Dataset: Maunalua Bay Biogeochemistry

Sampling locations:
Wailupe, Hawaii 21.275, -157.762 depth 2m
Black Point (Kupikipiki'o), Hawaii 21.2598, -157.789 depth 2m

Methodology:
Twenty water sampling locations were established at each site (n = 40 total) in an approximate grid, scaled to the width of the reef flat, for biogeochemistry measurements. At each location, we collected discrete diel water samples across four timepoints (during daytime and nighttime high and low tides) in the spring and fall (totaling eight samples per location, 320 samples overall). Sampling dates were 18 April 2015 and 28 September 2015 at Wailupe, and 2 May 2015 and 26 October 2015 at Kupikipiki'o. All sampling events happened during spring tide events. 

Sampling and analytical procedures:
Water samples for pH, TA, nitrate + nitrite (NO₃⁻ + NO₂⁻), phosphate (PO₄³⁻ ) and silicate (SiO₄²⁻) were hand collected directly above the benthos within 30 min of high or low tide in acid-washed HDPE bottles. pH was measured immediately using a tris calibrated Orion ROSS Ultra pH/ATC Triode following Dickson SOP 6a. TA samples were immediately preserved with 50% saturated HgCl2 in deionized water, stored in a cool dark place and later analyzed on a Mettler Toledo T-50 autotitrator following Dickson SOP 3b (precision = 2.68 µEq, accuracy = 0.48% ± 0.33% SD). Inorganic nutrient samples (SiO₄²⁻, NO₃⁻ + NO₂⁻, PO₄³⁻ ) were immediately filtered through pre-combusted GF/F filters (0.7 µm) and stored in a −20°C freezer until further processing. Nutrient samples were processed at the SOEST Laboratory for Analytical Biogeochemistry at the University of Hawai'i at Manoa using a Seal Analytical AA3 nutrient autoanalyzer (reported error [coefficient of variance]: 0.5% for SiO₄²⁻, 0.3% for NO₃⁻ + NO₂⁻, and 0.2% for PO₄³⁻). Temperature was recorded every 15 min on HOBO TidbiT v2 loggers and temperature values were extracted to match the time-discrete water samples were collected.