Coral bleaching in turbid waters of north-western Australia

2017 ◽  
Vol 68 (1) ◽  
pp. 65 ◽  
Author(s):  
A. Lafratta ◽  
J. Fromont ◽  
P. Speare ◽  
C. H. L. Schönberg
Keyword(s):  
Thermal Stress ◽  
Western Australia ◽  
Large Scale ◽  
Coral Cover ◽  
Coral Community ◽  
Soft Corals ◽  
Hard Coral ◽  
Turbid Waters ◽  
Benthic Survey ◽  
North Western

We report severe bleaching in a turbid water coral community in north-western Australia. Towed still imagery was used for a benthic survey near Onslow in March 2013 to assess thermal stress in hard and soft corals, finding 51–68% of all corals fully bleached in 10–15-m water depth. Tabulate or foliaceous Turbinaria was the locally most abundant hard coral (46%), followed by massives such as faviids and poritids (25%) and encrusting coral (12%), thus over 80% of the local corals could be considered to be bleaching resistant. All coral groups were bleached in similar proportions (massive hard corals 51%<soft corals 60%<encrusting hard corals 62%<Turbinaria 62%<‘others’ 68%). NOAA data and environmental assessments suggest previous recurrent thermal stress throughout the last 10 years in the study area. On the basis of these records this stress apparently changed the community structure from bleaching vulnerable species such as Acropora, leaving more tolerant species, and reduced coral cover. We could see no evidence for adaptation or acclimation of corals in this area. Towed still imagery was found to be a suitable means for rapid and large-scale bleaching studies in shallow, turbid areas where diving can be difficult or impossible.

scholarly journals Large‐scale eDNA metabarcoding survey reveals marine biogeographic break and transitions over tropical north‐western Australia

2021 ◽  
Author(s):  
Katrina West ◽  
Michael J. Travers ◽  
Michael Stat ◽  
Euan S. Harvey ◽  
Zoe T. Richards ◽  
...  
Keyword(s):  
Western Australia ◽  
Large Scale ◽  
North Western

scholarly journals Climate Change Induced Thermal Stress Caused Recurrent Coral Bleaching over Gulf of Kachchh and Malvan Marine Sanctuary, West Coast of India

2021 ◽  
Author(s):  
Mohit Arora ◽  
Kalyan De ◽  
Nandini Ray Chaudhury ◽  
Mandar Nanajkar ◽  
Prakash Chauhan ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Coral Reef ◽  
Coral Reefs ◽  
Coral Bleaching ◽  
Large Scale ◽  
Heat Waves ◽  
Southern Oscillation ◽  
Coral Cover ◽  
Imminent Threat ◽  
Marginal Reefs

Coral reefs are one of the most sensitive, productive, and invaluable biological resources on the earth. However, coral reefs are facing unprecedented stress due to ongoing climate changes and intensified anthropogenic disturbances globally. Elevated Sea Surface Temperature (SST) has emerged as the most imminent threat to the thermos-sensitive reef-building corals. The 2010–2014-2016 El Niño Southern Oscillation (ENSO) caused prolonged marine heat waves (MHWs) that led to the most widespread coral bleaching and mortality in the tropical Indi-Pacific regions. Coral bleaching prediction is vital for the management of the reef biodiversity, ecosystem functioning, and services. Recent decades, satellite remote sensing has emerged as a convenient tool for large-scale coral reef monitoring programs. As thermal stress is a critical physical attribute for coral bleaching hence, the present study examines the effectiveness of the elevated SSTs as a proxy to predict coral bleaching in shallow water marginal reefs. Advanced Very High-Resolution Radiometer (AVHRR) satellite data from the NOAA Coral Reef Watch’s (CRW) platform has been used for this study. Coral bleaching indices like Bleaching Threshold (BT), Positive SST Anomaly (PA), and Degree Heating Weeks (DHW) are computed to analyze the thermal stress on the coral reefs. The computed thermal stress from satellite-derived SST data over regions concurrence with the mass coral bleaching (MCB) events. This study concludes that in the last decades (2010 to 2019) the coral cover around these regions has dramatically declined due to higher SST, which indicates that the thermal stress induced recurrent bleaching events attributed to the coral loss.

scholarly journals Coral community bleaching response on a highly urbanised reef

2014 ◽  
Author(s):  
James R Guest ◽  
Jeffrey Low ◽  
Karenne Tun ◽  
Jani I Tanzil ◽  
Peter A Todd ◽  
...  
Keyword(s):  
Community Structure ◽  
Thermal Stress ◽  
Anthropogenic Impacts ◽  
Coral Cover ◽  
Regional Scale ◽  
Coral Community ◽  
Bleaching Response ◽  
Sea Surface Temperature Anomalies ◽  
Relative Cover ◽  
June July

Projected increases in the magnitude and frequency of sea surface temperature anomalies present a significant threat to the persistence of tropical coral reefs, however, detailed studies of community level responses to thermal stress are needed if its effect on reef resilience are to be understood. While many studies report on broad, regional scale responses to thermal stress (e.g., proportion of corals bleached), far fewer examine variation in susceptibility among taxa and change in coral community structure, before, during and after bleaching on individual reefs. Furthermore, relatively few studies of bleaching response come from highly urbanised reefs that experience chronic disturbances such as elevated sedimentation and turbidity. Here we report in detail on the bleaching response of corals at a highly urbanised reef site south of mainland Singapore during (June, July) and immediately after (October) a major thermal coral bleaching event in 2010. To estimate the capacity for resistance and resilience to thermal stress, we report on a) the overall bleaching severity during and after the event, b) differences in bleaching susceptibility among taxa during the event and c) the response of the reef in terms of taxonomic community structure before (2009) and after (2012) bleaching. Despite severe bleaching in 2010 (66% of colonies bleached), post-bleaching recovery appeared to be relatively rapid and coral taxa that are usually highly susceptible (e.g., Acropora and Pocillopora) were relatively unaffected, i.e., either they did not bleach or they bleached and recovered. Although there was no significant change in coral taxonomic community structure among years, taxa that bleached most severely tended to have the greatest reductions in relative cover. Several factors may have contributed to the overall high resistance of this site to bleaching including turbidity, symbiont affiliation and heterotrophy. A parsimonious explanation for the reversed pattern of bleaching susceptibility among taxa is that these coral populations have adapted and/or acclimatised to thermal stress. Despite ongoing chronic anthropogenic impacts, we suggest that this site has potential for rapid recovery of coral cover due to the dominant coral taxa and growth forms being capable of rapid regrowth from remnant colonies.

Domination of mesophotic ecosystems in the Wakatobi Marine National Park (Indonesia) by sponges, soft corals and other non-hard coral species

2018 ◽  
Vol 99 (4) ◽  
pp. 771-775 ◽  
Author(s):  
J.J. Bell ◽  
J. Jompa ◽  
A. Haris ◽  
S. Werorilangi ◽  
M. Shaffer ◽  
...  
Keyword(s):  
National Park ◽  
Coral Species ◽  
Coral Cover ◽  
Coral Triangle ◽  
Light Penetration ◽  
Soft Corals ◽  
Hard Coral ◽  
Reduced Light ◽  
Encrusting Organisms ◽  
Water Coral

AbstractMesophotic ecosystems have been relatively poorly studied in the Indo-Pacific and in particular within the Coral Triangle region. Here we used a mini-ROV to explore the changes in major benthic groups at two sites (~200 m apart) in the Wakatobi Marine National Park, SE Sulawesi, Indonesia spanning shallow water coral reefs (5 m) to deeper water mesophotic ecosystems (80 m). We found very similar patterns at both sites where coral cover peaked at 15 m, declined rapidly by 30 m, and was virtually absent at 50 m. As coral declined there was a marked increase in sponges, soft corals and other encrusting organisms (including ascidians, bryozoans, tubeworms, gorgonians and molluscs). Importantly, our results differ from most previous studies in other geographic locations where hard corals extend much deeper. It is unclear what drives this difference but it may be related to higher levels of turbidity and therefore reduced light penetration in the Wakatobi compared with other areas, which limits the vertical extent of coral development.

Seasonal occurrence, distribution and movements of the whale shark, Rhincodon typus, at Ningaloo Reef, Western Australia

1996 ◽  
Vol 47 (4) ◽  
pp. 637 ◽  
Author(s):  
JG Taylor
Keyword(s):  
Western Australia ◽  
Whale Shark ◽  
Gastropod Mollusc ◽  
Leeuwin Current ◽  
Mass Spawning ◽  
Ningaloo Reef ◽  
Turbid Waters ◽  
Large Numbers ◽  
Whale Sharks ◽  
North Western

Aerial surveys between 1989 and 1992 demonstrated that large numbers of whale sharks appear on Ningaloo Reef in north-western Australia during autumn, shortly after the coral has undergone mass spawning. This movement into the reef waters would allow whale sharks to capitalize on the increased production of zooplankton brought about as a result of this mass spawning of corals and other marine organisms. Sharks occupied mainly the relatively turbid waters on the reef front, where a northerly current prevailed, rather than the offshore, warmer waters of the southerly flowing Leeuwin Current. The sharks moved in to the reef front from offshore but, once inshore, the majority swam parallel to the reef. The maximum density in any sector of the reef at any one time was four sharks per km, recorded in May 1992. The longer the time since sharks first appeared on the reef, the greater was their tendency to aggregate in a particular region of the reef. Evidence is presented that indicates that whale shark numbers at the northern end of Ningaloo Reef declined during the latter half of the 1980s; this decline may be related to the massive destruction of coral by the gastropod mollusc Drupella cornus during this period.

scholarly journals Comparison of Standard Caribbean Coral Reef Monitoring Protocols and Underwater Digital Photogrammetry to Characterize Hard Coral Species Composition, Abundance and Cover

2021 ◽  
Vol 8 ◽  
Author(s):  
Erick Barrera-Falcon ◽  
Rodolfo Rioja-Nieto ◽  
Roberto C. Hernández-Landa ◽  
Edgar Torres-Irineo
Keyword(s):  
Coral Reefs ◽  
New Technologies ◽  
Coral Cover ◽  
Coral Community ◽  
Caribbean Region ◽  
Digital Photogrammetry ◽  
Hard Coral ◽  
Coral Communities ◽  
Caribbean Coral Reef ◽  
Monitoring Protocols

The precise assessing and monitoring of coral reefs are necessary to address and understand the threats and changes in coral communities. With the development of new technologies and algorithms for image processing, new protocols like underwater photogrammetry are implemented to study these ecosystems. This study compares the main ecological metrics for reef condition assessment, obtained with an underwater digital photogrammetry protocol (UWP) and traditional sampling design simulations in coral reefs of the Cozumel Reefs National Park. Three orthomosaics (380 m2) per reef on six fringing reefs were constructed, and the hard coral community characterized using a Geographic Information System (GIS). The orthomosaics were also used as a basis to simulate transect lines and obtain data on the hard coral community according to the video transect (VT) protocol, point intercept (PIT) protocol, and the Atlantic and Gulf Rapid Reef Assessment (AGRRA) protocol. Higher colony abundance, species richness, and lower coral cover estimates (p &lt; 0.05) were obtained with the UWP. This protocol was also sensitive to small sized species. All the sampling designs showed similar capability to identify dominant species in terms of colony abundance and coral cover. The VT, PIT, and AGGRA showed similar coral cover values (p &gt; 0.05), which seems to indicate that these sampling designs overestimate this important metric. Our results will help to understand and integrate the observations obtained with UWP with long-term data obtained with commonly used monitoring protocols in the Caribbean region.

Coral recovery at Aldabra Atoll, Seychelles: five years after the 1998 bleaching event

2005 ◽  
Vol 363 (1826) ◽  
pp. 251-255 ◽  
Author(s):  
Ben Stobart ◽  
Kristian Teleki ◽  
Raymond Buckley ◽  
Nigel Downing ◽  
Martin Callow
Keyword(s):  
Large Scale ◽  
Considerable Increase ◽  
Coral Cover ◽  
Method Comparison ◽  
Research Programme ◽  
Coralline Algae ◽  
Maximum Diameter ◽  
Bleaching Event ◽  
Hard Coral ◽  
Coral Recovery

Changes in reef benthos were assessed at Aldabra Atoll following the mass coral bleaching event of 1998. Video transects were used to survey the benthos and analysed using the Australian Institute of Marine Science five–dot method. Comparison of coral cover data collected by the Cambridge Southern Seychelles Atoll Research Programme with data collected during this study revealed that mortality of coral at Aldabra following the bleaching event was approximately 66% at 10 m depth and 38% at 20 m depth. Five years on, there are signs of hard coral recovery at some locations, but in spite of several years of high coral recruitment (7–9 recruits per m 2 at 10 m depth, 4–6 recruits per m 2 at 20 m depth, where recruits are defined as any colony under 5 cm maximum diameter), recovery of hard coral has not occurred at a significant level. There has been a considerable increase in soft coral cover at some locations, which was dominated by the genus Rhytisma . Macro algal cover did not increase following the bleaching event, although, as would be expected, dead corals have been colonized by coralline algae. There have been no further events leading to large–scale coral mortality at Aldabra since 1998.

scholarly journals POLLUTION OF COASTAL AREAS OF JAKARTA BAY: WATER QUALITY AND BIOLOGICAL RESPONSES

2018 ◽  
Vol 43 (1) ◽  
pp. 37-51 ◽  
Author(s):  
Andreas Kunzmann ◽  
Zainal Arifin ◽  
Gunilla Baum
Keyword(s):  
Water Quality ◽  
Elevated Temperature ◽  
Coral Reefs ◽  
Large Scale ◽  
Coral Cover ◽  
Marine Conservation ◽  
Coastal Development ◽  
Anthropogenic Pressure ◽  
Soft Corals ◽  
Thousand Islands

Coastal development, growing urbanization and industrialization are the most important stressors of coral reefs worldwide. Jakarta is one of the largest megacities worldwide. The coral reefs of the Thousand Islands north of Jakarta have degraded dramatically over the last 30-40 years. While large-scale gradients (i.e., regional drivers) have been extensively studied and shown shifts and declines in coral cover and composition, local drivers and their impact on spatial community composition have been neglected. The aim of our study is to investigate the spatial impact of anthropogenic stressors on local and regional scales on coral reefs north of Jakarta. Our results demonstrate that reefs in the north of the Thousand Islands are separated from the reefs in Jakarta Bay (JB), where a direct impact of Jakarta can be seen. Local anthropogenic effects rather than regional gradients have shaped a spatial patchwork of differentially degraded reefs along the nearshore islands. The main anthropogenic stressor is pollution and sedimentation rate, NO2, PO4 and chlorophyll-a explain over 80% of the variation. Surfactants and diesel-borne compounds from sewage and bilge water discharges are common pollutants. Responses to combinations of selected pollutant with elevated temperature (+3°C) were determined in the metabolic performance of the coral reef fish Siganus guttatus. During combined exposure, metabolic depression was observed. Effects of pollutants were not amplified by elevated temperature. In a study about two dominant soft coral genera, Sarcophyton spp. and Nephthea spp., on dissolved inorganic nutrients (DIN), turbidity (NTU), and sedimentation combined with measurements of photosynthetic yield and respiratory electron system (ETS) activity water quality seems to control the relative abundance and physiology of dominant soft corals in JB. In order to reverse or prevent phase shifts from hard to soft corals, there is a need to manage the water quality better. It is concluded that the intense anthropogenic pressure from local as well as regional sources is responsible for the spatial structure and health of reefs. Therefore, improved spatial management with a focus on both local and regional stressors is needed for effective marine conservation.

scholarly journals Recurrent coral bleaching in north-western Australia and associated declines in coral cover

2020 ◽  
Author(s):  
R. C. Babcock ◽  
D. P. Thomson ◽  
M. D. E. Haywood ◽  
M. A. Vanderklift ◽  
R. Pillans ◽  
...  
Keyword(s):  
Western Australia ◽  
Coral Bleaching ◽  
Coral Cover ◽  
North Western

scholarly journals Rapid increase in coral cover on an isolated coral reef, the Ashmore Reef National Nature Reserve, north-western Australia

2011 ◽  
Vol 62 (10) ◽  
pp. 1214 ◽  
Author(s):  
D. M. Ceccarelli ◽  
Z. T. Richards ◽  
M. S. Pratchett ◽  
C. Cvitanovic
Keyword(s):  
Coral Reef ◽  
Western Australia ◽  
Coral Cover ◽  
Taxonomic Composition ◽  
Coastal Pollution ◽  
Percent Cover ◽  
Community Recovery ◽  
Coral Communities ◽  
Coral Recovery ◽  
North Western

Against a background of coral reef ecosystem decline, understanding the propensity for coral communities to recover after acute disturbances is fundamental to forecasting and maintaining resilience. It may be expected that offshore reef ecosystems are less affected by anthropogenic disturbances compared with reefs closer to population centres, but that recovery may be slower on isolated reefs following disturbances. To test the hypothesis that community recovery is slow in isolated locations, we measured changes in coral cover and relative abundance of coral genera over a 4 year period (2005–09) at Ashmore Reef, north Western Australia, following severe bleaching. The percent cover of hard coral tripled, from 10.2% (±1.46 s.e.) in 2005 to 29.4% (±1.83 s.e.) in 2009 in all habitats (exposed and lagoonal) and depth zones (2–5 and 8–10 m), and the percent cover of soft corals doubled, from 4.5% (+0.63 s.e.) in 2005 to 8.3% (+1.4 s.e.) in 2009. Significant shifts in the taxonomic composition of hard corals were detected. Our results imply that coral recovery in isolated locations can occur rapidly after an initial delay in recruitment, presumably through the interacting effects of self-recruitment and reduced exposure to additive impacts such as coastal pollution.

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