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Influence of extreme climate events on sound production of Hippocampus hippocampus
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Resumo(s)
Seahorses are known to produce sounds in different behavioural contexts, but information on
the sound production in these organisms and how it may be affected by climate changes is still scarce.
These animals are currently experiencing an unprecedented level of anthropogenic pressures, thus being
crucial to understand how they will endure such pressures such as climate change. This study
characterizes the feeding behaviour and acoustic communication of the short-snouted seahorse
Hippocampus hippocampus and explores the effects of type II marine heatwaves (21.5 °C) and hypoxic
~ 27% dissolved oxygen (2.1 ± 0.1 mg O2 L
-1
) conditions. Feeding clicks were characterized by brief
high frequency broadband sounds with a mean duration of 25.3 ± 1.9 ms, and a mean peak frequency of
1838.0 ± 77.1 Hz. The duration of these clicks revealed changes under marine heatwaves and hypoxic
conditions compared to the control. During marine heatwave treatment, the duration decreased 15.8%
(down to 21.3 ± 2.2 ms), whereas under hypoxia, it increased 30.04% (up to 32.9 ± 7.1 ms). However,
there were no significant changes in the peak frequency across these treatments. Feeding clicks were
also consistently associated with food intake, revealing a significant positive correlation between the
number of clicks and food intake, working as an accurate measure of feeding activity. Under marine
heatwaves conditions, seahorses displayed increased production of 69.16% (83.4 ± 7.89) in feeding
clicks and 50.01% (51.5 ± 2.93) in food intake compared to control conditions (49.3 ± 5.01 and 34.3 ±
2.39, respectively). Additionally, sound production, exhibited a threshold effect. Specifically, below a
certain threshold of approximately 19.3°C, higher temperatures were associated with increased sound
production. However, beyond this threshold, further increases in temperature do not seem to have a
significant impact on sound production or food intake. In contrast, findings showed a significant
reduction of 75.45% (12.1 ± 1.71) in sound production and 77.19% (7.8 ± 1.14) in food intake within
just one day of hypoxic exposure.
Our findings suggest that climate change may impact seahorses in different ways, while higher
temperatures (ranging from 19.3°C to 21.5°C) may increase acoustic signaling and feeding, hypoxia
may result in decreased vocal activity and food consumption with potential impact on their growth and
survival. Moreover, the present study proposes the use of sound-based techniques to monitor seahorse
feeding behaviour and welfare. By detecting and analysing the soundscape, researchers can potentially
measure changes in normal behaviour due to adverse environmental conditions.
Descrição
Tese de mestrado, Ecologia Marinha , 2024, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Hippocampus hippocampus onda de calor marinha hipoxia clicks alimentação Teses de mestrado - 2024