Investigating links between thermal tolerance and oxygen supply capacity in shark neonates from a hyperoxic tropical environment

Bouyoucos, Ian, Trujillo, Jose E., Weideli, Ornella C., Nakamura, Nao, Mourier, Johann, Planes, Serge, Simpfendorfer, Colin A., and Rummer, Jodie L. (2021) Investigating links between thermal tolerance and oxygen supply capacity in shark neonates from a hyperoxic tropical environment. Science of the Total Environment, 782. 146854.

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Abstract

Temperature and oxygen limit the distribution of marine ectotherms. Haematological traits underlying blood-oxygen carrying capacity are thought to be correlated with thermal tolerance in certain fishes, and this relationship is hypothesised to be explained by oxygen supply capacity. We tested this hypothesis using reef shark neonates as experimental models because they live near their upper thermal limits and are physiologically sensitive to low oxygen conditions. We first described in situ associations between temperature and oxygen at the study site (Moorea, French Polynesia) and found that the habitats for reef shark neonates (Carcharhinus melanopterus and Negaprion acutidens) were hyperoxic at the maximum recorded temperatures. Next, we tested for in situ associations between thermal habitat characteristics and haematological traits of neonates. Contrary to predictions, we only demonstrated a negative association between haemoglobin concentration and maximum habitat temperatures in C. melanopterus. Next, we tested for ex situ associations between critical thermal maximum (CTMax) and haematological traits, but only demonstrated a negative association between haematocrit and CTMax in C. melanopterus. Finally, we measured critical oxygen tension (pcrit) ex situ and estimated its temperature sensitivity to predict oxygen-dependent values of CTMax. Estimated temperature sensitivity of pcrit was similar to reported values for sharks and skates, and predicted values for CTMax equalled maximum habitat temperatures. These data demonstrate unique associations between haematological traits and thermal tolerance in a reef shark that are likely not explained by oxygen supply capacity. However, a relationship between oxygen supply capacity and thermal tolerance remains to be demonstrated empirically.

Item ID: 70186
Item Type: Article (Research - C1)
ISSN: 1879-1026
Keywords: Critical thermal maximum, Haematocrit, Haemoglobin, Oxygen supply capacity, p crit, Reef sharks
Copyright Information: © 2021 Elsevier B.V. All rights reserved
Funders: Australian Research Council (ARC), ARC Centre of Excellence for Coral Reef Studies
Projects and Grants: ARC PDE150101266
Date Deposited: 23 Nov 2021 23:25
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 30%
41 ENVIRONMENTAL SCIENCES > 4101 Climate change impacts and adaptation > 410102 Ecological impacts of climate change and ecological adaptation @ 50%
41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410406 Natural resource management @ 20%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180502 Assessment and management of pelagic marine ecosystems @ 80%
19 ENVIRONMENTAL POLICY, CLIMATE CHANGE AND NATURAL HAZARDS > 1905 Understanding climate change > 190506 Effects of climate change on the South Pacific (excl. Australia and New Zealand) (excl. social impacts) @ 20%
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