Assessment of coral cover on Maldivian reefs after the 1998 bleaching event and 2004 tsunami

AbstractScleractinian corals are engineers on coral reefs that provide both structural complexity as habitat and sustenance for other reef-associated organisms via the release of organic and inorganic matter. However, coral reefs are facing multiple pressures from climate change and other stressors, which can result in mass coral bleaching and mortality events. Mass mortality of corals results in enhanced release of organic matter, which can cause significant alterations to reef biochemical and recycling processes. There is little known about how long these nutrients are retained within the system, for instance, within the tissues of other benthic organisms. We investigated changes in nitrogen isotopic signatures (δ15N) of macroalgal tissues (a) ~ 1 year after a bleaching event in the Seychelles and (b) ~ 3 months after the peak of a bleaching event in Mo’orea, French Polynesia. In the Seychelles, there was a strong association between absolute loss in both total coral cover and branching coral cover and absolute increase in macroalgal δ15N between 2014 and 2017 (adjusted r2 = 0.79, p = 0.004 and adjusted r2 = 0.86, p = 0.002, respectively). In Mo’orea, a short-term transplant experiment found a significant increase in δ15N in Sargassum mangarevense after specimens were deployed on a reef with high coral mortality for ~ 3 weeks (p < 0.05). We suggest that coral-derived nutrients can be retained within reef nutrient cycles, and that this can affect other reef-associated organisms over both short- and long-term periods, especially opportunistic species such as macroalgae. These species could therefore proliferate on reefs that have experienced mass mortality events, because they have been provided with both space and nutrient subsidies by the death and decay of corals.

Download Full-text

Assessing population collapse of Drupella spp. (Mollusca: Gastropoda) 2 years after a coral bleaching event in the Republic of Maldives

Hydrobiologia ◽

10.1007/s10750-021-04546-5 ◽

2021 ◽

Author(s):

L. Saponari ◽

I. Dehnert ◽

P. Galli ◽

S. Montano

Keyword(s):

Coral Bleaching ◽

Prey Availability ◽

Coral Cover ◽

Environmental Data ◽

High Plasticity ◽

Bleaching Event ◽

Coral Recovery ◽

The Republic ◽

The Impact ◽

Line Intercept

AbstractCorallivory causes considerable damage to coral reefs and can exacerbate other disturbances. Among coral predators, Drupella spp. are considered as delayer of coral recovery in the Republic of Maldives, although little information is available on their ecology. Thus, we aimed to assess their population structure, feeding behaviour and spatial distribution around 2 years after a coral bleaching event in 2016. Biological and environmental data were collected using belt and line intercept transects in six shallow reefs in Maldives. The snails occurred in aggregations with a maximum of 62 individuals and exhibited a preference for branching corals. Yet, the gastropods showed a high plasticity in adapting feeding preferences to prey availability. Drupella spp. were homogenously distributed in the study area with an average of 9.04 ± 19.72 ind/200 m2. However, their occurrence was significantly different at the reef scale with the highest densities found in locations with higher coral cover. The impact of Drupella spp. appeared to be minimal with the population suffering from the loss of coral cover. We suggest that monitoring programs collect temporal- and spatial-scale data on non-outbreaking populations or non-aggregating populations to understand the dynamics of predation related to the co-occurrence of anthropogenic and natural impacts.

Download Full-text

Species identity and depth predict bleaching severity in reef-building corals: shall the deep inherit the reef?

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.1551 ◽

2017 ◽

Vol 284 (1864) ◽

pp. 20171551 ◽

Cited By ~ 46

Author(s):

Paul R. Muir ◽

Paul A. Marshall ◽

Ameer Abdulla ◽

J. David Aguirre

Keyword(s):

Coral Cover ◽

Extinction Risk ◽

Species Level ◽

Population Recovery ◽

Bleaching Event ◽

Species Identity ◽

Resistant Species ◽

Repeated Events ◽

Coral Reef Ecosystems ◽

Reef Recovery

Mass bleaching associated with unusually high sea temperatures represents one of the greatest threats to corals and coral reef ecosystems. Deeper reef areas are hypothesized as potential refugia, but the susceptibility of Scleractinian species over depth has not been quantified. During the most severe bleaching event on record, we found up to 83% of coral cover severely affected on Maldivian reefs at a depth of 3–5 m, but significantly reduced effects at 24–30 m. Analysis of 153 species' responses showed depth, shading and species identity had strong, significant effects on susceptibility. Overall, 73.3% of the shallow-reef assemblage had individuals at a depth of 24–30 m with reduced effects, potentially mitigating local extinction and providing a source of recruits for population recovery. Although susceptibility was phylogenetically constrained, species-level effects caused most lineages to contain some partially resistant species. Many genera showed wide variation between species, including Acropora, previously considered highly susceptible. Extinction risk estimates showed species and lineages of concern and those likely to dominate following repeated events. Our results show that deeper reef areas provide refuge for a large proportion of Scleractinian species during severe bleaching events and that the deepest occurring individuals of each population have the greatest potential to survive and drive reef recovery.

Download Full-text

Early trajectories of benthic coral reef communities following the 2015/16 coral bleaching event at remote Aldabra Atoll, Seychelles

Scientific Reports ◽

10.1038/s41598-020-74077-x ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Anna Koester ◽

Valentina Migani ◽

Nancy Bunbury ◽

Amanda Ford ◽

Cheryl Sanchez ◽

...

Keyword(s):

Coral Reef ◽

Water Temperature ◽

Coral Bleaching ◽

Coral Cover ◽

Bleaching Event ◽

Hard Coral ◽

Reef Communities ◽

Remote Sites ◽

Hard Coral Cover ◽

Coral Reef Communities

Abstract Documenting post-bleaching trajectories of coral reef communities is crucial to understand their resilience to climate change. We investigated reef community changes following the 2015/16 bleaching event at Aldabra Atoll, where direct human impact is minimal. We combined benthic data collected pre- (2014) and post-bleaching (2016–2019) at 12 sites across three locations (lagoon, 2 m depth; seaward west and east, 5 and 15 m depth) with water temperature measurements. While seaward reefs experienced relative hard coral reductions of 51–62%, lagoonal coral loss was lower (− 34%), probably due to three-fold higher daily water temperature variability there. Between 2016 and 2019, hard coral cover did not change on deep reefs which remained dominated by turf algae and Halimeda, but absolute cover on shallow reefs increased annually by 1.3% (east), 2.3% (west) and 3.0% (lagoon), reaching, respectively, 54%, 68% and 93% of the pre-bleaching cover in 2019. Full recovery at the shallow seaward locations may take at least five more years, but remains uncertain for the deeper reefs. The expected increase in frequency and severity of coral bleaching events is likely to make even rapid recovery as observed in Aldabra’s lagoon too slow to prevent long-term reef degradation, even at remote sites.

Download Full-text

Wave exposure shapes reef community composition and recovery trajectories at a remote coral atoll

Coral Reefs ◽

10.1007/s00338-021-02184-w ◽

2021 ◽

Author(s):

Ines D. Lange ◽

Cassandra E. Benkwitt ◽

Jamie M. McDevitt-Irwin ◽

Kristina L. Tietjen ◽

Brett Taylor ◽

...

Keyword(s):

Community Composition ◽

Benthic Community ◽

Coral Cover ◽

Principal Component ◽

Wave Exposure ◽

Ecological Change ◽

Live Coral ◽

Bleaching Event ◽

Community Patterns ◽

Similar Survey

AbstractIn a time of unprecedented ecological change, understanding natural biophysical relationships between reef resilience and physical drivers is of increasing importance. This study evaluates how wave forcing structures coral reef benthic community composition and recovery trajectories after the major 2015/2016 bleaching event in the remote Chagos Archipelago, Indian Ocean. Benthic cover and substrate rugosity were quantified from digital imagery at 23 fore reef sites around a small coral atoll (Salomon) in 2020 and compared to data from a similar survey in 2006 and opportunistic surveys in intermediate years. Cluster analysis and principal component analysis show strong separation of community composition between exposed (modelled wave exposure > 1000 J m−3) and sheltered sites (< 1000 J m−3) in 2020. This difference is driven by relatively high cover of Porites sp., other massive corals, encrusting corals, soft corals, rubble and dead table corals at sheltered sites versus high cover of pavement and sponges at exposed sites. Total coral cover and rugosity were also higher at sheltered sites. Adding data from previous years shows benthic community shifts from distinct exposure-driven assemblages and high live coral cover in 2006 towards bare pavement, dead Acropora tables and rubble after the 2015/2016 bleaching event. The subsequent recovery trajectories at sheltered and exposed sites are surprisingly parallel and lead communities towards their respective pre-bleaching communities. These results demonstrate that in the absence of human stressors, community patterns on fore reefs are strongly controlled by wave exposure, even during and after widespread coral loss from bleaching events.

Download Full-text

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

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2004.1490 ◽

2005 ◽

Vol 363 (1826) ◽

pp. 251-255 ◽

Cited By ~ 38

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.

Download Full-text

The mortality, recovery, and community shifts of scleractinian corals in Puerto Rico one decade after the 2005 regional bleaching event

10.7287/peerj.preprints.2898v1 ◽

2017 ◽

Author(s):

Jorge R García-Sais ◽

Stacey M Williams ◽

Ali Amirrezvani

Keyword(s):

Puerto Rico ◽

Coral Cover ◽

Light Attenuation ◽

Coral Community ◽

Scleractinian Corals ◽

Partial Recovery ◽

Bleaching Event ◽

Before And After ◽

Coral Recovery ◽

And Shifts

This work analyzes the mortality, recovery, and shifts in the composition of scleractinian corals in Puerto Rico one decade after the 2005 regional coral bleaching event. Temporal and spatial patterns of coral community structure were examined using a stratified, non-random sampling approach based on five permanent transects per reef at 16 reef stations. A negative correlation between percent coral cover loss and light attenuation coefficient (Kd490) was observed, suggesting that water turbidity played a major role in coral protection during the bleaching event (“sunblock effect”). Loss of coral cover after the bleaching event was lower at nearshore reefs, and with increasing depth at oceanic and shelf-edge reefs. By 2015, coral recovery was observed at all reefs surveyed, but coastal reefs exhibited a higher rate of recovery. The responses of coral assemblages varied after the bleaching event, including shifts in cover from massive corals (Orbicella spp.) to turf algae and/or by opportunistic (Porites astreoides) and branching corals (Madracis auretenra, P. porites); partial recovery by O. annularis complex; and no measurable change in coral assemblages before and after the event.

Download Full-text

The mortality, recovery, and community shifts of scleractinian corals in Puerto Rico one decade after the 2005 regional bleaching event

10.7287/peerj.preprints.2898 ◽

2017 ◽

Author(s):

Jorge R García-Sais ◽

Stacey M Williams ◽

Ali Amirrezvani

Keyword(s):

Puerto Rico ◽

Coral Cover ◽

Light Attenuation ◽

Coral Community ◽

Scleractinian Corals ◽

Partial Recovery ◽

Bleaching Event ◽

Before And After ◽

Coral Recovery ◽

And Shifts

This work analyzes the mortality, recovery, and shifts in the composition of scleractinian corals in Puerto Rico one decade after the 2005 regional coral bleaching event. Temporal and spatial patterns of coral community structure were examined using a stratified, non-random sampling approach based on five permanent transects per reef at 16 reef stations. A negative correlation between percent coral cover loss and light attenuation coefficient (Kd490) was observed, suggesting that water turbidity played a major role in coral protection during the bleaching event (“sunblock effect”). Loss of coral cover after the bleaching event was lower at nearshore reefs, and with increasing depth at oceanic and shelf-edge reefs. By 2015, coral recovery was observed at all reefs surveyed, but coastal reefs exhibited a higher rate of recovery. The responses of coral assemblages varied after the bleaching event, including shifts in cover from massive corals (Orbicella spp.) to turf algae and/or by opportunistic (Porites astreoides) and branching corals (Madracis auretenra, P. porites); partial recovery by O. annularis complex; and no measurable change in coral assemblages before and after the event.

Download Full-text

Prey selection of corallivorous muricids at Koh Tao (Gulf of Thailand) four years after a major coral bleaching event

Contributions to Zoology ◽

10.1163/18759866-08503003 ◽

2016 ◽

Vol 85 (3) ◽

pp. 291-309 ◽

Cited By ~ 14

Author(s):

Michelangelo S. Moerland ◽

Chad M. Scott ◽

Bert W. Hoeksema

Keyword(s):

Coral Bleaching ◽

Resource Selection ◽

Prey Availability ◽

Prey Selection ◽

Coral Cover ◽

Coral Community ◽

Live Coral ◽

Bleaching Event ◽

Major Outbreak ◽

Depth Ranges

Corallivorous Drupella (Muricidae) snails at Koh Tao are reported to have extended their range of prey species following a major coral bleaching event in 2010. Populations of their preferred Acropora prey had locally diminished in both size and abundance, and the snails had introduced free-living mushroom corals in their diet. Although the coral community largely recovered, the Drupella population grew and reached outbreak proportions. For this study, corallivorous muricids at Koh Tao were studied more intensively to examine their identities, distribution and prey choice four years after the bleaching event. Drupella rugosa was identified as the major outbreak species and occurred at densities > 3 m-2 in depth ranges of 2-5 and 5-8 m. The density of D. rugosa was related to the live coral cover, Acropora colony density, and depth. Resource selection ratios revealed that species of Acropora, Psammocora and Pavona corals were attacked more frequently than would be expected based on their availability. Strikingly, fungiid corals were now avoided as prey in the recovered coral community, despite them being part of the preferred diet directly after the bleaching. Although D. rugosa showed a clear prey preference, it appears to be plastic by changing with prey availability. The muricids Drupella margariticola and Morula spinosa occurred in much lower densities and were less often associated with corals. Snails of the opportunistic corallivore D. margariticola usually co-occurred in D. rugosa aggregations, although they also formed feeding aggregations by themselves. Whether M. spinosa generally associates with corals as a corallivore or a scavenger has yet to be determined. Molecular analyses did not reveal cryptic speciation among snails sampled from different coral hosts and also no geographic variation. The present study also showed that corallivory is more common among D. margariticola and M. spinosa than previously known.

Download Full-text

MONITORING CORAL RECOVERY AT NEARSHORE CORAL REEFS IN PHANGNGA PROVINCE, THE ANDAMAN SEA FOLLOWING THE 2010 CORAL BLEACHING EVENT

Proceedings of International Conference "Managinag risks to coastal regions and communities in a changinag world" (EMECS'11 - SeaCoasts XXVI) ◽

10.31519/conferencearticle_5b1b936dde9b43.46989412 ◽

2017 ◽

Author(s):

Makamas Sutthacheep ◽

Thamasak Yeemin ◽

Sittiporn Pengsakun ◽

...

Keyword(s):

Coral Reef ◽

Coral Reefs ◽

Coral Bleaching ◽

Coral Cover ◽

Global Climate ◽

Andaman Sea ◽

Live Coral ◽

Bleaching Event ◽

Sea Star ◽

Coral Recovery

Mass bleaching and subsequent mortality of scleractinian corals in response to elevated seawater temperatures has been considered as one of the most impacts of global climate change. Three extensive coral bleaching events in the Andaman Sea were reported, in the years 1991, 1995 and 2010. Studies on survival of coral colonies, coral recruitment and community structure of coral reef associated macrofauna would predict the trends for coral recovery from the impacts of coral bleaching events. The present study aimed to examine the status of coral communities, density of coral recruits and coral reef associated macrofauna at nearshore coral reefs in Phangnga Province, the Andaman Sea following the 2010 coral bleaching event. The dead coral cover was high (>50%) while the live coral cover was in the range of 13-21%. There was high diversity of coral recruits on natural substrates. The average densities of macrobenthic fauna varied from 1.9 to 2.6 individuals.m-2, with significant differences among study sites. The dominant macrobenthic species were a soft coral (Lobophytum sp.), a sea star (Linckia laevigata) and a sea urchin (Echinostrephus molaris). Coral recovery at these coral reefs would be possible but local anthropogenic stressors must be overwhelmingly reduced in order to enhance coral reef resilience. The long-term monitoring programs in the Andaman Sea are required for decision makers to support their adaptive management approaches.

Download Full-text