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CISNet Projects
Estuarine Optical Properties
Measurements of estuarine optical properties allow us to monitor the state of the system,
while developing indicators of eutrophication and response to chronic and episodic nutrient
inputs. A WETLabs Spectral AC-9, 9 channel reflective-tube absorption and transmittance
meter was used to measure optical properties of the subestuary at hourly intervals in order
to estimate concentrations of SPM, Chl, and CDOM. Additionally, three Satlantic OCI-200
seven channel irradiance sensors were used to simultaneously measure upwelling and downwelling
spectral irradiance profiles on a weekly basis. These profiles were being used, along with
laboratory measurements of inherent optical properties, to develop algorithms for
interpreting data from the AC-9 in terms of SPM, Chl, and CDOM.
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Salinity Monitors
Because nitrate is correlated with freshwater inputs, salinity monitors allow us to
estimate nutrient inputs and exchange both from the local watershed, at the head, and from
the main stem of the Bay at the mouth. These monitors allow us to test hypotheses
about the effects of runoff and flushing on buildup of nutrients and phytoplankton within
the system.
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Benthic Nutrient Exchange
Sealed domes placed at various segments in the subestuary were used to determine spatial
and temporal variability in sediment nutrient release rates. Measurements of nutrient release
rates along with water exchanges based on salinity data indicated the variables leading
to interannual variability in frequency and magnitude of algal blooms. Water samples
collected from the sampling ports of the domes were periodically analyzed for DIC,
chlorophyll, dissolved oxygen, salinity, temperature, pH, dissolved phosphorus, NO3,
and NH4.
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In situ Mesocosms
Vertical polyethylene enclosures 1 m in diameter and 3 m tall with and without closed
bottoms were used to examine the response of in situ concentrations of chlorophyll, CDOM,
and SPM to inputs of nutrients (both watershed discharge and atmospheric deposition) and
particulate matter on event- to interannual time scales. A two factor design of nutrient
addition and sediment inclusion was established with the enclosures. Water was sampled from
the enclosures daily for five days after installation and treatment. Analyses of nutrients,
chlorophyll, and number and species composition of phytoplankton were made in the laboratory,
while profiles of spectral absorption and scattering coefficients were measured in situ.
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