Discrete seawater samples were collected during each sampling period for salinity, nutrients, total alkalinity (TA), and dissolved inorganic carbon (DIC). Temperature and depth were recorded with HOBO temperature loggers (September 2012) and Sensus Ultra dive data loggers (2015-2016). TA and DIC analyses were performed using a Versatile Instrument for the Determination of Total inorganic carbon and titration Alkalinity (VINDTA, Marianda Analytics and Data) and standardized using certified reference materials obtained from Andrew Dickson (Scripps Institution of Oceanography).

Salinity samples were analyzed at WHOI using a Guildline autosal salinometer, and nutrient samples were run at the WHOI Nutrient Analytical Facility.

Seawater samples, and in situ instrument time series were collected during seven expeditions to Jarvis Island between 2008 and 2017, aboard:

• NOAA ship Hi’ialakai (27–29 March 2008, 2–4 April 2010, 3–5 May 2012, 2–5 April 2017)
• Pangaea Exploration S/V Sea Dragon (13–16 September 2012)
• R/V Machias (12–15 November 2015)
• NOAA ship Oscar Elton Sette (17–23 May 2016)

Research activities and sample collection were conducted under U.S. Fish and Wildlife Service Pacific Reefs National Wildlife Refuge Complex Research and Monitoring Special Use Permits

• 12521-10001 (effective date: 15 Jan 2010; expiration date: 30 May 2010)
• 12521-12001 (effective date: 7 Feb 2012; expiration date: 31 Dec 2012)
• 12521-12005 (effective date: 29 Aug 2012; expiration date: 30 June 2014)
• 12521-14001 (effective date: 1 Jan 2015; expiration date: 31 Dec 2015)
• 12513-15001 (effective date: 11 Nov 2015; expiration date: 31 Dec 2015)

and in compliance with Presidential Proclamation 8336.