Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

General study design:
This experiment was designed to quantify and compare the influence of different benthic reef communities on diel seawater carbonate and nutrient chemistry under ambient and acidified conditions during summer and winter in flow-through mesocosms.

Methods description:
Different coral reef benthic communities (carbonate sand, crustose coralline algae, coral, fleshy macroalgae, and a mixed community) were created in outdoor flow-through mesocosms at Hawaii Institute of Marine Biology. Diurnal seawater chemistry was measured for communities experiencing ambient or acidified (ambient pH – 0.4) seawater conditions during summer (August 2013) and winter (January 2014). Acidification treatments were achieved by CO2 (g) bubbling of the header tank. Hourly water quality measurements were taken over the course of 26-hours with water samples collected for analysis of dissolved inorganic carbon and total alkalinity every 2 hours and for inorganic nutrients every 4 hours. A total of four experiments were conducted across two seasons (Summer and Winter) and two pH treatments (ambient and acidified). Seawater chemistry data were used to calculate diurnal net community production (NCP) and net community calcification (NCC) rates using modified standard equations (Langdon et al. 2010). In addition, the attribution of these processes to diurnal pH and saturation state changes were quantified.;

For additional details, please see Page et al. (2016).

Analytical Methods:
Seawater samples were collected by hand using 250 ml Pyrex glass bottles and immediately fixed with 100 µL HgCl2 as per standard protocols (Dickson et al. 2007). Handheld YSI multi-meter instrument was used to measure temperature, salinity, dissolved oxygen, and pH at the time of sampling. All seawater samples were transported to the Scripps Coastal and Open Ocean Biogeochemistry lab and analyzed for TA via an open-cell potentiometric acid titration system developed at Scripps Institution of Oceanography (SIO) by A. Dickson (Dickson et al. 2007) and DIC via an automated infra-red inorganic carbon analyzer (AIRICA, Marianda Inc).

Quality Control:
Standard protocols were followed for sampling and analysis of seawater TA and DIC (Dickson et al. 2007). YSI multi-meter instrument was calibrated prior to each sampling period with accuracies of 0.2 °C for temperature, 1% for salinity, ±2% for dissolved oxygen saturation, 0.2 mg/L for dissolved oxygen concentration, and 0.2 for pH. The accuracy and precision of TA (-0.2 ± 3.3 μmol/kg) and DIC (-1.0 ± 2.3 μmol/kg) measurements were evaluated using certified reference materials (CRM) provided by the laboratory of A. Dickson at SIO and analyzed every 5 samples for DIC and ~15-20 samples for TA.

Known Problems:
Rows where Date is 06-01-14 and Time values are 10:14 to 10:44 (inclusive) (lines 866-881 in original Excel file): The YSI Pro Plus Handheld Multi-meter temporarily malfunctioned, so temperature and salinity data were measured using an alternate handheld multi-meter probe.

Data Processing:
Carbonate chemistry (pH_calc, pCO2_calc, and omega_calc) was constrained using CO2SYS software (Lewis and Wallace 1998). Data were processed and statistically compared using R Software (v 3.2.0).

BCO-DMO Processing:
- added UTC date/time field in ISO8601 format.

NSF Award Abstract:
Because of well-known chemical principles, changes in the CO2 chemistry of seawater in the open ocean as a result of rising atmospheric CO2 can be predicted very accurately. On the other hand, in near-shore environments, these projections are much more difficult because the CO2 chemistry is largely modified by biogeochemical processes operating on timescales of hours to months. To make predictions on how near-shore seawater CO2 chemistry will change in response to ocean acidification (OA), it is critical to consider the relative influence of net ecosystem production (NEP) and net ecosystem calcification (NEC), and how these processes might change in response to this major perturbation. Understanding how future OA will alter near-shore seawater CO2 chemistry and variability was identified as a major critical knowledge gap at the recent IPCC WG II/WG I workshop on impacts of ocean acidification on marine biology and ecosystems in January of 2011, and also at the International Ocean Acidification Network workshop in Seattle in June of 2012.

With funding from this CAREER award, a researcher at the Scripps Institute of Oceanography and his students will study how biogeochemical processes and the relative contributions from NEP and NEC modify seawater CO2 chemistry in near-shore environments influenced by different benthic communities under well-characterized environmental and physical conditions, and how these processes might change in response to OA. The team will investigate a limited number of contrasting habitats in subtropical (reef crest, back/patch reef, lagoon, seagrass bed, algal mat) and temperate (kelp bed, inter- and sub-tidal, marsh) environments during summer and winter, employing a method that evaluates the function and performance of the carbon cycle of a system using a stoichiometric vector approach based on changes in total dissolved inorganic carbon (DIC) and total alkalinity (TA). These field studies will be complemented by controlled mesocosm experiments with contrasting and mixed benthic communities under different OA scenarios.

The project has two educational components: (1) developing a research-driven OA and biogeochemistry course based on inquiry-, experience-, and collaborative-based learning; and (2) working with the Ocean Discovery Institute (ODI) to engage individuals from a local underrepresented minority community in science through educational activities focused on OA, and also providing a moderate number of internships for high school and college students to engage in this research project.

Broader Impacts: This project will directly support one PhD student, one junior research technician, and two high school and college interns from underrepresented minorities (URM) each summer of the project. It will contribute to the education of 80 undergraduate and graduate students participating in the research based ocean acidification/biogeochemistry course offered four times throughout the duration of the project at SIO/UCSD. Education and curricular material on the topics of OA, including hands-on laboratories, classroom and field-based activities will be developed through the collaboration with the ODI and brought to hundreds of URM students and their teachers in the City Heights area, a community with the highest poverty and ethnic diversity in the San Diego region. This collaboration will enable URM students to directly engage in a rapidly evolving field of research that has high relevance at both the local and global scales. To ensure broad dissemination of this project and the topic of OA, the research team will work with the Google Ocean team to incorporate information and educational material in the Google Ocean Explorer.