Table of Contents

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

These data are published in Hirsh et al., see related publications section.

Continuous flow pumping experiments were conducted inside the kelp forest from a vessel within 15-m of the kelp mooring to obtain high temporal and vertical resolution biogeochemical data. Two experiments were conducted (July 11-13 and July 18-20, 2018) that overlapped with the kelp mooring pH timeseries data. Seawater was pumped from five depths spanning the water column using five sections of equal-length polypropylene tubing (3/8” ID, 1/2” OD) deployed over the side of a moored vessel. The depths presented here include the surface (valve #5), 6 mab (2-5 mbs, valve #3), and 1 mab (7-10 mbs, valve #1). A custom auto sampling manifold introduced water from each of the 5 tubes to a continuous flow system at 5-minute intervals, allowing the full suite of depths to be sampled every 25 minutes for the duration of each experiment (similar to Koweek et al., 2015a; Koweek et al., 2015b; Teneva et al., 2013). Seawater was drawn into the continuous flow system from each depth by a peristaltic pump operating at 2L/min.

Dissolved inorganic carbon (DIC) samples were automatically drawn every 5 minutes and analyzed using a custom-built sample acidification and delivery system coupled to a Li-COR 7000 infrared gas analyzer as described in Long et al. (2011). DIC was calibrated every hour using certified reference materials (CRM), Batch 169 (Dickson, 2010). Instrumental precision, based on 102 CRM analyses, was ± 5.7 μmol kg-1.

DIC samples were drawn from whichever depth was being actively pumped. The samples were later paired to the
appropriate depth by matching DIC sampling time to the valve control record of which depth was being pumped. Data processing was completed in Matlab.

BCO-DMO Processing notes:

• Converted Timestamp 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.