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Identifier 000451469
Title Eπίδραση υψηλών θερμοκρασιών στο μεταβολισμό εκτρεφόμενων ειδών ψαριών : συνδυάζοντας πειραματική προσέγγιση και μαθηματική μοντελοποίηση
Alternative Title Effects of high temperatures on the metabolism of farmed fish: combining experimental approach and mathematical modeling
Author Σταυρακίδης Ζάχου, Ορέστης Κ
Thesis advisor Λύκα, Κωνσταντίνα
Παπανδρουλάκης, Νίκος
Reviewer Παυλίδης, Μιχαήλ
Κεντούρη, Μαρουδιώ
Μούτου, Αικατερίνη
Στεργίου, Κωνσταντίνος
Αντωνοπούλου, Ευθυμία
Abstract Temperature is an important environmental factor for fish as it affects their metabolism and determines a large set of behavioural and physiological traits. According to the soCio-economic scenarios of the Intergovernmental Panel on Climate Change (IPCC), the global average sea temperature is expected to increase by several degrees by the end of the century, a trend that is projected to be more pronounced for the Mediterranean as it has been identified as a particularly vulnerable region to climate change. In this context, there is a clear need to study and predict the thermal responses and thermal limits of the organisms living in the Mediterranean, especially if they are species of major commercial interest, such as aquaculture species. The present thesis foCuses on the study of the effects of high temperatures on the metabolism of two farmed fish of interest for the Mediterranean aquaculture, European sea bass (Dicentrarchus labrax) and meagre (Argyrosomue regius). Preparing for and addressing the future challenges requires an integrated approach that contributes both to a better understanding of the responses of organisms to thermal stress, and to the development of appropriate tools, such as mathematical models, that allow further investigation and offer predictive power. For that reason, a combination of experimentatal approaches and mathematical modeling was adopted here. The aim of the experimental approach was to determine the thermal tolerance of the two species under chronic and acute thermal stress. The main questions foCus on the study of their physiological responses to increasing temperatures, the effects on the whole organismal level and its overall performance, and the determination of thermal tolerance limits under conditions of chronic and acute thermal stress. Regarding the mathematical modeling approach, the aim was to investigate the relationships between temperature and metabolism in both species and to simulate metabolic proCesses under the unified bioenergetic framework of the Dynamic Energy Budget (DEB) theory. DEB theory describes the metabolism of organisms using energy and mass balances and can simulate changes in key biological proCesses such as growth, energy assimilation, maintenance, maturation and reproduction as a function of temperature and food availability under dynamically changing environments. In the experimental approach, thermal stress was studied at time scales and intensities relevant to the study of climate change. Three acclimation temperatures representing typical (24 oC), maximum (28 - 29 oC), and predicted under climate change scenarios (33 - 34 oC) summer temperatures in the Mediterranean were investigated and fish responses to a set of biomarkers were studied including developmental, haematological, bioChemical, hormonal and molecular parameters as well as the measurement of metabolic rate and the determination of the Crtitical Thermal Maximum under acute thermal stress. The results indicate similar patterns of response for the two species and similar tolerance thresholds to chronic thermal stress, with some quantitative differences between species. The optimum temperature for growth for both E. sea bass and meagre was placed between 24 and 29 oC, with that of meagre being closer to the lower end of the range. A number of biomarkers such as anaerobic metabolism (lactic acid), protective (heat shoCk proteins, antioxidants) and stress (cortisol) markers indicate levels of mild thermal stress at intermediate temperatures (28 - 29 oC), while chronic exposure to even higher temperatures is not deemed sustainable for the rearing of the species as it has dramatic effects on fish performance and health with rapid deterioration of the physiological markers. Furthermore, the upper limits of survival appear conserved for both species within an extremely narrow temperature range surrounding 33 oC. Moreover, the overall reduction of biological performance when approaching these limits is mainly interpreted as the insufficient capacity for aerobic metabolism, which was reflected in the study of metabolic rate, the development of megacardia, and the increase of anaerobic metabolism markers. Finally, the two species show remarkable tolerance to acute thermal stress, with that of E. sea bass, however, being greater, suggesting that the species carry a significant capacity to cope with episodes of extreme weather events such as heat waves. With respect to mathematical modeling, DEB models for both species were developed using both literature and experimental data from this thesis for their parameterization. The models were then validated by comparing their predictions to field measurements. In addition, a mathematical module for predicting body composition was developed as well as an approach to simulate thermal tolerance limits during acute thermal stress induction. The goodness of fit of the models to the data showed that the thermal responses of the two species, both in terms of their growth and changes in their energy reserves, can be sufficiently described by a mechanistic framework that interprets metabolism as energy and mass balances. In addition, comparison of the bioenergetic budgets of the two species showed differences in their energetic strategies, with E. sea bass alloCating a greater proportion of its budget to maturation and reproduction proCesses as well as to maintenance, which may explain the higher growth rates observed for the meagre. Furthermore, analysis of the model parameters showed that some parameters, in particular those reflecting the ability to assimilate energy from the environment and the cost of physical maintenance, correlate with optimal temperature, thus allowing comparisons of thermal sensitivity between species. Finally, simulations of acute thermal stress have shown that assumptions based on thermodynamic constraints can provide a realistic approach to mechanistically describe the upper thermal limits of fish, capturing the basic trends that are observed experimentally. Overall, the results of this thesis have shown that the study of fish metabolism and thermal responses through a combination of experimental and mathematical modeling methods is a promising approach with interesting implications, since they complement each other while offering tools with predictive and interpretative power.
Language Greek
Subject Aquaculture
Climate change
DEB
Fish physiology
Thermal stress
Θερμική καταπόνηση
Κλιματική αλλαγή
Υδατοκαλλιέργεια
Φυσιολογία ψαριών
Issue date 2022-10-07
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Doctoral theses
  Type of Work--Doctoral theses
Permanent Link https://elocus.lib.uoc.gr//dlib/a/0/9/metadata-dlib-1665129702-79859-9951.tkl Bookmark and Share
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