On Wednsday the 8th of February Hrönn Egilsdóttir will defend her Ph.D. thesis in Earth Sciences.
The thesis is titled "Calcifying organisms in changing shallow and deep marine environments"
Opponents are Dr. Jean-Pierre Gattuso, CNRS Senior Research Scientist, Laboratoire d’Océanographie de Villefranche, France.
Professor Stephen Widdicombe, Head of Science “Marine Biodiversity and Ecology” at Plymouth Marine Laboratory (PML) in England.
Prof. Jón Ólafsson, professor emeritus, Faculty of Earth Sciences, University of Iceland Supervised.
The assessment committee included Dr. Karl Gunnarsson, Specialist at Marine Research Institute and
Dr. Þórarinn Sveinn Arnarson, project manager with the National Energy Authority of Icela
Anthropogenic CO2 emissions, which are resulting in ocean acidification and a decrease in the saturation state for calcium carbonate (Ω), are a particular threat to calcifying marine biota. The aim of this thesis is to fill important knowledge gaps that limits our understanding of the implication of these anthropogenically driven changes for calcifying organism in intertidal, coastal and deep sea environments.
Papers I and II investigate the intertidal environment where the range and rate of environmental changes are often extreme. Paper I describes seasonal and daily fluxes in the inorganic carbon system in tidal pool environments in relation to biological processes in a red calcifying coralline algal species (Ellisolandia elongata) through irradiance response curves. Paper II describes an experimental study where alga from the same population as studied in paper I were grown for 3 weeks at varying pCO2 concentrations: 380 µatm (representing modern day atmosphere) and 550, 750 and 1000 µatm (representing future atmospheric CO2 concentrations). Results suggest intertidal algae are less susceptible to future atmospheric CO2 concentrations compared to coralline alga from the subtidal marine environments.
Data on spatial and temporal variability in the inorganic carbon system in coastal regions is limited, which is an issue for understanding biological responses of coastal species to ocean acidification and for the construction of numerical biogeochemical models. Paper III investigates the seasonal variability in the inorganic carbon system in a pristine coastal region of Iceland, Breiðafjörður Bay. The study region was identified as a net sink of atmospheric CO2 at a rate of 1.8 mol C m-2 y-1 with surface pCO2 ranging from 212 to 417 µatm from summer to winter.
The deep sea is a relatively stable environment. Regardless, numerical model predictions suggest the Nordic Seas will be largely undersaturated with respect to aragonite by the year 2100, posing a severe threat to calcifying mollusc in the region. Paper IV provides previously lacking information on bivalve and gastropod occurrences and biodiversity in the high latitude North Atlantic, north and south of the Greenland-Iceland-Faroe (GIF) ridge. This information is fundamental for evaluating the effects of environmental changes in this regions on calcifying benthic molluscs.
Altogether, the research presented in this thesis contributes information needed to understand the implications of environmental changes, in particular ocean acidification, for calcifying biota in intertidal, coastal and deep sea environments
About the Ph.D. student
Hrönn Egilsdóttir was born in Reykjavík, in 1983. Her partner is Róbert Cabrera and together they have one son, born in 2013. In 2007 she completed a BS-degree in biology from the University of Iceland. In 2008 she received a Master of Research (MRes) degree in marine biology from the University of Plymouth in England. In 2009 she began working towards her PhD at the Faculty of Earth Sciences at the University of Iceland together with the Marine Research Institute, Iceland. The aim of the project was to increase understanding of the implications of ocean acidification for calcifying biota in the marine environment. The PhD project was originally funded by the Marine Research Institute and the European project EPOCA. The project has also received funds from the National Power Company of Iceland, Energy Research Fund and the Nature conservation fund of Pálmi Jónsson. The last stage of the project were funded by Fisheries Iceland which also fund Hrönn to continue work as a post-doctoral researcher at the Institute of Earth Sciences, University of Iceland.