Daily CO2 Cycles
Photosynthesis and respiration are key processes in the carbon cycle that can be observed in shallow coral reef environments. This data interactive presents measurements of dissolved inorganic carbon (DIC) and oxygen concentrations in the water column directly above healthy coral reefs. DIC represents dissolved carbon dioxide (which then dissociates into bicarbonate and carbonate ions). While DIC concentrations are largely controlled by photosynthesis and respiration, calcification and dissolution can also influence DIC concentrations to a lesser extent (based on total alkalinity measurements).
The graph below shows variability over several day-night cycles (20 -25 September 2012) in DIC and oxygen concentrations above a shallow coral reef in Palmyra Atoll (Koweek et al., 2015). Grey shading shows sundown to sunrise. What are the predominant trends in the data? What is the relationship between DIC and oxygen concentrations?
Drag slider controls left or right to change x axis scale. Drag area between slider controls to pan left or right across plot.
The graph below shows variability in oxygen concentrations (14-20 November 2011) over a shallow coral reef in Ofu, American Samoa (Koweek et al., 2015). In addition to photosynthesis and respiration, rising and falling tides will influence water column oxygen concentrations at a given location.
Drag slider controls left or right to change x axis scale. Drag area between slider controls to pan left or right across plot.
The globe below shows the locations of Palmyra Atoll and Ofu Island (American Samoa).
Hover over the marker for the island name.
Images
Palmyra from above with shallow coral reefs.
Ofu from above with shallow coral reefs.
Shallow coral reef in Palmyra.
Shallow coral reef in Ofu.
An oxygen sensor (SeapHOx) measures oxygen concentrations.
An automatic water sampler fills glass bottles with ocean water every hour. Samples are then analyzed for DIC concentrations in a laboratory.