Finding Toxic Diatoms

This past year the Santoro Laboratory became a part of the Southern California Coastal
and Ocean Observing System (SCCOOS), an observational network that provides real
time data to a diverse stakeholder community including policy makers, scientists and
the general public.

The Santoro Lab monitors harmful algal blooms (HABs) in the Santa Barbara Channel
by doing weekly plankton tows, whole water samples and a variety of water quality
metrics taken directly off of Stearns Wharf. One of the species that we monitor is a
diatom called Pseudo-nitzschia (PN) which produces domoic acid (DA). When DA is
produced, it passes up the food chain through a process called bioaccumulation. If there
is enough DA in the water column, it can sicken marine mammals.

This summer, there was a DA event in the channel. We were curious about why we
were having an increase in symptomatic marine mammals but we weren’t seeing high
levels of either PN or DA during our weekly samplings at the wharf. We found our
answer on a recent research cruise to the CalCOFI SBB Station (34.27490, -120.025)
where we sampled for PN. We were surprised to find a huge phytoplankton bloom in the
channel which was comprised almost entirely of the large size class of PN (see
microscopy image below, photo credit to Amber Briesach), which is thought to be the
major contributor of DA poisonings on the west coast. This was such an interesting find
because the cells were so concentrated in our net tow that it looked like we were pulling
soup out of the water. We have never seen this many PN cells in our samples at the
Wharf. Research like this will help us gain more understanding about PN blooms and
how to prevent them.

You can follow what HABs are currently in the water at Stearns Wharf by checking out
the Stearns Wharf HABMAP website here.