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Published (Version of record)CC BY V3.0, Open
Journal article
Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO2 tolerance in phytoplankton productivity
Biogeosciences, Vol.15(1), pp.209-231
27/09/2018
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Abstract
High-latitude oceans are anticipated to be some of the first regions affected by ocean acidification. Despite this, the effect of ocean acidification on natural communities of Antarctic marine microbes is still not well understood. In this study we exposed an early spring, coastal marine microbial community in Prydz Bay to CO2 levels ranging from ambient (343 µatm) to 1641 µatm in six 650 L minicosms. Productivity assays were performed to identify whether a CO2 threshold existed that led to a change in primary productivity, bacterial productivity, and the accumulation of chlorophyll a (Chl a) and particulate organic matter (POM) in the minicosms. In addition, photophysiological measurements were performed to identify possible mechanisms driving changes in the phytoplankton community. A critical threshold for tolerance to ocean acidification was identified in the phytoplankton community between 953 and 1140 µatm. CO2 levels ≥ 1140 µatm negatively affected photosynthetic performance and Chl a-normalised primary productivity (csGPP14C), causing significant reductions in gross primary production (GPP14C), Chl a accumulation, nutrient uptake, and POM production. However, there was no effect of CO2 on C : N ratios. Over time, the phytoplankton community acclimated to high CO2 conditions, showing a down-regulation of carbon concentrating mechanisms (CCMs) and likely adjusting other intracellular processes. Bacterial abundance initially increased in CO2 treatments ≥ 953 µatm (days 3–5), yet gross bacterial production (GBP14C) remained unchanged and cell-specific bacterial productivity (csBP14C) was reduced. Towards the end of the experiment, GBP14C and csBP14C markedly increased across all treatments regardless of CO2 availability. This coincided with increased organic matter availability (POC and PON) combined with improved efficiency of carbon uptake. Changes in phytoplankton community production could have negative effects on the Antarctic food web and the biological pump, resulting in negative feedbacks on anthropogenic CO2 uptake. Increases in bacterial abundance under high CO2 conditions may also increase the efficiency of the microbial loop, resulting in increased organic matter remineralisation and further declines in carbon sequestration.
Details
- Title
- Ocean acidification of a coastal Antarctic marine microbial community reveals a critical threshold for CO2 tolerance in phytoplankton productivity
- Creators
- Stacy Deppeler - University of TasmaniaKatherina Petrou - University of Technology SydneyKai G Schulz - Southern Cross UniversityKaren Westwood - Australian Antarctic Division and Antarctic Climate and Ecosystems CRCImojen Pearce - Australian Antarctic DivisionJohn Mckinlay - Australian Antarctic DivisionAndrew Davidson - Australian Antarctic Division and Antarctic Climate and Ecosystems CRC
- Publication Details
- Biogeosciences, Vol.15(1), pp.209-231
- Publisher
- Copernicus GmbH
- Grant note
- This study was funded by the Australian Government, Department of Environment and Energy as part of the Australian Antarctic Science Project 4026 at the Australian Antarctic Division and an Elite Research Scholarship awarded by the Institute for Marine and Antarctic Studies, University of Tasmania.
- Identifiers
- 991012926965402368
- Copyright
- © Author(s) 2018. This work is distributed under the Creative Commons Attribution 3.0 License.
- Academic Unit
- Centre for Coastal Biogeochemistry; Faculty of Science and Engineering; School of Environment, Science and Engineering; Science
- Language
- English
- Resource Type
- Journal article