Coral Bleaching and Mortality in the Chagos Archipelago

Sheppard, Charles; Sheppard, Anne; Mogg, Andrew O.M.; Bayley, Daniel T. I.; Dempsey, Alexandra C.; Roche, Ronan; Turner, John R. G.; Purkis, Sam J.

doi:10.5479/si.0077-5630.613

Cited by 52 publications

(73 citation statements)

References 28 publications

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“…Islands were otherwise similar in terms of size, location and environment. This assumption is reasonable given the aforementioned temperature anomalies and evidence of coral bleaching in the Chagos Archipelago during this time (Sheppard et al, 2017), as well as the isolation of the study region from other stressors (e.g. In response to these warmer water temperatures, corals across the region began exhibiting signs of bleaching in April-May 2015, with widespread mortality beginning in 2016 and extending into 2017 (Sheppard et al, 2017).…”

Section: Materials S and Me Thodsmentioning

confidence: 77%

“…On islands where rats were never introduced, there are large populations of seabirds, including 10 internationally recognized important bird areas (Carr, 2011). Shallow reefs in this area recovered from the 1998 worldwide bleaching event (Sheppard, Harris, & Sheppard, 2008), but suffered widespread coral mortality again as part of the 2015-2016 mass bleaching event that affected reefs throughout the Indian and Pacific Oceans (Hughes et al, 2018;Sheppard et al, 2017). However, coral bleaching events have affected reefs in the Chagos Archipelago several times in the past few decades.…”

Section: Materials S and Me Thodsmentioning

confidence: 98%

“…These differences in seabird densities translated to 251 times greater nitrogen loads on islands with seabirds compared to those without (190 kg ha −1 year −1 vs. 0.8 kg ha −1 year −1 ), some of which was then assimilated by benthic organisms and fishes on adjacent coral reefs . In response to these warmer water temperatures, corals across the region began exhibiting signs of bleaching in April-May 2015, with widespread mortality beginning in 2016 and extending into 2017 (Sheppard et al, 2017). In April 2015, sea surface temperatures in the Chagos Archipelago began exceeding the predicted bleaching threshold (degree heating weeks [DHW] >4°C-weeks) and remained above this threshold for 247 days between April 2015 and July 2016 (Liu, Strong, Skirving, & Arzayus, 2006;NOAA Coral Reef Watch, 2018).…”

Section: Materials S and Me Thodsmentioning

confidence: 99%

“…Indeed, sea surface temperatures during the 2015-2016 bleaching event were the warmest ever recorded(Hughes et al, 2018), and these extreme temperatures persisted for more than half of the year at some sites in the Chagos Archipelago(NOAA Coral Reef Watch, 2018;Sheppard et al, 2017). Indeed, sea surface temperatures during the 2015-2016 bleaching event were the warmest ever recorded(Hughes et al, 2018), and these extreme temperatures persisted for more than half of the year at some sites in the Chagos Archipelago(NOAA Coral Reef Watch, 2018;Sheppard et al, 2017).…”

mentioning

confidence: 99%

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Seabird nutrient subsidies alter patterns of algal abundance and fish biomass on coral reefs following a bleaching event

Benkwitt

Wilson

Graham

2019

Global Change Biology

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Cross‐ecosystem nutrient subsidies play a key role in the structure and dynamics of recipient communities, but human activities are disrupting these links. Because nutrient subsidies may also enhance community stability, the effects of losing these inputs may be exacerbated in the face of increasing climate‐related disturbances. Nutrients from seabirds nesting on oceanic islands enhance the productivity and functioning of adjacent coral reefs, but it is unknown whether these subsidies affect the response of coral reefs to mass bleaching events or whether the benefits of these nutrients persist following bleaching. To answer these questions, we surveyed benthic organisms and fishes around islands with seabirds and nearby islands without seabirds due to the presence of invasive rats. Surveys were conducted in the Chagos Archipelago, Indian Ocean, immediately before the 2015–2016 mass bleaching event and, in 2018, two years following the bleaching event. Regardless of the presence of seabirds, relative coral cover declined by 32%. However, there was a post‐bleaching shift in benthic community structure around islands with seabirds, which did not occur around islands with invasive rats, characterized by increases in two types of calcareous algae (crustose coralline algae [CCA] and Halimeda spp.). All feeding groups of fishes were positively affected by seabirds, but only herbivores and piscivores were unaffected by the bleaching event and sustained the greatest difference in biomass between islands with seabirds versus those with invasive rats. By contrast, corallivores and planktivores, both of which are coral‐dependent, experienced the greatest losses following bleaching. Even though seabird nutrients did not enhance community‐wide resistance to bleaching, they may still promote recovery of these reefs through their positive influence on CCA and herbivorous fishes. More broadly, the maintenance of nutrient subsidies, via strategies including eradication of invasive predators, may be important in shaping the response of ecological communities to global climate change.

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Section: Materials S and Me Thodsmentioning

confidence: 77%

Section: Materials S and Me Thodsmentioning

confidence: 98%

Section: Materials S and Me Thodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Seabird nutrient subsidies alter patterns of algal abundance and fish biomass on coral reefs following a bleaching event

Benkwitt

Wilson

Graham

2019

Global Change Biology

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“…Hence, both locations support relatively pristine and diverse parrotfish assemblages (Johnson et al, ; Samoilys, Roche, Koldeway, & Turner, ). Coral reefs of the CA and the GBR have experienced severe heat stress and consequent coral bleaching during 2015–2016 and 2016–2017, respectively, resulting in drastic losses of living coral cover (Head et al, ; Hughes, Kerry, et al, ; Sheppard et al, ).…”

Section: Methodsmentioning

confidence: 99%

Synchronous biological feedbacks in parrotfishes associated with pantropical coral bleaching

Taylor

Benkwitt

Choat

et al. 2019

Global Change Biology

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Biological feedbacks generated through patterns of disturbance are vital for sustaining ecosystem states. Recent ocean warming and thermal anomalies have caused pantropical episodes of coral bleaching, which has led to widespread coral mortality and a range of subsequent effects on coral reef communities. Although the response of many reef‐associated fishes to major disturbance events on coral reefs is negative (e.g., reduced abundance and condition), parrotfishes show strong feedbacks after disturbance to living reef structure manifesting as increases in abundance. However, the mechanisms underlying this response are poorly understood. Using biochronological reconstructions of annual otolith (ear stone) growth from two ocean basins, we tested whether parrotfish growth was enhanced following bleaching‐related coral mortality, thus providing an organismal mechanism for demographic changes in populations. Both major feeding guilds of parrotfishes (scrapers and excavators) exhibited enhanced growth of individuals after bleaching that was decoupled from expected thermal performance, a pattern that was not evident in other reef fish taxa from the same environment. These results provide evidence for a more nuanced ecological feedback system—one where disturbance plays a key role in mediating parrotfish–benthos interactions. By influencing the biology of assemblages, disturbance can thereby stimulate change in parrotfish grazing intensity and ultimately reef geomorphology over time. This feedback cycle operated historically at within‐reef scales; however, our results demonstrate that the scale, magnitude, and severity of recent thermal events are entraining the biological responses of disparate communities to respond in synchrony. This may fundamentally alter feedbacks in the relationships between parrotfishes and reef systems.

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Analysing detection gaps in acoustic telemetry data to infer differential movement patterns in fish

Williamson

Tebbs

Dawson

et al. 2021

Ecology and Evolution

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Coral Bleaching and Mortality in the Chagos Archipelago

Cited by 52 publications

References 28 publications

Seabird nutrient subsidies alter patterns of algal abundance and fish biomass on coral reefs following a bleaching event

Seabird nutrient subsidies alter patterns of algal abundance and fish biomass on coral reefs following a bleaching event

Synchronous biological feedbacks in parrotfishes associated with pantropical coral bleaching

Analysing detection gaps in acoustic telemetry data to infer differential movement patterns in fish

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