Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures


Comparing Chemistry and Census-Based Estimates of Net Ecosystem Calcification on a Rim Reef in Bermuda

Event Name/Location

13th International Coral Reef Symposium, Honolulu, Hawaii, June 19-24, 2016

Document Type

Conference Proceeding

Publication Date



Coral reef net ecosystem calcification (NEC) has decreased for many Caribbean reefs over recent decades primarily due to a combination of declining coral cover and changing coral reef community composition. Chemistry-based approaches to calculate NEC utilize the drawdown of seawater total alkalinity (TA) between the reef environment and offshore waters to calculate an instantaneous measurement of NEC. Census-based approaches combine annual growth rates with benthic cover and reef structural complexity to estimate NEC occurring over annual timescales. Here, we calculated NEC for Hog Reef in Bermuda using the chemistry and census-based NEC procedures to compare the mass-balance generated by the two methods. NEC was calculated via the chemistrybased approach using reef TA data from a carbonate chemistry monitoring project and offshore TA data collected by the Bermuda Atlantic Time-Series Study. To calculate NEC with the census-based approach, we used benthic surveys of line transects conducted at Hog Reef coupled with literature reported mean annual coral growth rates aggregated by the ReefBudget project, in-situ growth rates of Porites astreoides and Diploria labyrinthiformis during the time of the study, carbonate sediment dissolution rates from benthic chamber experiments, and photographic measurements of reef rugosity. Our initial findings indicate the annual mean NEC calculated by the two methods agrees within the range of uncertainties and highlights the high temporal variability of reef NEC in response to changing environmental conditions.



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