Citation:

NELSON, W. G. AND C. A. BROWN. Use of probability based sampling of water quality indicators in supporting water quality criteria development - 2/28/08. Presented at Pacific Estuarine Research Society 2008 Meeting, Newport, OR, February 28 - March 01, 2008.

Impact/Purpose:

We examine the proposition that water quality indicator data collected from large scale, probability based assessments of coastal condition such as the US Environmental Protection Agency National Coastal Assessment (NCA) can be used to support water quality criteria development for individual estuarine systems.

Description:

We examine the proposition that water quality indicator data collected from large scale, probability based assessments of coastal condition such as the US Environmental Protection Agency National Coastal Assessment (NCA) can be used to support water quality criteria development for individual estuarine systems. NCA water quality indicators such as dissolved inorganic nitrogen (DIN), phosphorus (DIP), and chlorophyll a can be subject to high levels of natural variation over short time scales. Median values for DIN, DIP, and chlorophyll a for data collected within Yaquina Bay, Oregon, USA over periods of up to seven years were compared to three regional, probability based data sets of differing spatial extent. All indicators were compared within two estuarine salinity zones. Medians from the long term sampling within Yaquina Bay were higher than from the probability based surveys. Stochastic variation related to interannual differences in coastal upwelling appears to be responsible for differences observed. It is concluded that further work is required to define upwelling based adjustments for regional survey data for direct use in regulatory applications. However, even without adjustment, such data can still be of value in determining the appropriate regional context for water quality criteria.

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