In-situ behavioural and physiological responses of Antarctic microphytobenthos to ocean acidification

James G Black,Simon Wootherspoon,Glenn J Johnstone,John W Runcie,Jonathan S Stark,Philip Boyd,John Mckinlay,Andrew Mcminn

doi:10.1038/s41598-018-36233-2

James G Black, Simon Wootherspoon + Show 6 more

Open Access

https://doi.org/10.1038/s41598-018-36233-2

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Abstract

Ocean acidification (OA) is predicted to alter benthic marine community structure and function, however, there is a paucity of field experiments in benthic soft sediment communities and ecosystems. Benthic diatoms are important components of Antarctic coastal ecosystems, however very little is known of how they will respond to ocean acidification. Ocean acidification conditions were maintained by incremental computer controlled addition of high fCO2 seawater representing OA conditions predicted for the year 2100. Respiration chambers and PAM fluorescence techniques were used to investigate acute behavioural, photosynthetic and net production responses of benthic microalgae communities to OA in in-situ field experiments. We demonstrate how OA can modify behavioural ecology, which changes photo-physiology and net production of benthic microalgae. Ocean acidification treatments significantly altered behavioural ecology, which in turn altered photo-physiology. The ecological trends presented here have the potential to manifest into significant ecological change over longer time periods.

Highlights

Ocean acidification (OA) is the change in seawater carbonate chemistry, including a reduction in pH, as a result of the absorption of atmospheric CO2 into the oceans[1]
Treatment water used in this experiment was pumped from the Antarctic Free Ocean Carbon Enrichment experiment experimental chambers, acidified treatments maintained a pH offset of 0.3825 ± 0.065, mean Ωar of 0.62 ± 0.14 and mean fCO2 values of 912.5 ± 155 μatm over the duration of their experiment
Treatment water pH, oxygen and salinity measurements were sampled from the Antarctic Free Ocean Carbon Enrichment experiment (antFOCE) sensor system at the time water was pumped from antFOCE treatments into respiration chambers, (Fig. 1)

Summary

Introduction

Ocean acidification (OA) is the change in seawater carbonate chemistry, including a reduction in pH, as a result of the absorption of atmospheric CO2 into the oceans[1]. The majority of OA research to date has been on single organisms in laboratory-based studies[7] These studies indicate that reduced pH will be detrimental to some organisms (some calcifying heterotrophs) but advantageous to others (non-calcifying algae), creating potential “winners” and “losers” in marine communities under future scenarios of higher atmospheric CO23,4,8. Whether these single organism responses will translate to actual changes in natural communities, once all ecological interactions are included, is largely untested. A review of MPB responses to OA by Marques da Silva, et al.[24] stongly emphazies the need for a better understanding of MPB response to OA

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