Gulf of Maine Alexandrium fundyense Model Results – 2010


Ruoying He1, Yizhen Li1, Dennis McGillicuddy2, Don Anderson2, Bruce Keafer2

1North Carolina State University

2Woods Hole Oceanographic Institution



Disclaimer: these simulations are for experimental purposes only.


Results here represent model solutions initiated from a cyst abundance map from October 2009, with germination, growth, and transport of Alexandrium fundyense cells driven by the factors listed below.


Physical circulation model

Multiple nested ROMS, ca. ~1km resolution in GOM

Tides (M2, S2, N2, K2, K1, O1, Q1)

6-hourly wind and heat fluxes from NOAA/NCEP NOMADS (35-km resolution)

River runoff data from USGS

Sea surface temperature from satellites

Initial conditions and open boundary conditions from large-scale parent model (HYCOM)


Alexandrium fundyense model

Population dynamics from Stock et al. (2005); McGillicuddy et al. (2005), He et al., (2008) and Li et al.(2009)

Cyst maps from Fall 2009 Survey in comparison with earlier years


Solar radiation from NOAA/NCEP

Monthly climatological nutrient fields from University of Maine

The mortality rate of A. fundyense is now parameterized using the temperature dependent Q10 formulation (Durbin and Durbin, 1992)


Modeled A. fundyense bloom

          An animation showing surface wind fields and modeled bloom conditions from February 1, 2010 to July 10, 12:00, 2010
An 3-D animation showing modeled surface and subsurface cell abundance from February 1, 2010 to July 10, 12:00, 2010

Model-data comparison

May/06~May/09,2010 ( Oceanus 460 ):


May/27~Jun/03,2010 ( Endeavor 476 ):



The 2010 Alexandrium forecast for the Gulf of Maine was not borne out
by cruise observations and shellfish toxicity measurements.  We
predicted a large regional bloom in the WGOM that did not happen.
Toxicity along the coast has been low, and cruise data show very few
cells in the region from Massachusetts and Cape Cod Bays to mid-coast

Two possible (and potentially related ) reasons for the absence of
the bloom in the WGOM are evident thus far:  1) there was a water
mass change that lies outside the envelope of observations from at
least the last six years, which were the basis of the ensemble
forecast that led to the 2010 prediction; and 2) along-coast surface
transport off southern Maine was slower than normal.

The deep basins of the Gulf of Maine were warmer than was observed in
2003 - 2008.  This water mass anomaly affects intermediate and
surface waters where Alexandrium resides.  In fact, surface waters
were several degrees warmer than in 2008, when a large Alexandrium
bloom took place.  Stratification, nutrient concentrations, grazers,
and other factors critical to Alexandrium growth could all have been
affected.  Our GOMTOX cruise data are being used to assess these

Should we be able to deduce the mechanisms responsible for the lack
of a bloom in the WGOM in 2010, those processes could then be
included in the population dynamics model.  Furthermore, we note that
the water mass changes mentioned above relate to the larger scale
circulation of the northwest Atlantic, and therefore are observable
months in advance of the Alexandrium season.  Therefore, it is
conceivable that forecasts can be made taking into account this type
of variability.  It is indeed fortunate that GOMTOX cruises were
scheduled for 2010, as this will allow us to understand the factors
that prevented a bloom and thereby allow us to improve our model.

Last update: July 8, 2010