Guest Post: Emergency Cyst Mapping in Hood Canal

written by Stephanie Moore, NOAA Northwest Fisheries Science Center

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.

Heading out of Pleasant Harbor aboard R/V Barnes

The Craib Corer takes a single, undisturbed core sample from the top of the sediment layer

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.

A videographer from NOAA Fisheries Ocean Media Center joined the cruise to document the effort