Abstract
BackgroundAs the oceans simultaneously warm, acidify and increase in P CO2, prospects for marine biota are of concern. Calcifying species may find it difficult to produce their skeleton because ocean acidification decreases calcium carbonate saturation and accompanying hypercapnia suppresses metabolism. However, this may be buffered by enhanced growth and metabolism due to warming.Methodology/Principal FindingsWe examined the interactive effects of near-future ocean warming and increased acidification/P CO2 on larval development in the tropical sea urchin Tripneustes gratilla. Larvae were reared in multifactorial experiments in flow-through conditions in all combinations of three temperature and three pH/P CO2 treatments. Experiments were placed in the setting of projected near future conditions for SE Australia, a global change hot spot. Increased acidity/P CO2 and decreased carbonate mineral saturation significantly reduced larval growth resulting in decreased skeletal length. Increased temperature (+3°C) stimulated growth, producing significantly bigger larvae across all pH/P CO2 treatments up to a thermal threshold (+6°C). Increased acidity (-0.3-0.5 pH units) and hypercapnia significantly reduced larval calcification. A +3°C warming diminished the negative effects of acidification and hypercapnia on larval growth.Conclusions and SignificanceThis study of the effects of ocean warming and CO2 driven acidification on development and calcification of marine invertebrate larvae reared in experimental conditions from the outset of development (fertilization) shows the positive and negative effects of these stressors. In simultaneous exposure to stressors the dwarfing effects of acidification were dominant. Reduction in size of sea urchin larvae in a high P CO2 ocean would likely impair their performance with negative consequent effects for benthic adult populations.
Highlights
As the oceans warm and absorb increasing amounts of CO2, marine biota are faced with a suite of stressors causing major change to marine ecosystems [1,2]
This study of the effects of ocean warming and CO2 driven acidification on development and calcification of marine invertebrate larvae reared in experimental conditions from the outset of development shows the positive and negative effects of these stressors
Reduction in size of sea urchin larvae in a high PCO2 ocean would likely impair their performance with negative consequent effects for benthic adult populations
Summary
As the oceans warm and absorb increasing amounts of CO2, marine biota are faced with a suite of stressors causing major change to marine ecosystems [1,2]. Ocean acidification is accompanied by a decrease in saturation of the calcium carbonate (CaCO3) minerals required to make skeletons and by increased organism PCO2 (hypercapnia) [5,6,7]. These stressors are likely to have deleterious interactive effects; increased temperature has a stimulatory effect on physiological processes (until thresholds are reached) while hypercapnia has a suppressive, narcotic effect [6,7]. Calcifying species may find it difficult to produce their skeleton because ocean acidification decreases calcium carbonate saturation and accompanying hypercapnia suppresses metabolism This may be buffered by enhanced growth and metabolism due to warming
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