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Integrated behavioural and physiological responses of sand smelt larvae to the effects of warming and hypoxia as combined stressors
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Advisor(s)
Abstract(s)
Forecasts indicate that rising temperatures towards the future and the expansion of dead zones will change
environmental suitability for fish early stages. Therefore, we assessed the chronic effects of warming (26 ◦C),
hypoxia (<2–2.5 mg L− 1
) or their combination on mortality rate, growth, behaviour, energy metabolism and
oxidative stress using Atherina presbyter larvae as a model species. There were no differences between the
treatments in terms of mortality rate. The combination of warming and hypoxia induced faster loss of body mass
(+22.7%). Warming, hypoxia or their combination enhanced boldness (+14.7–25.4%), but decreased exploration (− 95%–121%), increased the time in frozen state (+60.6–80.5%) and depleted swimming speed
(− 45.6–50.5%). Moreover, routine metabolic rate was depleted under hypoxia or under the combination of
warming and hypoxia (− 56.6 and 57.2%, respectively). Under hypoxia, increased catalase activity (+56.3%)
indicates some level of antioxidant defence capacity, although increased DNA damage (+25.2%) has also been
observed. Larvae also exhibited a great capacity to maintain the anaerobic metabolism stable in all situations, but
the aerobic metabolism is enhanced (+19.3%) when exposed to the combination of both stressors. The integrative approach showed that changes in most target responses can be explained physiologically by oxidative
stress responses. Increased oxidative damages (lipid peroxidation and DNA damage) and increased interaction
between antioxidant enzymes (superoxide dismutase and catalase) are associated to increased time in frozen
state and decreased swimming activity, growth rates and boldness. Under all stressful situations, larvae reduced
energy-consuming behaviours (e.g. depleted exploration and swimming activity) likely to stabilize or compensate for the aerobic and anaerobic metabolisms. Despite being an active small pelagic fish, we concluded that the
sensitive larval phase exhibited complex coping strategies to physiologically acclimate under thermal and
hypoxic stress via behavioural responses.
Description
Keywords
Climate change Ocean warming Oxygen depletion Fish metabolism Growth patterns Oxidative stress Early life stages Small pelagic fish
Citation
Lima, A. R. A., Lopes, A. R., Martins-Cardoso, S., Moutinho, A. B., Lemos, M. F. L., Novais, S. C., & Faria, A. M. (2024). Integrated behavioural and physiological responses of sand smelt larvae to the effects of warming and hypoxia as combined stressors. Marine Environmental Research, 199. https://doi.org/10.1016/j.marenvres.2024.106609
Publisher
Elsevier B.V.