The moorings were deployed from June to October 2018. The moorings consisted of a subsurface mooring buoy anchored to a weight so that it was approximately 1 m below the surface at spring low tide. A 5 m line connected the subsurface buoy to a small float at the surface.

Inside Kelp Forest Mooring Instruments:

3 MiniDO2T dissolved oxygen loggers (Precision Measurement Engineering (PME), 5 minute sampling frequency)
3 SBE 56 thermistors (Sea-Bird Electronics, 1 minute sampling frequency)
2 HOBO Pro v2 temperature loggers (Onset Data Loggers, 1 minute sampling frequency)
1 HOBO U20L pressure sensor (Onset Data Loggers, 1 minute sampling frequency)
1 miniPAR sensor (PME, 1 minute sampling frequency). PME miniPAR sensors were paired with PME miniWIPERs set to wipe the PAR sensors every six hours to prevent biofouling.
7 pH loggers were deployed on the kelp mooring between July and October. The kelp mooring configuration included two SeapHOx instrument packages (Bresnahan et al., 2014) deployed 1 meter above the bottom (mab) and just below the subsurface mooring buoy. Each SeapHOx consisted of a Honeywell Durafet pH electrode (Martz et al., 2010), an Aanderaa 4835 oxygen optode, and an SBE-37 MicroCAT CTD equipped with a pressure sensor. The other 5 pH loggers (mFETs) were custom built at the Monterey Bay Aquarium Research Institute utilizing Honeywell Durafet electrodes (Martz et al., 2010). SeapHOxes measured pH, O2, temperature, salinity and pressure every 10 minutes, whereas mFETs measured pH and temperature every 5 minutes.
An SBE 37-SM MicroCAT CTD recorder was deployed at mid depth on the mooring beginning in mid-August with sampling frequencies of 5 minutes.
A miniDO2T sensor was installed on a surface buoy located ~50 m from the kelp mooring between July 18 and August 1. This two-week miniDO2T deployment provided the only in situ surface O2 data inside the kelp forest.

Outside Kelp Forest Mooring Instruments:

3 MiniDO2T dissolved oxygen loggers (Precision Measurement Engineering (PME), 5 minute sampling frequency)
3 SBE 56 thermistors (Sea-Bird Electronics, 1 minute sampling frequency)
2 HOBO Pro v2 temperature loggers (Onset Data Loggers, 1 minute sampling frequency)
1 HOBO U20L pressure sensor (Onset Data Loggers, 1 minute sampling frequency)
1 miniPAR sensor (PME, 1 minute sampling frequency). PME miniPAR sensors were paired with PME miniWIPERs set to wipe the PAR sensors every six hours to prevent biofouling.
1 pH logger (mFET) was deployed between July and October and measured pH and temperature
every 5 minutes. The mFET was custom built at the Monterey Bay Aquarium Research Institute
utilizing Honeywell Durafet electrodes (Martz et al., 2010).
An SBE 37-SM MicroCAT CTD recorder was deployed at 13.5 man beginning in mid-August with
sampling frequencies of 5 minutes.

Calibration by taking discrete samples alongside sensors in situ can lead to relatively large uncertainties, especially in highly dynamic coastal environments (Bresnahan et al. 2014); therefore, we decided to calibrate sensors in a flow through tank where the pH is more stable, and multiple discrete samples for DIC and TA analysis could be collected. Prior to deployment, the mFET sensors logged in a tank for 6 days (3 discrete samples) and the SeapHOxes logged in an adjacent tank for 1 day (2 discrete samples). We estimate the accuracy of the pH sensor data to be ± 0.015.

Oxygen sensors were calibrated by making measurements in a black bucket filled with freshwater while bubbling air for 8 hours. We assumed 100% saturation and applied a gain correction to the raw sensor output (Bittig & Körtzinger, 2015; Bushinsky & Emerson, 2013; Johnson et al., 2015). Because the air-stone was placed at the bottom of the bucket, elsewhere we would expect slight over-saturation. However, since the depth of the bucket was < 40 cm, we estimate the accuracy of this calibration to be better than 1-2%. Post-deployment calibration indicated no drift in the oxygen sensors.