Hobart

Seminar Abstract

Friday 16 July 2010, 11.30am (Tas time)
CSIRO Auditorium, Hobart

Chris Langdon
Associate Professor
RSMAS/MBF
University of Miami, USA

Measuring coral reef calcification on different temporal and spatial scales

Measurements of coral reef calcification provide an excellent means of judging the health of the ecosystem. Healthy reefs need to achieve a net rate of carbonate production on an annual basis that equals or exceeds the loss of carbonate due to biological, chemical and physical erosive processes. On longer time scales net carbonate production also needs to keep up with the rate of sea level rise. Global warming and ocean acidification threaten reefs because both can result in significant reductions of coral calcification, possibly to the point where a tipping point is exceeded and coral reef carbonate production swings from net positive to net negative. It is important, therefore, that we begin monitoring the calcification of coral reefs so that we can determine if they are approaching a critical threshold. Two new methods of measuring coral reef calcification and primary production will be discussed. One is the alkalinity anomaly method using the geochemical tracer Be-7 to calculate the water residence time. This method is being used to look at broad scale spatial and temporal patterns of primary production and calcification across the entire Florida Keys reef tract (240 km). Every four months a ship goes out and runs seven onshore-offshore lines across the reef from Miami to Key West. Primary production/respiration and calcification/dissolution are determined from the difference in DIC and TA between oceanic water and the water overlying the outer and inner reefs. The second method is a boundary layer gradient flux technique that yields an hourly rate with a spatial scale of approximately 50 m2. This method has been trialed at La Parguera, Puerto Rico where it was compared with an enclosure technique over a seven day period and found to give rates of photosynthesis and respiration that agreed well with the enclosure method. The boundary layer- gradient flux method has a number of advantages over enclosure and control volume approaches. It is less expensive in terms of equipment and manpower and employable at any depth. Also the intermediate size of the measurement footprint can be useful for relating rates of photosynthesis and calcification to community type. However, until TA sensors become available the method can only measure calcification if discrete water samples are collected.

Seminar recording

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
Clothilde Langlais, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5399
Natalie Kelly, (Biology/Modelling seminars) CSIRO Marine and Atmospheric Research 0438 452 483
Jillian Enraght-Moony, (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5320
Communications Manager, Antarctic Climate and Ecosystems CRC (03) 6226 2265
Tracey Cochrane, Institute for Marine and Antarctic Studies (IMAS), University of Tasmania (03) 6226 2937

Last updated 23/07/10