Publication Date:
2022-05-25
Description:
Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Estuaries and Coasts 38 (2015): 2240-2258, doi:10.1007/s12237-015-9949-z.
Description:
A highly resolved, 3-d model of hydrodynamics and Alexandrium fundyense in an estuarine embayment
has been developed to investigate the physical and biological controls on a recurrent harmful algal bloom.
Nauset estuary on Cape Cod (MA, USA) consists of three salt ponds connected to the ocean through a
shallow marsh and network of tidal channels. The model is evaluated using quantitative skill metrics
against observations of physical and biological conditions during three spring blooms. The A. fundyense
model is based on prior model applications for the nearby Gulf of Maine, but notable modifications were
made to be consistent with the Nauset observations. The dominant factors controlling the A. fundyense
bloom in Nauset were the water temperature, which regulates organism growth rates, and the efficient
retention of cells due to bathymetric constraints, stratification, and cell behavior (diel vertical migration).
Spring-neap variability in exchange altered residence times, but for cell retention to be substantially
longer than the cell doubling time required both active vertical migration and stratification that inhibits
mixing of cells into the surface layer by wind and tidal currents. Unlike in the Gulf of Maine, the model
results were relatively insensitive to cyst distributions or germination rates. Instead, in Nauset, high
apparent rates of vegetative cell division by retained populations dictated bloom development. Cyst
germination occurred earlier in the year than in the Gulf of Maine, suggesting that Nauset cysts have
different controls on germination timing. The model results were relatively insensitive to nutrient
concentrations, due to eutrophic conditions in the highly impacted estuary or due to limitations in the
spatial and temporal resolution of nutrient sampling. Cell loss rates were inferred to be extremely low
during the growth phase of the bloom, but increased rapidly during the final phase due to processes that
remain uncertain. The validated model allows a quantitative assessment of the factors that contribute to
the development of a recurrent harmful algal bloom and provides a framework for assessing similarly
impacted coastal systems.
Description:
This work was supported by the National Science Foundation (OCE-0430724, OCE-0911031, and OCE-1314642) and National Institutes of Health (NIEHS-1P50-ES021923-01) through the Woods Hole Center
for Oceans and Human Health, and by National Park Service (NPS) Cooperative Agreement
H238015504.
Description:
2016-03-17
Keywords:
Harmful algal bloom
;
Hydrodynamic-biological model
;
Alexandrium fundyense
;
Residence time
;
Cyst germination
;
Growing degree day
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
