Studies of shelter use can provide key insights into the ecology, and structural needs of mobile ... more Studies of shelter use can provide key insights into the ecology, and structural needs of mobile organisms. Using videos, we examined the usage of tabular corals by large reef fishes, over a 10 week period, compared to multiple environmental drivers: visibility, tide (and depth), irradiance, wind speed (as a proxy for wave energy) and water temperature. We found that two of these predictor variables (visibility and wind speed) had a significant effect and together accounted for almost half of the variation in tabular coral usage by fishes. Increases in both variables correlated with increased shelter use. To date use of shelters by fishes has primarily been attributed to UV avoidance. Our results support this notion as more turbid conditions (reduced visibility) have an attenuating effect on UV irradiance. Additionally, tabular corals may reduce the energetic costs of increased wave energy by reducing incidental water velocity beneath the structure.
During 2015-2016, record temperatures triggered a pan-tropical episode of coral bleaching, the th... more During 2015-2016, record temperatures triggered a pan-tropical episode of coral bleaching, the third global-scale event since mass bleaching was first documented in the 1980s. Here we examine how and why the severity of recurrent major bleaching events has varied at multiple scales, using aerial and underwater surveys of Australian reefs combined with satellite-derived sea surface temperatures. The distinctive geographic footprints of recurrent bleaching on the Great Barrier Reef in 1998, 2002 and 2016 were determined by the spatial pattern of sea temperatures in each year. Water quality and fishing pressure had minimal effect on the unprecedented bleaching in 2016, suggesting that local protection of reefs affords little or no resistance to extreme heat. Similarly, past exposure to bleaching in 1998 and 2002 did not lessen the severity of bleaching in 2016. Consequently, immediate global action to curb future warming is essential to secure a future for coral reefs.
Climate change is radically altering the frequency, intensity and spatial scale of severe weather... more Climate change is radically altering the frequency, intensity and spatial scale of severe weather events, such as heatwaves, droughts, floods and fires 1 . As the time interval shrinks between recurrent shocks 2-5 , the responses of ecosystems to each new disturbance are increasingly likely to be contingent on the history of other recent extreme events. Ecological memory-defined as the ability of the past to influence the present trajectory of ecosystems 6,7 -is also critically important for understanding how species assemblages are responding to rapid changes in disturbance regimes due to anthropogenic climate change 2,3,6-8 . Here, we show the emergence of ecological memory during unprecedented back-to-back mass bleaching of corals along the 2,300 km length of the Great Barrier Reef in 2016, and again in 2017, whereby the impacts of the second severe heatwave, and its geographic footprint, were contingent on the first. Our results underscore the need to understand the strengthening interactions among sequences of climate-driven events, and highlight the accelerating and cumulative impacts of novel disturbance regimes on vulnerable ecosystems. Changes through time are fundamental to the study of ecology and evolution, yet our understanding of the contemporary condition of ecosystems often discounts the role of non-equilibrial dynamics and history . Emerging theoretical frameworks and models point to the important effects of time lags and memory, as the enduring influences of past experiences and changing conditions unfold over time . For example, the responses of ecosystems during ecological succession, and the evolution of life history traits, are key legacy effects of the history of recurrent disturbances 2 . On most coral reefs, for instance, where recurrent tropical cyclones have historically been the most significant external disturbance 10 , regional-and global-scale bleaching of corals has become a major additional agent of mortality of reef-building corals in recent decades . Here, we document how ecological memory of severe coral bleaching on the Great Barrier Reef in 2016 12 subsequently transformed the response of corals to heat stress during a second marine heatwave in 2017. We show further that the geographic pattern of heat exposure in 2016 had a lingering impact on the spatial footprint of bleaching along the 2,300 km length of the world's largest reef system during the subsequent heatwave one year later-history has a geographic signal. Our results demonstrate the need to understand the combined, interactive effects of sequences of recurrent climate-related
Global warming is rapidly emerging as a universal threat to ecological integrity and function, hi... more Global warming is rapidly emerging as a universal threat to ecological integrity and function, highlighting the urgent need for a better understanding of the impact of heat exposure on the resilience of ecosystems and the people who depend on them . Here we show that in the aftermath of the record-breaking marine heatwave on the Great Barrier Reef in 2016 , corals began to die immediately on reefs where the accumulated heat exposure exceeded a critical threshold of degree heating weeks, which was 3-4 °C-weeks. After eight months, an exposure of 6 °C-weeks or more drove an unprecedented, regional-scale shift in the composition of coral assemblages, reflecting markedly divergent responses to heat stress by different taxa. Fast-growing staghorn and tabular corals suffered a catastrophic die-off, transforming the three-dimensionality and ecological functioning of 29% of the 3,863 reefs comprising the world's largest coral reef system. Our study bridges the gap between the theory and...
Studies of shelter use can provide key insights into the ecology, and structural needs of mobile ... more Studies of shelter use can provide key insights into the ecology, and structural needs of mobile organisms. Using videos, we examined the usage of tabular corals by large reef fishes, over a 10 week period, compared to multiple environmental drivers: visibility, tide (and depth), irradiance, wind speed (as a proxy for wave energy) and water temperature. We found that two of these predictor variables (visibility and wind speed) had a significant effect and together accounted for almost half of the variation in tabular coral usage by fishes. Increases in both variables correlated with increased shelter use. To date use of shelters by fishes has primarily been attributed to UV avoidance. Our results support this notion as more turbid conditions (reduced visibility) have an attenuating effect on UV irradiance. Additionally, tabular corals may reduce the energetic costs of increased wave energy by reducing incidental water velocity beneath the structure.
During 2015-2016, record temperatures triggered a pan-tropical episode of coral bleaching, the th... more During 2015-2016, record temperatures triggered a pan-tropical episode of coral bleaching, the third global-scale event since mass bleaching was first documented in the 1980s. Here we examine how and why the severity of recurrent major bleaching events has varied at multiple scales, using aerial and underwater surveys of Australian reefs combined with satellite-derived sea surface temperatures. The distinctive geographic footprints of recurrent bleaching on the Great Barrier Reef in 1998, 2002 and 2016 were determined by the spatial pattern of sea temperatures in each year. Water quality and fishing pressure had minimal effect on the unprecedented bleaching in 2016, suggesting that local protection of reefs affords little or no resistance to extreme heat. Similarly, past exposure to bleaching in 1998 and 2002 did not lessen the severity of bleaching in 2016. Consequently, immediate global action to curb future warming is essential to secure a future for coral reefs.
Climate change is radically altering the frequency, intensity and spatial scale of severe weather... more Climate change is radically altering the frequency, intensity and spatial scale of severe weather events, such as heatwaves, droughts, floods and fires 1 . As the time interval shrinks between recurrent shocks 2-5 , the responses of ecosystems to each new disturbance are increasingly likely to be contingent on the history of other recent extreme events. Ecological memory-defined as the ability of the past to influence the present trajectory of ecosystems 6,7 -is also critically important for understanding how species assemblages are responding to rapid changes in disturbance regimes due to anthropogenic climate change 2,3,6-8 . Here, we show the emergence of ecological memory during unprecedented back-to-back mass bleaching of corals along the 2,300 km length of the Great Barrier Reef in 2016, and again in 2017, whereby the impacts of the second severe heatwave, and its geographic footprint, were contingent on the first. Our results underscore the need to understand the strengthening interactions among sequences of climate-driven events, and highlight the accelerating and cumulative impacts of novel disturbance regimes on vulnerable ecosystems. Changes through time are fundamental to the study of ecology and evolution, yet our understanding of the contemporary condition of ecosystems often discounts the role of non-equilibrial dynamics and history . Emerging theoretical frameworks and models point to the important effects of time lags and memory, as the enduring influences of past experiences and changing conditions unfold over time . For example, the responses of ecosystems during ecological succession, and the evolution of life history traits, are key legacy effects of the history of recurrent disturbances 2 . On most coral reefs, for instance, where recurrent tropical cyclones have historically been the most significant external disturbance 10 , regional-and global-scale bleaching of corals has become a major additional agent of mortality of reef-building corals in recent decades . Here, we document how ecological memory of severe coral bleaching on the Great Barrier Reef in 2016 12 subsequently transformed the response of corals to heat stress during a second marine heatwave in 2017. We show further that the geographic pattern of heat exposure in 2016 had a lingering impact on the spatial footprint of bleaching along the 2,300 km length of the world's largest reef system during the subsequent heatwave one year later-history has a geographic signal. Our results demonstrate the need to understand the combined, interactive effects of sequences of recurrent climate-related
Global warming is rapidly emerging as a universal threat to ecological integrity and function, hi... more Global warming is rapidly emerging as a universal threat to ecological integrity and function, highlighting the urgent need for a better understanding of the impact of heat exposure on the resilience of ecosystems and the people who depend on them . Here we show that in the aftermath of the record-breaking marine heatwave on the Great Barrier Reef in 2016 , corals began to die immediately on reefs where the accumulated heat exposure exceeded a critical threshold of degree heating weeks, which was 3-4 °C-weeks. After eight months, an exposure of 6 °C-weeks or more drove an unprecedented, regional-scale shift in the composition of coral assemblages, reflecting markedly divergent responses to heat stress by different taxa. Fast-growing staghorn and tabular corals suffered a catastrophic die-off, transforming the three-dimensionality and ecological functioning of 29% of the 3,863 reefs comprising the world's largest coral reef system. Our study bridges the gap between the theory and...
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Papers by James Kerry