University of Tasmania
Browse

File(s) under permanent embargo

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

journal contribution
posted on 2023-05-20, 02:28 authored by Karen WestwoodKaren Westwood, Thomson, PG, van den Enden, RL, Maher, LE, Simon WrightSimon Wright, Davidson, AT

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 (68°35′ S, 77°58′ E). For each experiment, six minicosm tanks (650 L) were filled with 200 μm filtered coastal seawater containing natural communities of Antarctic marine microbes. Assemblages were incubated for 10 to 12 days 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, mg C mg chl a− 1 h− 1) decreased with elevated CO2, clearly reducing rates of total gross primary production (mg C L− 1 h− 1). Rates of cell-specific bacterial productivity (μg C cell− 1 h− 1) also decreased under elevated CO2, yet total bacterial production (μg C L− 1 h− 1) and cell abundances increased with CO2 over Days 0–4. 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 (> 780 ppm), 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 < 1.5 μM 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.

History

Publication title

Journal of Experimental Marine Biology and Ecology

Volume

498

Pagination

46-60

ISSN

0022-0981

Department/School

Institute for Marine and Antarctic Studies

Publisher

Elsevier Science Bv

Place of publication

Po Box 211, Amsterdam, Netherlands, 1000 Ae

Rights statement

Copyright 2017 Crown Copyright

Repository Status

  • Restricted

Socio-economic Objectives

Antarctic and Southern Ocean oceanic processes

Usage metrics

    University Of Tasmania

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC