scholarly journals Photoacclimatory and photoprotective responses to cold versus heat stress in high latitude reef corals

2017 ◽  
Vol 53 (2) ◽  
pp. 308-321 ◽  
Author(s):  
Stefanie Pontasch ◽  
Paul L. Fisher ◽  
Thomas Krueger ◽  
Sophie Dove ◽  
Ove Hoegh-Guldberg ◽  
...  
Keyword(s):  
Heat Stress ◽  
High Latitude ◽  
Reef Corals

scholarly journals Living on the Edge: Protective Mechanisms Underlying Thermal Tolerance in High Latitude Symbiodinium spp.

2021 ◽  
Author(s):  
◽  
Stefanie Pontasch
Keyword(s):  
Heat Stress ◽  
High Latitude ◽  
Thermal Sensitivity ◽  
Pocillopora Damicornis ◽  
Short Term ◽  
Cellular Mechanisms ◽  
Protective Mechanisms ◽  
Sod Activity ◽  
Lord Howe Island ◽  
D1 Turnover

<p>The association between symbiotic dinoflagellates (Symbiodinium spp.) and corals extends to subtropical and temperate regions, where sea surface temperatures (SSTs) are generally lower than in the tropics and can vary substantially over the course of the year due to seasonal changes. These high latitude coral-dinoflagellate symbioses might be better able to withstand thermal variability and might be particularly well equipped to cope with lower SSTs compared to their tropical relatives. The aim of this thesis was to analyze the cellular mechanisms that underlie heat and/or cold tolerance in a range of reef-building corals (Acropora yongei, Acropora solitariensis, Isopora palifera, Pocillopora damicornis, Porites heronensis and Stylophora sp.), as well as the symbiotic sea anemone Entacmaea quadricolor. In particular, the study focussed on protective mechanisms in their dinoflagellate symbionts as a potential determinant of thermal sensitivity (i.e. bleaching) or resistance of the intact symbiosis. High latitude reef-building corals were analyzed at the world’s southernmost coral reef at Lord Howe Island, while E. quadricolor was sampled at the subtropical coral community at North Solitary Island; both sites are located in New South Wales, Australia. The specific objectives were to assess the roles of: (1) xanthophyll deepoxidation; (2) thylakoid fatty acid composition; (3) Symbiodinium superoxide dismutase (SOD) and ascorbate peroxidase (APX) activity; and (4) D1 repair on the photophysiology, bleaching susceptibility and survivorship of a range of high-latitude coral-Symbiodinium associations from Lord Howe Island when exposed to elevated or decreased temperature. Furthermore, I aimed to: (5) characterise Symbiodinium diversity in the anemone E. quadricolor on the west coast of Australia; and (6) measure the dynamics of Symbiodinium ITS2 populations and SOD activity in two E. quadricolor phenotypes (green and pink colour phenotypes) in response to elevated temperature. I showed that thermal responses in high latitude corals and their dinoflagellate symbionts are highly variable, depending on host species (or phenotype) and Symbiodinium genotype, and that the activation of protective mechanisms in Symbiodinium was not necessarily correlated with sub-lethal bleaching susceptibility or survivorship of their coral hosts. More specifically: (1) In response to short-term heat stress and cold stress, xanthophyll de-epoxidation increased in some but not all bleaching susceptible (e.g. P. damicornis) and bleaching tolerant (P. heronensis) corals; (2) overall unsaturated thylakoid fatty acids increased in symbionts of a bleaching tolerant coral association, yet was not correlated with PSII photochemical efficiency; and (3) SOD and APX activity remained unchanged in the majority of Symbiodinium types regardless of bleaching susceptibility of the coral host, but decreased in bleaching susceptible Pocillopora damicornis when exposed to short-term heat stress. Elevated temperatures resulted in enhanced D1 turnover in two warm-water bleaching susceptible Symbiodinium-host combinations; however a direct link between increased dependence on D1 turnover and bleaching susceptibility was not demonstrated. From the results obtained it seems unlikely that the specific cellular adaptations in Symbiodinium alone determine the tolerance of Lord Howe corals to thermal variations. In contrast, the results highlight the significance of the particular host-symbiont combination and it appears that the host is important in determining, at least in part, the thermal response of the coral. Additionally, this study revealed a high diversity of Symbiodinium ITS2 (internal transcribed spacer 2) types in E. quadricolor from five locations on the west coast of Australia. E. quadricolor predominantly associated with six types of clade C (four of which were novel) and most anemones harboured multiple types simultaneously. At North Solitary Island, anemones simultaneously harboured Symbiodinium C25 and C3.25 (a novel variant of C3). Experimentally, I showed that anemones shuffled the relative proportions of C25 and C3.25 in response to elevated temperature, but not in both anemone colour phenotypes analyzed. Furthermore, baseline photobiological characteristics were distinct in the two different anemone colour morphs but were not correlated with the ratio of Symbiodinium C25 to C3.25, suggesting that host mechanisms such as pigmentation were involved in regulating light utilization by the symbionts. My hypothesis that symbiont shuffling was related to SOD activity, as such that those symbionts with enhanced SOD activity and increased capability to scavenge superoxide anion would increase in relative abundance in response to short-term heat stress, could not be proved. In summary, this thesis provides detailed information on some key cellular mechanisms that could underpin thermal sensitivity and resistance in high latitude Symbiodinium, and most importantly highlights the significance of the host-symbiont combination in determining the response to thermal stress. The various mechanistic findings described here further our understanding of the coral bleaching process in general and particularly give insight into physiological and cellular responses to coldwater stress in reef-building corals at high-latitude sites. The results of this thesis indicate that in light of ongoing climate change, as episodes of cold-water and warm-water anomalies will become more frequent, branching corals such as Acropora yongei or Pocillopora damicornis and their symbionts will experience physiological stress more frequently than massive species such as Porites heronensis. This might have profound impacts on the long-term stability and species composition of high latitude coral reefs.</p>

scholarly journals The Reef Coral Coscinaraea marshae Is Not a High-Latitude Endemic

Diversity ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 681
Author(s):  
Bert W. Hoeksema ◽  
Ofri Johan ◽  
Andreas Kunzmann
Keyword(s):  
Western Australia ◽  
High Latitude ◽  
Reef Coral ◽  
Range Limit ◽  
Reef Corals ◽  
Temperate Reef ◽  
West Sumatra

The ‘temperate’ reef coral Coscinaraea marshae Wells, 1962, is reported from Siberut Island (West Sumatra, Indonesia), a near-equatorial locality, 3375 km away from its northernmost range limit in Western Australia, where it is considered a high-latitude endemic. This tropical record suggests that the latitudinal distributions of poorly recorded reef corals may not yet be fully understood, which might be relevant in the light of progressing seawater warming.

scholarly journals Thermal stress-related spatiotemporal variations in high-latitude coral reef benthic communities

Coral Reefs ◽  
2020 ◽  
Vol 39 (6) ◽  
pp. 1661-1673
Author(s):  
Nicholas P. Jones ◽  
Joana Figueiredo ◽  
David S. Gilliam
Keyword(s):  
Heat Stress ◽  
Thermal Stress ◽  
Coral Reef ◽  
High Latitude ◽  
Coral Cover ◽  
Benthic Communities ◽  
Spatiotemporal Variations ◽  
Reef Recovery ◽  
Reef Tract

AbstractHigh-latitude coral reef communities have been postulated as the first areas to undergo reorganisation under climate change. Tropicalisation has been identified in some high-latitude communities and is predicted in others, but it is unclear how the resident benthic taxa are affected. We conducted a long-term (2007–2016) assessment of changes to benthic community cover in relation to thermal stress duration on the Southeast Florida Reef Tract (SEFRT). Thermal stress events, both hot and cold, had acute (thermal stress duration affected benthic cover that year) and chronic (thermal stress duration affected benthic cover the following year) impacts on benthic cover. Chronic heat stress was associated with declines in cover of the reef-building coral families Acroporidae, Montastraeidae, Meandrinidae, Mussidae and Siderastreidae, which coupled with the absence of cold stress and rising annual temperatures boosted macroalgae cover. Cover of smaller, weedy coral families, Poritidae, Agariciidae and Astrocoeniidae, was either unaffected or positively related to heat stress duration and rising mean temperature. Thermal stress was related to spatiotemporal variations in benthic cover on the SEFRT, likely enhanced by local stressors, such as elevated nutrients and sedimentation. Coral and octocoral cover declined within four of six sub-regions, sponge cover increased in half of the sub-regions, and macroalgae cover increased in four sub-regions during the study. Under current conditions, increased macroalgae and weedy coral cover are anticipated to inhibit reef recovery.

scholarly journals Living on the Edge: Protective Mechanisms Underlying Thermal Tolerance in High Latitude Symbiodinium spp.

2021 ◽  
Author(s):  
◽  
Stefanie Pontasch
Keyword(s):  
Heat Stress ◽  
High Latitude ◽  
Thermal Sensitivity ◽  
Pocillopora Damicornis ◽  
Short Term ◽  
Cellular Mechanisms ◽  
Protective Mechanisms ◽  
Sod Activity ◽  
Lord Howe Island ◽  
D1 Turnover

<p>The association between symbiotic dinoflagellates (Symbiodinium spp.) and corals extends to subtropical and temperate regions, where sea surface temperatures (SSTs) are generally lower than in the tropics and can vary substantially over the course of the year due to seasonal changes. These high latitude coral-dinoflagellate symbioses might be better able to withstand thermal variability and might be particularly well equipped to cope with lower SSTs compared to their tropical relatives. The aim of this thesis was to analyze the cellular mechanisms that underlie heat and/or cold tolerance in a range of reef-building corals (Acropora yongei, Acropora solitariensis, Isopora palifera, Pocillopora damicornis, Porites heronensis and Stylophora sp.), as well as the symbiotic sea anemone Entacmaea quadricolor. In particular, the study focussed on protective mechanisms in their dinoflagellate symbionts as a potential determinant of thermal sensitivity (i.e. bleaching) or resistance of the intact symbiosis. High latitude reef-building corals were analyzed at the world’s southernmost coral reef at Lord Howe Island, while E. quadricolor was sampled at the subtropical coral community at North Solitary Island; both sites are located in New South Wales, Australia. The specific objectives were to assess the roles of: (1) xanthophyll deepoxidation; (2) thylakoid fatty acid composition; (3) Symbiodinium superoxide dismutase (SOD) and ascorbate peroxidase (APX) activity; and (4) D1 repair on the photophysiology, bleaching susceptibility and survivorship of a range of high-latitude coral-Symbiodinium associations from Lord Howe Island when exposed to elevated or decreased temperature. Furthermore, I aimed to: (5) characterise Symbiodinium diversity in the anemone E. quadricolor on the west coast of Australia; and (6) measure the dynamics of Symbiodinium ITS2 populations and SOD activity in two E. quadricolor phenotypes (green and pink colour phenotypes) in response to elevated temperature. I showed that thermal responses in high latitude corals and their dinoflagellate symbionts are highly variable, depending on host species (or phenotype) and Symbiodinium genotype, and that the activation of protective mechanisms in Symbiodinium was not necessarily correlated with sub-lethal bleaching susceptibility or survivorship of their coral hosts. More specifically: (1) In response to short-term heat stress and cold stress, xanthophyll de-epoxidation increased in some but not all bleaching susceptible (e.g. P. damicornis) and bleaching tolerant (P. heronensis) corals; (2) overall unsaturated thylakoid fatty acids increased in symbionts of a bleaching tolerant coral association, yet was not correlated with PSII photochemical efficiency; and (3) SOD and APX activity remained unchanged in the majority of Symbiodinium types regardless of bleaching susceptibility of the coral host, but decreased in bleaching susceptible Pocillopora damicornis when exposed to short-term heat stress. Elevated temperatures resulted in enhanced D1 turnover in two warm-water bleaching susceptible Symbiodinium-host combinations; however a direct link between increased dependence on D1 turnover and bleaching susceptibility was not demonstrated. From the results obtained it seems unlikely that the specific cellular adaptations in Symbiodinium alone determine the tolerance of Lord Howe corals to thermal variations. In contrast, the results highlight the significance of the particular host-symbiont combination and it appears that the host is important in determining, at least in part, the thermal response of the coral. Additionally, this study revealed a high diversity of Symbiodinium ITS2 (internal transcribed spacer 2) types in E. quadricolor from five locations on the west coast of Australia. E. quadricolor predominantly associated with six types of clade C (four of which were novel) and most anemones harboured multiple types simultaneously. At North Solitary Island, anemones simultaneously harboured Symbiodinium C25 and C3.25 (a novel variant of C3). Experimentally, I showed that anemones shuffled the relative proportions of C25 and C3.25 in response to elevated temperature, but not in both anemone colour phenotypes analyzed. Furthermore, baseline photobiological characteristics were distinct in the two different anemone colour morphs but were not correlated with the ratio of Symbiodinium C25 to C3.25, suggesting that host mechanisms such as pigmentation were involved in regulating light utilization by the symbionts. My hypothesis that symbiont shuffling was related to SOD activity, as such that those symbionts with enhanced SOD activity and increased capability to scavenge superoxide anion would increase in relative abundance in response to short-term heat stress, could not be proved. In summary, this thesis provides detailed information on some key cellular mechanisms that could underpin thermal sensitivity and resistance in high latitude Symbiodinium, and most importantly highlights the significance of the host-symbiont combination in determining the response to thermal stress. The various mechanistic findings described here further our understanding of the coral bleaching process in general and particularly give insight into physiological and cellular responses to coldwater stress in reef-building corals at high-latitude sites. The results of this thesis indicate that in light of ongoing climate change, as episodes of cold-water and warm-water anomalies will become more frequent, branching corals such as Acropora yongei or Pocillopora damicornis and their symbionts will experience physiological stress more frequently than massive species such as Porites heronensis. This might have profound impacts on the long-term stability and species composition of high latitude coral reefs.</p>

Heat stress in a high-latitude seabird: effects of temperature and food supply on bathing and nest attendance of great skuas Catharacta skua

2008 ◽  
Vol 39 (2) ◽  
pp. 163-169 ◽  
Author(s):  
Stephen A. Oswald ◽  
Stuart Bearhop ◽  
Robert W. Furness ◽  
Brian Huntley ◽  
Keith C. Hamer
Keyword(s):  
Heat Stress ◽  
High Latitude ◽  
Food Supply ◽  
Nest Attendance ◽  
Effects Of Temperature

Physiology of Heat Stress and Tolerance Mechanisms - An Overview

2018 ◽  
Vol 34 (1) ◽  
pp. 51-64
Author(s):  
A. Hemantaranjan ◽  
◽  
C.P. Malik ◽  
A. Nishant Bhanu ◽  
◽  
...  
Keyword(s):  
Heat Stress ◽  
Tolerance Mechanisms
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