Responses of three tropical seagrass species to CO2 enrichment

Ow, Y.X., Collier, C.J., and Uthicke, S. (2015) Responses of three tropical seagrass species to CO2 enrichment. Marine Biology, 162 (5). pp. 1005-1017.

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Increased atmospheric carbon dioxide leads to ocean acidification and carbon dioxide (CO₂) enrichment of seawater. Given the important ecological functions of seagrass meadows, understanding their responses to CO₂ will be critical for the management of coastal ecosystems. This study examined the physiological responses of three tropical seagrasses to a range of seawater pCO₂ levels in a laboratory. Cymodocea serrulata, Halodule uninervis and Thalassia hemprichii were exposed to four different pCO₂ treatments (442–1204 μatm) for 2 weeks, approximating the range of end-of-century emission scenarios. Photosynthetic responses were quantified using optode-based oxygen flux measurements. Across all three species, net productivity and energetic surplus (P G:R) significantly increased with a rise in pCO₂ (linear models, P < 0.05). Photosynthesis–irradiance curve-derived photosynthetic parameters—maximum photosynthetic rates (P max) and efficiency (α)—also increased as pCO₂ increased (linear models, P < 0.05). The response for productivity measures was similar across species, i.e. similar slopes in linear models. A decrease in compensation light requirement (E c) with increasing pCO₂ was evident in C. serrulata and H. uninervis, but not in T. hemprichii. Despite higher productivity with pCO₂ enrichment, leaf growth rates in C. serrulata did not increase, while those in H. uninervis and T. hemprichii significantly increased with increasing pCO₂ levels. While seagrasses can be carbon-limited and productivity can respond positively to CO₂ enrichment, varying carbon allocation strategies amongst species suggest differential growth response between species. Thus, future increase in seawater CO₂ concentration may lead to an overall increase in seagrass biomass and productivity, as well as community changes in seagrass meadows.

Item ID: 38053
Item Type: Article (Research - C1)
ISSN: 1432-1793
Additional Information:

Great Barrier Reef Foundation Project title: Investigating the effects of seagrass productivity on pH at local scales.

Funders: National Environmental Research Program (NERP), Great Barrier Reef Foundation (GBRF)
Date Deposited: 31 Mar 2015 03:41
FoR Codes: 06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060701 Phycology (incl Marine Grasses) @ 50%
06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060705 Plant Physiology @ 30%
05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050101 Ecological Impacts of Climate Change @ 20%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts) @ 50%
96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960802 Coastal and Estuarine Flora, Fauna and Biodiversity @ 50%
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