Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

These data are from SeapHOx deployments from in and around the La Jolla Kelp Forest and include pH, dissolved oxygen, temperature, and salinity. The data were collected using two "SeapHOx" instrument packages. The SeapHOx consists of a Honeywell Durafet III pH sensor (Martz et al. 2010), an Aanderaa 3835 oxygen optode, and an SBE-37 MicroCAT CTD. The sensors were attached to a mooring line at a given water depth below the surface (e.g. 7 m).  There are four moorings utilized in this study and there is one data file which accompanies each mooring.

Related publication: Frieder, C. A., Nam, S. H., Martz, T. R., and Levin, L. A.: High temporal and spatial variability of dissolved oxygen and pH in a nearshore California kelp forest, Biogeosciences., 9, 4099-4132, doi:10.5194/bgd-9-4099-2012, 2012.
Abstract Page
Manuscript

To calibrate the pH sensors, discrete water samples were taken during each SeapHOx deployment for the determination of total alkalinity (TA) and total dissolved inorganic carbon (DIC). The calibration samples were collected via SCUBA next to the sensor with a 5L niskin bottle. The collected seawater was transferred to a 500 ml clean borosilicate glass bottle with a ground glass neck and stopper. The samples were poisoned with a saturated mercuric chloride solution. TA measurements were determined using an open-cell, potentiometric titration (Dickson et al. 2007).  DIC measurements were determined by acid extraction and coulometric detection of CO2 (Dickson et al. 2007). pH was calculated from TA and DIC using the Matlab version of CO2SYS (van Heuven et al. 2011) as recommended by Dickson et al. 2007. The calculated pH at in situ temperature from the calibration sample was used to determine the electrode-specific calibration coefficients. The calibration sample produced a pH accuracy of 0.01 units for each SeapHOx instrument. The oxygen sensors were factory calibrated by Aanderaa and before each deployment a two-point (0% and 100% saturation) offset was applied as recommended in the manual.

References:

Martz, T. R., Connery, J. G., and Johnson, K. S.: Testing the Honeywell Durafet® for seawater pH applications, Limnol. Oceanogr. Methods, 8, 172-184, 2010.

Dickson, A. G., Sabine, C. L., and Christian, J. R.: Guide to Best Practices for Ocean CO2 5 Measurements, Vol. 3, 374 PICES Spec. Publ., Sidney, British Columbia, 2007.

van Heuven et al. 2011. Matlab version of CO2SYS.

Extreme salinity outliers (= 3 SD) were removed and salinity data was smoothed with a 1-hr moving average. Oxygen was logged with factory settings. This assumes a salinity of 0 and pressure of 0. Salinity corrections (from CTD data) and pressure corrections (water depth) were applied to the oxygen data as suggested by the manufacturer’s manual. pH was calculated at in situ temperature (temperature data from CTD) using calibration coefficients as described above.

BCO-DMO Processing Notes
Generated from original files "SeapOHx_Mooring [A-D].txt" contributed by Christina Frieder

BCO-DMO Edits
- Time column spilt into Date and Time and reformatted as YYYYMMDD and HHMM
- Temp, Sal, O2 and pH data values reported to appropriate decimal places
- "NaN" values converted to "nd" (no data)
- Parameter names modified to conform to BCO-DMO convention

Increased concentrations of atmospheric carbon dioxide are acidifying the marine environment at unprecedented rates. However, relative to the open ocean, predictions of ocean acidification for the coastal ocean are confounded by the greater inherent variability of carbonate chemistry which includes macrophyte photosynthesis and respiration. This proposal addresses the interplay between anthropogenically driven pH changes and the inherently variable coastal ocean carbonate chemistry, and will directly test the implications for a potentially sensitive life form, invertebrate larvae.

The objectives of this study are to measure the impact of key coastal habitats on natural pH variance, and to evaluate the implications these pH regimes have for developing invertebrate larvae. To achieve these objectives the investigators will characterize temporal and spatial carbonate chemistry variability inside and outside kelp forests in San Diego, California. With discrete water samples for the determination of total alkalinity and dissolved inorganic carbon, and continuous autonomous instruments which measure pH, dissolved oxygen, salinity, and temperature, a statistical characterization of carbonate chemistry variability will identify diurnal, seasonal and spatial trends as well as frequencies of maximum variation, rates of change, lowest potential pH (extreme statistics), and biologically-significant thresholds. Subsequently, prominent macrophyte-induced pH regimes will be mimicked in laboratory experiments and incorporated with ocean acidification predictions to test effects of (a) decreased pH, (b) varying pH about the mean, (c) changing variance about mean pH, and (c) pulsed exposure to extreme low pH, on larval survivorship, growth, and calcification responses of multiple species. Together, these laboratory and field studies will offer a mechanistic understanding of the effects of natural variance of carbonate chemistry in the context of ocean acidification for marine invertebrate larvae.

Four moorings identified as SeapHOx Moorings have been deployed in the San Diego La Jolla Kelp Forest in the vicinity of 32.8 N 117.3 W.

Mooring Locations

The Ocean Carbon and Biogeochemistry (OCB) program focuses on the ocean's role as a component of the global Earth system, bringing together research in geochemistry, ocean physics, and ecology that inform on and advance our understanding of ocean biogeochemistry. The overall program goals are to promote, plan, and coordinate collaborative, multidisciplinary research opportunities within the U.S. research community and with international partners. Important OCB-related activities currently include: the Ocean Carbon and Climate Change (OCCC) and the North American Carbon Program (NACP); U.S. contributions to IMBER, SOLAS, CARBOOCEAN; and numerous U.S. single-investigator and medium-size research projects funded by U.S. federal agencies including NASA, NOAA, and NSF.

The scientific mission of OCB is to study the evolving role of the ocean in the global carbon cycle, in the face of environmental variability and change through studies of marine biogeochemical cycles and associated ecosystems.

The overarching OCB science themes include improved understanding and prediction of: 1) oceanic uptake and release of atmospheric CO2 and other greenhouse gases and 2) environmental sensitivities of biogeochemical cycles, marine ecosystems, and interactions between the two.

The OCB Research Priorities (updated January 2012) include: ocean acidification; terrestrial/coastal carbon fluxes and exchanges; climate sensitivities of and change in ecosystem structure and associated impacts on biogeochemical cycles; mesopelagic ecological and biogeochemical interactions; benthic-pelagic feedbacks on biogeochemical cycles; ocean carbon uptake and storage; and expanding low-oxygen conditions in the coastal and open oceans.