Os peixes amazônicos vivem perto dos seus limites térmicos? O efeito das mudanças climáticas sobre a ecofisiologia de peixes de Igarapé da Amazônia Central

Abstract

Since the industrial revolution, the earth has been facing increases in CO2 concentration which, consequently, have led to an increase in global average temperatures. Of the last 23 years, 22 have had temperatures above the global average. Temperature is the main factor affecting the life of ectothermic species. In addition, tropical species are expected to be especially vulnerable to temperature increases, since many of them appear to have a narrower thermal tolerance range and live closer to their thermal limits. However, to date, studies that assess the vulnerability of Amazonian species are scarcet. Among these species, fish from igarapé appear to be especially vulnerable, since they occur in an extremely stable thermal environment. Therefore, the present thesis aims to evaluate the adaptability to the increase of temperature and CO2 on the physiological parameters in Igarapé fish species. In chapter I our results showed that active species present high energy demand in order to supply maintenance costs for a high activity and, therefore, have a low thermal tolerance. In Chapter II, Hyphessobrychon melazonatus, an active species, acclimated to the extreme climate change scenario, presented great osmoregulatory disturbances, which may have important impacts on the long-term survival capacity. In fact, in chapter III we observed that all three species present metabolic alterations and acclimate cellular damages the future climatic conditions, however, H. melazonatus was the species that presented the highest mortality rates, lipid damages and reduction in the thermal safety margin. In chapter IV we showed that Pyrrhullina brevis acclimated for 180 days in the extreme scenario presents a reduction in body size, according to the third universal response to temperature. However, contrary to the OCLTT hypothesis, reduction in size is not linked to an inability to supply oxygen to tissues, but rather appears to be related to an increase in levels of cellular damage that impede growth according to life-history trade-off theory. Our results highlight the importance of public policies aimed at reducing the agents that cause climate change and the preservation of forest areas that play a fundamental role in maintaining the temperature of the Igarapés.