Abstract
Anthropogenic emissions of carbon dioxide (CO2) are causing ocean acidification, lowering seawater aragonite (CaCO3) saturation state (Ωarag), with potentially substantial impacts on marine ecosystems over the 21st Century. Calcifying organisms have exhibited reduced calcification under lower saturation state conditions in aquaria. However, the in situ sensitivity of calcifying ecosystems to future ocean acidification remains unknown. Here we assess the community level sensitivity of calcification to local CO2-induced acidification caused by natural respiration in an unperturbed, biodiverse, temperate intertidal ecosystem. We find that on hourly timescales nighttime community calcification is strongly influenced by Ωarag, with greater net calcium carbonate dissolution under more acidic conditions. Daytime calcification however, is not detectably affected by Ωarag. If the short-term sensitivity of community calcification to Ωarag is representative of the long-term sensitivity to ocean acidification, nighttime dissolution in these intertidal ecosystems could more than double by 2050, with significant ecological and economic consequences.
Highlights
Anthropogenic emissions of carbon dioxide (CO2) are causing ocean acidification, lowering seawater aragonite (CaCO3) saturation state (Ωarag), with potentially substantial impacts on marine ecosystems over the 21st Century
We find that on hourly timescales nighttime community calcification is strongly influenced by Ωarag, with greater net calcium carbonate dissolution under more acidic conditions
An alternative approach has been applied at sites that are isolated from the open ocean during low tides and can experience large temporal variability in calcium carbonate saturation state due to localised photosynthesis and respiration[15,16]
Summary
Anthropogenic emissions of carbon dioxide (CO2) are causing ocean acidification, lowering seawater aragonite (CaCO3) saturation state (Ωarag), with potentially substantial impacts on marine ecosystems over the 21st Century. In situ observations of the sensitivity of calcifying communities to natural saturation state variability are increasingly valued[13], as they incorporate complex species interactions, and capture the carbonate chemistry conditions to which communities are acclimatised Such analyses may better represent the community level sensitivity to long-term ocean acidification. An alternative approach has been applied at sites that are isolated from the open ocean during low tides and can experience large temporal (hourly) variability in calcium carbonate saturation state due to localised photosynthesis and respiration[15,16] It is this approach that is utilised in this study to investigate the sensitivity of calcifiers to saturation state variability in temperate intertidal ecosystems. Our intertidal study site at Bodega Marine Reserve in Northern California www.nature.com/scientificreports/
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