“the role of microalgae as a key tool to characterize the potential effects associated with co2 enrichment on aquatic ecosystems”/ “la importancia de las microalgas como herramienta clave para la caracterización de los posibles efectos asociados con la acidificación de los sistemas acuáticos”

Abstract

The rapid increase in atmospheric CO2 levels caused by anthropogenic activities is causing climate change and endangering oceans and marine life. Besides, there are other natural and anthropogenic sources of CO2 enrichment in the marine environment which are contributing to changes on the carbonate chemistry of seawater, on a process known as acidification. To simulate CO2 enrichment scenarios in laboratory, different toxicity tests with microalgae have been designed, using the CO2 Injection System®. Along this work some fundamental questions in global change biology are addressed. With this aim, the presented Thesis was divided into several approaches through the exposure of marine microalgae to different scenarios: microalgae exposed individually and in multispecies to CO2 enrichment, microalgae exposed to acidification with external variables such as the presence of metals (Zn) or high temperature and salinity, and the exposure of microalgae to acidification conditions through consecutive generations. The results obtained in this Thesis indicated that acidification caused by CO2 enrichment may cause adverse effects on the phytoplankton community and would lead to changes in the toxicity of metals. Microalgae lethal and sub-lethal responses were very sensitive to stress. This sensitiveness turns them into a useful tool to evaluate the potential impact of global changes in marine environment. Conclusions obtained from this work may be used to improve environmental monitoring and risk assessment studies on this topic.