Table of Contents

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

Discrete seawater samples were collected at the surface, 1 m below the surface, and 1 m above the bottom two times a week at each mooring (Kelp and Outside) from June 12, 2018 to August 3, 2018 between 10:30 and 14:00 local time. Water was collected using a 1.7 L Niskin bottle and subsampled into a 30 mL glass serum bottle (with rubber stopper and crimp cap) for DIC and a 120 mL glass bottle for TA. All samples were immediately preserved with 1 μL of saturated mercuric chloride solution for every 1 mL of sample (Dickson et al., 2007)

DIC and TA samples were analyzed within four months of sample collection. TA was analyzed with a Metrohm 855 Robotic Titrosampler using a standardized 0.1 M HCl (Acros, 124200010) in a 0.6 M NaCl background. TA was calculated using a modified gran method in an open cell (Dickson et al., 2003). The acid concentration was calibrated by measuring certified reference materials (Dickson, 2010) every 10 samples (36 CRM runs; batch numbers 169, 172, 175, and 176). Precision and accuracy were estimated as 3.4 mol kg-1, based on the measured CRM values. DIC samples were analyzed using a custom-built instrument loosely based on the design of O’Sullivan and Millero (1998). The DIC instrument was calibrated using CRMs approximately every hour. Instrumental precision was estimated as 0.8 mol kg-1, based on 60 measured CRM values (batch numbers 169, 172, and 175). DIC accuracy was estimated at 2 mol
kg-1. Discrete DIC and TA samples were used to calculate in situ pH using CO2SYS (van Heuven et al., 2011) for comparison with moored pH logger data.

Sometimes the depth was too shallow for the CTD to measure an accurate surface salinity. Salinity measurements lower than 33.4 were flagged and replaced by the mean near surface salinity measured at the kelp mooring site = 33.6.

Salinity was flagged (and replaced with the mean salinity, 33.6) for 4 samples reported here:

• Outside Surface July 6, 2017 11:08
• Kelp Surface July 24, 2017 13:02
• Outside Surface July 31, 2017 11:30
• Kelp Surface July 31, 2017 12:04

BCO-DMO Processing notes:

• Adjusted column headers to comply with database requirements
• Added ISO_DateTime_UTC column, converting Date and Time  to ISO format, and timezone from Pacific Standard Time (PST) to UTC

NSF Award Abstract:
Kelp forest ecosystems are of ecological and economic importance globally and provide habitat for a diversity of fish, invertebrates, and other algal species. In addition, they may also modify the chemistry of surrounding waters. Uptake of carbon dioxide (CO2) by giant kelp, Macrocystis pyrifera, may play a role in ameliorating the effects of increasing ocean acidity on nearshore marine communities driven by rising atmospheric CO2. Predicting the capacity for kelp forests to alter seawater chemistry requires understanding of the oceanographic and biological mechanisms that drive variability in seawater chemistry. The project will identify specific conditions that could lead to decreases in seawater CO2 by studying 4 sites within the southern Monterey Bay in Central California. An interdisciplinary team will examine variations in ocean chemistry in the context of the oceanographic and ecological characteristics of kelp forest habitats. This project will support an early career researcher, as well as train and support a postdoctoral researcher, PhD student, thesis master's student, and up to six undergraduate students. The PIs will actively recruit students from underrepresented groups to participate in this project through Stanford University's Summer Research in Geosciences and Engineering (SURGE) program and the Society for Advancement of Hispanics/Chicanos and Native Americans in Science (SACNAS). In addition, the PIs and students will actively engage with the management community (Monterey Bay National Marine Sanctuary and California Department of Fish and Wildlife) to advance products based on project data that will assist the development of management strategies for kelp forest habitats in a changing ocean.

This project builds upon an extensive preliminary data set and will link kelp forest community attributes and hydrodynamic properties to kelp forest biogeochemistry (including the carbon system and dissolved oxygen) to understand mechanistically how giant kelp modifies surrounding waters and affects water chemistry using unique high-resolution measurement capabilities that have provided important insights in coral reef biogeochemistry. The project sites are characterized by different oceanographic settings and kelp forest characteristics that will allow examination of relationships between kelp forest inhabitants and water column chemistry. Continuous measurements of water column velocity, temperature, dissolved oxygen, pH, and photosynthetically active radiation will be augmented by twice-weekly measurements of dissolved inorganic carbon, total alkalinity, and nutrients as well as periods of high frequency sampling of all carbonate system parameters. Quantifying vertical gradients in carbonate system chemistry within kelp forests will lead to understanding of its dependence on seawater residence time and water column stratification. Additional biological sampling of kelp, benthic communities, and phytoplankton will be used to 1) determine contributions of understory algae and calcifying species to bottom water chemistry, 2) determine contributions of kelp canopy growth and phytoplankton to surface water chemistry, and 3) quantify the spatial extent of surface chemistry alteration by kelp forests. The physical, biological, and chemical data collected across multiple forests will allow development of a statistical model for predictions of kelp forest carbonate system chemistry alteration in different locations and under future climate scenarios. Threshold values of oceanographic conditions and kelp forest characteristics that lead to alteration of water column chemistry will be identified for use by managers in mitigation strategies such as targeted protection or restoration.