Detecting water quality patterns in New Hampshire's estuaries using National Coastal Assessment probability-based survey data

Between 2000 and 2006, the New Hampshire Department of Environmental Services and the University of New Hampshire collected water quality samples at 25 to 40 stations per year in a 56.5-km² estuary as part of the Environmental Protection Agency's National Coastal Assessment program. Due to the...

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Bibliographic Details
Published in:Environmental monitoring and assessment 2009-03, Vol.150 (1-4), p.129-142
Main Authors: Trowbridge, Philip R, Jones, Stephen H
Format: Article
Language:English
Subjects:
Ammonium
Animal and plant ecology
Animal, plant and microbial ecology
Animals
Applied ecology
Atmospheric Protection/Air Quality Control/Air Pollution
Bacteria
Biological and medical sciences
Brackish water ecosystems
Chlorophyll
Climate change
Coasts
Data Collection - methods
Datasets
Dissolved oxygen
Earth and Environmental Science
Ecology
Ecotoxicology
Ecotoxicology, biological effects of pollution
Environment
Environmental Management
Environmental monitoring
Environmental Monitoring - methods
Environmental protection
Environmental services
Estuaries
Fundamental and applied biological sciences. Psychology
General aspects
Laboratories
Monitoring/Environmental Analysis
National Coastal Assessment
New Hampshire
Nitrogen
Probability
Probability-based monitoring
Salinity
Sediments
Studies
Synecology
Total suspended solids
Trends
Water Pollutants, Chemical - analysis
Water quality
Water Supply
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Summary:Between 2000 and 2006, the New Hampshire Department of Environmental Services and the University of New Hampshire collected water quality samples at 25 to 40 stations per year in a 56.5-km² estuary as part of the Environmental Protection Agency's National Coastal Assessment program. Due to the high density of stations, probabilistic statistics for the estuary could be calculated with low uncertainty. The proportions of the estuary exceeding thresholds in each year were calculated for temperature, salinity, dissolved oxygen, chlorophyll a, nitrogen as nitrate and nitrite, nitrogen as ammonium, phosphorus as orthophosphate, total suspended solids, and fecal coliform bacteria. These values were tested for trends over time and correlations with climate variables. The same statistical tests were applied to monthly grab sample data from a representative station in the estuary. The outcomes of the statistical tests on the two datasets were compared to determine if they provided similar information to coastal managers. Trends and correlations were equally likely to be detected using the probability-based data and the fixed station data, but the results were different for the two datasets. The differences were likely due to the distributed nature of the probability-based sampling design, which places stations in all sections of the estuary. In addition, expressing the probabilistic datasets as estimated proportions reduced variability in volatile parameters, such as bacteria, relative to the grab sample dataset. It will be important to develop tools to rectify trends from probability-based surveys with fixed station monitoring to provide clear information to managers.
ISSN:0167-6369
1573-2959
DOI:10.1007/s10661-008-0683-x