Líffræðifélag Íslands
Líffræðiráðstefnan 2015

Erindi/veggspjald / Talk/poster E75

Geothermally heated stream ecosystems as model in climate warming studies

Jón S. Ólafsson(1), Jonathan P. Benstead(2), Wyatt F. Cross(3), Benoit L. Demars (4), Nikolai Friberg(5), Gísli M. Gíslason(6), Eoin O‘Gorman(7), Rakel Guðmundsdóttir(6), Elísabet R. Hannesdóttir(1,6), James M. Hood(3), Alex D. Huryn(2), James R. Junker(3), Ragnhildur Þ. Magnúsdóttir(1), Daniel Nelson(2), Jill Welter(8) and Guy Woodward(7)

"1. Institute of Freshwater Fisheries, Reykjavík, Iceland; 2. University of Alabama, Tuscaloosa, USA; 3. Montana State Univeristy, Bozeman, USA; 4. James Hutton Institute, Aberdeen, Scotland; 5. NIVA, Norsk Institutt for Vannforskning, Oslo, Norway; 6. University of Iceland, Reykjavík, Iceland; 7. Imperial College London, UK; 8. St. Catherine University, Saint Paul, Minnesota, USA"

Kynnir / Presenter: Jón S. Ólafsson

Tengiliður / Corresponding author: Jón S. Ólafsson (jsol@veidimal.is)

"It is inevitable to most of us that climate driven changes are affecting freshwater ecosystems worldwide. Clear indications of rapid warming are seen in the Arctic and sub-Arctic regions. So far, most observations are on species range shift, phenology and changes in body size. In stream ecology, our understanding and predictions on how warming may affect the ecosystem function, food-web structure and species assemblages have been limited. To study the effect of temperature on ecosystems, various approaches have been used e.g. mesocosms, heated stream channels or space-for-time substitutions. In our studies on stream ecosystems we are using geothermal fields in Iceland where we can find temperature gradients within confined areas to increase our understanding of possible consequences of warming and to test relevant ecological theories. The streams we are using are all alkaline. For the warm streams, the stream water has been warmed up underground when flowing in the vicinity of hot bedrock. This scenario provides an ideal “Natural laboratory” with the possibilities of replication. Our main focus is on the ecosystem structure and function, species assemblages and metacommunity structure. For this we are conducting our study at landscape scale were we with emphasis on metacommunity structure, assemblages and function; at local scale we focus on ecosystem function and food-webs at temperature gradients in replicated streams in confined area and lastly with experiments where we warm up a cold spring-fed stream to study species assemblages, ecosystem function and food-webs. The main results show that, 1) Algal biomass increases with temperature, which is mainly due to an increase in cyanobacteria biomass, 2) Stream macro-invertebrate assemblages are highly temperature related, 3) Invertebrate taxa richness decreases with increasing temperature, 4) Invertebrate taxa similarity decreases as pairwise temperature differences increases and 5) The invertebrate assemblages shift from chironomid dominated to communities dominated by Oligochaeta, Gastrapoda, Acarina and other Diptera larvae than Chironomidae. Invertebrate growth rate increases with temperature e.g. eurythermal taxa grow faster at higher temperatures and complete more generations per year."