Monthly cross-shore transects of biogeochemical properties in La Jolla, CA

Website: https://www.bco-dmo.org/dataset/839175
Data Type: Cruise Results
Version: 1
Version Date: 2021-01-29

Project
» CAREER: Biogeochemical Modification of Seawater CO2 Chemistry in Near-Shore Environments: Effect of Ocean Acidification (Nearshore CO2)
ContributorsAffiliationRole
Andersson, AndreasUniversity of California-San Diego (UCSD-SIO)Principal Investigator
Kekuewa, SamuelUniversity of California-San Diego (UCSD-SIO)Student, Contact
Rauch, ShannonWoods Hole Oceanographic Institution (WHOI BCO-DMO)BCO-DMO Data Manager

Abstract
These data result from monthly cross-shore transects of biogeochemical properties in La Jolla, CA. 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.


Coverage

Spatial Extent: N:32.865 E:-117.259 S:32.865 W:-117.2701
Temporal Extent: 2017-03-08 - 2018-09-27

Acquisition Description

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.


Processing Description

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


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Related Publications

Dickson, A.G., Sabine, C.L. and Christian, J.R. (Eds.) 2007. Guide to Best Practices for Ocean CO2 Measurements. PICES Special Publication 3, 191 pp https://isbnsearch.org/isbn/1-897176-07-4
Methods
Kekuewa, S. A. (2020). Seawater CO2-Chemistry Variability in the Near-Shore Environment of the Southern California Bight. UC San Diego. ProQuest ID: Kekuewa_ucsd_0033M_19412. Merritt ID: ark:/13030/m5md47st. Retrieved from https://escholarship.org/uc/item/5ng2r1p5
Results

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Parameters

ParameterDescriptionUnits
SampleSample number for reference unitless
StationStation number along transect unitless
DateDate of the survey (local time; PST); format: MM/DD/YYYY unitless
TimeTime of survey in local time (PST; GMT-7/-8); format: hh:mm unitless
ISO_DateTime_UTCDate and time of survey (UTC) in ISO8601 format: YYYY-MM-DDThh:mmZ unitless
LatLatitude of survey station degrees North
LongLongitude of survey station degrees East
DepthDepth of seawater sample meters (m)
TempTemperature of seawater degrees Celsius
SalinitySalinity of seawater PSU
DODissolved oxygen of seawater micromoles per kilogram (umol/kg)
DICDissolved inorganic carbon of seawater micromoles per kilogram (umol/kg)
TATotal alkalinity of seawater micromoles per kilogram (umol/kg)
pHpH of seawater unitless
ArAragonite saturation state of seawater unitless
NO3Dissolved Inorganic nitrate concentration of seawater micromoles per kilogram (umol/kg)
PO4Dissolved Inorganic phosphate concentration of seawater micromoles per kilogram (umol/kg)
SILDissolved Silicate (H4SiO4) concentration of seawater micromoles per kilogram (umol/kg)
NO2Dissolved Nitrite concentration of seawater micromoles per kilogram (umol/kg)
NH3Dissolved Nitrite concentration of seawater micromoles per kilogram (umol/kg)


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Instruments

Dataset-specific Instrument Name
YSI Professional Plus handheld multi-parameter instrument (YSI 6600 V2)
Generic Instrument Name
Water Quality Multiprobe
Dataset-specific Description
The instrument was used to measure in situ temperature (±0.2°C), salinity (± 1%), and DO (both mg/L and %; ± 2%).
Generic Instrument Description
An instrument which measures multiple water quality parameters based on the sensor configuration.

Dataset-specific Instrument Name
AFT-pH (SAMI, Sunburst)
Generic Instrument Name
Automatic titrator
Dataset-specific Description
Over a 5 minute time period, the AFT-pH uses a pump and extracts 10 mL of the seawater sample, introduces the sample with mCP indicator dye and is spectrophotometrically analyzed within a pH range of 7.4 to 8.5.
Generic Instrument Description
Instruments that incrementally add quantified aliquots of a reagent to a sample until the end-point of a chemical reaction is reached.

Dataset-specific Instrument Name
Open-cell potentiometric acid titrator
Generic Instrument Name
Automatic titrator
Dataset-specific Description
The open-cell potentiometric acid titration system was developed by the laboratory of A.G. Dickson. Briefly, a known amount of seawater is added to an open cell temperature controlled beaker. Hydrochloric acid (0.1 N) is added using a Methrom Dosimat to a pH of 3.5-4.0. Following equilibration, small increments of hydrochloric acid are then added to the seawater until pH equals ~ 3.0. The titration is monitored by a glass electrode and the total alkalinity of the sample is calculated using a non-linear least-squares method following Dickson et al. (2007).
Generic Instrument Description
Instruments that incrementally add quantified aliquots of a reagent to a sample until the end-point of a chemical reaction is reached.

Dataset-specific Instrument Name
Seal Analytical continuous-flow AutoAnalyzer 3
Generic Instrument Name
Continuous Flow Analyzer
Dataset-specific Description
For NO3: Instrument utilizes an analytical method where N-1-N (NEDD) and sulfanilamide are reacted with the sample to form a red dye, which is measured at an absorbance of 520-540 nm. For nitrate analysis, the nitrate is first reduced to nitrite by the sample being mixed with a buffer solution (ie., Ammonium Chloride or Imidazole) and passed over a cadmium column that has been treated with copper sulfate, which catalyzes the reduction reaction. The resulting nitrite is then analyzed and the final output for the ‘nitrate’ channel is a sum of both nitrate and nitrite. It is important therefore to analyze nitrite separately so that nitrate can be determined by subtracting from the total nitrate plus nitrite concentration (Becker et al., 2019). For analysis of PO4 in seawaters acidic solution of molybdate is added, followed by the addition of a reducing compound (dihydrazine sulfate or ascorbic acid) to form a phospho-molybdenum blue complex with the absorbance measured at approximately 820 or 880nm, depending on the method and availability of filters (Becker et al., 2019). For analysis of SIL, acidified ammonium molybdate is added to a seawater sample to produce silicomolybdic acid, which is then reduced to a silicomolybdenum blue complex following the addition of stannous chloride or ascorbic acid, and measured at 660nm for stannous chloride or 820nm for ascorbic acid (Becker et al., 2019). For NO2: Instrument utilizes an analytical method where N-1-N (NEDD) and sulfanilamide are reacted with the sample to form a red dye, which is measured at an absorbance of 520-540 nm. For nitrate analysis, the nitrate is first reduced to nitrite by the sample being mixed with a buffer solution (ie., Ammonium Chloride or Imidazole) and passed over a cadmium column that has been treated with copper sulfate, which catalyzes the reduction reaction. The resulting nitrite is then analyzed and the final output for the ‘nitrate’ channel is a sum of both nitrate and nitrite. It is important therefore to analyze nitrite separately so that nitrate can be determined by subtracting from the total nitrate plus nitrite concentration (Becker et al., 2019). For NH3: In the fluorometric method, without using any membrane diffusion, the sample is combined with a working reagent made up of OPA, sodium sulfite, a borate buffer, and then heat to 75°C. Fluorescence proportional to the ammonium concentration is measured at 460nm following excitation at 370nm (Becker et al., 2019).
Generic Instrument Description
A sample is injected into a flowing carrier solution passing rapidly through small-bore tubing. 

Dataset-specific Instrument Name
AIRICA (Marianda)
Generic Instrument Name
Inorganic Carbon Analyzer
Dataset-specific Description
The Automated Infra Red Inorganic Carbon Analyzer (AIRICA) utilizes infrared detection of CO2 gas purged from an acidified seawater sample. A pump extracts the seawater sample, acidifies the sample with phosphoric acid, and analyzes the gas released with an infrared light analyzer (LICOR). The CO2 signal is integrated for four individual peaks for each sample and the three closest integrated peaks are averaged for a single given sample.
Generic Instrument Description
Instruments measuring carbonate in sediments and inorganic carbon (including DIC) in the water column.


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Deployments

La_Jolla_2017-18

Website
Platform
small boat - Boston Whaler 17’ SIO7/9
Start Date
2017-03-01
End Date
2018-09-30
Description
Monthly cruises from March 2017 to September 2018 on SIO's 17' Boston Whaler. Latitude: 32.865 Longitude: 117.259 to 117.2701 Depth: 0 to 40 m


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Project Information

CAREER: Biogeochemical Modification of Seawater CO2 Chemistry in Near-Shore Environments: Effect of Ocean Acidification (Nearshore CO2)

Coverage: San Diego, California; Bermuda; Oahu, Hawaii


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.



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Funding

Funding SourceAward
NSF Division of Ocean Sciences (NSF OCE)

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