TY - JOUR
T1 - Nutrient Loading and Transformations in the Columbia River Estuary Determined by High-Resolution In Situ Sensors
AU - Gilbert, Melissa
AU - Needoba, Joseph
AU - Koch, Corey
AU - Barnard, Andrew
AU - Baptista, Antonio
N1 - Funding Information:
Acknowledgments We are indebted to the operational field and cyber teams of the National Science Foundation Science and Technology Center for Coastal Margin Observation and Prediction for their help with instrument deployment and data analysis. We also thank the summer undergraduate intern Ezra-Mel Pasikatan for creation of a data processing program. This research was supported through the National Science Foundation cooperative agreement OCE-0424602 and the M.J. Murdock Charitable Trust. We would like to thank the captain and crew of the R/V Wecoma. Frederick Prahl facilitated the sample collection aboard the R/V Wecoma and provided valuable feedback on this manuscript. WET Labs provided the phosphate data as part of a pilot study in the Columbia River, under NSF contract OCE-0838099.
PY - 2013/7
Y1 - 2013/7
N2 - The Columbia River estuary is characterized by relatively large tidal currents and water residence times of a few days or less. These and other environmental conditions tend to suppress water column productivity and favor the export of riverborne nutrients to the coastal ocean. However, hotspots of biological activity may allow for significant nutrient transformation and removal within the estuary, but these processes have previously been difficult to quantify due to the challenges of obtaining measurements at appropriate frequency and duration. In this study, nutrient biogeochemical dynamics within the salt-influenced region of the estuary were quantified using high-resolution in situ observations of nutrients and physical water properties. During 2010, three autonomous nutrient sensors (Satlantic SUNA, SubChem Systems Inc. APNA, WET Labs Cycle-PO4) that together measured nitrate + nitrite, orthophosphate, ammonium, silicic acid, and nitrite were deployed on fixed observatory platforms. Hourly measurements captured tidal fluctuations and permitted an analysis of river and ocean end-member mixing. The results suggested that during summer, the lower estuary released high concentrations of ammonium and phosphate despite low concentrations in the river and coastal ocean. This was likely a result of organic matter accumulation and remineralization in the estuarine turbidity maximum and the lateral bays adjacent to the main channel.
AB - The Columbia River estuary is characterized by relatively large tidal currents and water residence times of a few days or less. These and other environmental conditions tend to suppress water column productivity and favor the export of riverborne nutrients to the coastal ocean. However, hotspots of biological activity may allow for significant nutrient transformation and removal within the estuary, but these processes have previously been difficult to quantify due to the challenges of obtaining measurements at appropriate frequency and duration. In this study, nutrient biogeochemical dynamics within the salt-influenced region of the estuary were quantified using high-resolution in situ observations of nutrients and physical water properties. During 2010, three autonomous nutrient sensors (Satlantic SUNA, SubChem Systems Inc. APNA, WET Labs Cycle-PO4) that together measured nitrate + nitrite, orthophosphate, ammonium, silicic acid, and nitrite were deployed on fixed observatory platforms. Hourly measurements captured tidal fluctuations and permitted an analysis of river and ocean end-member mixing. The results suggested that during summer, the lower estuary released high concentrations of ammonium and phosphate despite low concentrations in the river and coastal ocean. This was likely a result of organic matter accumulation and remineralization in the estuarine turbidity maximum and the lateral bays adjacent to the main channel.
KW - Columbia River Estuary
KW - Estuary
KW - In situ sensors
KW - Nutrient cycles
KW - Remineralization
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U2 - 10.1007/s12237-013-9597-0
DO - 10.1007/s12237-013-9597-0
M3 - Article
AN - SCOPUS:84878736295
SN - 1559-2723
VL - 36
SP - 708
EP - 727
JO - Estuaries and Coasts
JF - Estuaries and Coasts
IS - 4
ER -