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Science Nugget – Spring Bloom, 2021

more planktonic organisms spring 2021

Massive, early spring bloom in the northern Gulf of Alaska, April-May 2021

Satellite measurements

Some of the highest chlorophyll concentrations recorded during the 24-year occupation of the Seward Line were seen in late April – early May 2021, in association with a massive spring bloom of diatoms. As an illustration, satellite imagery from NASA’s VIIRS (Visible Infrared Imaging Radiometer Suite) shows the bloom developing rapidly between April 18th and 25th.

Chlorophyll-a April 18 2021
Satellite measurements of Chlorophyll-a in the Gulf of Alaska, April 18, 2021 [Credit: Rachel Potter from NASA VIIRS data]
Chlorophyll-a April 25 2021
Satellite measurements of Chlorophyll-a in the Gulf of Alaska, April 25, 2021 [Credit: Rachel Potter from NASA VIIRS data]

Field sampling provided details

Our field sampling from R/V Sikuliaq coincided with this bloom. We found relatively cool ocean temperatures and, in places, fresher conditions than usual, as shown below for the GAK line. High chlorophyll was mostly confined to the upper 20 m of the water column (as seen in the fluorescence section below). Likely, this bloom was a response to intermittent sunny days and light winds. Late April chlorophyll-a concentrations reached almost 30 μg liter-1 on the inner MID line. In contrast, in some springs the peak concentrations are only one-tenth this level. Surface macronutrients (nitrate and silicic acid) had been drawn down to levels usually observed in summer (<1 μM liter-1).

temperature and salinity plot
Anomalies of temperature and salinity along the Seward Line, spring 2021 [Credit: Seth Danielson]
fluorescence plot
Fluorescence along the Seward Line, spring 2021 [Credit: Russ Hopcroft]

Microscopy conducted on board showed a diverse mixture of chain diatoms and colonial Phaeocystis comprising the bloom phytoplankton community. Concurrently, late-stage juveniles of the spring dominant Neocalanus copepod community had large amounts of lipid stores. At some stations, these copepods were already beginning their seasonal descent to deep diapause depths. Conversely, seabird abundances were some of the lowest ever observed during the >20-year time series, and few marine mammals were sighted.

The early, intense bloom of large, lipid-rich phytoplankton bodes well for survival and growth of krill and larval fish in 2021.

Planktonic organisms
Planktonic organisms in the Gulf of Alaska, Spring 2021

For further information contact Russ Hopcroft (rrhopcroft@alaska.edu) or Suzanne Strom (stroms@wwu.edu)

Post Doctoral Fellow – Gulf Watch Alaska (GWA)

The Oceanography Department in UAF’s College of Fisheries and Ocean Sciences is seeking a post doctoral scholar to work with Gulf Watch Alaska. The postdoc will contribute to existing data synthesis efforts and lead new analyses.

Gulf Watch Alaska

Gulf Watch Alaska (GWA) is the long-term ecosystem monitoring program of the Exxon Valdez Oil Spill Trustee Council.  GWA partners with the Northern Gulf of Alaska Long-Term Ecological Research (NGA LTER) project to monitor the northern Gulf of Alaska ecosystem. In fact, NGA LTER is an example of an GWA project that has existed for multiple decades with resulting long-term physical and biological time series for the Gulf of Alaska. 

GWA investigates three main ecosystem components: 

  • Environmental Drivers (physical and biological oceanography),
  • Nearshore Ecosystems (intertidal and coastal food web), and 
  • Pelagic Ecosystems (forage fish and predators of the pelagic food web).

GWA Science Synthesis

GWA supports annual field sampling efforts. However, it is also conducting cross-component science syntheses that focus on the effects of the recent northeast Pacific marine heatwave.

The postdoctoral scholar for this project will contribute as lead author and as co-author to GWA program synthesis products. They will collaborate with their UAF faculty advisor, GWA investigators, and the GWA Science Coordinator and ecosystem component leads.  Together, they will design and conduct studies related to the phenology, magnitude, spatial variability, and recovery time of biological responses to and physical drivers of the marine heatwave. Additionally, other biophysical mechanisms of population regulation in the Gulf of Alaska may also be addressed.

Sunrise over the Gulf of Alaska

Ecosystem Indicators and Management

These synthesis activities will support management actions by informing the ecosystem-based fisheries management of the North Pacific Fishery Management Council. For instance, the postdoctoral scholar will work with the GWA Science Coordinator to update existing and develop new ecosystem indicators to be used in NOAA’s Gulf of Alaska Ecosystem Status reports and Ecosystem and Socioeconomic Profiles.

In addition, the post-doctoral scholar will also provide technical review and editing of manuscripts, reports, and work plans for the GWA Program Management Team. They will also present results of their research at GWA meetings, scientific conferences, and to the public.

Learn More

To learn more about this position and to apply, please visit Careers at UA.  The deadline is November 30, 2020.

Jellyfish Make News

Methot net for catching jellyfish
Heidi Mendoza-Islas stands in front of a Methot net used for collecting large jellyfish in the Gulf of Alaska. Photo credit: Loring Schaible.

Lauren Frisch, Public Information Officer for the College of Fisheries and Ocean Sciences, UAF, wrote a news item describing interesting NGA LTER research:
Overlooked jellyfish play big role in Gulf of Alaska.

Yes, until now even the NGA LTER project website has overlooked jellyfish. Instead, our major research components focus on the primary producers and zooplankton that are the base of the food chain. Worse, at sea, jellyfish are often simply a nuisance whose tentacles drape on instruments and clog sensors. However, Heidi Mendoza-Islas, a graduate student in the NGA LTER project, studies the important role that jellyfish play in the Gulf of Alaska ecosystem. Read the article to find out more.