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Effects of ocean warming throughout the life cycle of Sparus aurata: a physiological and proteomic approach
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Resumo(s)
Climate change is a major environmental problem, known to cause pervasive effects on marine ecosystems, impacting goods and services provided to society. It alters biodiversity patterns, abundance and distribution of species, biological interactions, phenology, and organisms’ physiology. However, the vulnerability of fish stocks towards ocean warming is still far from clear due to the lack of integrative approaches that address physiological and molecular compensation mechanisms throughout all the stages of the life-cycle. This thesis aimed at uncovering the vulnerability of a highly commercial sea bream Sparus aurata to ocean warming throughout the various stages of its life cycle, considering organism-, cellular- and molecular-level approaches. The first two assays revealed that larvae are very sensitive to both acute and chronic thermal stress (>22ºC), showing a CTmax (Critical Thermal Maximum) of 30ºC and a reduced capacity to employ the cellular stress response (leading to protein denaturation) and perform the energetic adjustments that would have been necessary to sustain a temperature increase. This probably led to the observed tissue injury (in muscle and kidneys) and elevated mortality rates. Juveniles were the most resistant and plastic to warming with a CTmax of 35.5ºC although temperatures of ≥ 28ºC in the acute assay induced significant tissue damage related to protein denaturation and oxidative stress. Exposure to chronic warming elicited the cellular stress response coupled with an enhanced glycolytic potential (vital organs were highly responsive). However, after 21 days fish showed signs of inflammation and mortality was significantly increased. Adult fish were less resistant than juveniles because vital organs were less responsive and showed the highest tissue injury level (damage to lipids and proteins, inflammation, atrophy) leading to elevated mortality. This suggests a response to damage rather than a plastic response. Thus, the effort and mechanisms of protection against thermal challenge are differentially allocated by distinct organs, depending on developmental stage. Moreover, the larval phase is the key developmental stage that will determine life cycle closure of S. aurata under the projected ocean warming scenarios.
Descrição
Palavras-chave
Temperature Climate change Fish Physiology Proteomics Life-cycle