmental monitoring, in addition to adding important information to the collection and analyses of biological data.

First Record of Bioluminescence in a Sipunculan Worm

During a search for bioluminescent marine annelids around the island of Carrie Bow Cay, Belize, we discovered bioluminescence in the sipunculan worm Nephasoma pellucidum. The identification of N. pellucidum was verified by DNA barcoding of ∼650 bp of the mitochondrial cytochrome c oxidase I gene, using sequences of the same species from previous studies as references. Our study constitutes the first record of a bioluminescent sipunculan species. Green luminescence was detected in four of the five individuals of N. pellucidum collected from coral rubble from a shallow reef flat and one deeper (14 m) site. To test for bioluminescent activity, all collected annelids (including sipunculans) were sorted into morphotypes and identified to the lowest taxonomic level possible. After several hours of dark adaptation, they were mechanically stimulated, and luminescent reactions were noted and recorded by photography and/or video whenever possible. Of a total of nine examined sipunculan species, N. pellucidum was the only one that showed bioluminescent activity. The underlying biochemical processes for the bioluminescence are so far unknown, but transcriptome data indicate the presence of proteins with similarities to Renilla-type luciferases. We did not find similarities to any known photoproteins. Our findings broaden the known diversity of bioluminescent annelid taxa and support the notion that bioluminescence arose multiple times in annelids. The bioluminescent properties of N. pellucidum add a new reason to pursue this species as a model species, as has been previously proposed.

The biology and ecology of coral rubble and implications for the future of coral reefs

The biology and ecology of coral rubble and implications for the future of coral reefs

On the occurrence of Antillesoma antillarum (Grube, 1858) (Sipuncula, Antillesomatidae) on the south-central part of the Colombian Caribbean coast

We document here the first confirmed report of the sipunculan worm Antillesoma antillarum (Grube, 1858) based on freshly collected, taxonomically verified specimens from the south-central Colombian Caribbean coast. This species was encountered on massive coralline rocks, coral rubble, and coral boulder at San Antero. We briefly describe and illustrate this species and provide notes on its distribution, ecology, and habitat.

Gastropods in the Intertidal Shore of Kota Kinabalu, Sabah (Malaysian Borneo)

Intertidal gastropods provide numerous ecological benefits and are responsible for the dynamics of the intertidal shores habitat and its community assemblages. This study examined the community structure of gastropods in the intertidal shore located near the city of Kota Kinabalu, the capital of Sabah where coastal areas are rapidly developed for various purposes and consequently destroying natural habitats. A total of 36 gastropods species from 15 families were recorded. The Planaxis sulcatus was the most abundant species with a density of 480 ind. m-2 followed by Nodilittorina pyramidalis (182 ind. m-2) and Cellana radiata (97 ind. m-2) respectively. The number of species and their abundance, respectively, are almost three times lower than the number ever recorded for intertidal shores located in non-urban areas or remote locations. This suggests that the rapidly growing coastal urban areas threatening the diversity and abundance of intertidal gastropods. The density of gastropod (i.e. P. sulcatus & N. pyramidalis) was significantly (p<0.05) high at the lower intertidal shore where slope gradient is steeper with rocks and crevices are the major component of substrates compared to the upper or middle zone which is flatter and composed mainly of coral rubble and sand. Our study suggests that gastropod communities in intertidal shores located adjacent to the urban areas are threatened especially by anthropogenic factors such as frequent human visitations and modification of natural habitat. Future development in the intertidal shore should minimise habitat destruction and should consider infrastructures that encourage gastropod populations to grow and highlighting their ecological role for conservation reasons.

Technology requirements, and social impacts of technology for at-scale coral reef restoration

The coral reefs of the world are in decline as a result of local and global stressors. Significant impacts are caused by ocean heat waves associated with increasing ocean temperatures as the oceans accommodate more and more of the heat produced as a result of the global emissions of greenhouse gases. In response, a global reef restoration sector is emerging with the aspiration to restore many of the worlds' reefs and increase their resilience to climate change and other stressors. However, the scale of the challenge is vast, and will realistically only be achieved through the development and application of new marine technology including for environmental surveillance and monitoring, material transfer (corals and coral rubble), new more resilient varieties of corals and the underpinning required data analytics. In addition, most reefs are located in low-income nations, including Small Island Nations and the level of complexity and ease of use of technologies being developed will dictate who can participate in at-scale restoration of the world's reefs, and correspondingly may lead to considerable social distributional impacts as some communities will be able to utilise emerging technologies whilst others may not.

Nitrogen fixation and denitrification activity differ between coral- and algae-dominated Red Sea reefs

Coral reefs experience phase shifts from coral- to algae-dominated benthic communities, which could affect the interplay between processes introducing and removing bioavailable nitrogen. However, the magnitude of such processes, i.e., dinitrogen (N2) fixation and denitrification levels, and their responses to phase shifts remain unknown in coral reefs. We assessed both processes for the dominant species of six benthic categories (hard corals, soft corals, turf algae, coral rubble, biogenic rock, and reef sands) accounting for > 98% of the benthic cover of a central Red Sea coral reef. Rates were extrapolated to the relative benthic cover of the studied organisms in co-occurring coral- and algae-dominated areas of the same reef. In general, benthic categories with high N2 fixation exhibited low denitrification activity. Extrapolated to the respective reef area, turf algae and coral rubble accounted for > 90% of overall N2 fixation, whereas corals contributed to more than half of reef denitrification. Total N2 fixation was twice as high in algae- compared to coral-dominated areas, whereas denitrification levels were similar. We conclude that algae-dominated reefs promote new nitrogen input through enhanced N2 fixation and comparatively low denitrification. The subsequent increased nitrogen availability could support net productivity, resulting in a positive feedback loop that increases the competitive advantage of algae over corals in reefs that experienced a phase shift.

High plasticity of nitrogen fixation and denitrification of common coral reef substrates in response to nitrate availability

Nitrogen cycling in coral reefs may be affected by nutrient availability, but knowledge about concentration-dependent thresholds that modulate dinitrogen fixation and denitrification is missing. We determined the effects of different nitrate concentrations (ambient, 1, 5, 10 μM nitrate addition) on both processes under two light scenarios (i.e., light and dark) using a combined acetylene assay for two common benthic reef substrates, i.e., turf algae and coral rubble. For both substrates, dinitrogen fixation rates peaked at 5 μM nitrate addition in light, whereas denitrification was highest at 10 μM nitrate addition in the dark. At 10 μm nitrate addition in the dark, a near-complete collapse of dinitrogen fixation concurrent with a 76-fold increase in denitrification observed for coral rubble, suggesting potential threshold responses linked to the nutritional state of the community. We conclude that dynamic nitrogen cycling activity may help stabilise nitrogen availability in microbial communities associated with coral reef substrates.

Second finding, first complete specimen and range extension of the rare alpheid shrimp Bermudacaris britayevi Anker, Poddoubtchenko amp; Marin, 2006 (Caridea: Alpheidae).

The very uncommon alpheid shrimp Bermudacaris britayevi Anker, Poddoubtchenko Marin, 2006, previously known only from the incomplete holotype from Nha Trang Bay, Vietnam, is recorded from Guam, Mariana Islands, extending its previously known distribution range into the oceanic islands of the western Pacific. The single specimen from Guam, an ovigerous female, was collected adjacent to a near-shore coral reef, on fine sand under a large piece of coral rubble, at a depth of about 10 m. This habitat is different from the collection data of the holotype, which was extracted from a burrow of unknown host on an intertidal sand-mud flat close to mangroves. Despite these ecological differences, the specimen from Guam corresponds to the holotype of B. britayevi in all diagnostic morphological characters and can be distinguished from the closely related B. australiensis Anker Komai, 2004 and B. harti Anker Iliffe, 2000. Since the holotype of B. britayevi was lacking one of the chelipeds, the complete specimen from Guam enables to complement the original description of the species. The stouter (= major) cheliped of the Guam specimen is illustrated to show a marked difference in the armature of the cheliped fingers, between the left and right cheliped. The colour pattern of B. britayevi, which was superficially described in the original description, is herein illustrated by photographs of the living individual. The relatively low number and large size of eggs in the Guam specimen of B. britayevi suggests an abbreviated larval development in this species.

Description of Paraxiopsis/ kensleyi/ n. sp., a new axiid lobster from the Gulf of Mexico (Crustacea: Decapoda: Axiidea).

A new species of axiid was discovered during sampling offshore deep banks on the middle continental shelf off Louisiana. Paraxiopsis kensleyi n. sp. appears to inhabit interstices and cavities of coralline algal rubble, rhodoliths, coral rubble, and other eroded calcareous substrates. Weakly separated from Eutrichocheles Wood-Mason, 1876 on the basis of morphology, present assignments of western Atlantic species to Paraxiopsis de Man, 1905 are regarded as provisional. The new species is described morphologically, and the coloration of freshly captured specimens is documented and compared to related species where possible. Coloration readily distinguishes mature specimens of the new species from Paraxiopsis spinipleura Kensley, 1996, with which it was initially confused. The diagnosis includes GenBank accession numbers for COI sequences to allow future molecular phylogenetic comparisons. Compared to regional species that share a similar dentation or spination on the submedian carina, the pleon of the new species is distinctive in the truncate ventral margin on pleura 2-4, as opposed to being broadly rounded or directed ventrally in an acutely triangular tip. The new species is the eighteenth species of Paraxiopsis worldwide and the ninth from western Atlantic waters, seven of which are now known to range into the Gulf of Mexico. An updated key to western Atlantic members of the genus is provided.

Coral associated bryozoans and their role in reviving the depleting coral ecosystem

Coral reefs are one of the important habitats of marine biodiversity in shallow tropical waters as they sustain numerous crucial ecosystem services. This study provides the taxonomic account and sheds light on the habitat of Bryozoan species, which exclusively considers corals as its substratum for their growth and their role in reviving the depleting coral ecosystem. The systematic description of 12 coral associated bryozoans is, discussed here. Among the described 12 species, six of them, Parasmittina collifera (Robertson, 1908), Smittipora philippinensis (Canu and Bassler, 1929), Onychocella angulosa (Reuss, 1848), Plesiocleidochasma porcellanum (Busk, 1860), Robertsonidra argentea (Hincks, 1881) and Schizoporella errata (Waters, 1878) are reported for the first time in Indian waters. The survey was conducted during April 2013–April 2015 in Gulf of Mannar Marine Biosphere Reserve (GoMBR). Bryozoan species were, collected from the coral rubble and coral skeletal framework in the shallow waters (up to 5 m) and illustrated by scanning electron microscopy (SEM). A conclusion was drawn from this study, where Bryozoans, which colonise dead coral skeletal framework and rubble, can revive the depleting coral reef ecosystem as they play a major role in cementation and act as pioneer species in succession.

Spatial assessment of seagrass ecosystem using the Unmanned Aerial Vehicle (UAV) in Teluk Awur, Coastal Water of Jepara

Seagrass ecosystem are highly sensitive to environmental changes. They are also in global decline and under threat from global climate change and a variety of anthropogenic factors. There is now, a spatial assessment method for the monitoring of the seagrass beds is needed, so that changes in seagrass condition can be understood. Typical monitoring approaches have included remote sensing from satellites and unmanned aerial vehicle platform, and ground base ecological survey. The techniques can suffer from temporal and spatial inconsistency, or are very localised making it hard to assess seagrass meadows in a structurer manner. The aim of research was present the technique using a lightweight drone and consumer grade cameras to produce very high spatial resolution mosaics of intertidal site in Teluk Awur, Jepara water, Indonesia. The data collection methodologies followed by digitation method techniques to produce coverage estimates, with ground check at location, with data drone analysis. This result show that digitation method, can show between the observed and classified low coverage seagrass (<25%), to middle coverage seagrass (between 25< and <50%), also can detect other biotic features, like massive coral, macroalgae also the flat sand and coral rubble.

Large-scale interventions may delay decline of the Great Barrier Reef

On the iconic Great Barrier Reef (GBR), the cumulative impacts of tropical cyclones, marine heatwaves and regular outbreaks of coral-eating crown-of-thorns starfish (CoTS) have severely depleted coral cover. Climate change will further exacerbate this situation over the coming decades unless effective interventions are implemented. Evaluating the efficacy of alternative interventions in a complex system experiencing major cumulative impacts can only be achieved through a systems modelling approach. We have evaluated combinations of interventions using a coral reef meta-community model. The model consisted of a dynamic network of 3753 reefs supporting communities of corals and CoTS connected through ocean larval dispersal, and exposed to changing regimes of tropical cyclones, flood plumes, marine heatwaves and ocean acidification. Interventions included reducing flood plume impacts, expanding control of CoTS populations, stabilizing coral rubble, managing solar radiation and introducing heat-tolerant coral strains. Without intervention, all climate scenarios resulted in precipitous declines in GBR coral cover over the next 50 years. The most effective strategies in delaying decline were combinations that protected coral from both predation (CoTS control) and thermal stress (solar radiation management) deployed at large scale. Successful implementation could expand opportunities for climate action, natural adaptation and socioeconomic adjustment by at least one to two decades.

Spectral characteristics of coral reef benthic compositions in Gulf of Mannar

Spectral characteristics of nine coral species (Acropora Nobilis, Acropora Hyacinthus, Acropora Varibalis, Favia Speciosa, Favia Stelligera, Porites Lobdata, Porites sp., Pocillopora Domicornis and branched dead corals), two seagrass species (Zosteraceae and Posidoniaceae), two sand benthic communities (sand mixed with coral rubble and carbonate sand), reef vegetation and sea moss were recorded using RAMSES-TriOS Hyperspectral radiometer from Mandapam group of islands, Gulf of Mannar, India. Based on the reflectance features, coral reef benthic compositions were categorized as brown mode and blue mode. Brown mode of corals was identified by a triple peaked pattern exhibiting local maxima or shoulders near 575, 600 and 650 nm. The blue modes of corals were identified by a plateau-like shape between 600 and 650 nm. The non-coral benthic compositions such as seagrass and sea moss can be identified by a peak between 550 and 560 nm. Results exhibited that, most of the coral reef benthic compositions falling under either blue mode or brown mode of corals and the patterns of spectral signatures exhibited in this region are matching with existing global signatures.

A new species of Deutella (Amphipoda: Caprellidae) from the Gulf of Mexico

A new species of the genus Deutella Mayer, 1890 is described and illustrated, and a key to identify the Deutella species from the Gulf of Mexico is given. The specimens were collected from coral rubble at 18 m depth in Tuxpan-Lobos coral reef system, W Gulf of Mexico. Deutella pseudoincerta n. sp. is remarkably close to Deutella incerta (Mayer, 1903), but can be easily distinguished by: length and shape of pereopod 5 especially distal article; length and width of adult male gnathopod 2; shape and size of tubercles in male abdominal appendages. The new species increases the number of Deutella species to 14 worldwide, and 18 species of Caprellidae from the Gulf of Mexico.

Benthic Resource Baseline Mapping of Cakaunisasi and Yarawa Reef Ecosystem in the Ba Region of Fiji

Coastal habitats form a critical source of livelihood for a large number of inhabitants in Fiji. The absence of historical and baseline information creates a significant challenge in effectively designing suitable management plans. This study aimed at developing reliable benthic cover maps of village intertidal resource harvest areas (Cakaunisasi and Yarawa reefs) and anthropogenic perceptions of Votua Village in the Ba region of Fiji for better resource management planning and monitoring. Images captured by the WorldView2 satellite were used as a base for mapping out the resources. Data logging on-site, Global Positioning System (GPS) recordings, local interviews and high-resolution video capturing were utilised for ground-truthing techniques. Six classes of benthic cover were identified, which included algae, coral, sand and gravel, buried reef, coral rubble and seagrass. Accuracy assessment and supervised classification were done using ground reference points. There was an existing marine protected area (MPA) on the Yarawa reef, which did not seem to be working as well as anticipated by observing the habitat maps of the two reefs. Baseline maps constructed here and possibly ecosystem maps can allow for monitoring of the existing MPA as well as the formation of a new and more informed MPA. The maps generated in this study serve as baseline information about resource distribution on Cakaunisasi and Yarawa reefs to inform management decisions.

Contrasting effects of the El Niño 2015–16 event on coral reefs from the central pacific coast of Mexico

AbstractCoral reefs are highly diverse and productive ecosystems, and certain oceanographic processes, such as El Niño, have resulted in severe coral bleaching and mortality of reef‐building corals and to the global decline of the area covered by coral reefs. Here, we report the response of corals and both green and red filamentous and coralline algae from the central Mexican Pacific coast to the 2015–16 El Niño event. Sea surface temperature (SST) was recorded in the area between june 2012 and December 2018. Additionally, SST, DHW and the Oceanic El Niño Index (ONI) provided by NOAA for the El Niño 3 region during the same period were considered. Relative cover (%) of healthy, pale, bleached and dead corals, coral rubble, filamentous algae, rocks, and sand were recorded at five reefs during 2010, 2015, and 2018. Between April 2015 and April 2016, the SST was warmer than average, and the ONI showed temperature anomalies near 3, indicating a strong El Niño event. The response of corals varied among reefs and years. No relevant changes in substrata cover were recorded at two reefs through the years, but extensive coral bleaching occurred at the other reefs in June 2015, with dramatic coral mortality as a consequence. An inability to recover and the resulting dominance of filamentous algae over dead corals was evident at two reefs in January 2018. Multivariate analysis based on the cover of substrata and the comparison with previous studies suggested that the response of the coral reefs was not related to the previous state of conservation or the level of anthropogenic impact at each reef. The causes of such thermal resistance are uncertain; nonetheless, it has a high potential to cope with future El Niño impacts.

Monitoring the seagrass ecosystem using the unmanned aerial vehicle (UAV) in coastal water of Jepara

Seagrass ecosystem in the world were highly sensitive to environmental changes. They were also in global decline and under threat from a variety of anthropogenic factors and global climate change. There was now an urgency to establish robust monitoring methodologies so that changed in seagrass abundance and distribution in these sensitive coastal environments can be understood. Typical monitoring approaches have included remote sensing from satellites and airborne platform, ground base ecological survey. The techniques can suffer from temporal and spatial inconsistency, or were very localised, making it hard to assess seagrass meadows in a structurer manner. The aim of this research was to present the technique of using a lightweight drone and consumer grade cameras to produce very high spatial resolution mosaic of intertidal site in Bandengan, Jepara waters, Indonesia. The data collection methodologies followed by digitation method techniques to produce coverage estimates, with ground check at location, with data drone analysis. This result showed that digitation method can show between the observed and classified low coverage seagrass 7-12% (<25%) compare to middle coverage seagrass 34-48% (between 25< and <50%), also was able to detect the other biotic features, such as colonies of macroalgae, massive coral, the flat sand and coral rubble at the observation location.