California Current Integrated Ecosystem Assessment

Harmful Algal Blooms - U.S. West Coast Impacts and Implications (WORK IN PROGRESS - DRAFT REVIEW VERSION)

Table of Contents

Quick Links to Harmful Algal Bloom-Related Tools / Data

What are harmful algal blooms (HABs) and who do they harm? 

Harmful algal blooms (HABs) occur when certain algae grow to levels that cause toxic or harmful effects on people, animals, and the environment. HABs are a recurring concern along the U.S. West Coast, particularly HABs caused by some species of the diatom Pseudo-nitzschia that produce the toxin domoic acid (Anderson et al., 2021). Domoic acid can accumulate in filter feeders and extend through food webs to contaminate seafood leading to fishery closures and cause marine wildlife strandings.


HABs are reported in the annual California Current Ecosystem Status Report to the Pacific Fishery Management Council because they affect keystone fisheries, like the commercial Dungeness crab (Metacarcinus magister) fishery, that are highly lucrative and draw heavy participation from local fishing communities. Because of this reliance on Dungeness crab, fishing communities are sensitive to any perturbation directed at this fishery, such as a HAB event (Fisher et al., 2021). Fishing effort from the Dungeness crab fishery can also “spillover” into other fisheries that the council manages.

 

HABs of Pseudo-nitzschia can cost tens of millions of dollars and cause a wide range of social and cultural impacts in fishing communities. These impacts include economic losses associated with reduced commercial fish harvests and reduced tourism due to curtailed recreational fishing opportunities; food insecurity stemming from economic losses and from loss of subsistence harvest activities; and disruption of cultural and spiritual practices and loss of community identity and social interactions tied to coastal resource use. Read more about the Effects of Harmful Algal Blooms on West Coast Fishing Communities.

 

HABs can also have broad ecosystem impacts. For example, the massive 2015 HAB event on the West Coast created a perfect storm of conditions that led to unprecedented whale entanglements, prompting Integrated Ecosystem Assessment (IEA) scientists to develop tools to reduce entanglements while continuing to support economically valuable fisheries, illustrating the need for an ecosystem approach to HAB management that also considers social-ecological tradeoffs.

crab fisherman hauling his pot full of crabs

Fisherman hauling a pot of Dungeness crab onboard. Photo credit: Benjamin Drummond /bdsjs.com.

sick sea lion on beach

California sea lion stricken by the neurotoxin domoic acid from a harmful algal bloom in Santa Barbara County, California. Photo credit: Channel Islands Marine & Wildlife Institute.

What's the current status of HABs in the California Current ecosystem?

High level summary of the last available regional report, e.g.: 

"Ocean Heatwave Has Triggered New Toxic Algal Blooms on the California Current. A harmful algal bloom (HAB), specifically one caused by the diatom Pseudo-nitzschia, is currently impacting the US West Coast, particularly southern California, and has been linked to numerous strandings of marine mammals like sea lions and dolphins. This bloom is producing the toxin domoic acid, which accumulates in shellfish and can cause illness and even death in higher-level predators like marine mammals and humans."

Chlorophyll-a

Figure 1

Chlorophyll concentration based on satellite-derived ocean color, courtesy of NOAA NESDIS CoastWatch and stored in ERDDAP data archive. Data are derived from the Joint Polar Satellite System, NASA, Copernicus Mission, RADARSAT Constellation Mission, Candian Space Agency, Japan Aerospace Exploration Agency, and EUMETSAT.

Daily SST Anomalies

Figure 1

Daily sea surface temperature anomalies (SSTa) in the California Current ecosystem. Color represents SSTa, with the thick black line encircling regions which are in "heatwave status"; arrows represent wind speed and direction; thin lines represent atmospheric pressure at sea level. An animation of daily images through 2022 can be viewed here. SST data from Multi-scale Ultra-high Resolution (MUR) SST Analysis Anomaly; sea level pressure and wind data from NCEP/NCAR Reanalysis.

Bakun Upwelling Index 48N

Figure 1

Traditional Bakun Index upwelling calculation plot 45N_125W at near real time (6-hourly, 1st day of the current month to 0600 h PST of current day, updated daily). Downloads of visual plots and /or data (text form) courtesy of NOAA Fisheries, Southwest Fisheries Science Center, Environmental Research Data Services.

Bakun Upwelling Index 42N

Figure 1

Traditional Bakun Index upwelling calculation plot 42N_125W at near real time (6-hourly, 1st day of the current month to 0600 h PST of current day, updated daily). Downloads of visual plots and /or data (text form) courtesy of NOAA Fisheries, Southwest Fisheries Science Center, Environmental Research Data Services.

Bakun Upwelling Index 36N

Figure 1

Traditional Bakun Index upwelling calculation plot 36N_122W at near real time (6-hourly, 1st day of the current month to 0600 h PST of current day, updated daily). Downloads of visual plots and /or data (text form) courtesy of NOAA Fisheries, Southwest Fisheries Science Center, Environmental Research Data Services.

Bakun Upwelling Index 30N

Figure 1

Traditional Bakun Index upwelling calculation plot 30N_119W at near real time (6-hourly, 1st day of the current month to 0600 h PST of current day, updated daily). Downloads of visual plots and /or data (text form) courtesy of NOAA Fisheries, Southwest Fisheries Science Center, Environmental Research Data Services.

C-HARM NowCast

Figure 1

C-HARM model nowcast of the probability of Pseudo-nitzschia concentrations of in excess of 10,000 cells/L, the probability of particulate domoic acid > 500 nanograms/L, and the probability of cellular domoic acid > 10 picograms/cell in California and Southern Oregon coastal water. For more details, see associated metadata on the NOAA CoastWatch West Coast Node, which generates and serves the C-HARM model output.

C-HARM 3-day forecast

Figure 1

C-HARM model 3-day forecast of the probability of Pseudo-nitzschia concentrations of in excess of 10,000 cells/L, the probability of particulate domoic acid > 500 nanograms/L, and the probability of cellular domoic acid > 10 picograms/cell in California and Southern Oregon coastal water. For more details, see associated metadata on the NOAA CoastWatch West Coast Node, which generates and serves the C-HARM model output.

How do we track the impacts of HABs in the California Current? 

The California Current IEA focuses on HAB impacts to Dungeness crab (Metacarcinus magister) and razor clam (Siliqua patula) because of the extensive engagement and dependence of communities on the fisheries. The commercial Dungeness crab fishery is one of the most economically valuable fisheries on the U.S. West Coast and generates a large fraction of revenue for many fishery participants (Fuller et al., 2017). The recreational razor clam fishery can draw tens of thousands of diggers to coastal communities in a single day, and local businesses depend on commerce associated with clamming activities (Ritzman et al., 2018). Razor clams are also a “cultural keystone species” for the Quinault Indian Nation as they are a staple food, key source of income, and integral to cultural identity (Crosman et al., 2019). We track levels of domoic acid in razor clams and impaired harvest opportunities for the commercial Dungeness crab fishery due to domoic acid and evaluate the status and trends over the most recent 5-year period relative to the long-term mean.  

Domoic Acid data from the CCIEA indicators website

Domoic acid levels in WA clams

Maximum monthly domoic acid concentrations in razor clams (courtesy of Washington State Department of Health); these data are compiled from tests conducted by a variety of Tribal, State, and County partners on Washington beaches. Click on the image for a larger version, or access the CCIEA indicator data server to download data or access a customizable image.

Explore the California Current IEA HAB indicator

The interactive graphic below provides a summary of management actions in the commercial Dungeness crab fishery from the 2019-20 to 2023-24 fishing seasons in response to domoic acid and other issues, such as poor body condition and marine life entanglement risk. Orange colors represent management actions related to HABs while blue colors represent management actions related to marine life entanglement risk. Click on the image below or on the following link to access an interactive version of this figure (Shiny app), which allows users to specify a date and latitude range of interest: https://emlab-ucsb.shinyapps.io/dcrab_season_status/

Dungeness crab season status viewer

Screen shot of Dungeness crab season status by latitude over time

Graphic depicting the status of crab fisheries along the U.S. West Coast (vertical axis - latitude N) over time (horizontal axis). Click on the image to access the interactive version of this figure and specify particular spatial and temporal ranges.

Alignment with the West Coast Ocean Alliance HAB indicator

HABs are assessed using multiple approaches to provide historical perspective for evaluating HAB impacts within a given period of time. The West Coast Ocean Alliance (WCOA) employs a similar approach to the California Current IEA and calculates their HAB indicator as the proportion of shellfish harvest opportunity impaired by HABs within a given year. The WCOA indicator focuses on the reduction in shellfish harvesting opportunities for bivalve shellfish only, whereas the CCIEA indicator focuses on impaired harvest opportunities to the commercial Dungeness crab fishery due to HABs in the context of other management actions. Together these indicators provide a holistic way to track HAB impacts to commercial and recreational fisheries that are important for the social and economic well-being of coastal communities.

How else do we keep tabs on HABs? 

IEA scientists also monitor harmful algal species and toxins in water samples as part of fisheries surveys to help understand when and where HABs occur and what causes them. We use robotic microscopes called Imaging FlowCytobots (IFCB) to modernize data collection efforts, allowing us to map the distribution and abundance of harmful algae at high temporal and spatial resolution (Fischer et al., 2024). Since 2019, an IFCB has sailed on the Integrated West Coast Pelagics Survey (formerly the Joint U.S.-Canada Integrated Ecosystem and Pacific Hake Acoustic Trawl Survey) aboard the NOAA ship Bell M. Shimada to autonomously monitor the microalgal community while the ship is either underway or on station. Click on the map icon below to explore the data.

Map of sampling locations and phytoplankton images

Example of the IFCB dashboard, showing sampling locations and corresponding images of sampled phytoplankton. Click on this image to access the website for images collected during the Integrated survey.

Why do HABs occur?

Of the 5,000+ known species of marine microalgae, only a few dozen of them repeatedly cause HABs. These species are often present in the environment in numbers too small to be harmful, but when conditions are just right, they can rapidly grow to reach levels that can cause a diverse array of impacts including human poisoning syndromes (e.g., amnesic shellfish poisoning caused by consumption of shellfish that have accumulated domoic acid), mortalities of fish and wildlife, ecosystem disruption, and hypoxia and anoxia from high biomass blooms (Anderson et al., 2021).

HABs of Pseudo-nitzschia are common in the California Current. This marine ecosystem thrives on the nutrients brought up from the deep ocean by strong winds. But this upwelling of nutrients, particularly nitrogen, can also fuel the rapid growth of Pseudo-nitzschia species and their production of domoic acid. Upwelling has been found to be a main driver of domoic acid events off California over the last 20 years (Sandoval-Belmar et al., 2023). A range of other factors have been found to be important drivers of domoic acid production for different species in different geographic areas, such as riverine and wastewater discharge, climate modes of variability, and the depletion of certain nutrients such as silicic acid (Anderson et al., 2021 and references therein). Toxic cells of Pseudo-nitzschia have also been found to accumulate in retentive oceanographic features such as the Juan de Fuca eddy and Heceta Bank (Hickey and Banas, 2003), and storm events that drive downwelling can push these cells towards coastal beaches where they can impact shellfish beaches (Hickey et al., 2013).

A handful of other HAB species also occasionally bloom in the California Current, each with their own set of impacts and environmental drivers. 

Pseudo-nitschia cells

A chain of Pseudo-nitzschia cells. Photo credit: Gabriela Hannach.

Pseudo-nitzschia spp.

  • A diatom, some species of which can produce the toxin domoic acid.
  • Domoic acid can sicken marine birds and mammals and is responsible for the human illness called Amnesic Shellfish Poisoning (ASP).
  • Symptoms of ASP are gastrointestinal illness, headache, dizziness, confusion, disorientation, permanent short-term memory loss, and motor weakness, with severe intoxication resulting in seizures, cardiac arrhythmias, coma, and death.
Alexandrium close-up image

Alexandrium sp. Photo credit: Gabriela Hannach.

Alexandrium spp.

  • A dinoflagellate that produces a suite of toxins referred to as paralytic shellfish toxins (PSTs), the most potent of which is saxitoxin.
  • PSTs are responsible for the human illness called Paralytic Shellfish Poisoning (PSP).
  • Symptoms of PSP are gastrointestinal illness, numbness and tingling of the lips, mouth, face, and neck, with severe intoxication resulting in paralysis of the muscles of the chest and abdomen leading to respiratory failure and death.
Dinophysis spp. closeup

Dinophysis sp. Photo credit: Gabriela Hannach.

Dinophysis spp.

  • A dinoflagellate, some species of which produce okadaic acid and Dinophysis toxins (DTXs) and/or pectenotoxins (PTXs).
  • DTXs can cause the human illness Diarrhetic Shellfish Poisoning (DSP) and PTXs can cause shellfish mortalities.
  • Symptoms of DSP are gastrointestinal illness.  

Akashiwo sanguinea. Photo credit: Gabriela Hannach.

Akashiwo sanguinea

  • A dinoflagellate that is generally considered non-toxic, but can kill fish and birds.
  • Mortality events are caused by the production of surfactants that can strip oils from bird feathers leading to hypothermia, clogging of fish and shellfish gills, or oxygen depletion when blooms decay.

Heterosigma akashiwo. Photo credit: Gabriela Hannach.

Heterosigma akashiwo

  • A raphidophyte that may produce an uncharacterized toxin or toxins.
  • Not known to be harmful to humans, but cells can irritate the gills of fish, causing mortality.

 

Lingulodinium bloom. Photo credit: Peter Franks.

Lingulodinium spp.

  • A dinoflagellate, some species of which can produce a group of toxins called yessotoxins (YTXs).
  • Although YTXs have not been linked to any reported cases of human illness, they can accumulate in shellfish and are highly toxic to mice.
  • They can form dense, red colored blooms that display bioluminescence at night. 

 

Regulatory agencies

Monitoring programs

Forecasting products

Status and trends

General information

References

References

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  • Crosman, K.M., Petrou, E.L., Rudd, M.B., Tillotson, M.D., 2019. Clam hunger and the changing ocean: characterizing social and ecological risks to the Quinault razor clam fishery using participatory modeling. Ecol Soc 24, 16. https://doi.org/10.5751/ES-10928-240216.

  • Dyson, K., Huppert, D.D., 2010. Regional economic impacts of razor clam beach closures due to harmful algal blooms (HABs) on the Pacific coast of Washington. Harmful Algae 9(3), 264-271, doi: 210.1016/j.hal.2009.1011.1003.

  • Fischer, A.D., Houliez, E., Bill, B.D., Kavanaugh, M.T., Alin, S.R., Collins, A.U., Kudela, R.M., Moore, S.K., Nutrient limitation dampens the response of a harmful algae to a marine heatwave in an upwelling system. Limnol Oceanogr n/a(n/a).

  • Fisher, M.C., Moore, S.K., Jardine, S.L., Watson, J.R., Samhouri, J.F., 2021. Climate shock effects and mediation in fisheries. Proceedings of the National Academy of Sciences 118(2), e2014379117.

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  • Ritzman, J., Brodbeck, A., Brostrom, S., McGrew, S., Dreyer, S., Klinger, T., Moore, S.K., 2018. Economic and sociocultural impacts of fisheries closures in two fishing-dependent communities following the massive 2015 U.S. West Coast harmful algal bloom. Harmful Algae 80, 35-45 

  • Sandoval-Belmar, M., Smith, J., Moreno, A.R., Anderson, C., Kudela, R.M., Sutula, M., Kessouri, F., Caron, D.A., Chavez, F.P., Bianchi, D., 2023. A cross-regional examination of patterns and environmental drivers of Pseudo-nitzschia harmful algal blooms along the California coast. Harmful Algae 126, 102435.

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