Mapping of Alexandrium catenella cysts to enhance understanding of harmful algal blooms and paralytic
shellfish toxins in Puget Sound, Washington State
Jessica Peters, Graduate research – TESC, MES
Stephanie Moore – NOAA-NWFSC
Julie Masura – UWT
Cheryl Greengrove – UWT
Gerardo Chin-Leo – TESC
Alexandrium catenella is a marine dinoflagellate responsible for producing a suite of toxins collectively
called paralytic shellfish toxins (PSTs) in Puget Sound, Washington State. A. catenella forms a dormant
cyst that settles onto the sea floor when conditions are unfavorable for growth of the free-swimming,
vegetative cell. When conditions are again favorable, the cyst germinates introducing A. catenella back
into the water column. These cells provide the inoculum for harmful algal blooms (HABs) of A. catenella
that threatens the safety of shellfish consumption and human health. Understanding the factors controlling
encystment and germination of A. catenella cysts and their distribution in sediments is needed for
predicting A. catenella blooms. We examine 11 sample sites from the Main, Whidbey, and Hood Canal
basins of Puget Sound that were collected during the 23rd Puget Sound Regional Synthesis Model
(PRISM) research cruise in February 2009. Surface sediment samples were analyzed for cyst abundance
as well as total organic content (TOC) and sediment grain-size. Cyst mapping will identify areas with
high concentrations of cysts that are at greater risk of developing and being impacted by HABs. Temporal
changes in cyst distribution in Puget Sound will be assessed by comparing our cyst map with cyst
distribution patterns of surveys from 2005 and 2006. Relationships between cysts and PST events, A.
catenella blooms, TOC, and sediment grain-size will also be examined. Understanding the connections
between cyst dynamics, bloom events, and concentrations of PSTs in shellfish will assist in efforts to
understand HABs and mitigate negative impacts. These data contribute to the long-term goal of creating a
forecasting model for A. catenella blooms in Puget Sound.