Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 103 (2014): 6-26, doi:10.1016/j.dsr2.2013.10.002.
Here we document Alexandrium fundyense cyst abundance and distribution patterns over
nine years (1997 and 2004-2011) in the coastal waters of the Gulf of Maine (GOM) and identify
linkages between those patterns and several metrics of the severity or magnitude of blooms
occurring before and after each autumn cyst survey. We also explore the relative utility of two
measures of cyst abundance and demonstrate that GOM cyst counts can be normalized to
sediment volume, revealing meaningful patterns equivalent to those determined with dry weight
normalization.Cyst concentrations were highly variable spatially. Two distinct 1 seedbeds (defined here as
accumulation zones with 〉 300 cysts cm-3) are evident, one in the Bay of Fundy (BOF) and one
in mid-coast Maine. Overall, seedbed locations remained relatively constant through time, but
their area varied 3-4 fold, and total cyst abundance more than 10 fold among years. A major
expansion of the mid-coast Maine seedbed occurred in 2009 following an unusually intense A.
fundyense bloom with visible red-water conditions, but that feature disappeared by late 2010.
The regional system thus has only two seedbeds with the bathymetry, sediment characteristics,
currents, biology, and environmental conditions necessary to persist for decades or longer.
Strong positive correlations were confirmed between the abundance of cysts in both the 0-1 and
the 0-3 cm layers of sediments in autumn and geographic measures of the extent of the bloom
that occurred the next year (i.e., cysts → blooms), such as the length of coastline closed due to
shellfish toxicity or the southernmost latitude of shellfish closures. In general, these metrics of
bloom geographic extent did not correlate with the number of cysts in sediments following the
blooms (blooms → cysts). There are, however, significant positive correlations between 0-3 cm
cyst abundances and metrics of the preceding bloom that are indicative of bloom intensity or
vegetative cell abundance (e.g., cumulative shellfish toxicity, duration of detectable toxicity in
shellfish, and bloom termination date). These data suggest that it may be possible to use cyst
abundance to empirically forecast the geographic extent of the forthcoming bloom and,
conversely, to use other metrics from bloom and toxicity events to forecast the size of the
subsequent cyst population as the inoculum for the next year’s bloom. This is an important step
towards understanding the excystment/encystment cycle in A. fundyense bloom dynamics while
also augmenting our predictive capability for this HAB-forming species in the GOM.
Research support provided by the ECOHAB
Grant program through NOAA Grants NA06NOS4780245 and NA09NOS4780193, and through the Woods Hole Center for Oceans and Human Health, National 1 Science Foundation (NSF)
Grants OCE-0430724, OCE-0911031, and OCE-1314642; and National Institute of
Environmental Health Sciences (NIEHS) Grants 1-P50-ES012742-01 and 1-P01-ES021923-01,
and funding through the states of ME, NH, and MA. We are also grateful for event response
funding provided for many of the cruises. Funding for J.L. Martin was provided by Fisheries and
Gulf of Maine
Harmful algal bloom
Paralytic shellfish poisoning
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