Stress response in temperate and polar benthos: from populations to moleculesDoris Abele, Alfred-Wegner Institute for Polar and Marine Reserach, Bremerhaven, Germany (dabele@awi-bremerhaven.de)The Antarctic Peninsula is an area of rapid recent climate change. Mean air temperature has risen by 2.5°centigrade over the last 5 decades, and glaciers are melting mainly along the Western coasts and on the adjacent islands. This results in increased sediment transport to coastal areas, freshening of coastal surface waters and high incidence of iceberg scours in shallow environments. Additionally, animals at shallow depths receive high doses of detrimental UVB radiation during ozone hole conditions in the southern spring.Antarctic animals are adapted to very constant and predictable cold water conditions. They generally have low metabolic rates and especially sedentary species also have low scope for activity, resulting in slower growth and development (Peck et al. 2004), but longer life expectancy compared to temperate animals with a similar lifestyle (Philipp et al. 2005). Stress sensitivity is increased by specific features at the tissue and cell level like loss of the inducible heat shock response in ice fish (Hofmann et al. 2000). Also the extremely high tissue iron levels found in molluscs around the volcanic South Shetland islands may render these animals more sensitive to stress (Gonzalez unpublished), because the fraction of free tissue iron acts as Fenton catalyst producing reactive oxygen species, which may interfere with cellular signalling.In stress research, two possible scenarios should be distinguished: Subcritical stress (slow changes of temperature or tolerable exposure to heavy metals like iron) will raise costs for tissue maintenance and repair. This will limit the aerobic scope, meaning the amount of energy an animal can use to perform activity and to grow (Peck et al 2004). Populations under constant stress will therefore have different age to size relations than unstressed populations. Contrary, frequent impact of acute critical stress which the animal needs to actively counteract, like unearthing from the sediment by iceberg scours, predator attack eliciting vigorous flight response, or sudden intense exposure to bright sunlight including UV-radiation in transparent amphipods (Obermüller et al. ms submitted), will raise energy expenditure for escape and defence and reduce investment into body maintenance. Both forms of stress will eventually shorten animal life expectancy although by different mechanisms.Thus any form of subcritical or critical stress is bound to shorten life span, and population growth-age curves can serve the assessment of stress levels acting on two differently impacted populations from the same climatic background. Moreover, biochemical markers accumulating in a tissue over age can be assessed to describe the loss of maintenance in differently stressed populations.In my talk I will present data that fuse life history and changes of biochemical stress markers in cold stenothermal and cold boreal mollusc species and discuss the potential of these markers in stress research. I will also present the approach from our IPY program ClicOPEN with respect to stress research in changing coastal ecosystems at the Western Antarctic Pensinsula.Peck, LS, Webb K E, Bailey, DM (2004). Extreme sensitivity of biological function to temperature in Antarctic marine species. Funct. Ecol. 18:625-630.Philipp, E, Brey T, Pörtner H-O, Abele D (2005). Chronological and physiological ageing in a polar and a temperate mud clam. Mech. Ageing Dev. 126:589-609.Hofmann GE, Buckley, BA, Airaksinen S, Keen JE, Somera GN (2000). Heat-shock protein expression is absent in the Antarctic fish Trematomus bernacchii (Family Nototheniidae). J. Exp. Biol. 203:2331-2339.Obermüller, B, Puntarulo, S, Abele, D (2006). UV-tolerance and instantaneous physiological stress responses of two Antarctic amphipod species Gondogeneia antarctica and Djerboa furcipes during exposure to UV radiation. Ms submitted