Grantee Research Project Results
2021 Progress Report: Evaluating agricultural management practices benefiting the Monterey Bay: reducing nutrient loads and Harmful Algal Bloom (HAB) events
EPA Grant Number: R840083Title: Evaluating agricultural management practices benefiting the Monterey Bay: reducing nutrient loads and Harmful Algal Bloom (HAB) events
Investigators: Clark, Ross , Bowers, Holly
Current Investigators: Bowers, Holly , O'Connor, Kevin , Clark, Ross
Institution: San Jose State University
Current Institution: San Jose State University , Moss Landing Marine Labs
EPA Project Officer: Ludwig-Monty, Sarah
Project Period: September 1, 2020 through April 28, 2025
Project Period Covered by this Report: September 1, 2020 through August 31,2021
Project Amount: $999,999
RFA: Approaches to Reduce Nutrient Loadings for Harmful Algal Blooms Management (2020) RFA Text | Recipients Lists
Research Category: Harmful Algal Blooms , Water
Objective:
The proposed project will demonstrate the effectiveness of farm runoff treatment systems in reducing nutrient discharges to coastal waterways and provide a blueprint for scaling-up treatment systems within two key agricultural watersheds of the Monterey Bay, CA. In addition, this project will examine the potential link between agricultural nutrient discharges and the growth of harmful algal blooms (HABs).
Progress Summary:
HAB Culturing. An initial experiment was performed to determine the cell concentration that should be used for spiking (5 cells/ml, 50 cells/ml, or 125 cells/ml). Filtered water (0.22 micron) from pre- and post-treatment (described above) was used (10%) to amend base media (0.22 micron filtered seawater, half strength nutrients [F/4]) for spiking in of Pseudo-nitzschia cells. These results will help guide our efforts to scale up to mesocosms and to test different nutrient amendments. This experiment was repeated using Alexandrium cells, to determine the number of cells that need to be spiked in for achieving growth.
Subwatershed Nutrient loading has been calculated for both watersheds. Loading from each of the Salinas Valley watersheds is similarly high (3000-5000kg N/year) while two of the four the Pajaro sub-watersheds were identified to have the majority of spring nutrient loading. These initial data will be compared with fall loading numbers for 2021 and replicate data collection for 2022. These loading data will help validate watershed models and help to size treatment systems in these drainages to reduce loading to receiving waters and the initiation of HAB events. Nitrate reduction of treatment systems. All nitrogen fertilizer constituents have been collected at select treatment systems for each of the four seasons needed to document preferential reduction of specific nitrogen constituents. All of the treatment systems have documented a reduction in nitrate concentrations as well as other nitrogen constituents but reductions among constituents are nonlinear and variable among treatment systems. We will finalize treatment system data collection this year (filling in gaps in seasonal samples during year one) and will generate reduction rate estimates for different treatment systems.
HAB response to treatment systems. We used water collected from various sub-watersheds to test HAB mesocosm experimental approaches. Initial results document different response of the two focus algae to the various source waters (Figure 1). These differences suggest a complex relationship between water chemistry components that we hope to disassociate during year two of the HAB mesocosm experiments.
Figure 1. Response of two key harmful algal bloom species to pre-treated agricultural waters. The two metrics used to assess response are biomass (F0) changes over time (days 1-7) and cell health (yield) measured at the same time points (cells measuring 0.5 or greater are considered to be in a healthy state). All measurements are obtained from a PAM fluorometer (all y-axes are fluorescence units) located at EBL. These early flask-based experiments will help guide the larger mesocosm experiments which will focus on the different responses by a diatom (P. pungens) and a dinoflagellate (Alexandrium sp.) to pre- and post-treated agricultural waters.
Receiving water quality sampling. The Salinas Valley receiving water monitoring array has been installed and is functioning well to quantify hourly nitrate load to the Monterey Bay (Figure 2). These data will be compared with ongoing monthly grab samples and instantaneous flow measurements to confirm accuracy and evaluate if monthly grab samples adequately document nitrate loading within a variable environment. Initial data estimate nitrate loading varies throughout the tidal cycle with greatest loading to the bay during low/low tides. Hourly loading ranges from 0 kg/hr to more than 300kg/hr. Loading has decreased since the initial rains ended in October.
Figure 2. Web based data output from real time water monitoring array on the Salinas/Tembladero drainage. Nitrate concentration and flow rate are used to calculate hourly nitrate loading to the Monterey Bay (kg/hr)
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.