Coral Bay Research Articles

Rhodenigma contortum, an obscure new genus and species of Rhodogorgonales (Rhodophyta) from Western Australia.

An unknown microscopic, branched filamentous red alga was isolated into culture from coral fragments collected in Coral Bay, Western Australia. It grew well unattached or attached to glass with no reproduction other than fragmentation of filaments. Cells of some branch tips became slightly contorted and digitated, possibly as a substrate-contact-response seen at filament tips of various algae. Attached multicellular compact disks on glass had a very different cellular configuration and size than the free filaments. In culture the filaments did not grow on or in coral fragments. Molecular phylogenies based on four markers (rbcL, cox1, 18S, 28S) clearly showed it belongs to the order Rhodogorgonales, as a sister clade of Renouxia. Based on these results, the alga is described as the new genus and species Rhodenigma contortum in the Rhodogorgonaceae. It had no morphological similarity to either of the other genera in Rhodogorgonaceae and illustrates the unknown diversity in cryptic habitats such as tropical coral rubble.

Coral Bay Shore Zones Tar Ball Distribution

Oil spill and wastewater discharge to the marine waters contribute to the tar ball formation after the residue washout to the sandy beaches. The oil degrades over time through dynamic changes of the hydrocarbon compounds once exposed to the environmental factors which influences the fate and transport of the oil residue. Tar balls collected from Coral Bay shore zone which is used for recreational activities are 100 gm/strip with up to 6cm in diameter. The collected tar ball was analyzed using FID gas chromatography after 50% n-hexane and dichloromethane extraction and fingerprint to the diesel and crude oils. The tar ball sample contains beta-pregnane (22-29%) and dotriacontane (52-68%) which accumulate over long time from crude oil spills in the Strait of Malacca.

Taganito HPAL Plant Project

This paper will present Commissioning and Operation Status of Taganito HPAL Plant Project in the Philippines. The Project will produce 30,000 Ni-tons and 2600 Co-tons per year as Mixed (Ni/Co) Sulfide for export to Sumitomo Metal Mining Co., Ltd. (SMM) Nickel Refinery in Japan as its raw material. The plant is designed taking into consideration the improvements, technical data and operation know-how gained from the successful operation of Coral Bay Nickel Corporation (CBNC) in the Philippines, the sister company of Taganito HPAL Nickel Corporation (THPAL). The Plant Commissioning was completed in June 2014 and reached monthly production corresponding to its nameplate capacity in August 2014. After that, the operation has been stable. This paper will also discuss nickel leaching and removal performance of iron and aluminum in the autoclave at elevated temperatures for more efficient HPAL operation.

Resilience of coral calcification to extreme temperature variations in the Kimberley region, northwest Australia

We report seasonal changes in coral calcification within the highly dynamic intertidal and subtidal zones of Cygnet Bay (16.5°S, 123.0°E) in the Kimberley region of northwest Australia, where the tidal range can reach nearly 8 m and the temperature of nearshore waters ranges seasonally by ~9 °C from a minimum monthly mean of ~22 °C to a maximum of over 31 °C. Corals growing within the more isolated intertidal sites experienced maximum temperatures of up to ~35 °C during spring low tides in addition to being routinely subjected to high levels of irradiance (>1500 µmol m−2 s−1) under near stagnant conditions. Mixed model analysis revealed a significant effect of tidal exposure on the growth of Acropora aspera, Dipsastraea favus, and Trachyphyllia geoffroyi (p ≤ 0.04), as well as a significant effect of season on A. aspera and T. geoffroyi (p ≤ 0.01, no effect on D. favus); however, the growth of both D. favus and T. geoffroyi appeared to be better suited to the warm summer conditions of the intertidal compared to A. aspera. Through an additional comparative study, we found that Acropora from Cygnet Bay calcified at a rate 69 % faster than a species from the same genus living in a backreef environment of a more typical tropical reef located 1200 km southwest of Cygnet Bay (0.59 ± 0.02 vs. 0.34 ± 0.02 g cm−2 yr−1 for A. muricata from Coral Bay, Ningaloo Reef; p < 0.001, df = 28.9). The opposite behaviour was found for D. favus from the same environments, with colonies from Cygnet Bay calcifying at rates that were 33 % slower than the same species from Ningaloo Reef (0.29 ± 0.02 vs. 0.44 ± 0.03 g cm−2 yr−1, p < 0.001, df = 37.9). Our findings suggest that adaption and/or acclimatization of coral to the more thermally extreme environments at Cygnet Bay is strongly taxon dependent.

The spatiotemporal dynamics of habitat use by blacktip (Carcharhinus limbatus) and lemon (Negaprion brevirostris) sharks in nurseries of St. John, United States Virgin Islands

Shark nursery areas are widely regarded as essential habitats for the growth and survival of young individuals. The effective management and protection of shark nursery habitat are contingent upon a clear understanding of how individual species utilize such habitat both spatially and temporally. Although shark nurseries have been identified in the Caribbean, this information is generally lacking. From 2006 to 2012, we used passive acoustic telemetry to monitor the presence, movements, and habitat use of 65 juvenile blacktip sharks (Carcharhinus limbatus) and 42 juvenile lemon sharks (Negaprion brevirostris) within Fish Bay and Coral Bay, two shark nurseries in St. John, United States Virgin Islands. Both species were present in each bay during all months of the year, but abundance peaked during the summer (June–September). Although telemetry data indicated that blacktip and lemon sharks moved throughout each embayment, each species exhibited strong site fidelity to core areas across all years of the study. Habitat partitioning was observed in both nurseries as blacktip sharks generally occurred in areas characterized by water depths of 1.5–6 m with seagrass and sand/mud substrate, while lemon sharks remained in close proximity to or within shallow (<1 m), mangrove-fringed seagrass habitat. Blacktip sharks were also observed to exhibit greater activity space during the nighttime hours (1900–0659 h) within Coral Bay. The results of this study indicate that Fish Bay and Coral Bay are nursery areas that warrant designation as essential fish habitat and exemplify the need for additional focused management measures.

Reduced calcification in Western Australian corals during anomalously high summer water temperatures

Here we report the seasonal response of calcification rates over two years, for three coral species (Acropora pulchra, Pocillopora damicornis and Goniastrea aspera), to anomalously warm summer water temperatures (2012 and 2013), following the most severe marine heat wave on record (2010–2011). The study sites at Coral Bay (Ningaloo Reef), the Houtman Abrolhos Islands and Marmion Reef (Perth) spanned over 10° of latitude and ranged from tropical to temperate habitats. Calcification rates were determined using repeated measurements of buoyant weight normalized to surface area and rates were monitored over two winters and two summers from 2011 to 2013. Average growth rates followed predicted latitudinal trends, with the fastest growth in the tropics (Coral Bay) and slowest growth rates in the temperate zone (Marmion). However, calcification rates did not show the expected seasonality (higher in summer, lower in winter), even at high latitude locations. Instead, there was either little difference between summer and winter growth or growth was slower in the summer (on average, a reduction of ~40% across locations and species). Additionally, differences in species growth rates did not follow expected trends, with usually fast growing branching corals not calcifying much faster than the normally slower growing massive corals (A. pulchra, grew ~40% faster than G. aspera, which grew ~6% faster than P. damicornis across all latitudes and seasons). Survival rates were also reduced in the summer months, while among species, P. damicornis had the lowest survival and G. aspera the highest. We conclude that high temperature stress through the summers of 2011 to 2013 was the most likely cause for the lack of seasonality in calcification rates, the similarity in calcification rates among species and the increased mortality of susceptible species in the summer months. The effect of prolonged elevated temperature anomalies (1.5 to 3°C) on the growth and survival of colonies over consecutive years was often greater than the fundamental influences of season and species, highlighting the extent to which climate change could now be re-structuring the life histories of corals on Western Australian reefs.

Notes on the occurrence of a rare Cardinal Fish at Coral Bay, Southern Palawan, Philippines

A team of researchers led by Haribon Palawan and the author with staff from DENR-PENRO, assisted by Coral Bay Nickel Corporation (CBNC) staff conducted coastal habitat monitoring in several areas of Coral Bay, southern Palawan in March 2008 and 2014, under the auspices of CBNC. While diving in one of the survey stations (Maranto Point), the author observed an unusual solitary fish, of which he has seen for the first time in his three-decade work in marine fishes of Palawan. The author took photographs of the fish under water to document fish occurence (Figure 1). The fish was found in a shallow (2-3 meters deep) reef patch off the Maranto Point, located west of the mouth of Rio Tuba River in Coral Bay, Southern Palawan. The exact location of the site was: Latitude, 8.50400o; Longitude, 117.28290o. Although A. griffini might have been previously recorded in Palawan waters, it has not appeared in the pictorial guides of Palawan fishes (Schroeder 1980; Gonzales 2013) Seale also described this species from Bantayan Island, Philippines in 1910. In January 2009, the fish photograph was sent to Dr. Kent Carpenter of the Department of Biological Science of the Old Dominion University, Virginia, USA for identification. After about a month, Dr. Carpenter identified the fish as Apogon griffini (Seale, 1910), a rarely seen kind of cardinal fish called northern spiny dogfish. Seale described this species from Bantayan Island, Philippines in 1910. The genus of this species was renamed to Ostorhinchus (Fishbase 2014). This cardinal fish is found only from the Philippines to Northern Borneo (Malaysia, Indonesia and Brunei), which is a relatively limited range of distribution for a marine fish. Ostorhinchus griffini is a fish native to Philippines. One alarming issue is that during the period of five-year underwater survey in Coral Bay, only one living individual of this fish species was recorded, found in a very restricted area of Coral Bay, indicating that the population of this fish species is at high risk in the area. The author again went with the same monitoring team to Coral Bay on March 23-28, 2014 and observed most probably the same solitary fish in the very same area at Maranto reef. Through fish visual estimate, the fish has grown three times its original length in 2008. Although the CITES status of this fish has not yet been evaluated (FishBase 2014), this fish needs some degree of protection, especially in its local population. Its habitat is further threatened being only about 50 m distance from the shore, fronting a fishing village, open to human activities. Possible flush flood from Rio Tuba River and rampant dynamite fishing in the bay are other threats to the existence of this fish species. Basing from its population status, area occupied, the extent where it occurs, and the threats it is facing, it is apparent that this species needs immediate protection in order to ensure its survival and prevent its loss in Coral Bay. Something has to be done to save this population, like protection of the Maranto Point coral reefs.

Sea temperature shapes seasonal fluctuations in seaweed biomass within the Ningaloo coral reef ecosystem

Environmental drivers of seaweed biomass were investigated at Ningaloo, Western Australia, a coral reef ecosystem with negligible anthropogenic influences on seaweeds from fishing, farming, or eutrophication. Periodic surveys of benthic macroalgae occupying seaweed‐dominated beds within the lagoon at two locations (Coral Bay, Tantabiddi) were made during winter, spring, and late summer over a 26 month period. Canopy‐forming Sargassum spp. biomass fluctuated over a seasonal growth—decay cycle, with highest values in the warm summer months (up to 1013 g fresh weight 0.25 m−2 at Coral Bay) and lowest values in winter (down to 155 g fresh weight 0.25 m−2 at Tantabiddi). Conversely, prominent understory seaweed genera Dictyopteris and Lobophora reached peak biomass in winter, when the Sargassum spp. canopy was lowest. Sargassum spp. biomass variation could be attributed largely to time (52%), location (21%), and site (26%), with low variation within individual seaweed beds (1%). Statistical analysis of the influence of five environmental variables (temperature, light, wind‐driven upwelling, rainfall, significant wave height) indicated that location and sea temperature (1 month antecedent to biomass) provided the best explanation for Sargassum spp. biomass fluctuations. While sea temperature is a key driver of seaweed temporal dynamics, heterogeneity at the kilometer scale suggests that spatial context is also important. Given the important role of seaweeds in many ecosystem processes, this strong biophysical coupling between Sargassum spp. biomass and sea temperature suggests that thermal climate change will significantly affect coral reef productivity and biodiversity.

Atmospheric forcing intensifies the effects of regional ocean warming on reef‐scale temperature anomalies during a coral bleaching event

We investigate how local atmospheric conditions and hydrodynamic forcing contributed to local variations in water temperature within a fringing coral reef‐lagoon system during the peak of a marine heat wave in 2010–2011 that caused mass coral bleaching across Western Australia. A three‐dimensional circulation model Regional Ocean Modeling System (ROMS) with a built‐in air‐sea heat flux exchange module Coupled Ocean Atmosphere Experiment (COARE) was coupled with a spectral wave model Simulating Waves Nearshore (SWAN) to resolve the surface heat exchange and wave‐driven reef circulation in Coral Bay, Ningaloo Reef. Using realistic oceanic and atmospheric forcing, the model predictions were in good agreement with measured time series of water temperature at various locations in the coral reef system during the bleaching event. Through a series of sensitivity analyses, we found that the difference in temperature between the reef and surrounding offshore waters (ΔT) was predominantly a function of both the daily mean net heat flux ( ) and residence time, whereas diurnal variations in reef water temperature were dependent on the diurnal fluctuation in the net heat flux. We found that reef temperatures were substantially higher than offshore in the inner lagoon under normal weather conditions and over the entire reef domain under more extreme weather conditions (0.7°C–1.5°C). Although these temperature elevations were still less than that caused by the regional ocean warming (2°C–3°C), the arrival of peak seasonal temperatures in the summer of 2010–2011 (when net atmospheric heat fluxes were positive and abnormally high) caused substantially higher thermal stresses than would have otherwise occurred if offshore temperatures had reached their normal seasonal maxima in autumn (when net atmospheric heat fluxes were negative or cooling). Therefore, the degree heating weeks calculated based on offshore temperature substantially underestimated the thermal stresses experienced by the reef in the period leading up to the observed bleaching event (3 versus 11°C‐weeks).

Presettlement schooling behaviour of a priacanthid, the Purplespotted Bigeye Priacanthus tayenus (Priacanthidae: Teleostei)

We report in situ behavioural observations of presettlement schooling in Priacanthus tayenus off Coral Bay, Western Australia collected using pelagic Baited Remote Underwater stereo-Video systems. Two groups of fish (8 and 9 individuals) were observed that aggregated into a single school. Mean total length was 24.1 mm (12.5–30.2 mm). The fish swam at a mean speed of 8.5 cm s−1 in a group spacing themselves more or less evenly at a distance of around one body length from the nearest neighbour within the school. P. tayenus appeared to be sometimes associated with juveniles of other species. The results presented here add to the limited, but growing body of literature on the schooling behaviour of the early pelagic stages of demersal fishes.

Transmitter attachment and release methods for short-term shark and stingray tracking on coral reefs

This study details a simple and cost-effective means of attaching acoustic transmitters to coral reef sharks and stingrays, which potentially allows for retrieval and reuse on completion of tracks. Between 2008 and 2011, galvanised timed releases were trialled in both static field tests and on blacktip reef sharks Carcharhinus melanopterus, cowtail Pastinachus atrus, and porcupine Urogymnus asperrimus rays in Coral Bay (−23°08′41″, 113°45′53″), Western Australia. The timed releases remained attached to animals for the duration required for tracking and in four out of five deployments transmitters were recovered after release from the animals. The use of modified Rototags for sharks and stainless steel darts for stingrays allowed rapid and effective attachment to animals, with limited impact on their welfare in the short term. External attachment for short-term tracking of coral reef-associated elasmobranchs should be considered as a complementary option to internal placement of transmitters in animals either by surgery or by ingestion.

The combined influence of hydrodynamic forcing and calcification on the spatial distribution of alkalinity in a coral reef system

We investigated the influence of hydrodynamic forcing (waves, tides, alongshore currents and winds) and net calcification by coral reef organisms on the spatial distribution of total alkalinity (TA) in a fringing reef system through a combination of field measurements and numerical modeling. A field experiment was conducted over 10 days in Coral Bay (Ningaloo Reef, Western Australia) during which we measured wave heights, currents, and tides as well as the spatial distribution of TA across the fore reef, reef crest, and lagoon. We used observed changes in TA on the adjacent reef flat, along with synoptic measurements of cross‐reef transport, to estimate in situ rates of net calcification (gcv) using a control volume approach. Based on the gcv estimated, we simulated light‐driven, diurnal variations in benthic net calcification within a three‐dimensional ocean circulation model, ROMS (Regional Ocean Modeling System). By coupling ROMS with a spectral wave model (Simulating Waves Nearshore), we were able to simulate currents within Coral Bay reef‐lagoon system that were in good agreement with the field observations and demonstrate that circulation with the system was wave‐dominated. Both the field measurements and numerical model output confirmed that both residence time (τR) and TA varied primarily with offshore wave heights and location within the bay. However, variations in TA were also affected by the nonlinear interaction between rates of net calcification that varied as a function of diurnally changing light and water residence time that varied as a function of offshore wave heights.

Tropical inshore dolphins of north-western Australia: Unknown populations in a rapidly changing region.

Australian Snubfin Orcaella heinsohni, Indo-Pacific Humpback Sousa chinensis and Indo-Pacific Bottlenose Dolphins Tursiops aduncus inhabit Australia’s tropical north-western coastline, a region undergoing extensive port development associated with the massive expansion of the oil, gas and mining industries. The current lack of data on dolphin population sizes or trends precludes impact assessments of developments on these protected species. Furthermore, the Western Australian and Commonwealth Government conservation listings of tropical inshore dolphins do not reflect their international listings. From April to July, 2010, we conducted ad hoc boat-based surveys (n=55) of inshore delphinids at seven sites across north-western Australia from Coral Bay in the south (23.1°S: 113.8°E) to Cable Beach in the north (17.9°S: 122.2°E). We documented the locations of these three species from which we obtained photoidentification and biopsy data, as well as reports of Australian Snubfin Dolphin sightings from researchers and community groups. The data from this limited field effort confirm that Indo-Pacific Humpback and Indo-Pacific Bottlenose Dolphins occur in the waters adjacent to each north-western Australian urban centre and show that the range of the Australian Snubfin Dolphin extends considerably further south-west than previously reported. Given the scale of coastal developments and the vulnerability of isolated cetacean populations to fragmentation or extirpation, assessments of the viability of dolphin populations are required. Our data suggest that the Australian Snubfin, Indo-Pacific Humpback and Indo-Pacific Bottlenose Dolphins need to be considered as likely to be impacted by coastal developments across north-western Australia.

Bioturbation by stingrays at Ningaloo Reef, Western Australia

Stingrays are an important part of the biomass of the fishes in shallow coastal ecosystems, particularly in inter-reefal areas. In these habitats, they are considered keystone species – modifying physical and biological habitats through their foraging and predation. Here, we quantify the effects of bioturbation by rays on sand flats of Ningaloo Reef lagoon in Western Australia. We measured the daily length, breadth and depth of 108 feeding pits over three 7‐day periods, created by stingrays (Pastinachus atrus, Himantura spp. Taeniura lymma and Urogymnus asperrimus) in Mangrove Bay. Additionally, an area of ~1 km2 of the lagoon at Coral Bay was mapped three times over 18 months, to record patterns of ray and pit presence. Over 21 days at Mangrove Bay, a total of 1.08 m3 of sediment was excavated by rays, equating to a sediment wet weight of 760.8 kg, and 2.42% of the total area sampled, or 0.03% of the whole intertidal zone. We estimate that up to 42% of the soft sediments in our study area would be reworked by stingrays each year. Based on a model predicting the probability of pit presence over time, there was a 40% probability of ray pits persisting for 4 days before being filled in but only a 15% probability of a pit being present after 7 days. Changes in pit volume over time were static, providing evidence for secondary use. Our results imply that rays play an important ecological role creating sheltered habitats for other taxa in addition to the turnover of sediments.

Trophic ecology of reef sharks determined using stable isotopes and telemetry

Establishing the ecological role of predators within an ecosystem is central to understanding community dynamics and is useful in designing effective management and conservation strategies. We analysed differences in the trophic ecology of four species of reef sharks (Carcharhinus melanopterus, Carcharhinus amblyrhynchos, Triaenodon obesus and Negaprion acutidens) at Ningaloo Reef, Western Australia, by analysing tissue stable isotopes (δ15N and δ13C). We also monitored animals using acoustic telemetry to determine long-term residency patterns in a bay at the southern end of the reef, Coral Bay. Overall, mean δ13C was similar among species, ranging between −10.9 and −11.8‰, suggesting a food-web dependency on coastal producers. Classification and regression tree analysis identified an effect of species on δ15N that separated C. amblyrhynchos and C. melanopterus from N. acutidens and T. obesus. For C. amblyrhynchos and C. melanopterus, animals were also divided by size classes, with smaller sharks having lower average δ15N than larger animals; this suggests that δ15N increases with size for these two species. Juvenile C. melanopterus, juvenile N. acutidens and adult T. obesus had trophic levels of 3.7, for juvenile C. amblyrhynchos and adult C. melanopterus it was 4, and adult C. amblyrhynchos had a value of 4.3. Trophic-level estimates for C. melanopterus and C. amblyrhynchos corroborate previous conclusions based on diet studies. We found no evidence for a difference in isotopic composition between resident and non-resident sharks. The lack of variation in isotopic composition was consistent with high mean residency of these species recorded using acoustic telemetry, which was 79% (±0.09 SE) of days monitored for T. obesus, followed by N. acutidens (57 ± 19.55%), C. amblyrhynchos (54 ± 13%) and C. melanopterus (33 ± 8.28%). High δ13C composition in reef sharks and long-term residency behaviour suggest that coastal marine reserves might provide effective conservation refuges for some species.

White shores of longing: ‘Impossible subjects’ and the frontiers of citizenship

This essay begins with an incident that occurred in 2001, the arrival of a group of asylum seekers from Sri Lanka who arrived off the coast of Coral Bay, Western Australia. It follows these castaway figures through a sequence of discursive histories and representational contexts, situating their stories against practices of embodied citizenship at the intersection of law, land (as territorialized geo-body) and nation, in the United Kingdom, Sri Lanka and Australia, the sites of different, but deeply entwined, dramas of citizenship.

3-D distribution of nongeniculate corallinales: a case study from a reef crest of South Sinai (Red Sea, Egypt)

An innovative technique for the estimation of species and growth-form abundance of coralline algae, including information on their vitality, was adopted on the reef crest of Ras Nosrani and Coral Bay, South Sinai. Data of coralline abundance from visual census and collection of voucher specimens were plotted on a 3-D sketched representation of the horizontal and vertical planes of the reef crest and of its crannies. Coralline dominance at the two investigated sites was not significantly different, with values ranging from 8.55 and 10.06% on the vertical plane and from 5.3 to 7.17% on the horizontal plane. About one-third of total corallines of the South Sinai reef crest was located in crannies, where the algae are completely overlooked by routine field surveys. Pink to violet, healthy corallines with encrusting growth-form, mainly belonging to Hydrolithon onkodes and Neogoniolithon, with subordinate fruticose Lithophyllum kotschyanum dominated the reef crest at both sites. The fruticose growth form, usually associated with L.kotschyanum, was more common in the horizontal than in the vertical plane. Purple, healthy, encrusting Sporolithon uncommonly occurred. Whitish, gray or green unhealthy or dead corallines were more common on the horizontal plane at both sites, possibly resulting from excessive solar radiation.

Patterns of recovery in catastrophically disturbed reef fish assemblages

Direct and lethal natural disturbances to coral reef fish assemblages are rare, as the fishes mobility usually allows for rapid migration away from such events. However, in 1989 and again in 2002, coral spawn 'slicks' off Coral Bay in Western Australia caused many reef organisms to be asphyxiated resulting in catastrophic mortality. A survey in 2002 revealed significant recovery of hard corals within the area disturbed in 1989 (6 to 32%), but little recovery of the fish assemblages with their structure being highly skewed towards herbivorous species. The lack of recovery in the fish assemblages was unexpected for 2 reasons: (1) the existence of healthy fish populations in adja- cent areas and (2) the well-known positive association between many species of reef fish and their benthic habitat. We identified a combination of minimal recruitment to the disturbed area of the bay and a significantly changed coral community structure to be likely causes of the prolonged recovery process. Although just as lethal to the reef community, the 2002 disturbance was significantly smaller and patchy in its extent. In contrast to the 1989 event, the overall effects of this smaller disturbance were positive with species richness and abundance of fish increasing during the weeks after the event, primarily via migration from nearby areas of reef. Together, these results demonstrate the importance of scale when defining disturbance outcomes on coral reefs and highlight the significant role that 'local' factors can play in mediating outcomes from disturbance. This type of information is especially pertinent to reef managers trying to formulate effective plans for conservation of their local reef systems.

Twenty-five years of change in scleractinian coral communities of Daya Bay (northern South China Sea) and its response to the 2008 AD extreme cold climate event

Coral reefs worldwide are becoming increasingly and detrimentally impacted upon by a variety of factors including significant climate changes, such as global warming and increased El Nino-Southern Oscillation activity. Generally, the persistence of coral reefs, especially at low-latitudes, is governed, in part, by sea surface temperatures not exceeding the critical limit (similar to 30A degrees C) at which mass mortality can occur. Thus, it is thought that corals living at high-latitudes (i.e., currently cooler sea surface temperatures) will likely respond more favourably to hypothesized future temperature increases than corals living at low-latitudes (i.e., currently warmer sea surface temperatures). Consequently, high-latitude coral communities may have the potential to act as regions of refugia for many coral species in the face of potential future global warming. The Daya Bay (22A degrees 31'aEuro22A degrees 50'N), northern South China Sea, contains several high-latitude non-reefal coral communities and represents one of the most northerly distributions of scleractinian corals within the region. Significantly, Daya Bay has experienced dramatic warming in both air and sea surface temperatures throughout the past 50 years. In this paper, we analyze 25 years of change in the Daya Bay coral communities, based both on historic surveys and our latest 2006-2008 regional ecological surveys. Our results suggest that, contrary to predictions, there have been significant declines in coral cover within the Daya Bay during the past 25 years (i.e., 76.6% coral cover in 1983/1984 to only 15.3% coral cover by 2008). Such changes also reflect a significant shift in the most abundant coral species, from Acropora pruinosa to Favites abdita. Most of the modern coral communities became established between 15 and 30 years ago, corresponding to a period of increased winter sea surface temperature. However, very few colonies have become established within the last 15 years, despite a more intense period of warming. By taking into account additional factors, we hypothesize that direct anthropogenic impacts, rather than climatic events, have both restricted the development, and drove the decline, of Daya Bay coral communities in the last 15 years. The Daya Bay has also been subjected to occasional extreme cold events during the past 50 years, with the most recent occurring in early 2008 (13 January-13 February). During the 2008 cold event, the lowest air temperature reaches only 6.6A degrees C, and the mean sea surface temperature for February fall to < 14A degrees C, including six continuous days at 12.3A degrees C. Significantly, the sea surface temperatures fall below the hypothesized critical lower temperature threshold (similar to 13A degrees C) that commonly leads to mass mortality in scleractinian coral communities. Surprisingly, our coral community surveys, conducted both before (August 2007) and after (late February 2008) the extreme 2008 cold event, demonstrate that the Daya Bay coral ecosystems are barely impacted upon during the cold period. Those observations suggest that the Daya Bay scleractinian coral communities have developed adaptations to low sea surface temperatures. Overall, our data support the hypothesis that high-latitude coral communities, such as Daya Bay, have the potential to act as areas of refugia for scleractinian corals in the advent of potential future global warming.

Quantification of reef benthos communities and variability inherent to the monitoring using video transect method

Long-term monitoring program of organisms is the most recommended for understanding changing processes on reefs. The video transect method presents advantages for that. Specialists state that it is important to make sure that the recorded coverage is always the same between campaigns, so that differences in results may be entirely attributed to environmental changes. This study aimed to test the capability of implementing this requirement through tracking simulation and its validity for monitoring the benthic communities of reefs using the video transect method. Ten transects 20 m long were established in Todos os Santos Bay coral reefs. Subsequent to the first transect capture, a second diver repeated the same track, simulating two different monitoring campaigns. Data were transformed and a matrix of similarity was generated using Bray-Curtis' Index. ANOSIM analysis was performed to test the similarity of the ten transects and its repetitions. The result, R = 0.08 (P = 0.928), shows that reef monitoring using video transect, the way it is described in the literature, is appropriate, but it is important to consider some premises discussed in this work.