Happy New Year.
The Neuse has kicked off the new decade with an impressive bloom of Prorocentrum minimum. We saw the beginnings of this bloom a month ago in December but it’s a lot more dense now. The surface water at station 100 was actually scummy (see attached photo taken by Melissa LaCroce) and the YSI measured 200 ug/L chl-a at 0.3 m depth. The bloom extended throughout the water column at station 100. Upstream to station 50, the bloom was concentrated just below the surface, and downstream at station 120 the bloom was concentrated along the pycnocline. Subsurface aggregations are really common for Prorocentrum minimum, but in my experience such dense surface scums are less common. However, there is a nice photo from an airplane of a Neuse River P. minimum bloom in Springer et al. (Harmful Algae 2005). P. minimum is not know to be toxic, and despite the high biomass levels there aren’t reports of problems associated with these blooms (e.g. hypoxia, fish kills, etc.). While we await further laboratory measurements, I think it’s safe to assume that such high biomass levels are at least partly the result of physical concentration of highly motile cells along a frontal zone. Other than the bloom, the river is about 4-6 degrees warmer than normal for this time of year. The river is also quite salty with salinity near 20 at throughout the water column at the lower stations.