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Ocean acidification impacts primary and bacterial production in Antarctic coastal waters during austral summer

Citation

Westwood, KJ and Thomson, PG and van den Enden, RL and Maher, LE and Wright, SW and Davidson, AT, Ocean acidification impacts primary and bacterial production in Antarctic coastal waters during austral summer, Journal of Experimental Marine Biology and Ecology, 498 pp. 46-60. ISSN 0022-0981 (2018) [Refereed Article]

Copyright Statement

Copyright 2017 Crown Copyright

DOI: doi:10.1016/j.jembe.2017.11.003

Abstract

Polar waters may be highly impacted by ocean acidification (OA) due to increased solubility of CO2 at colder water temperatures. Three experiments examining the influence of OA on primary and bacterial production were conducted during austral summer at Davis Station, East Antarctica (6835′ S, 7758′ E). For each experiment, six minicosm tanks (650L) were filled with 200μm filtered coastal seawater containing natural communities of Antarctic marine microbes. Assemblages were incubated for 10 to 12days at CO2 concentrations ranging from pre-industrial to post-2300. Primary and bacterial production rates were determined using NaH14CO3 and 14C-leucine, respectively. Net community production (NCP) was also determined using dissolved oxygen. In all experiments, maximum photosynthetic rates (Pmax, mgCmgchl a1h1) decreased with elevated CO2, clearly reducing rates of total gross primary production (mgCL1h1). Rates of cell-specific bacterial productivity (μgCcell1h1) also decreased under elevated CO2, yet total bacterial production (μgCL1h1) and cell abundances increased with CO2 over Days 04. Initial increases in bacterial production and abundance were associated with fewer heterotrophic nanoflagellates and therefore less grazing pressure. The main changes in primary and bacterial productivity generally occurred at CO2 concentrations >2 present day (>780ppm), with the same responses occurring regardless of seasonally changing environmental conditions and microbial assemblages. However, NCP varied both within and among experiments, largely due to changing nitrate+nitrite (NOx) availability. At NOx concentrations <1.5μM photosynthesis to respiration ratios showed that populations switched from net autotrophy to heterotrophy and CO2 responses were suppressed. Overall, OA may reduce production in Antarctic coastal waters, thereby reducing food availability to higher trophic levels and reducing draw-down of atmospheric CO2, thus forming a positive feedback to climate change. NOX limitation may suppress this OA response but cause a similar decline.

Item Details

Item Type:Refereed Article
Keywords:ocean acidification, primary production, bacterial production, net community production, photosynthesis, Antarctica
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical Oceanography
Objective Division:Environment
Objective Group:Other Environment
Objective Field:Antarctic and Sub-Antarctic Oceanography
UTAS Author:Westwood, KJ (Dr Karen Westwood)
UTAS Author:Wright, SW (Dr Simon Wright)
UTAS Author:Davidson, AT (Dr Andrew Davidson)
ID Code:131772
Year Published:2018
Web of Science® Times Cited:6
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2019-04-04
Last Modified:2019-05-08
Downloads:0

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