Líffræðifélag Íslands
Líffræðiráðstefnan 2015

Erindi/veggspjald / Talk/poster E77

Understanding the effect of warming on productivity, species composition, and nutrient cycling in river ecosystems

J.R. Welter (1), W.F. Cross (2), J.P. Benstead (3), A.D. Huryn (3), J.M. Hood (2), T.W. Williamson (2), D. Nelson (3), P.C. Furey (1), J.R. Junker (2), P.W. Johnson (3), J.S. Olafsson (4), G.M. Gislason (5)

1. St. Catherine University, 2. Montana State University, 3. University of Alabama, 4. Institute of Freshwater Fisheries, 5. University of Iceland

Kynnir / Presenter: Jill R. Welter

Tengiliður / Corresponding author: Jill R. Welter (jrwelter@stkate.edu)

"Ecologists have recently uncovered strong relationships between temperature and key metabolic processes including growth, metabolism, and nutrient acquisition, resulting in an emerging ‘metabolic theory of ecology’. Considerable uncertainty, however, remains with regard to how effects of temperature on organisms will be manifested in ecosystems at larger scales due to interactions and synergistic effects among different species and metabolic processes. To study how warming influences the structure and function of stream ecosystems, we have employed a multi-scale investigation that utilizes experimental warming as well as a naturally occurring gradient of stream temperatures in a geothermally-active watershed. The Hengill Valley, Iceland contains a steep gradient of ambient stream temperatures (4°C to >30°C across 15 streams). Results indicate that warming leads to increased gross primary production and ecosystem respiration; however, rates in warming experiments exhibit steeper temperature dependence than predicted by metabolic theory. This pattern may be explained by observed parallel increases in nitrogen fixation rates and cyanobacteria biomass with warming, which increases nitrogen availability necessary for growth. Experimental warming also caused shifts in invertebrate assemblages, which coupled with changes in dominant primary producers suggest that food web dynamics may be altered in unexpected ways due to climate warming. Many nitrogen-fixing species are largely inedible, which may result in increased nitrogen export from stream ecosystems as they warm."