The Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) 2017


Grant Number: NA18NOS4780174 

Project Period: June 1, 2018 - May 31, 2023

Principal Investigator: Daniele Bianchi, UCLA    

Co-PIs: Clarissa Anderson, UCSD, Raphe Kudela, UCSC, Martha Sutula, SCCWRP

Collaborators: Chris Edwards (UCSC), James McWilliams (UCLA), Allison Moreno (UCLA), Marco Sandoval Belmar (UCLA), Pierre Damien (UCLA), Jayme Smith (SCCWRP), Faycal Kessouri (SCCWRP), Christina Frieder (SCCWRP), Minna Ho (SCCWRP), Karen McLaughlin (SCCWRP)

Executive Summary

Pseudo-nitzschia spp., a genus of marine diatoms, is one of the leading causes of toxic harmful algal blooms (HABs) along the U.S. West Coast. Approximately half of known Pseudo-nitzschia strains can produce domoic acid (DA), a neurotoxin that can negatively impact wildlife and fisheries and put human life at risk through amnesic shellfish poisoning. DA accumulates via trophic transfer into pelagic and benthic food webs, causing sickness and mass mortality events in a variety of marine animals including sea lions, sea otters, whales and seabirds. Understanding the mechanism that result in PN blooms and toxic DA events has been the focus of much HAB research to date and is essential to supporting ecosystem conservation and coastal water quality management. PN HABS events are naturally occurring but are increasing with climate change and through the coastal export of anthropogenic nutrients; but the extent of this influence would be expected to vary along the coast and remains to be explicitly quantified.

Understanding the relative influence of climate warming, natural variability and anthropogenic carbon and nutrients inputs requires an integrated systems modeling approach. The goal of this project was to develop an integrated modeling system, validated against available observations, to investigate the natural and anthropogenic drivers of PN HABs in the southern California Current System (CCS). Our approach builds upon the development of such a modeling framework, based on the Regional Oceanic Modeling System (ROMS) and the Biogeochemical Elemental Cycling model (BEC), comprising circulation, biogeochemical cycles, and lower-trophic ecosystem, used to investigate the physical circulation and biogeochemical cycles (in particular, ocean acidification, hypoxia, eutrophication) along the US West Coast. The specific project objectives can be summarized as follows: (1) develop an end-to-end predictive capacity for the simulation of PN-derived DA, in the southern CCS, evaluated against observations; (2) apply our integrated model to investigate the relative importance of anthropogenic inputs and natural drivers on the frequency and severity of PN HAB events in the southern CCS; and (3) provide our findings to coastal zone managers to improve marine resource management and pollution control. 

To achieve this goal, we undertook three major scientific research thrusts:

First, we compiled and analyzed existing data. We completed a synthesis of existing observations along the U.S. West Coast to build a comprehensive dataset of particulate DA that enables coast-wide analysis of DA pattern and drivers, and lays the foundation for model validation (Sandoval Belmar et al., 2023). This included: (1) Conducting a cross-regional observational analysis of environmental drivers of PN and DA along the U.S. West coast, focusing on three HAB hotspots in Monterey Bay and Southern California Bight; (2) Documenting the persistence of DA in marine sediments and benthic infauna in the Southern California Bight, with leveraged funding from the Southern California Bight Regional Monitoring Program (Smith et al., submitted). This observational analysis supports the consistency across regions of several environmental drivers in increasing the probability and strength of DA events (e.g., chlorophyll-a, nutrient ratios), while highlighting key differences related to climate and terrestrial inputs.

Second, we developed and validated predictive models of lower trophic ecosystem and biogeochemistry with explicit functionality for PN HABs. This work began by an extensive effort, leveraged with state support, to set up, develop, then conduct a validation of ROMS-BEC, including at the West Coast wide scale and at scales of anthropogenic influence within the southern California Bight. A nested model domain was established, scaling from 4-km (horizontal) resolution CCS-wide, two 1-km nests in California and Oregon/Washington nearshore, then to 300-m nests in the Southern California Bight (SCB) and the San Francisco and Monterey Coasts (SFMC), where investigations of local anthropogenic inputs were focused. Terrestrial and atmospheric nutrient and carbon inputs, including anthropogenic sources, were assembled as modeling forcing. A decade of model simulations (1997-2007) were validated against available climatological, coast-wide data sets. Reanalysis solutions for the SCB at 300-m resolution adeptly reproduced anthropogenically-enhanced gradients in NPP, oxygen and carbon system parameters resulting from anthropogenic nutrient inputs to the SCB (Kessouri et al., 2021a). A new SCB-focused validation effort is underway with a parallel effort ongoing in the SFMC.

We expanded the ecosystem component of ROMS-BEC to include a mechanistic representation of PN and DA based on a 0-D model parameterization optimized against PN lab culture data. This was done by adding DA production capability to the diatom component of BEC and tracking DA through the model’s compartments. We included explicit DA production as a function of PN abundance, photosynthesis rates, and nutrient ratios, and allow its accumulation and transport by the model circulation. The parameterization of this module was informed by chemostat experimental findings. The model formulation and code is accessible via Moreno et al. 2022. We then incorporated our PN module into the 3-D ROMS-BEC model to conduct high-resolution hindcast simulations of PN and DA distribution throughout the Southern CCS. We then conducted verification and testing to compare predicted observations of DA. We fine-tuned the model constants to predict DA occurred at this stage.

Third, we applied ROMS-BEC to investigate natural and anthropogenic drivers of productivity and their link to the risk of toxic PN blooms. While ROMS-BEC-PN underwent verification and refinement, OPC-leveraged investigations have targeted the natural and anthropogenic drivers of productivity and the linkage to algal blooms, ocean acidification and hypoxia, at scales from the entire California Current to a focus on the Santa Barbara Channel, a PN HABS hot spot. ROMS-BEC was used to investigate the relative importance of oceanic versus anthropogenic nutrient drivers of primary productivity. This was first published focused on the coastal band of 10 km in Proceedings of the National Academy of Sciences, based on simulations of 1997-2000 (Kessouri et al., 2021b). We updated that analysis to recent years, expanding the analysis offshore, that anthropogenic nutrients are greatly amplifying productivity and influencing oxygen and pH loss offshore (Kessouri et al., 2023). We quantified the effect of anthropogenically enhanced productivity on O2 and pH-related habitat compression for marine organisms (Frieder et al., submitted). We examined how reducing primary production via nitrogen management in wastewater outfalls, in combination with reduced volumes from wastewater recycling, could diminish environmental effects. Finally, we investigated the specific mechanisms behind how changes in outfall volume and nitrogen form impacted primary productivity (Ho et al., submitted). We have then continued to investigate how oceanic versus anthropogenic nutrients are controlling diatom productivity, focused in the Santa Barbara channel, then estimated how ocean versus anthropogenic drivers were specifically linked to an increased risk of DA-related marine mammal stranding events (Smith et al., in preparation).

Finally, we transmitted our findings to coastal zone water quality and natural resource managers. These outreach and management translation efforts resulted in important project outcomes, summarized as (1) progress in stakeholder acceptance of ROMS-BEC as a decision support tool, (2) multiple new California and Oregon strategies/policies adopted or under development that are relevant to ocean health, climate change, nutrient management, HABS and OAH, and (3) use of ROMS-BEC as a data source for West Coast ocean health report cards, specifically for OA, kelp, and HABs.

Key Findings




Data Access

  • Access to all data sets will be provided upon publication through an accessible DOI or upon request.

Progress Reports


PI's listed in bold. 

Bernstein, S., Ruiz-Cooley, R. I., Kudela, R., Anderson, C. R., Dunkin, R., & Field, J. C. (2021). Stable isotope analysis reveals differences in domoic acid accumulation and feeding strategies of key vectors in a California hotspot for outbreaks. Harmful Algae, 110, 102117.

Deutsch, C., Frenzel, H., McWilliams, J.C., Renault, L., Kessouri, F., Howard, E., Liang, J.H., Bianchi, D. and Yang, S., 2021. Biogeochemical variability in the California Current system. Progress in Oceanography, 196, p.102565.

Grigoratou, Grigoratou, E. Montes, A. J. Richardson, J. D. Everett, E. Acevedo-Trejos, C. Anderson, B. Chen, T. Guy-Haim, J. Hinners, C. Lindemann, T. Martins Garcia, K. O. Möller, F. M. Monteiro, A. R. Neeley, T. D. O'Brien, A. P. Palacz, A. J. Poulton, A. E. F. Prowe, Áurea E. Rodríguez-Santiago, C. S. Rousseaux, J. Runge, J. F. Saad, I. Santi, R. Stern, A. Soccodato, Selina Våge, M. Vogt, S. Zervoudaki, F. E. Muller-Karger 2022. The marine biodiversity observation network plankton workshops: plankton ecosystem function, biodiversity, and forecasting—research requirements and applications. Bulletin Limnology and Oceanography.

Hamilton, D., Anderson, C., Hense, I., & Chapra, S. (2021). Future Perspectives in Modeling Harmful Algal Bloom (HAB) Responses to Climate Change: Guidelines for HABs modeling. Guidelines for the Study of Climate Change Effects on HABs, 120pp. doi: 10.25607/OBP-1692 

Kessouri, F., Bianchi, D., Renault, L., McWilliams, J. C., Frenzel, H., & Deutsch, C. A. (2020). Submesoscale currents modulate the seasonal cycle of nutrients and productivity in the California Current System. Global Biogeochemical Cycles, 34, e2020GB006578.

Kessouri, F., McLaughlin, K., Sutula, M., Bianchi, D., Ho, M., McWilliams, J.C., Renault, L., Molemaker, J., Deutsch, C. and Leinweber, A., (2021a). Configuration and validation of an oceanic physical and biogeochemical model to investigate coastal eutrophication in the Southern California Bight. Journal of Advances in Modeling Earth Systems, 13(12), p.e2020MS002296.

Kessouri, F., McWilliams, J.C., Bianchi, D., Sutula, M., Renault, L., Deutsch, C., Feely, R.A., McLaughlin, K., Ho, M., Howard, E.M. and Bednaršek, N., (2021b). Coastal eutrophication drives acidification, oxygen loss, and ecosystem change in a major oceanic upwelling system. Proceedings of the National Academy of Sciences, 118(21). 

Kessouri, F., Sutula, M., Bianchi, D., Ho, M., Damien, P., McWilliams, J., ... & Deutsch, C. (2023). Importance of cross-shore transport and eddies in promoting large scale response to urban eutrophication. Scientific Reports.

Kudela, R., Anderson, C., & Ruhl, H. (2021). The California Harmful Algal Bloom Monitoring and Alert Program: A Success Story for Coordinated Ocean Observing. Frontiers in Ocean Observing: Documenting Ecosystems, Understanding Environmental Changes, Forecasting Hazards, A Supplement to Oceanography, 34(4), 84-85.

Moreno, A.R., Anderson, C., Kudela, R.M., Sutula, M., Edwards, C. and Bianchi, D., 2022. Development, calibration, and evaluation of a model of Pseudo-nitzschia and domoic acid production for regional ocean modeling studies. Harmful Algae, 118, p.102296.

Renault, L., McWilliams, J.C., Kessouri, F., Jousse, A., Frenzel, H., Chen, R. and Deutsch, C., 2021. Evaluation of high-resolution atmospheric and oceanic simulations of the California Current System. Progress in Oceanography, 195, p.102564.

Sandoval-Belmar, M., Smith, J., Moreno, A. R., Anderson, C., Kudela, R. M., Sutula, M., ... & Bianchi, D. (2023). A cross-regional examination of patterns and environmental drivers of Pseudo-nitzschia harmful algal blooms along the California coast. Harmful Algae126, 102435.

Sutula, M., Ho, M., Sengupta, A., Kessouri, F., McLaughlin, K., McCune, K., & Bianchi, D. (2021). Dataset of terrestrial fluxes of freshwater, nutrients, carbon, and iron to the Southern California Bight, U.S.A. Data in Brief, 106802. doi:

Sutula, M., Ho, M., Sengupta, A., Kessouri, F., McLaughlin, K., McCune, K. and Bianchi, D., 2021. A baseline of terrestrial freshwater and nitrogen fluxes to the Southern California Bight, USA. Marine Pollution Bulletin, 170, p.112669.

Trainer, V.L., Kudela, R.M., Hunter, M.V., Adams, N.G. and McCabe, R.M., 2020. Climate extreme seeds a new domoic acid hotspot on the US west coast. Frontiers in Climate, 2, p.23.

Trainer, V.L., Moore, S.K., Hallegraeff, G., Kudela, R.M., Clement, A., Mardones, J.I. and Cochlan, W.P., 2020. Pelagic harmful algal blooms and climate change: Lessons from nature’s experiments with extremes. Harmful Algae, 91, p.101591. 

Weber, E. D., Auth, T. D., Baumann-Pickering, S., Baumgartner, T. R., Bjorkstedt, E. P., Bograd, S. J., ... & Zeman, S. M. (2021). State of the California Current 2019–2020: back to the future with marine heatwaves?. Frontiers in Marine Science8, 709454. 

Submitted or In prep

Frieder C.A., F. Kessouri, M. Ho, M. Sutula, D. Bianchi, J. C. McWilliams, C. Deutsch, E. Howard, Effects of eutrophication on pelagic habitat capacity in the Southern California Bight, Submitted, Scientific Reports.

Ho M., F. Kessouri, C. A. Frieder, M. Sutula, D. Bianchi, J.C. McWilliams, Effect of management of ocean outfall discharge volume and dissolved inorganic nitrogen load on coastal eutrophication outcomes in the Southern California Bight, Submitted, Scientific Reports.

Hoel, P., Ho, M., Kessouri, F., Sutula, M., McWilliams, J., Bianchi, D. Nutrients, buoyancy and biomass: exploring the relationships of biogeochemistry plume dynamics from subsurface ocean outfalls the Southern California Bight. In Preparation.

Sandoval-Belmar M., Damien P., Kessouri F., Ho M., Sutula M., Edwards C., McWilliams J., Bianchi D. Simulations of coastal domoic acid accumulation with and without anthropogenic nutrient inputs in the Southern California Bight, In Preparation-b.

Sandoval-Belmar M., Damien P., Kessouri F., Ho M., Sutula M., Edwards C., McWilliams J., Bianchi D. Effects of terrestrial nutrient inputs on coastal eutrophication and ecosystem in Central California, In Preparation-b.

Smith J., Cram J., Berndt M., Hoard V., Shultz D., Deming A. Out of sight, not out of mind: region wide observations of domoic acid improve models of California sea lion (Zalophus californiaus) strandings, In Preparation