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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/217732
Thermal compensation in marine copepods: long-term ecophysiological implications in Paracartia grani
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[eng] Ectothermic animals are highly sensitive to changes in the environmental temperature. As ocean temperatures rise, a major concern is the potential impact of warming on copepods, which are crucial contributors to marine food webs. However, our understanding of how copepods respond to chronic temperature changes and the underlying physiological mechanisms is limited due to a scarcity of long- term studies. This thesis presents a series of experiments investigating the direct effects of temperature on copepod phenotypic traits across multiple generations. We specifically focused on the calanoid copepod Paracartia grani, exposed at long-term to warmer conditions (+3°C and +6°C). We explored the implications of chronic thermal stress for production, energetics, life-history as well as the copepod’s resilience to extreme events and low food availability.
The results showed that higher rearing temperatures accelerated copepod hatching and development rates, resulting in a reduction of the adult body size and elemental content (carbon, nitrogen and phosphorous). Initially, temperature increased the copepod main physiological rates (ingestion, respiration and reproduction), but these effects were compensated within a few generations under warmer conditions, with no relevant costs on multiple life-history traits, including the efficiency of food utilized for reproduction, energetics, nauplii hatching success or the sex ratio. Adult body stoichiometric ratios (C:N, C:P, and N:P) were either altered across generations. P. grani exhibited a broad thermal tolerance range (11-32ºC), and long-term warming (+6ºC) even expanded their tolerance to acute high temperatures (>30ºC). However, prolonged exposure to these temperatures reduced its survival after a week, diminishing the advantage gained from warm rearing. At these extreme temperatures, reproduction was reduced but sustained, thereby expanding the fitness of copepods reared under warming conditions. The thermal resilience of this species to extreme temperatures was highlighted when subjected to sub- lethal thermal stress (28ºC), which did not affect the metabolic balance of copepods regardless of the rearing temperatures (19, 22 and 25ºC). As a main trade-off, following chronic warming the food uptake under low food conditions of the prey Rhodomonas salina was highly reduced, potentially indicating a decline in feeding efficiency and subsequent reduction in reproductive activity.
Overall, the research carried out in this thesis suggests that P. grani has a large capability to adapt to temperature increases, maintaining key activities, like grazing and production. Nevertheless, an increase in thermal anomalies, low food availability, or the combination of both factors may limit their capacity to persist in their local environment. Given that the thermal effects on development were not compensated at long-term, size reductions in copepods might be a major consequence of ocean warming, with important ramifications for marine food webs and biogeochemical cycles.
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JUAN CARBONELL, Carlos de. Thermal compensation in marine copepods: long-term ecophysiological implications in Paracartia grani. [consulta: 3 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/217732]