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. 2009 Jun 9;106(23):9316-21.
doi: 10.1073/pnas.0811143106. Epub 2009 May 26.

Elevated Water Temperature and Carbon Dioxide Concentration Increase the Growth of a Keystone Echinoderm

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Elevated Water Temperature and Carbon Dioxide Concentration Increase the Growth of a Keystone Echinoderm

Rebecca A Gooding et al. Proc Natl Acad Sci U S A. .
Free PMC article

Abstract

Anthropogenic climate change poses a serious threat to biodiversity. In marine environments, multiple climate variables, including temperature and CO(2) concentration ([CO(2)]), are changing simultaneously. Although temperature has well-documented ecological effects, and many heavily calcified marine organisms experience reduced growth with increased [CO(2)], little is known about the combined effects of temperature and [CO(2)], particularly on species that are less dependent on calcified shells or skeletons. We manipulated water temperature and [CO(2)] to determine the effects on the sea star Pisaster ochraceus, a keystone predator. We found that sea star growth and feeding rates increased with water temperature from 5 degrees C to 21 degrees C. A doubling of current [CO(2)] also increased growth rates both with and without a concurrent temperature increase from 12 degrees C to 15 degrees C. Increased [CO(2)] also had a positive but nonsignificant effect on sea star feeding rates, suggesting [CO(2)] may be acting directly at the physiological level to increase growth rates. As in past studies of other marine invertebrates, increased [CO(2)] reduced the relative calcified mass in sea stars, although this effect was observed only at the lower experimental temperature. The positive relationship between growth and [CO(2)] found here contrasts with previous studies, most of which have shown negative effects of [CO(2)] on marine species, particularly those that are more heavily calcified than P. ochraceus. Our findings demonstrate that increased [CO(2)] will not have direct negative effects on all marine invertebrates, suggesting that predictions of biotic responses to climate change should consider how different types of organisms will respond to changing climatic variables.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Sea star growth and feeding rates increased linearly with water temperature. (A) Mean relative sea star growth (percentage of change from initial wet mass) with water temperature. (B) Mean number of mussels consumed daily per sea star with water temperature. Each data point is a within-tank mean of 2 sea stars.
Fig. 2.
Fig. 2.
Mean sea star growth (percentage of change from initial wet mass) over time with increased water temperature and [CO2]. Error bars represent ±1 standard error (SE) of the mean.
Fig. 3.
Fig. 3.
Mean number of mussels consumed daily per sea star under 4 factorial temperature and [CO2] combinations. Error bars represent ±1 SE of the mean.
Fig. 4.
Fig. 4.
Mean proportion of sea star wet mass consisting of calcified material under 4 factorial temperature and [CO2] combinations. Error bars represent ±1 SE of the mean. To account for the confounding effect of sea star size on feeding rate, data were adjusted to the approximate median sea star wet mass (12 g).

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