written by Stephanie Moore, NOAA Northwest Fisheries Science Center
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| The dinoflagellate Alexandrium catenella. Photo credit: Gabriela Hannach, King County |
In September and October 2014, there was an unprecedented
harmful algal bloom of Alexandrium in Hood Canal that contaminated shellfish
with potent biotoxins. The area where the bloom took place has historically
been biotoxin free. Alexandrium produce a suite of neurotoxins, called saxitoxins,
which can cause paralytic shellfish poisoning in humans who consume
contaminated shellfish. The regulatory limit for human consumption is 80 ug
saxitoxin equivalents per 100 g shellfish tissue. At the peak of the event,
shellfish toxicity was 12,688 ug STX equiv./100 g.
The Washington State Dept. of
Health and the local shellfish growers are concerned that the large bloom may
have resulted in a new "seed bed" forming (i.e., a concentrated area
of cysts that are deposited to benthic sediments and provide the inoculum for
blooms the following season) that could increase bloom risk in this area next
year.
In late January, scientists
from NOAA
Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) and collaborators Cheryl Greengrove and
Julie Masura at the University of Washington Tacoma participated in a research
cruise aboard the UW’s R/V Barnes to do some small scale cyst mapping in the
area of the large bloom. Ian Jefferds from Penn Cove Shellfish contributed
funds to purchase lab consumables needed to do the cyst mapping.
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| Heading out of Pleasant Harbor aboard R/V Barnes |
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The Craib Corer takes a single, undisturbed core sample from
the top of the sediment layer
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| Prepping the Craib Corer for deployment |
The samples were taken back to the lab is Seattle and analysis will begin this week. If cysts were deposited in the area, the Washington State
Dept. of Health will need to be more vigilant and dedicate more resources for
biotoxin monitoring in this area, and any future dredging activity that could
disturb the cysts and suspend them up into the water column where they could
germinate should be planned outside of the time of year that supports
blooms.
Visit the NANOOS
HABs Information Page for more information on Harmful Algal Blooms in the Pacific Northwest.
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| A videographer from NOAA Fisheries Ocean Media Center joined the cruise to document the effort |
