Sampling Dates:
2021:
Gump Station, Moorea, French Polynesia
Aug 10 to Aug 19, 2021
Chief Scientist - Linda Wegley Kelly (SIO, lwegley@ucsd.edu)

2022:
Gump Station, Moorea, French Polynesia
Mar 29 to Apr 15, 2022
Chief Scientist - Linda Wegley Kelly

2023:
Gump Station, Moorea, French Polynesia
Aug 17 to Aug 25, 2023
Chief Scientist - Linda Wegley Kelly

Sample Collection. At every site on the fore- or backreef, salinity and temperature were measured using Manta Probes multi-parameter sondes (Eureka Instruments). Approximately 1.2 liters (L) of reef water was collected via peristalsis through 0.2 micrometer (µm) polyethersulfone filter cartridges (Sterivex, Millipore, UK) directly into durable, food-grade, flexible pouches (1.5 liter, blended foil and EVOH (ethylene vinyl alcohol) plastic, AstraPouch) before being transported to the laboratory for further processing. Ten milliliters (mL) of whole seawater was also collected into a syringe using peristalsis and immediately fixed with paraformaldehyde at a final concentration of 0.5% for subsequent flow cytometry analysis of microbial abundances. The Sterivex filtrate was used to rinse bottles to collect samples for inorganic nutrients, which were frozen and stored at -40 degrees Celsius (°C). For dissolved organic carbon (DOC) measurements, Sterivex filtrate was used to triple sample-rinse borosilicate vials with Teflon septa caps before collecting 40 mL (for deployment 2 and 3 in duplicates). Additionally, 500 mL of filtrate was transferred to triple-rinsed polycarbonate bottles for solid-phase dissolved organic matter (DOM) extraction. DOC and DOM samples were acidified to pH 2 using trace metal grade HCl. Acidified DOM samples were solid-phase extracted using the multichannel pump operating at a flow rate of 18 mL per minute onto Bond Elut PPL resin cartridges (200 milligrams (mg) bed mass, Agilent 2105005, USA). After desalinating the resin with LC-MS grade water (Fisher Chemical, Belgium), the cartridges were dried using Ultra High Purity compressed N₂ gas and kept frozen at -40°C.

Biogeochemical Measurements. Inorganic nutrients were analyzed using a Seal AA3 Segmented Flow Injection Autoanalyzer at the University of Hawai'i SOEST Laboratory for Analytical Biogeochemistry: Nitrate+nitrite (N+N) and silicate concentrations, ammonium, phosphate. Additionally, total dissolved nitrogen and total dissolved phosphorus were determined through separate injections, with UV and alkaline or acid persulfate in-line oxidation, respectively. DOC samples were analyzed using high-temperature platinum catalytic oxidation on a Shimadzu TOC-V at the University of Hawaii SOEST Laboratory. The analysis of fluorescent dissolved organic matter (fDOM) was conducted using a Horiba Aqualog scanning fluorometer. Samples for microbial cell concentrations were thawed and 200 microliters (µL) of each sample was stained with SYBR Green I stain for a final concentration of 1X. Bacterial cell counts were enumerated using an Attune Acoustic Focusing Cytometer (Applied Biosystems).

Note that while the instruments were the same from year to year, samples were not all run at the same time.