Remote Sensing of Coral Bleaching Using Temperature and Light: Progress towards an Operational Algorithm

Skirving, William; Enríquez, Susana; Hedley, John D.; Dove, Sophie; Eakin, C. Mark; Mason, Robert A. B.; Cour, Jacqueline L. De La; Liu, Gang; Høegh-Guldberg, Ove; Strong, A. E.; Mumby, Peter J.; Iglesias-Prieto, Roberto

doi:10.3390/rs10010018

Cited by 65 publications

(88 citation statements)

References 55 publications

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“…By the end of the 7-day heat stress event, ambient corals had experienced 2.5 DHW and warm-acclimated corals had experienced 4.5 DHW (conditions classified as "likely" to cause bleaching by NOAA), yet the light levels during the experiment were relatively low (arising from an abnormal period of cloudy weather; Figure 1C). Since temperature and light are synergistic stressors of coral bleaching, it is possible that the low light conditions that prevailed during the experiment alleviated the impact of the 4.5 DHW treatment to some extent (Skirving et al, 2018). While unexpected, such conditions emphasized the impact of heat stress on coral holobiont metabolism, without the interference of excessive light.…”

Section: Discussionmentioning

confidence: 95%

Short-Term Thermal Acclimation Modifies the Metabolic Condition of the Coral Holobiont

et al. 2018

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The nutritional symbiosis between coral hosts and photosynthetic dinoflagellates is fundamental to the functioning of coral reefs. Rising seawater temperatures destabilize this relationship, resulting in drastic declines in world-wide coral cover. Thermal history is thought to play an important role in shaping a coral's response to subsequent thermal stress. Here, we exposed Pocillopora damicornis to two thermal acclimation regimes (ambient vs. warm) and compared the effect that acclimation had on the coral holobiont's response to a subsequent seven day heat stress event. We conducted daily physiological measurements at the holobiont level (gross photosynthesis, respiration, host protein content, symbiont density and chlorophyll content) throughout the heating event, as well as cellular-level imaging of 13 C-bicarbonate and 15 N-nitrate assimilation (using NanoSIMS) at the end of the heat stress event. Thermal acclimation history had a negligible effect on the measurements conducted at the holobiont level during the heat stress event. No differences were observed in the O 2 -budget between ambient and warm-acclimated corals and only small fluctuations in host protein, symbiont density and chlorophyll content were detected. In contrast, this lack of differential response, was not mirrored at the cellular level. Warm-acclimated corals had substantially higher 13 C enrichment in the host gastrodermis and lipid bodies, but significantly lower 15 N-nitrate assimilation in the symbionts and the host tissue layers, relative to the ambient-acclimated corals. We discuss potential reasons for the disconnect that occurred between symbiont bicarbonate and nitrate assimilation (in the absence of photosynthetic breakdown) in the warm-acclimated corals. We suggest this represents either a shift in nitrogen utilization, or supply limitation by the host. Our findings raise several interesting hypotheses regarding the role that nitrogen metabolism plays in thermal stress, which will warrant further investigation if we are to understand the acclimatization capacity of the coral holobiont.

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Section: Discussionmentioning

confidence: 95%

Short-Term Thermal Acclimation Modifies the Metabolic Condition of the Coral Holobiont

et al. 2018

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“…The performance of the LSD and DHW indices has been compared for three summertime water temperature anomalies (in 2002, 2004, and 2006), each separated by two years of no anomaly, at the for each of the three years suggested that the better prediction of bleaching severity by the LSD algorithm may be due to the combined use of light and temperature anomalies (Skirving et al 2018). …”

Section: A New Bleaching Prediction Methodsmentioning

confidence: 99%

“…A recent algorithm for the prediction of coral bleaching has been designed to incorporate some of these missing variables, whilst still remaining simple enough to be practically implemented. This algorithm, Light Stress Damage (LSD), incorporates a model of bleaching that includes photosynthetically active radiation (PAR) and temperature, and using this model it attempts to predict bleaching-induced mortality and recovery time following bleaching with increased accuracy (Skirving et al 2018).…”

Section: A New Bleaching Prediction Methodsmentioning

confidence: 99%

“…To determine the relative F v /F m from both of these factors, physiological experiments were performed to measure the actual F v /F m in corals at many points along a continuum of anomalous temperatures and light levels (Scheufen et al 2017). In the LSD algorithm, these experimental values are used as reference data to estimate the relative F v /F m for a given satellite-derived temperature anomaly and light level (Skirving et al 2018). …”

Section: A New Bleaching Prediction Methodsmentioning

confidence: 99%

“…The LSD bleaching prediction algorithm (Skirving et al 2018) is based on a physiological model of coral bleaching. The LSD algorithm uses the sum of the change in relative F v /F m (defined as the rise or decline in the relative quantum yield of photosystem II) to derive an index of physiological stress in corals.…”

Section: A New Bleaching Prediction Methodsmentioning

confidence: 99%

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Coral responses to temperature, irradiance and acidification stress: linking physiology to satellite remote sensing

Mason¹

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The success of the symbiosis of scleractinian corals with dinoflagellates of the genus Symbiodinium is highly dependent on the availability of sufficient, but not excess, light for photosynthesis. After decades of fundamental research into the effect of light on the coral-dinoflagellate symbiosis, an important practical application is emerging in remote monitoring of bleaching at coral reefs. Coral bleaching that originates with the dysfunction of photosynthesis can be either photoacclimatory, a controlled adjustment in response to environmental change, or it can be associated with photodamage, an uncontrolled response to environmental change. It is the latter that tends to lead to severe bleaching events that decrease the rate of carbon fixation, generate excessive oxygen radicals and may ultimately lead to coral death if unfavourable conditions persist. Current best practice methods for the prediction of coral bleaching use water temperature as detected via satellite, and predict the onset of coral bleaching accurately, but not the percent of corals bleached at a reef or the extent of the ensuing mortality.Due to its central role in causing photodamage, the use of light level (in addition to temperature) as a predictive variable may improve the accuracy of predictions of coral bleaching severity. The rate of photoacclimation affects the duration of elevated stress following an increase or decrease in incident light level and so it is potentially important for predicting the severity of coral bleaching.As coral reef management practitioners aim to predict bleaching and bleaching-induced mortality at entire reef locales, which are typically composed of a multi-species coral community, differences in coral physiological responses are of importance in designing accurate prediction methods. The interaction of high light and high temperature with a third stressor, ocean acidification, may influence coral bleaching, as ocean acidification changes oceanic chemical parameters that are key to cellular mechanisms of homeostasis and to dinoflagellate photosynthesis.Using multiple-stressor aquarium experiments, I investigated the photoacclimation rate in corals, differences in response to light and temperature stress among coral species, and the interaction of light, temperature and ocean acidification on coral bleaching onset and severity (at the colony scale). My investigation of photoacclimation (via 24 days of exposure to a large increase, a moderate increase, and a large decrease in light) in Acropora muricata and mounding Porites spp.indicated that the direction of light change and the water temperature influenced photoacclimation duration. However, the exact patterns were specific to the variable used to measure photoacclimation (for instance, changes in net areal photosynthesis, or changes in quantum 2 efficiency of photosystem II), with important ramifications for the development of a combined light and temperature bleaching prediction method.I investigated species-specific physiological responses in A. mu...

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Seeking Resistance in Coral Reef Ecosystems: The Interplay of Biophysical Factors and Bleaching Resistance under a Changing Climate

et al. 2019

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If we are to ensure the persistence of species in an increasingly warm world, of interest is the identification of drivers that affect the ability of an organism to resist thermal stress. Underpinning any organism's capacity for resistance is a complex interplay between biological and physical factors occurring over multiple scales. Tropical coral reefs are a unique system, in that their function is dependent upon the maintenance of a coral-algal symbiosis that is directly disrupted by increases in water temperature. A number of physical factors have been identified as affecting the biological responses of the coral organism under broadscale thermal anomalies. One such factor is water flow, which is capable of modulating both organismal metabolic functioning and thermal environments. Understanding the physiological and hydrodynamic drivers of organism response to thermal stress improves predictive capabilities and informs targeted management responses, thereby increasing the resilience of reefs into the future.

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Remote Sensing of Coral Bleaching Using Temperature and Light: Progress towards an Operational Algorithm

Cited by 65 publications

References 55 publications

Short-Term Thermal Acclimation Modifies the Metabolic Condition of the Coral Holobiont

Short-Term Thermal Acclimation Modifies the Metabolic Condition of the Coral Holobiont

Coral responses to temperature, irradiance and acidification stress: linking physiology to satellite remote sensing

Seeking Resistance in Coral Reef Ecosystems: The Interplay of Biophysical Factors and Bleaching Resistance under a Changing Climate

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