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From 2005 to 2022, the main node of the ARC Centre of Excellence for Coral Reef Studies was headquartered at James Cook University in Townsville, Queensland (Australia)

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Ocean acidification – What is the evidence for it and how do we measure the response of coral reefs to it?


11.00am - 12.00pm Thursday, 29 July 2010

Sir George Fisher Building (DB 32) Conference Room 114 JCU
Chris Langdon, University of Miami, USA

Chris Langdon is a biological/chemical oceanographer and Associate Professor at the Rosenstiel School of Marine and Atmospheric Science of the University of Miami.  He has been working on various aspects of ocean acidification for over ten years.  He and his students are working on observing and understanding the impacts of ocean acidification on coral biology and ecology at the organismal and community level.


Ocean acidification is the decrease in the pH of the ocean.  The decrease over the last 20 years is well substantiated by observation and is indistinguishable from the calculated decline assuming that the surface ocean is in near thermodynamic equilibrium with increasing CO2 concentration of the atmosphere.  As a result there is really no controversy about the cause of the declining pH.  The decline in pH of 0.1 units since the 1800s and the present rate of decline of -0.0017 units per year bear the clear stamp of the hand of man, i.e. the burning of fossil fuels.  If the rate of increase of CO2 emissions continues unchecked the pH could decline by an additional 0.3 units by the year 2100. The problems presented by ocean acidification are incredibly rich.  Biological, chemical and geological oceanographers can all find aspects of ocean acidification that are of interest.  Within the field of biology ocean acidification has been shown to adversely impact skeleton and shell formation of a wide range of taxa, sexual reproduction, larval development, metabolism and chemoreception.  In the field of chemical oceanography it has been found impact the speciation of trace metals that are both critical for life at low levels and toxic at higher levels.  Geologists are interested because ocean acidification has been implicated as one of the causes of the mass extinctions and these events may present useful analogs to the present situation.  So, how bad could the present ocean acidification event be for marine life?  In the tropics where the carbonate saturation could decline by 30-40% but still be supersaturated the likely consequences are that effected organisms will grow more slowly, reproduce less successfully, perhaps be less able to deal with other forms of stress such as high temperatures and respond incorrectly to chemical cues.  While all these impacts are non-lethal they will likely result in decreased abundance of effected species, less live coral cover, reduced biodiversity and resilience to disturbances.  On the physical side some coral reefs, particularly those at higher latitudes, may experience a loss of reef framework as the production of carbonate falls below the loss rate due to biological and physical erosion.  Given the threat of all these changes it is important that we start to look for them at many reef locations around the world.  I will describe efforts in the Florida Keys to characterize the spatial and temporal variability of the carbonate chemistry of the water and the net community production and calcification of the reef community.  The objective of this study is to establish a baseline against which changes in reef water chemistry and coral reef metabolic performance can be judged.


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