Table of Contents

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

General study design:
In this study, seawater samples were collected between 0-40m on a monthly transect extending from the coastline to ~2km offshore in La Jolla, CA. Seawater samples were collected for analysis of dissolved carbonate chemistry parameters and inorganic nutrient concentrations. The study was designed to characterize the biogeochemical near-shore spatiotemporal variability in the Southern California Bight, and in particular, the influence of seasonal upwelling.

Methods description:
Seawater was collected with a 5 L Niskin bottle between the surface and bottom in 10 m intervals at four stations between the end of the SIO pier and ~2 km offshore. Transect stations were separated by ~400 m. Seawater carbonate chemistry samples were collected into 250 ml Pyrex Corning glass bottle and immediately poised with 100 μL HgCL₂ following standard protocols (Dickson et al., 2007). Inorganic nutrient samples were filtered through a 0.45 μm polycarbonate filter into 30 mL Falcon tubes and immediate placed on ice and kept frozen until analysis. Temperature, salinity, and dissolved oxygen were measured in the residual seawater in the Niskin bottle following seawater collection using a YSI multiprobe.

Analytical Methods:
Seawater samples were analyzed for DIC and TA at the Scripps Coastal and Open Ocean Biogeochemistry lab. DIC analyses were conducted with an automated infrared inorganic carbon analyzer (AIRICA, Marianda) and TA with an open-cell potentiometric acid titration system developed at Scripps Institution of Oceanography (SIO) by A. Dickson (Dickson et al. 2007).

Inorganic nutrient samples were analyzed for dissolved NO3, PO4, H4SIO4, NO2, and NH3 at the Ocean Data Facilities (ODF) at the Scripps Institution of Oceanography either spectrophotometrically or fluorometrically via an analytical continuous-flow autoanalyzer. For details see: https://scripps.ucsd.edu/ships/shipboard-technical-support/odf/documentation/nutrient-analysis.

Quality Control:
Samples for seawater carbon chemistry analysis were collected and analyzed following standard protocol (Dickson et al., 2007). The handheld YSI multiprobe was calibrated prior to each survey with and accuracy of ±0.2°C for temperature and 1% for salinity. The accuracy and precision for DIC and TA samples were 0.45 ± 1.57 and 0.93 ± 1.40, respectively and were evaluated using CRMs provided by the laboratory of A. Dickson at SIO. CRMs were analyzed every 5 samples for DIC and every 10 for TA.

BCO-DMO Processing:
-added UTC date/time field in ISO8601 format;
- converted longitude values from positive to negative.

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.

NSF Award Abstract:
Iron is critically needed for growth of all marine phytoplankton, the microscopic plants at the base of the ocean food chain. Consequently, lack of iron in large regions of the global ocean limits phytoplankton growth and commercial fisheries. Ocean acidification (OA) is the ongoing decrease in seawater pH due to the ocean absorbing carbon dioxide from the atmosphere. OA is predicted to affect seawater chemistry by reducing the concentration of carbonate ions. Carbonate ions are required for phytoplankton to take up iron from their environment, which suggests that OA might inhibit iron nutrition. Further complicating the scenario, pH changes affect iron chemistry in seawater, such that OA is predicted to shift the relative abundance of various forms of iron. But despite these expectations, little is known about how the changes in ocean chemistry due to OA will impact the availability of iron to phytoplankton. Changes in phytoplankton iron uptake and associated growth rates would likely have large effects on how the ocean captures atmospheric carbon dioxide (CO2). This has important consequences for ecosystem productivity and for global cycles of critical chemical elements, such as carbon and nitrogen, and their chemistry. This project aims to help us understand how shifts in seawater pH and the chemistry of dissolved inorganic carbon will affect both iron uptake rates and iron acquisition strategies in the laboratory and in natural communities. This project also includes development of educational outreach activities which target primary school students in the areas of microbiology, biogeochemical cycles and current global change topics. These science outreach activities benefit from collaborations with the following San Diego-based organizations: the League of Extraordinary Scientists and Engineers (LXS), The Birch Aquarium at Scripps (BAS), and The Ocean Discovery Institute (ODI).

This project seeks to understand the differential sensitivity of diatom iron acquisition strategies to changes in seawater pH and carbonate chemistry. Ultimately a more thorough and detailed mechanistic understanding of diatom iron uptake pathways will facilitate a much-improved ability to forecast the impact of anticipated changes in ocean pH and inorganic carbon chemistry on rates of iron uptake by diatoms. This critical biogeochemical issue is addressed through trace metal clean manipulation experiments incorporating state-of-the-art analytical methodology to probe phytoplankton cellular physiology and biogeochemistry in laboratory cultures and natural communities. In the first year, laboratory experiments with a model pennate diatom leverage a collection of targeted knockout transgenic lines to evaluate the substrate specificity and relative importance of distinct iron assimilation pathways under a range of pCO2 and iron availability conditions. Additionally, quantitation of mRNA and proteins for key diatom iron assimilation pathways in natural communities in the Southern California Current further clarify the relative importance and sensitivity of distinct iron assimilation pathways in relation to pCO2 and iron availability. In year two a Lagrangian study of iron uptake rates and associated mRNA and protein abundance is performed on upwelled high pCO2 water over the course of offshore advection. Additionally, the investigators are conducting mesocosm experiments using naturally elevated high pCO2 seawater as well as laboratory experiments on multiplex knockout lines. Year three is dedicated to data analyses and overall project synthesis. Overall aims of the research activities include, 1) development and validation of a refined conceptual model of iron uptake in key marine phytoplankton and subsequent utilization of the model to characterize the sensitivity of distinct iron uptake pathways to the effects of ocean acidification, and 2) determination of the effects of acidification on iron uptake, and quantification of the relative contribution of distinct iron acquisition pathways in high pCO2 phytoplankton communities.

Related Datasets:
NSF award OCE-1756860 (PI: Katherine Barbeau) partially supported several students on CCE LTER process cruise P1908 to generate datasets for water column samples for dissolved Fe and biogenic Si that are pertinent to this funded project. These datasets, cited below, are available from the EDI Data Portal.

California Current Ecosystem LTER and K. Barbeau. 2023. Measurements, from CCE LTER process cruises in the California Current region, of dissolved inorganic concentrations of nutrient iron and of iron limitation at selected stations and depths, 2006 - 2019 (ongoing). ver 6. Environmental Data Initiative. https://doi.org/10.6073/pasta/50a0a46193bc6cbe7eaa1ba7510278e3.

California Current Ecosystem LTER and K. Barbeau. 2023. Vertical profiles of in-situ biogenic silica (bSi) from discrete rosette bottle samples from CCE-LTER starting with cruise P1706. ver 2. Environmental Data Initiative. https://doi.org/10.6073/pasta/265091f2b7435d010e69ab27b7a0aa47.