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PROCTOR, Christopher W., Geology Department, Bowdoin College, 776 Smith
Union, Brunswick, ME 04011, cproctor@bowdoin.edu.
The Abagadasset River
is a tidal freshwater tributary that empties into Merrymeeting
Bay, mid-coast Maine. During summer 2004, a hydrological
and biogeochemical assessment of the river system included high-resolution
sampling across the lower channel over spring and neap tidal cycles. An
Acoustic Doppler Current Profiler provided discharge estimates that were
reproducible to within several percent, as well as records of backscatter
that can be correlated to suspended-sediment concentrations. Depth-integrated
water samples and CTD profiles, taken hourly at 5 stations across the
25-m-wide channel, demonstrated that flow is vertically and horizontally well
mixed throughout the tidal cycle. Nutrient analyses of water samples indicate
that, relative to the larger bay, the Abagadasset
watershed is enriched in total organic carbon, nitrogen, and phosphorus, but
lower in dissolved silica. Concentrations of silica were low overall (0-1.6
mg/l), as were those of dissolved inorganic nitrogen (generally <0.05
mg/l). Thus dissolved organic nitrogen was the primary form of N. Continuous
sampling of water level, temperature, specific conductivity, dissolved oxygen
and turbidity with an automated datalogger provided
longer-term data on water exchange through the section. During spring tides
with low freshwater input to Merrymeeting
Bay by the Androscoggin and Kennebec Rivers, specific conductivity within
the Abagadasset rose with the incoming tide. During
neap tides, however, salinity in the Abagadasset
fell with rising tide, demonstrating the complex circulation in the larger
bay. Turbidity was generally higher during outgoing tides, and increased
quickly when local rain events impacted intertidal
surfaces. Semidiurnal fluctuations in dissolved oxygen decreased from summer
into fall, as temperature fluctuations and biological activity diminished.
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Session No.
19--Booth# 45
Undergraduate
Research (Posters) II
Prime Hotel and Conference Center: Whitney Room
8:00 AM-12:00 PM, Tuesday, March 15, 2005
Geological Society of America Abstracts with Programs, Vol. 37, No. 1,
p. 63
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© Copyright 2005 The Geological Society of America
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