Abstract
Abstract. Due to their aragonitic shell, thecosome pteropods may be particularly vulnerable to ocean acidification driven by anthropogenic CO2 emissions. This applies specifically to species inhabiting Arctic surface waters that are projected to become temporarily and locally undersaturated with respect to aragonite as early as 2016. This study investigated the effects of rising partial pressure of CO2 (pCO2) and elevated temperature on pre-winter juveniles of the polar pteropod Limacina helicina. After a 29 day experiment in September/October 2009 at three different temperatures and under pCO2 scenarios projected for this century, mortality, shell degradation, shell diameter and shell increment were investigated. Temperature and pCO2 had a significant effect on mortality, but temperature was the overriding factor. Shell diameter, shell increment and shell degradation were significantly impacted by pCO2 but not by temperature. Mortality was 46% higher at 8 °C than at in situ temperature (3 °C), and 14% higher at 1100 μatm than at 230 μatm. Shell diameter and increment were reduced by 10 and 12% at 1100 μatm and 230 μatm, respectively, and shell degradation was 41% higher at elevated compared to ambient pCO2. We conclude that pre-winter juveniles will be negatively affected by both rising temperature and pCO2 which may result in a possible decline in abundance of the overwintering population, the basis for next year's reproduction.
Highlights
Anthropogenic CO2 emissions affect the seawater carbonate chemistry and cause a decrease of seawater pH and carbonate ions in the worlds’ oceans, thereby diminishing the saturation state of seawater with respect to calcite and aragonite
Due to increasing CO2 emissions since the industrial revolution, global mean surface temperatures have risen by 0.76 ◦C and global mean seawater pH has decreased by 0.1 unit (IPCC, 2007)
The present paper reports on the first experimental study that focuses on the combined effects of ocean acidification and elevated temperature on juveniles of the pteropod L. helicina from the Arctic Kongsfjord (Svalbard) prior to the overwintering period
Summary
Anthropogenic CO2 emissions affect the seawater carbonate chemistry and cause a decrease of seawater pH (termed ocean acidification) and carbonate ions in the worlds’ oceans, thereby diminishing the saturation state of seawater with respect to calcite and aragonite. This effect is strongest in high-latitude surface waters, which are experiencing the steepest increase in surface ocean temperature (Orr et al, 2005; Steinacher et al, 2009). Calcite and aragonite are two common types of calcium carbonate secreted by marine organisms. Organisms’ response of calcification to carbonate system variations is diverse
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