Reef Surface Research Articles

Ecosystem restructuring along the Great Barrier Reef following mass coral bleaching.

Global warming is markedly changing diverse coral reef ecosystems through an increasing frequency and magnitude of mass bleaching events1-3. How local impacts scale up across affected regions depends on numerous factors, including patchiness in coral mortality, metabolic effects of extreme temperatures on populations of reef-dwelling species4 and interactions between taxa. Here we use data from before and after the 2016 mass bleaching event to evaluate ecological changes in corals, algae, fishes and mobile invertebrates at 186 sites along the full latitudinal span of the Great Barrier Reef and western Coral Sea. One year after the bleaching event, reductions in live coral cover of up to 51% were observed on surveyed reefs that experienced extreme temperatures; however, regional patterns of coral mortality were patchy. Consistent declines in coral-feeding fishes were evident at the most heavily affected reefs, whereas few other short-term responses of reef fishes and invertebrates could be attributed directly to changes in coral cover. Nevertheless, substantial region-wide ecological changes occurred that were mostly independent of coral loss, and instead appeared to be linked directly to sea temperatures. Community-wide trophic restructuring was evident, with weakening of strong pre-existing latitudinal gradients in the diversity of fishes, invertebrates and their functional groups. In particular, fishes that scrape algae from reef surfaces, which are considered to be important for recovery after bleaching2, declined on northern reefs, whereas other herbivorous groups increased on southern reefs. The full impact of the 2016 bleaching event may not be realized until dead corals erode during the next decade5,6. However, our short-term observations suggest that the recovery processes, and the ultimate scale of impact, are affected by functional changes in communities, which in turn depend on the thermal affinities of local reef-associated fauna. Such changes will vary geographically, and may be particularly acute at locations where many fishes and invertebrates are close to their thermal distribution limits7.

Connecting Flow over Complex Terrain to Hydrodynamic Roughness on a Coral Reef

AbstractFlow over complex terrain causes stress on the bottom leading to drag, turbulence, and formation of a boundary layer. But despite the importance of the hydrodynamic roughness scale z0 in predicting flows and mixing, little is known about its connection to complex terrain. To address this gap, we conducted extensive field observations of flows and finescale measurements of bathymetry using fluid-lensing techniques over a shallow coral reef on Ofu, American Samoa. We developed a validated centimeter-scale nonhydrostatic hydrodynamic model of the reef, and the results for drag compare well with the observations. The total drag is caused by pressure differences creating form drag and is only a function of relative depth and spatially averaged streamwise slope, consistent with scaling for k–δ-type roughness, where k is the roughness height and δ is the boundary layer thickness. We approximate the complex reef surface as a superposition of wavy bedforms and present a simple method for predicting z0 from the spatial root-mean-square of depth and streamwise slope of the bathymetric surface and a linear coefficient a1, similar to results from other studies on wavy bedforms. While the local velocity profiles vary widely, the horizontal average is consistent with a log-layer approximation. The model grid resolution required to accurately compute the form drag is O(10–50) times the dominant horizontal hydrodynamic scale, which is determined by a peak in the spectra of the streamwise slope. The approach taken in this study is likely applicable to other complex terrains and could be explored for other settings.

A review of the sponge increase hypothesis for Caribbean mesophotic reefs

Sponges are major components of benthic ecosystems, particularly on Caribbean reefs, where their importance in carbon cycling and ecosystem function is only beginning to be understood. There is a recurring statement in the literature, herein called the “sponge increase hypothesis,” asserting that the biomass and diversity of sponges increase with depth on Caribbean reefs through the mesophotic zone (to 150 m). We reviewed evidence for the sponge increase hypothesis, beginning with electronically searchable contributions to the literature, then working backward in time through the bibliographies of more recent citations. We found 17 studies that report one or more metrics associated with sponge abundance or diversity as a function of depth through all or part of the mesophotic zone. None of these studies reported data on either overall sponge biomass or diversity as a function of reef surface area. Among abundance metrics, including cover and density, patterns as a function of depth were disparate across sites and locations. We conclude that there is no evidence to support the sponge increase hypothesis for Caribbean mesophotic reefs and suggest that patterns of sponge abundance as a function of depth are likely to vary for a number of reasons, including substratum type, slope, and orientation. General theories of sponge abundance and diversity as a function of depth await more sophisticated survey studies that employ standardized methods for relating sponge biomass and diversity to reef surface area.

An improved primer set and amplification protocol with increased specificity and sensitivity targeting the Symbiodinium ITS2 region.

The Internal Transcribed Spacer 2 (ITS2) rRNA gene is a commonly targeted genetic marker to assess diversity of Symbiodinium, a dinoflagellate genus of algal endosymbionts that is pervasively associated with marine invertebrates, and notably reef-building corals. Here we tested three commonly used ITS2 primer pairs (SYM_VAR_5.8S2/SYM_VAR_REV, ITSintfor2/ITSReverse, and ITS-DINO/ITS2Rev2) with regard to amplification specificity and sensitivity towards Symbiodinium, as well as sub-genera taxonomic bias. We tested these primers over a range of sample types including three coral species, coral surrounding water, reef surface water, and open ocean water to assess their suitability for use in large-scale next generation sequencing projects and to develop a standardised PCR protocol. We found the SYM_VAR_5.8S2/SYM_VAR_REV primers to perform superior to the other tested ITS2 primers. We therefore used this primer pair to develop a standardised PCR protocol. To do this, we tested the effect of PCR-to-PCR variation, annealing temperature, cycle number, and different polymerase systems on the PCR efficacy. The Symbiodinium ITS2 PCR protocol developed here delivers improved specificity and sensitivity towards Symbiodinium with apparent minimal sub-genera taxonomic bias across all sample types. In particular, the protocol’s ability to amplify Symbiodinium from a range of environmental sources will facilitate the study of Symbiodinium populations across biomes.

Fringing reef growth over a shallow last interglacial reef foundation at a mid-shelf high island: Holbourne Island, central Great Barrier Reef

Fringing reefs are rare on the mid-shelf of the central Great Barrier Reef, with Holocene development histories established for a few examples. The paucity of reef growth records from mid-shelf fringing reefs has limited opportunities for comparisons with inshore fringing reef growth records to better understand the influence of changes in environmental conditions on reef growth with distance offshore. The long-term development of the mid-shelf fringing reef at Holbourne Island was reconstructed using nine percussion and drill cores that captured the entire Holocene period of reef growth. The cores were chronologically constrained by 16 high-precision 230Th ages. A weathered, Pleistocene reef substrate was U-Th dated as last interglacial (open system age of 131,100 ± 1000 cal yBP) and this provides the underlying foundation upon which the Holocene reef initiated prior to ~7520 ± 20 cal yBP. The last interglacial reef was encountered 5.9 m below the present reef surface and is the shallowest confirmed last interglacial reef in the central GBR region to date. Most of the Holocene reef structure was emplaced within 1000 years of initiation. The chronostratigraphy and contemporary geomorphology of the fringing reef at Holbourne Island preserve evidence of re-working and stripping of the reef structure by cyclones. This evidence includes: 1) an age hiatus in core data of ~3500 years (6238 ± 18 to 2683 ± 10 cal yBP); 2) the abundance of detrital branching coral rubble material within the core facies; 3) the surface elevations and ages of fossil microatolls, which reveal that storm-induced ponding of water during low tidal stages up to 55 cm deep has been active (but intermittent) across the reef flat for at least 600 years and is still active today; and 4) long-standing shingle ridges onshore and modern shingle ridges on the reef flat.

A study of tsunami-like solitary wave transformation and run-up over fringing reefs

After the 2004 Indian Ocean tsunami, the effectiveness of fringing reefs in protecting coastlines from tsunami-induced inundation has aroused great attention in the post-tsunami surveys. To better understand the role of fringing reefs in the mitigation of a tsunami hazard, laboratory experiments were conducted in a wave flume to study the transformation and run-up of tsunami-like solitary waves over various fringing reef profiles. The effects of incident wave height, reef-flat submergence, lagoon width and reef surface roughness were examined. Cylinder arrays were employed to create artificial roughness elements on the reef surface. Empirical formulas based on the experimental data were also proposed for the wave run-up. The ratio of the reef flat submergence to the incident wave height was always found to be the dominant parameter to characterize the wave run-ups over various tested reef profiles. Subsequently, a numerical model based on the improved Boussinesq equations including the drag effect of roughness elements was validated by the experimental data. The validated model was then applied to investigate the impacts of variations of reef morphologies (fore-reef slope, back-reef slope, reef-flat width, reef-crest width) on the solitary wave run-up.

Aerial images can detect 3D small patch reefs that are potential habitats for anemonefish Amphiprion frenatus

Patchy habitats often enhance species coexistence and, consequently, abundance of each species. The present study examined two indicators of potential habitats for anemonefish Amphiprion frenatus: total area of dark-colored patch reefs that are detectable on an aerial image with image analysis software, and total area of tall patch reefs (>1.5 m in height) that are detectable on stereoscopic aerial images with a stereoscope. Relationships between patch reef area and anemonefish abundance, as estimated by number of host anemone Entacmaea quadricolor, were investigated at Shiraho Reef, Ishigaki Island, Japan. Total number of anemones was not correlated with total area of tall patch reefs but was highly correlated with total area of dark-colored patch reefs. Underwater observations confirmed that upper surface of tall patch reefs often involved bare substratum, whereas dark-colored patch reefs did not include this substratum. Because reef area approximately reflected reef volume within shallow back reefs, total area of dark-colored patch reefs that are detectable by aerial photography will reflect total volume of reef fish habitat. The present study suggests that aerial photography with a drone can provide a useful predictor of reef fish abundance.

Comprehensive and comparative ecotoxicological and human risk assessment of polycyclic aromatic hydrocarbons (PAHs) in reef surface sediments and coastal seawaters of Iranian Coral Islands, Persian Gulf

The concentration and spatial distribution along with ecotoxicological risk of 30 polycyclic aromatic hydrocarbons were investigated in the reef surface sediments (RSSs) and coastal seawater (CSW) of ten coral Islands from the Persian Gulf, Iran, in January 2015. For all sampling sites, assessment of ecological risk was undertaken using several approaches. Mean concentration of ∑30PAHs varied between 70 and 884ngL-l with an overall mean value of 464ngL-l in the CSW, while the RSS ranged from 274 to 1098ngg−1dw with a total average of 619ngg−1dw. The results showed a gradient in PAH concentration and toxicity estimates from the northern Hormoz site increasing to the eastern Kharg site. Most of the toxicity estimates were in the moderate range or less than risk values for damage to the marine environment. The calculated Dermal Hazard Quotient (HQs), the sum of HQs (HI) and other cancer risk values of most compounds were less than safety values at most sites. It means that the possibility of negative effects of PAHs via dermal absorption from sediments for children and adults is low. Some sampling sites studied have already been impacted with hazardous pollutants for an extended period of time and evidence from this investigation demonstrates that mixtures of PAHs may be carcinogenic to humans, especially in the western part of the Gulf.

Bacterial Biofilm Communities and Coral Larvae Settlement at Different Levels of Anthropogenic Impact in the Spermonde Archipelago, Indonesia

Populations on small islands surrounded by coral reefs often heavily depend on the services provided by these reefs. The health and recovery of reefs are strongly influenced by recruitment of coral larvae. Their settlement relies on cues such as those emitted from bacterial communities forming biofilms on reef surfaces. Environmental conditions can change these bacterial community compositions (BCC) and may in turn affect settlement of coral larvae. At three small inhabited islands in the Spermonde Archipelago, Indonesia, with different distance from the mainland, BCC and coral recruitment were investigated on artificial ceramic tiles after 2-8 weeks exposure time and on natural reef substrate. Water parameters showed a clear separation between inshore and near-shore/mid-shelf sites, with distinct benthic communities at all three sites. No coral recruitment was observed at the inshore site with highest natural and anthropogenic stressors. At the other two sites coral recruitment occurred on natural surfaces (recruits per 100 cm2: 0.73 ± 1.75 near-shore, 0.90 ± 1.97 mid-shelf), but there was no significant difference between the two sites. On artificial substrates coral recruitment differed between these two sites, with tile orientation and with exposure time of the tiles in the reef. The most abundant bacteria on both substrates were Gammaproteobacteria, Alphaproteobacteria and Cyanobacteria. BCC was strongly correlated with water quality and significant differences in BCC between the inshore site and near-shore/mid-shelf were found. On artificial substrates there was a significant difference in BCC also with exposure time in the reef. Our study highlights the value of taking both BCC and coral recruitment into account, in addition to the environmental conditions, when considering the recovery potential of coral reefs.

Spatial distribution, ecological and health risk assessment of heavy metals in marine surface sediments and coastal seawaters of fringing coral reefs of the Persian Gulf, Iran

Concentrations of 13 heavy metals (Al, Fe, Mn, Zn, Cu, Cr, Co, Ni, V, As, Cd, Hg, Pb) in 360 reef surface sediments (0–5 cm) and coastal seawater samples from ten coral Islands in the Persian Gulf were analyzed to determine their spatial distribution and potential ecological risks. Different sediment quality indices were applied to assess the surface sediment quality. The mean concentrations of metals in studied sediments followed the order: Al > Fe > Ni > V > Mn > Zn > Cu > Cr > Co > As > Cd > Pb > As. Average Cd and Hg exceeded coastal background levels at most sampling sites. With the exception of As, concentrations of heavy metals decreased progressively from the west to the east of the Persian Gulf. Based on the Enrichment Factor (EF) and Potential Ecological Risk Index (RI), concentrations of V, Ni, Hg and Cd indicated moderate contamination and is of some concern. The mean values of heavy metals Toxic Units (TUs) were calculated in the following order: Hg (0.75)> Cr (0.41)> Cd (0.27)> As (0.23)> Cu (0.12)> Zn (0.05)> Pb (0.009). Furthermore, the mean contributing ratios of six heavy metals to Toxic Risk Index (TRI) values were 79% for Hg, 11.48% for Cd, 6.16% for Cr, 3.27% for Cu, 0.07% for Zn and 0.01% for Pb. Calculated values of potential ecological risk factor, revealed that the risk of the heavy metals followed the order Cd > Pb > Ni > Cr > V > Cu > Zn. The results reflected that the level of heavy metals, especially Hg and Cd, are on rise due to emerging oil exploration, industrial development, and oil refineries along the entire Gulf. Fe, Mn, Cu, Zn, V and Ni concentrations in seawater were significantly higher (p < 0.05) than the other detected dissolved heavy metals in the sampling sites. A health risk assessment using the hazard quotient index (HQ) recommended by the USEPA suggests that there is no adverse health effect through dermal exposure, and there is no carcinogenic and non-carcinogenic harm to human health.

Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters.

Discrepancies between bioavailable nitrogen (N) concentrations and phytoplankton growth rates in the oligotrophic waters of the Great Barrier Reef (GBR) suggest that undetermined N sources must play a significant role in supporting primary productivity. One such source could be biological dinitrogen (N2) fixation through the activity of “diazotrophic” bacterioplankton. Here, we investigated N2 fixation and diazotroph community composition over 10° S of latitude within GBR surface waters. Qualitative N2 fixation rates were found to be variable across the GBR but were relatively high in coastal, inner and outer GBR waters, reaching 68 nmol L-1 d-1. Diazotroph assemblages, identified by amplicon sequencing of the nifH gene, were dominated by the cyanobacterium Trichodesmium erythraeum, γ-proteobacteria from the Gamma A clade, and δ-proteobacterial phylotypes related to sulfate-reducing genera. However, diazotroph communities exhibited significant spatial heterogeneity, correlated with shifts in dissolved inorganic nutrient concentrations. Specifically, heterotrophic diazotrophs generally increased in relative abundance with increasing concentrations of phosphate and N, while Trichodesmium was proportionally more abundant when concentrations of these nutrients were low. This study provides the first in-depth characterization of diazotroph community composition and N2 fixation dynamics within the oligotrophic, N-limited surface waters of the GBR. Our observations highlight the need to re-evaluate N cycling dynamics within oligotrophic coral reef systems, to include diverse N2 fixing assemblages as a potentially significant source of dissolved N within the water column.

Tiling the reef – Exploring the first step of an ecological engineering tool that may promote phase-shift reversals in coral reefs

Phase shifts from coral- to algal-dominated reefs have grave effects on reef biodiversity and key ecosystem functions, further influencing management approaches that have generated fewer returns than desired. Harnessing the ability of corals to ‘self-anchor’ to substrates and of tissue fusions between isogeneic fragments, we develop here a novel ecological engineering approach based on the 2D Coral Preparative (2D-CP) tool. Using this tool we propose to create flat, two dimensional coral units that are first grown in a mid-water coral nursery and then transplanted to overlay phase-shifted coral reef surfaces as floor tiles. Here, we assess the feasibility of the 2D-CP’s first stage- growth in the nursery. Ten coral colonies from each of the species: Stylophora pistillata, Pocillopora damicornis and Cyphastrea spp. were collected from localities at the northern Gulf of Eilat (Red Sea, Israel), fragmented into nubbins and glued onto flat surfaces (CDs) to create 235 2D-CP units (32 nubbins/unit). All 2D-CPs were hung in a mid-water coral nursery, in both horizontal and vertical positions, and were digitally photographed once a month for a year. Images of each 2D-CP were used to determine the percentages of live coral tissue coverage on the substrates and the nubbins’ survival percentage. Results revealed high survival rates, with >80% of the 2D-CPs possessing live coral tissues at 12 months post setup (mps). The nubbins of all three species displayed an extensive 2D growth on the substrates, and as of 6–7 months (species and genotype specific) many of the 2D-CPs were completely covered with coral tissue (20% of all the 2D-CPs showed >100% coral coverage at 12mps). The coral coverage of S. pistillata and P. damicornis 2D-CPs was significantly higher in the vertical placement position, 1.5 and 3 times, respectively.Overall, these results imply that the 2D-CP units can be successfully grown in a coral nursery for the purpose of creating ‘live tiles’ that can be placed directly over a denuded reef covered by turf algae, a novel ecological engineering tool to be used for coral-algae phase shifts reversals. We further anticipate that even in completely/partially dead 2D-CP units, newly exposed calcium carbonates would be expended as preferable substrates for either coral larval recruitment or coralline algae growth, boosting reef rehabilitation.

Spatial distribution and composition of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons and hopanes in superficial sediments of the coral reefs of the Persian Gulf, Iran

This study is the first quantitative report on petroleum biomarkers from the coral reefs systems of the Persian Gulf. 120 reef surface sediment samples from ten fragile coral reef ecosystems were collected and analyzed for grain size, biogenic elements, elemental ratios, and petroleum biomarkers (n-alkanes, PAHs1 and Hopanes) to assess the sources and early diagenesis of sedimentary organic matter. The mean grain size of the reef sediments ranged from 13.56 to 37.11% (Clay), 26.92 to 51.73% (Sand) and 35.97 to 43.85% (Silt). TOC2 (3.35–9.72 mg.g−1) and TON3 (0.4–1.10 mg.g−1) were identified as influencing factors on the accumulation of petroleum hydrocarbons, whilst BC4 (1.08–3.28 mg.g−1) and TIN5 (0.13–0.86) did not exhibit any determining effect. Although BC and TIN demonstrated heterogeneous spatial distribution, TOC and TON indicated homogenous distribution with continually upward trend in concentration from the east to west ward of the Gulf. The mean calculated TOC/TN ratios vacillated according to the stations (p < 0.05) from 2.96 at Shidvar Island to 8.64 at Hengam Island. The high TOC/TN ratios were observed in the Hengam (8.64), Kharg (8.04) and Siri (6.29), respectively, suggesting a predominant marine origin. The mean concentrations of ∑C11–35n-alkanes, ∑30 PAHs and ∑9Hopanes were found in the ranges of 385–937 μg.g−1dw, (overall mean:590 μg.g−1dw), 326–793 ng.g−1dw (499 ng.g−1dw), 88 to 568 ng.g−1 d (258 ng.g−1dw), respectively. Higher concentrations of detected petroleum biomarkers in reef sediments were chiefly distributed near main industrial areas, Kharg, Lavan and Siri, whilst the lower concentrations were in Hormoz and Qeshm. In addition, one-way ANOVA6 analysis demonstrated considerably significant differences (p < 0.05) among concentration of detected total petroleum hydrocarbons between most sampling locations. Some sampling sites especially Kharg, Lavan, Siri and Lark indicated higher concentration of n-alkanes due to the higher maintenance of organic matter by high clay content in the sediments. Furthermore, most sediment samples, except for Hormoz, Qeshm and Hengam showed an even carbon preference for n-alkanes which could be correlated to bacterial input. NPMDS7 analysis also demonstrated that among the congeners of petroleum biomarkers, n-C12,n-C14, n-C16,n-C18 and n-C20 for n-alkanes, Phe8 and Naph9 along with their Alkyl homologues for PAHs (2–3 rings accounted for 60%) and C30αβ and C29αβ for Hopanes were discriminated from their other congeners in the whole study area. Our results based on the PCA10 analysis and diagnostic indices of AHs11 and PAHs along with ring classification of PAHs, in addition, the ubiquitous presence of UCM,12 and Hopanes revealed that the main sources of the pollution were petroleum and petroleum combustion mainly from offshore oil exploration and extraction, discharge of pollutants from shipping activities.

Sand-mediated divergence between shallow reef communities on horizontal and vertical substrata in the western Indian Ocean

Distinctions are rarely made between vertical and horizontal surfaces when assessing reef community composition, yet physical differences are expected because of hydrodynamic differences and sediment accumulation on flat surfaces. As sand often diminishes biotic cover, we hypothesised that vertical surfaces will support a greater biomass but have lower diversity due to domination by a few species. To test this, we quantified sessile communities on vertical and horizontal surfaces at three sites in the Delagoa Bioregion on the east coast of South Africa. Community composition consistently differed: vertical communities were dominated by various filter feeders, especially the ascidian Pyura stolonifera, whereas those on horizontal reef comprised a mixture of filter feeders and various algae. The total number of species and all diversity metrics were significantly greater for horizontal reef surfaces. Contrastingly, Simpson’s dominance and biomass were significantly greater for vertical reef surfaces. Percentage cover of sand explained much of the variation in community composition whereas depth did not. Small-scale topographic differences in substratum orientation associated with differences in sand inundation will therefore influence both α and β diversity. Coastal developments and activities that alter sand movements and delivery to the coastal zone are therefore likely to have a profound influence on the maintenance and diversity of shallow subtidal communities.

Parrotfish erosion underpins reef growth, sand talus development and island building in the Maldives

Parrotfish play a key functional role on coral reefs as external bioerosion agents and produce large quantities of carbonate sediment as a by-product of grazing on reef surfaces. Parrotfish are therefore an important potential source of sediment for island construction and maintenance within atoll reef environments, particularly under future scenarios of sea level rise and island morphological change. Here, we present the first field-based estimates of excavating parrotfish erosion (Chlorurus sordidus and Chlorurus strongylocephalus) within the Indian Ocean and quantify the contribution of parrotfish to the carbonate and sediment budgets of an atoll interior reef platform in the Maldives. We note that parrotfish erosion rates are high (6.3kgm−2 y−1), generating large amounts of new coral-based sediment (2.6kgm−2 y−1) that has a comparable grain size distribution to island deposits. Mean erosion rates by individual C. strongylocephalus (405kg individual y−1) were higher than C. sordidus (55kg individual y−1), but their contribution to erosion per unit area of reef was less due to a lower relative biomass (C. strongylocephalus: 1.3kgm−2 y−1; C. sordidus: 5.0kgm−2 y−1). Parrotfish also facilitate sediment export from reefs (0.7kgm−2 y−1), which contributes extensively to the development of the sand talus on the fore-reef slope and to the evolution of the wider atoll basin. Our results provide strong evidence that parrotfish erosion (and sediment generation) underpins island morphology on Maldivian reefs and highlight the importance of larger parrotfish as producers of island-grade sediment. Ecological processes must therefore be considered within future coastal management strategies for enhancing island stability.

On the use of blast furnace slag and steel slag in the preparation of green artificial reef concrete

This study is motivated by the need for the development of green artificial reef concrete (GARC) and the reuse of granulated blast furnace slag (GBFS) and steel slag (SS) from the steel manufacturers located near coastline. GARC was developed with industrial waste including GBFS, SS and flue gas desulfurization gypsum as the major raw materials. Physical properties and compressive strength development of the prepared GARC were examined. Hydration products of GARC paste were investigated through X-ray diffraction, differential scanning calorimetry and scanning electron microscope techniques. The developed GARC shows a 28-day compressive strength of 71.4MPa and a density of 2765.5kg/m3, which contains industrial waste accounting for 98% by weight of its total solid raw materials. Investigation of hydration products in GARC paste reveals that the major hydration products are ettringite and C–S–H gel with a very dense microstructure, without considerable amount of portlandite that is commonly found in traditional concrete. The absence of portlandite is favorable for lowering the pH valve of artificial reefs, which would be benefit for avoiding the accumulation of fouling organisms like barnacles on the surface of concrete artificial reefs. An experimental-scale deployment of GARC specimens in the sea preliminarily demonstrates that GARC is suitable for the attachment growth of algae. The successful development of GARC mainly composed of GBFS and SS could potentially offer great benefits in promoting the sustainable development of steel manufacturers closely located to coastline as well as fishery industry.

Macrobenthic assemblages in an artificial reef in central-west Portugal: Preliminary results

Macrobenthic assemblages in an artificial reef in central-west Portugal: Preliminary results

Spawning Behavior of Lingcod in the Seattle Aquarium

Lingcod (Ophiodon elongates) are members of the family Hexagrammidae and are found in the northeast coastal waters of the Pacific Ocean. Hexagrammids are demersal spawners with the male fish guarding eggs until hatching occurs. The spawning behavior of Lingcod has only been observed and described once in the literature (Wilby 1937). Although other investigators have described various aspects of Lingcod life history and reproductive activity (for example, Jewell 1968; Low and Beamish 1978; LaRiviere and others 1981; Giorgi 1981; Cass and others 1990; Jagielo 1994), none directly observed spawning. Withler and others (2004) genetically evaluated progeny and documented polygamous mating by Lingcod. This note describes a Lingcod spawning event in the Seattle Aquarium and compare this spawning to that described previously by Wilby (1937). The Underwater Dome exhibit of the Seattle Aquarium is in the form of an igloo-like public observation volume immersed in a large cylindrical vessel. The vessel is approximately 20 m in diameter and 6 m deep, containing more than 1800 m of filtered seawater pumped from adjacent Elliot Bay, in an open system with the water discharged back to the bay. The surface of the vessel is not enclosed, and is protected by an awning covering a portion of the water surface. Environmental conditions inside the exhibit, such as temperature and lighting, match ambient conditions. A low-light level is maintained in the exhibit at night. The exhibit topography mimics rocky and nearshore habitat conditions found in the Salish Sea. The highrelief rocky reef structure is made of concrete, and the bottom is covered with a shallow layer of coarse beach sand. The exhibit is home to a variety of fish and invertebrate species found in local waters. The animals are fed a variety of fish and shellfish similar to their natural diet. The Lingcod feed primarily on forage fish and squid, and occasionally prey on smaller exhibit fish, usually salmonids. Lingcod in the exhibit typically spawn each season between mid-December and mid-March, usually near year-end, using one or more of 3 specific locations. Characteristics of the 3 sites are consistent with sites selected by fish in the wild (KWJ, pers. obs.), distinguished by rocky reef ledges with deep cracks or crevices suitable for deposition of egg masses, supporting the premise that physical characteristics of the exhibit are conducive for display specimens to behave and reproduce in near-natural conditions. The site of the observed spawning is an approximately parallel-sided cavity 20 cm wide between a flat-sided boulder and a vertical reef surface. The site is about 2 m from viewing windows. The dome exhibit was home to 5 adult Lingcod ranging from 75to 110-cm total length at the time of the observed spawning. Two of the fish were known to be female and 2 were known to be male. The sex of the 5th fish was unknown. The ages of the fish were also not known. Observations were visual and notes were made after the event. Measurements were made using a 1-m-long plastic tube graduated in 10-cm increments. On 1 January 2015, a pair of Lingcod spawned in the Underwater Dome exhibit of the Seattle Aquarium. The spawners were the largest female and largest male in the exhibit. The female was gravid and swollen to the point of concern by aquarium staff that she was egg-bound. The site selected by the spawners was the site most frequently used for egg laying in previous years. The male fish had established long-standing dominance of this site during the spawning season by remaining at the location, performing courtship display when females were present, and chasing other fish from the area. At approximately 08:30 Pacific Standard Time, in crepuscular conditions, the female Lingcod was observed by a maintenance diver at the spawning location. She was aligned with the cavity with her ventral side up. The fish was alternately squirming and quivering. The male was nearby (Fig. 1A). After an GENERAL NOTES

Effects of submarine power transmission cables on a glass sponge reef and associated megafaunal community

We examined the effects of submarine power transmission cable installation and operation on glass sponge reef condition and associated megafauna. Video and still imagery were collected using a Remotely Operated Vehicle twice a year for 4 years following cable installation. The effects of cables on glass sponges were assessed by comparing sponge cover along fixed transects and at marked index sites. Megafauna counts along transects were used to explore the effects on associated community. We found no evidence of cable movement across the sponge reef surface. Live sponge cover was found to be consistently lower along cable transects and at cable index sites compared to controls. Live sponge cover was the lowest (55 ± 1.1% decrease) at cable index sites 1.5 years after installation and recovered to 85 ± 30.6% of the original size over the following 2 years. Our data suggest 100% glass sponge mortality along the direct cable footprint and 15% mortality in the surrounding 1.5 m corridor 3.5 years after cable installation. Growth rate of a new glass sponge was 1 and 3 cm/year in first and second year, respectively, and appeared to be seasonal. We observed a diverse megafaunal community with representatives from 7 phyla and 14 classes. Total megafauna, spot prawn, and other Arthropoda abundances were slightly lower along cable transects although the effect of cable presence was not statistically significant. The following measures could be taken to reduce the amount of damage to glass sponge reefs and associated fauna: routing the cable around reefs, whenever possible, minimizing cable movement across the surface of the reef at installation and routine operation, and assessing potential damage to glass sponges prior to decommissioning.

Induction of Larval Settlement in the Reef Coral Porites astreoides by a Cultivated Marine Roseobacter Strain.

Successful larval settlement and recruitment by corals is critical for the survival of coral reef ecosystems. Several closely related strains of γ-proteobacteria have been identified as cues for coral larval settlement, but the inductive properties of other bacterial taxa naturally occurring in reef ecosystems have not yet been explored. In this study, we assayed bacterial strains representing taxonomic groups consistently detected in corals for their ability to influence larval settlement in the coral Porites astreoides. We identified one α-proteobacterial strain, Roseivivax sp. 46E8, which significantly increased larval settlement in P. astreoides. Logarithmic growth phase (log phase) cell cultures of Roseivivax sp. 46E8 and filtrates (0.22μm) from log phase Roseivivax sp. 46E8 cultures significantly increased settlement, suggesting that an extracellular settlement factor is produced during active growth phase. Filtrates from log phase cultures of two other bacterial isolates, Marinobacter sp. 46E3, and Cytophaga sp. 46B6, also significantly increased settlement, but the cell cultures themselves did not. Monospecific biofilms of the three strains did not result in significant increases in larval settlement. Organic and aqueous/methanol extracts of Roseivivax sp. 46E8 cultures did not affect larval settlement. Examination of filtrates from cell cultures showed that Roseivivax sp. 46E8 spontaneously generated virus-like particles in log and stationary phase growth. Though the mechanism of settlement enhancement by Roseivivax sp. 46E8 is not yet elucidated, our findings point to a new aspect of coral-Roseobacter interactions that should be further investigated, especially in naturally occurring, complex microbial biofilms on reef surfaces.