Dinoflagellate blooms and physical systems in the Gulf of Maine
Citable URI
https://hdl.handle.net/1912/5430Location
Gulf of MaineDOI
10.1575/1912/5430Keyword
Dinoflagellates; HydrographyAbstract
Numerous studies have shown dinoflagellate blooms to be
closely related to density discontinuities and fronts in the ocean. The
spatial and temporal patterns of the dinoflagellate population
depend on the predominant mode of physical forcing, and its scales
of variability. The present study combined field sampling of
hydrographic and biological variables to examine the relationship of
dinoflagellate population distributions to physical factors along the
southwestern cost of the Gulf of Maine.
A bloom of Ceratium longipes occurred along this coast during
the month of June, 1987. A simple model which coupled along-isopycnal
diffusion with the logistic growth equation suggested that
the cells had a growth rate of about 0.1 d-1 , and had reached a
steady horizontal across-shelf distribution within about 10 d.
Fur~her variations in population density appeared to be related to
fluctuations of light with periods of -10 d. To our knowledge, this
was the first use of this simple diffusion model as a diagnostic tool
for quantifying parameters describing the growth and movement of
a specific phytoplankton population.
Blooms of the toxic dinoflagellate, Alexandrium tamarense
have been nearly annual features along the coasts of southern
Maine, New Hampshire and Massachusetts since 1972; however the
mechanisms controlling the distribution of cells and concomitant
shellfish toxicity are relatively poorly understood. Analysis of field
data gathered from April to September, 1987-1989, showed that in
two years when toxicity was detected in the southern part of this
region, A. tamarense cells were apparently transported into the
study area between Portsmouth and Cape Ann, Massachusetts, in a
coastally trapped buoyant plume. This plume appears to have been
formed off Maine by the outflow from the Androscoggin and Kennebec Rivers. Flow rates of these rivers, hydrographic sections,
and satellite images suggest that the plume had a duration of about
a month, and extended alongshore for several hundred kilometers.
The distribution of cells followed the position of the plume as it was
influenced by wind and topography. Thus when winds were
downwelling-favourable, cells were moved alongshore to the south,
and were held to the coast; when winds were upwelling-favourable,
the plume sometimes separated from the coast, advecting the cells
offshore.
The alongshore advection of toxic cells within a coastally
trapped buoyant plume can explain the temporal and spatial
patterns of shellfish toxicity along the coast. The general observation
of a north-to-south temporal trend of toxicity is consistent with the
southward advection of the plume. In 1987 when no plume was
present, Alexandrium tamarense cells were scarce, and no toxicity
was recorded at the southern stations. A hypothesis was formulated
explaining the development and spread of toxic dinoflagellate
blooms in this region. This plume-advection hypothesis included:
source A. tamarense populations in the north, possibly associated
with the Androscoggin and Kennebec estuaries; a relationship
between toxicity patterns and river flow volume and timing of flow
peaks; and a relationship between wind stresses and the distribution
of low salinity water and cells. Predictions of the plume-advection hypothesis were tested
with historical records of shellfish toxicity, wind speed and direction,
and river flow. The predictions tested included the north-south
progression of toxic outbreaks, the occurrence of a peak in river flow
prior to the PSP events, the relationship of transit time of PSP
toxicity along the coast with river flow volume, and the influence of
surface wind stress on the timing and location of shellfish toxicity.
All the predictions tested were supported by the historical records.
In addition it was found that the plume-advection hypothesis
explains many details of the timing and spread of shellfish toxicity,
including the sporadic nature of toxic outbreaks south of
Massachusetts Bay, and the apparently rare occurrence of toxicity
well offshore on Nantucket Shoals and Georges Bank.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1990
Collections
Suggested Citation
Thesis: Franks, Peter J. S., "Dinoflagellate blooms and physical systems in the Gulf of Maine", 1990-05, DOI:10.1575/1912/5430, https://hdl.handle.net/1912/5430Related items
Showing items related by title, author, creator and subject.
-
Phenotypic diversity within two toxic dinoflagellate genera : environmental and transcriptomic studies of species diversity in Alexandrium and Gambierdiscus
Pitz, Kathleen (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2016-09)Dinoflagellates are a diverse group of single-celled eukaryotic phytoplankton that are important for their unique genetics and molecular biology, the multitude of ecological roles they play, and the ability of multiple ... -
Phylogeny and biogeography of the toxic dinoflagellate Alexandrium
Lilly, Emily L. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2003-09)The incidence and known distribution of paralytic shellfish poisoning (PSP) have both increased dramatically in recent decades. A concurrent rise in bloom frequency and geographic range of PSP toxin-producing Alexandrium ... -
Blooms of the toxic dinoflagellate Alexandrium fundyense in the Gulf of Maine : investigations using physical-biological model
Stock, Charles A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2005-02)Blooms of the toxic dinoflagellate Alexandriumfundyense are annually recurrent in the western Gulf of Maine (WGOM) and pose a serious economic and public health threat. Transitions between and vital rates within the life ...