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Principal Investigators: Doug Vandemark and Joe Salisbury |
Chris Hunt and Doug Vandemark recently spent two
weeks aboard the R/V Oceanus acquiring the first comprehensive
spatial survey of several greenhouse (carbon dioxide and methane)
and other dissolved gases in Gulf of Maine surface waters. The
primary mission of the cruise, headed by Chief Scientist Bruce
Keafer of the Woods Hole Oceanographic Institute, was to map
(see map to the right) Alexandrium cyst population across the
muddy bottom of the Gulf. Alexandrium is the organism responsible
for red tide shellfish closures in our region. Their work involved
collecting ocean bottom sediment cores at more than 150 sites
across the region. Information on that program can be found
at (http://www.whoi.edu/redtide/).
Our effort focused on measuring surface water properties using
the UNH flow-through system usually deployed on the R/V Gulf
Challenger as well as collection of discrete water samples for
laboratory analysis. The underway measurement system includes
a fast rate surface CO2 measurement system that allowed us to
map out CO2 concentrations along the shiptrack (see image to
the right) - providing a spatially dense snapshot of surface
layer carbon dioxide across a large portion of this marginal
sea. We also collected trace gas samples from both sides of
the air-sea interface ( 3 m above and below the sea surface)
at 60 measurement stations. These 1L canisters of air are being
analyzed back in the laboratory by UNH/EOS researchers Ruth
Varner and Barkley Sive to look at a suite of trace gases including
methane, halocarbons, and carbon dioxide.
Discrete water samples were also collected for analysis of
dissolved organic and inorganic carbon, total alkalinity and
pH, nutrients, fluorometric chlorophyll, HPLC chlorophyll, CDOM
absorption, and caffeine. The suite of measurements will help
us to connect results from our ongoing (2004-present) Western
Gulf of Maine sampling efforts to the larger Gulf and to address
several key issues related to coastal margin carbon dynamics.
Specific objectives related to these measurements include:
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evaluation of spatial variations in the
fall season surface carbon signature (carbon dioxide and
total inorganic carbon (see maps to right) of the coastal
Gulf of Maine |
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testing several relationships that we've developed
for the Western Gulf of Maine including how well they
translate to the wider Gulf; this encompasses relationships
between alkalinity and salinity, CDOM and salinity, DOC
and CDOM, fluorosensing derived CDOM and gelbstoff absorption |
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acquisition of the first spatial survey of surface
layer methane for this region and evaluation of possible
spatial dynamics associated with benthic sources |
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acquisition of a surface water caffeine concentration
data set to evaluate the potential for caffeine as a tracer
of point source land-ocean input (e.g. water treatment
facilities) along the coastline |
Much thanks to Bruce Keafer and Principal Investigator Dennis
McGillicuddy for inviting us aboard and to all the crew for
their support in making this a very successful cruise.
