Spatial distribution of benthic cysts of Alexandrium catenella in surface sediments of Puget Sound, Washington, USA

Alexandrium catenella cyst distribution and abundance in the surface sediments throughout Puget Sound, Washington, were mapped for the first time in 2005. Cyst density varied from 0 to >12,000 cysts cm−3 surface sediment, with Quartermaster Harbor having the highest concentration of cysts. A higher resolution 2006 spatial survey of surface sediment cysts in two central Puget Sound bays, Quartermaster Harbor and Dyes Inlet, found cyst distribution to be patchy. Surface sediment properties were also determined for all samples. Given the diverse hydrographic conditions associated with the different basins in Puget Sound, no correlation was found between cyst abundance and grain size or total organic content (TOC) for the large scale Puget Sound wide survey, but cyst abundance was positively correlated with finer grained and higher TOC sediments within bays from the higher resolution survey. Sediment metal concentrations were also determined and cyst abundance was positively correlated only with Cd concentration. These results are consistent with previous studies in other locations.

► First map of Alexandrium catenella cyst abundance in surface sediments in Puget Sound.
► A. catenella cysts occur throughout Puget Sound where PSP has been reported.
► Distribution positively correlated with sediment Cd.
► Distribution not correlated with TOC and grain size on Puget Sound wide scale, but is with higher TOC and finer grain size on small bay scale.
► Cyst distribution patchy and a function of local environmental conditions.