Dataset: Diel Carbonate and Nutrient Chemistry

General study design:
This experiment was designed to quantify and compare the influence of different benthic reef communities on diel seawater carbonate and nutrient chemistry under ambient and acidified conditions during summer and winter in flow-through mesocosms.

Methods description:
Different coral reef benthic communities (carbonate sand, crustose coralline algae, coral, fleshy macroalgae, and a mixed community) were created in outdoor flow-through mesocosms at Hawaii Institute of Marine Biology. Diurnal seawater chemistry was measured for communities experiencing ambient or acidified (ambient pH – 0.4) seawater conditions during summer (August 2013) and winter (January 2014). Acidification treatments were achieved by CO2 (g) bubbling of the header tank. Hourly water quality measurements were taken over the course of 26-hours with water samples collected for analysis of dissolved inorganic carbon and total alkalinity every 2 hours and for inorganic nutrients every 4 hours. A total of four experiments were conducted across two seasons (Summer and Winter) and two pH treatments (ambient and acidified). Seawater chemistry data were used to calculate diurnal net community production (NCP) and net community calcification (NCC) rates using modified standard equations (Langdon et al. 2010). In addition, the attribution of these processes to diurnal pH and saturation state changes were quantified.;

For additional details, please see Page et al. (2016).

Analytical Methods:
Seawater samples were collected by hand using 250 ml Pyrex glass bottles and immediately fixed with 100 µL HgCl2 as per standard protocols (Dickson et al. 2007). Handheld YSI multi-meter instrument was used to measure temperature, salinity, dissolved oxygen, and pH at the time of sampling. All seawater samples were transported to the Scripps Coastal and Open Ocean Biogeochemistry lab and analyzed for TA via an open-cell potentiometric acid titration system developed at Scripps Institution of Oceanography (SIO) by A. Dickson (Dickson et al. 2007) and DIC via an automated infra-red inorganic carbon analyzer (AIRICA, Marianda Inc).

Quality Control:
Standard protocols were followed for sampling and analysis of seawater TA and DIC (Dickson et al. 2007). YSI multi-meter instrument was calibrated prior to each sampling period with accuracies of 0.2 °C for temperature, 1% for salinity, ±2% for dissolved oxygen saturation, 0.2 mg/L for dissolved oxygen concentration, and 0.2 for pH. The accuracy and precision of TA (-0.2 ± 3.3 μmol/kg) and DIC (-1.0 ± 2.3 μmol/kg) measurements were evaluated using certified reference materials (CRM) provided by the laboratory of A. Dickson at SIO and analyzed every 5 samples for DIC and ~15-20 samples for TA.

Known Problems:
Rows where Date is 06-01-14 and Time values are 10:14 to 10:44 (inclusive) (lines 866-881 in original Excel file): The YSI Pro Plus Handheld Multi-meter temporarily malfunctioned, so temperature and salinity data were measured using an alternate handheld multi-meter probe.