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Growth response of an early successional assemblage of coralline algae and benthic diatoms to ocean acidification


James, RK and Hepburn, CD and Cornwall, CE and McGraw, CM and Hurd, CL, Growth response of an early successional assemblage of coralline algae and benthic diatoms to ocean acidification, Marine Biology, 161, (7) pp. 1687-1696. ISSN 0025-3162 (2014) [Refereed Article]

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Copyright 2014 Springer

DOI: doi:10.1007/s00227-014-2453-3


The sustained absorption of anthropogenically released atmospheric CO2 by the oceans is modifying seawater carbonate chemistry, a process termed ocean acidification (OA). By the year 2100, the worst case scenario is a decline in the average oceanic surface seawater pH by 0.3 units to 7.75. The changing seawater carbonate chemistry is predicted to negatively affect many marine species, particularly calcifying organisms such as coralline algae, while species such as diatoms and fleshy seaweed are predicted to be little affected or may even benefit from OA. It has been hypothesized in previous work that the direct negative effects imposed on coralline algae, and the direct positive effects on fleshy seaweeds and diatoms under a future high CO2 ocean could result in a reduced ability of corallines to compete with diatoms and fleshy seaweed for space in the future. In a 6-week laboratory experiment, we examined the effect of pH 7.60 (pH predicted to occur due to ocean acidification just beyond the year 2100) compared to pH 8.05 (present day) on the lateral growth rates of an early successional, cold-temperate species assemblage dominated by crustose coralline algae and benthic diatoms. Crustose coralline algae and benthic diatoms maintained positive growth rates in both pH treatments. The growth rates of coralline algae were three times lower at pH 7.60, and a non-significant decline in diatom growth meant that proportions of the two functional groups remained similar over the course of the experiment. Our results do not support our hypothesis that benthic diatoms will outcompete crustose coralline algae under future pH conditions. However, while crustose coralline algae were able to maintain their presence in this benthic rocky reef species assemblage, the reduced growth rates suggest that they will be less capable of recolonizing after disturbance events, which could result in reduced coralline cover under OA conditions.

Item Details

Item Type:Refereed Article
Keywords:ocean acidification, seaweed, diatom, benthic community
Research Division:Environmental Sciences
Research Group:Climate change impacts and adaptation
Research Field:Ecological impacts of climate change and ecological adaptation
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Adaptation to climate change
Objective Field:Ecosystem adaptation to climate change
UTAS Author:Cornwall, CE (Dr Chris Cornwall)
UTAS Author:Hurd, CL (Professor Catriona Hurd)
ID Code:91440
Year Published:2014
Web of Science® Times Cited:20
Deposited By:IMAS Research and Education Centre
Deposited On:2014-05-20
Last Modified:2017-10-31

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