Krill hotspots in the California Current

Oceanic processes that concentrate zooplankton and forage fish in so-called hotspots (areas of enhanced species abundance, diversity and/or trophic interactions) have remained elusive. Zooplankton including euphausiids (krill) and copepods are important grazers of phytoplankton and prey species for a diverse array of predators; therefore, they represent a key link in marine food webs. The distribution of zooplankton is patchy and often decoupled from phytoplankton in space and time. Consequently, it has been difficult to predict the abundance and distribution of fish, seabirds and marine mammals, which depend directly on zooplankton for growth and reproduction, from remotely-sensed variables such as chlorophyll or primary production.

A NASA-funded project (80NSSC17K0574) combined remote sensing products, ecosystem models and in situ data to investigate zooplankton hotspots along the U.S. West Coast and their relationship with environmental forcing, lower and higher trophic levels. We simulated the distribution of hotspots using two different, complementary approaches: 1) a high-resolution coupled biophysical model (Fiechter et al., 2020), and 2) a simple combination of satellite-based winds and currents with plankton growth and grazing equations (Messié et al., 2022). Our simulations were evaluated against in situ observations of krill from fisheries surveys and distributions of krill predators (e.g., seabirds and marine mammals). Our results highlight the importance of the upwelling process and oceanic circulation in shaping the mesoscale distribution of biological hotspots. Here we present routine products for the prediction of zooplankton hotspots along the U.S. West Coast from remotely-sensed variables.  

Team: Monique Messié & Francisco Chavez (MBARI), Jerome Fiechter (UCSC), Jarrod Santora (NOAA).

Data available for download: a monthly retrospective and near real-time modeled zooplankton concentrations is available as a NetCDF file (1993-present). These were obtained using the growth-advection method described in Messié et al. (2022), using nitrate supply computed from CCMP winds and AVISO geostrophic currents (available for download on the Nsupply webpage) and GlobCurrent 15 m depth currents. Recent data (exact date given in the file summary attribute) are based on near real-time (NRT) satellite products and are subject to caution. The non-NRT data (1993-2018) is also available at doi:10.5281/zenodo.6415214. Please refer to Messié et al. (2022) when using this product.

Reference: Messié, M., D. A. Sancho-Gallegos, J. Fiechter, J. A. Santora and F. P. Chavez (2022). Satellite-based Lagrangian model reveals how upwelling and oceanic circulation shape krill hotspots in the California Current System. Frontiers in Marine Science, 9:835813, doi:10.3389/fmars.2022.835813 (in press, available upon request)


Krill spatio-temporal patterns

Current conditions

Fig. 1: Latest modeled zooplankton concentrations in the California Current (left) and corresponding anomaly relative to the 1993-2018 seasonal cycle (right).

Average patterns (1993-2018)

Fig. 2: Modeled zooplankton hotspot spatial distribution and timing (1993-2018). Left: mean concentration, middle: seasonal maximum concentration, right: timing of the seasonal maximum. Red bars indicate the location of major hotspots and the black contour is 150 km from shore. Reproduced from Messié et al. (2022, Fig. 7).

Hotspot temporal variability

Fig. 3: Time series zooplankton concentrations within the 4 hotspots identified with red bars in Fig. 4, averaged each year over their peak months. Horizontal lines display the mean and standard deviation over the 1993-2018 time period.


Monthly zooplankton hotspot maps were obtained by modeling plankton concentration as a function of satellite winds and currents using the “growth-advection” approach (Messié and Chavez, 2017; Messié et al., 2020, 2022). The method considers the evolution of plankton communities within the surface mixed layer of a water mass advected by surface currents, following an input of nutrients by a given process, here coastal upwelling. A detailed description of the method can be found in Messié et al. (2022) and the Matlab functions used to run the full growth-advection method are available at

Fig. 4: Growth-advection method schematic. Step 1: a simple plankton model calculates zooplankton concentration over time (Zbig, black) following an upwelling event. Step 2: the model is initialized at each latitude and the result mapped on oceanic currents (example for one daily run). Step 3: daily runs are combined into monthly maps. Reproduced from Messié et al. (2022, Fig. 1).

The plankton model was tuned to represent krill similarly to NEMURO in Fiechter et al. (2020). The result matches in situ krill data measured during the yearly Rockfish Recruitment and Ecosystem Analysis Survey (RREAS) fairly well. Relative to in situ surveys, the model has the advantage to provide krill estimates for the full year and the entire California Current. More extensive validation can be found in Messié et al. (2022).

Fig. 5: Comparison of modeled zooplankton from the growth-advection method with yearly in situ krill surveys in May-June (RREAS) for the central hotspot. Reproduced from Messié et al. (2022, Fig. 6a).


Fiechter, J., J.A. Santora, F.P. Chavez, D. Northcott and M. Messié, 2020. Krill hotspot formation and phenology in the California Current Ecosystem. Geophysical Research Letters, 47(13), e2020GL088039, doi:10.1029/2020GL088039

Messié, M. and F.P. Chavez, 2017. Nutrient supply, surface currents and plankton dynamics predict zooplankton hotspots in coastal upwelling systems. Geophysical Research Letters, 44(17), 8979-8986, doi:10.1002/2017GL074322 (press release)

Messié, M., A. Petrenko, A.M. Doglioli, C. Aldebert, E. Martinez, G. Koenig, S. Bonnet and T. Moutin, 2020. The delayed island mass effect: How islands can remotely trigger blooms in the oligotrophic ocean. Geophysical Research Letters, 47(2), e2019GL085282, doi:10.1029/2019GL085282

Messié, M., D.A. Sancho-Gallegos, J. Fiechter, J.A. Santora and F.P. Chavez, 2022. Satellite-based Lagrangian model reveals how upwelling and oceanic circulation shape krill hotspots in the California Current System. Frontiers in Marine Science, 9:835813, doi:10.3389/fmars.2022.835813


This work was supported by NASA grant 80NSSC17K0574 and by the David and Lucile Packard Foundation.


Upper-ocean systems
Acoustical ocean ecology
Acoustic instruments
Acoustic fingerprinting
Acoustic community ecology
Acoustics in the news
Biological oceanography
Global modes of sea surface temperature
Krill hotspots in the California Current
Nitrate supply estimates in upwelling systems
Chemical sensors
Chemical data
Land/Ocean Biogeochemical Observatory in Elkhorn Slough
Listing of floats
SOCCOM float visualization
Periodic table of elements in the ocean
Biogeochemical-Argo Report
Profiling float
Interdisciplinary field experiments
Ecogenomic Sensing
Genomic sensors
Field experiments
Harmful algal blooms (HABs)
Water quality
Environmental Sample Processor (ESP)
ESP Web Portal
In the news
Ocean observing system
Midwater research
Midwater ecology
Deep-sea squids and octopuses
Food web dynamics
Midwater time series
Respiration studies
Zooplankton biodiversity
Seafloor processes
Revealing the secrets of Sur Ridge
Exploring Sur Ridge’s coral gardens
Life at Sur Ridge
Mapping Sur Ridge
Biology and ecology
Effects of humans
Ocean acidification, warming, deoxygenation
Lost shipping container study
Effects of upwelling
Faunal patterns
Previous research
Technology development
High-CO2 / low-pH ocean
Benthic respirometer system
Climate change in extreme environments
Station M: A long-term observatory on the abyssal seafloor
Station M long-term time series
Monitoring instrumentation suite
Sargasso Sea research
Antarctic research
Geological changes
Arctic Shelf Edge
Continental Margins and Canyon Dynamics
Coordinated Canyon Experiment
CCE instruments
CCE repeat mapping data
Monterey Canyon: A Grand Canyon beneath the waves
Submarine volcanoes
Mid-ocean ridges
Magmatic processes
Volcanic processes
Explosive eruptions
Hydrothermal systems
Back arc spreading ridges
Near-ridge seamounts
Continental margin seamounts
Non-hot-spot linear chains
Eclectic seamounts topics
Margin processes
Hydrates and seeps
California borderland
Hot spot research
Hot-spot plumes
Magmatic processes
Volcanic processes
Explosive eruptions
Volcanic hazards
Hydrothermal systems
Flexural arch
Coral reefs
ReefGrow software
Eclectic topics
Submarine volcanism cruises
Volcanoes resources
Areas of study
Bioluminescence: Living light in the deep sea
Microscopic biology research
Open ocean biology research
Seafloor biology research
Automated chemical sensors
Methane in the seafloor
Volcanoes and seamounts
Hydrothermal vents
Methane in the seafloor
Submarine canyons
Earthquakes and landslides
Ocean acidification
Physical oceanography and climate change
Ocean circulation and algal blooms
Ocean cycles and climate change
Past research
Molecular ecology
Molecular systematics
SIMZ Project
Bone-eating worms
Gene flow and dispersal
Molecular-ecology expeditions
Ocean chemistry of greenhouse gases
Emerging science of a high CO2/low pH ocean