Oceanic patterns of thermal stress and coral community degradation on the island of Mauritius

McClanahan, Tim R.; Muthiga, Nyawira A.

doi:10.1007/s00338-020-02015-4

Cited by 17 publications

(18 citation statements)

References 75 publications

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“…Previous bleaching index assessments in 2005 at sites spanning the same reefs we assessed, recorded indexes ranging from 11-30, with an average of 17 [24]. This was during an anomalously warm period in the region when temperatures peaked at 28 • C at Two-mile Reef, and followed an unusually large temperature change on 26th December when temperatures rose from 18.3 to 25.1 • C over 33 h. The peak bleaching index we measured also corresponds with subsequent surveys by McClanahan and Muthiga (2021) [27] in Mauritius in 2019, which averaged 17 and ranged between 0 and 56 depending on the site.…”

Section: Coral Bleachingsupporting

confidence: 76%

“…Alveopora was also previously noted to undergo relatively high levels of bleaching in the region by Celliers and Schleyer (2002) [21] but we did not find this during the most recent surveys. Similar inconsistencies in bleaching index among coral taxa over different time periods have been found in Mauritius between 2004 and 2019 [27]. Such inconsistencies in bleaching index among genera exposed to different levels of thermal stress over varying timescales may be due to different taxon-specific non-linear responses and threshold effects.…”

Section: Coral Bleachingmentioning

confidence: 51%

“…Furthermore, reefs in the Northern Complex are furthest from the shelf edge and submarine canyons relative to reefs further south, and are likely to experience reduced canyon-induced upwelling and cooling effects, making them potentially more vulnerable to bleaching [14]. Understanding the responses of high-latitude coral communities to thermal stress driven by climate change will provide an indication of their ecological resilience and be important in predicting their future and potential for range expansion [27].…”

Section: Introductionmentioning

confidence: 99%

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The Third Global Coral Bleaching Event on the Marginal Coral Reefs of the Southwestern Indian Ocean and Factors That Contribute to Their Resistance and Resilience

2021

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Coral reefs reach their southernmost limits in the southwestern Indian Ocean in Maputaland, South Africa. Here, we investigate the recent global coral bleaching event of 2016, the thermal dynamics of these marginal high-latitude reefs and the potential environmental factors regulating the responses of coral communities. Pre-, peak- and post-bleaching surveys of over 9850 coral colonies from 29 genera were undertaken over 3 years across 14 sites spanning 120 km of coastline using point-intercept and visual bleaching index survey methodologies. Bleaching data were related to several environmental variables including temperature, degree heating weeks (DHW), depth, latitude, and upwelling intensity. These reefs have experienced a history of relatively low thermal stress based on DHW. Long-term in situ temperature records nevertheless showed no obvious trend of increase. In situ temperatures also displayed poor relationships, with temperatures predicted by the Representative Concentration Pathway models. Mild coral bleaching with no significant mortality was recorded across sites with taxon-specific bleaching responses evident. Latitude and cumulative daily DHW were significantly related to the bleaching index whereas depth and interactions of depth with latitude and DHW were not. While upwelling of cooler water may offer some refuge to coral communities, especially in the Central and Southern Reef Complexes where it is more pronounced, this may only be transient as the upwelled water may also experience some degree of warming in future, thereby limiting such protection from global warming.

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Section: Coral Bleachingsupporting

confidence: 76%

Section: Coral Bleachingmentioning

confidence: 51%

Section: Introductionmentioning

confidence: 99%

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The Third Global Coral Bleaching Event on the Marginal Coral Reefs of the Southwestern Indian Ocean and Factors That Contribute to Their Resistance and Resilience

2021

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“…We investigated these issues by surveying predation occurring on corals in the lagoon of Mauritius, an area known to contain abundant Stegastes spp. and subject to anthropogenic and climate-related stressors, causing loss of coral cover and biodiversity (Bhagooli and Kaullysing 2019;McClanahan and Muthiga 2020). Specifically, we quantified the extent of predation received by wild-occurring and outplanted Porites lutea in the absence of Stegastes spp.…”

Section: Introductionmentioning

confidence: 99%

Outplanting of branching Acropora enhances recolonization of a fish species and protects massive corals from predation

et al. 2021

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Damselfish of the genus Stegastes inhabit territories and cultivate algal gardens on branching corals of the genus Acropora, aggressively protecting their territories from other fish and preventing predation upon corals within the territory. This behaviour has important ecological impacts and could also be useful in reducing predation on outplanted corals during reef restoration efforts. However, the degree of protection from predators may depend on the ability of Stegastes spp. to recolonise outplanted or newly established coral colonies. Protection of bleaching-resilient massive corals within territories may be of particular importance due to the role of these corals in maintaining coral cover following bleaching events. This study examined whether the presence of Stegastes spp. reduces predation on the massive bleaching-resilient coral Porites lutea in the Mauritian lagoon, and whether Stegastes spp. readily colonise outplanted branching coral fragments and provide adjacent massive corals with indirect protection from predation. Predation levels on wild-occurring and outplanted P. lutea within and outside Stegastes spp. territories were measured. In addition, Acropora muricata branches were outplanted adjacent to wild P. lutea colonies outside Stegastes spp. territories, and recolonisation of these outplants by Stegastes spp. and the impacts of recolonisation on predation were monitored. Both wild and outplanted P. lutea colonies within Stegastes spp. territories sustained less predation damage compared to colonies outside territories. Stegastes spp. recolonized outplanted A. muricata colonies within six months of outplanting, and in doing so returned predation protection to adjacent P. lutea colonies. The ability of Stegastes spp. to colonise outplanted corals and provide indirect protection to adjacent massive bleaching-resilient corals may inform coral outplanting efforts in systems where Stegastes spp. are common. Encouraging Stegastes spp. recolonisation may help to reduce predation damage to corals within territories and potentially improve the success of rehabilitation efforts.

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“…Because of the multiple local human and climate change-driven impacts, some predictions suggest that reef corals of Mauritius might face local "extinction dates" between 2025 and 2070, depending on level of adaptation of corals and the shifting thermal limits of bleaching (Bhagooli & Sheppard, 2012). A recent study found that nearly a third of studied coral taxa have already declined greatly, associated with repeated thermal stresses since 2004 (McClanahan & Muthiga, 2021). Three nonendemic coral taxa were found, for example, to potentially be locally extinct.…”

Section: Coral Reef Endemismmentioning

confidence: 99%

Rare coral and reef fish species status, possible extinctions, and associated environmental perceptions in Mauritius

McClanahan

MUNBODHE

Naggea

et al. 2021

Conservat Sci and Prac

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Mauritius is reported to have the highest marine species endemism in the Western Indian Ocean faunal Province but the status of these species has not been evaluated. To address this knowledge gap, 119 reef sites were sampled to evaluate populations of 16 species of rare and endemic reef fish and corals using scuba-based surveys conducted by citizen scientists and marine science professionals. Additionally, we interviewed $1,000 households in 27 coastal villages to determine their perceptions of the environmental concerns and rare and endemic marine species. In general, population numbers of both studied corals and fish were low and distributions were patchy, with little indication that the fisheries management zones were protecting these species. The Mauritian gregory and Mauritian anemonefish were the most abundant species. The Mauritian and Creole damselfishes, which are range-restricted Mascarene endemics, were not observed and potentially extinct. Endemic fish and coral population numbers were higher on the leeward than windward side of the island. The leeward side has higher tourism use and conservation activities that could promote endemic conservation. Environmental concerns of interviewees were high but varied by district and their socioeconomic contexts. Respondents showed an overall concern for the environment and agreed that endemic and rare species had a right to survive. Nevertheless, these rare and endemic coral reef species are threatened by isolation and habitat loss combined with rapid climate and human resource use change. National and district-specific plans of actions could help to secure their futures.

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Oceanic patterns of thermal stress and coral community degradation on the island of Mauritius

Cited by 17 publications

References 75 publications

The Third Global Coral Bleaching Event on the Marginal Coral Reefs of the Southwestern Indian Ocean and Factors That Contribute to Their Resistance and Resilience

The Third Global Coral Bleaching Event on the Marginal Coral Reefs of the Southwestern Indian Ocean and Factors That Contribute to Their Resistance and Resilience

Outplanting of branching Acropora enhances recolonization of a fish species and protects massive corals from predation

Rare coral and reef fish species status, possible extinctions, and associated environmental perceptions in Mauritius

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