Nutrient reference concentrations and trophic state boundaries in subtropical reservoirs

Nutrient reference concentrations and trophic state boundaries in subtropical reservoirs

Nutrient criteria as reference concentrations and trophic state boundaries are necessary for water management worldwide because anthropogenic eutrophication is a threat to the water uses. We compiled data on total phosphorus (TP), nitrogen (TN) and chlorophyll a (Chl a) from 17 subtropical reservoir...

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Bibliographic Details
Published in:Water science and technology Vol. 65; no. 8; pp. 1461 - 1467
Main Authors: Cunha, D G F, Ogura, A P, Calijuri, M d C
Format: Journal Article
Language:English
Published: England IWA Publishing 01-01-2012
Subjects:
Anthropogenic factors
Boundaries
Brazil
Chlorophyll
Chlorophyll - analysis
Chlorophyll a
Environmental monitoring
Environmental protection
Eutrophic waters
Eutrophication
Fresh water
Mineral nutrients
Nitrogen - analysis
Nutrient concentrations
Phosphorus
Phosphorus - analysis
Reference Values
Regional analysis
Reservoirs
Symptoms
Trophic state
Water management
Water Quality
Water Supply
Brazil
USA
Brazil, Sao Paulo
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Summary:Nutrient criteria as reference concentrations and trophic state boundaries are necessary for water management worldwide because anthropogenic eutrophication is a threat to the water uses. We compiled data on total phosphorus (TP), nitrogen (TN) and chlorophyll a (Chl a) from 17 subtropical reservoirs monitored from 2005-2009 in the São Paulo State (Brazil) to calculate reference concentrations through the trisection method (United States Environmental Protection Agency). By dividing our dataset into thirds we presented trophic state boundaries and frequency curves for the nutrient levels in water bodies with different enrichment conditions. TP and TN baseline concentrations (0.010 mg/L and 0.350 mg/L, respectively) were bracketed by ranges for temperate reservoirs available in the literature. We propose trophic state boundaries (upper limits for the oligotrophic category: 0.010 mg TP/L, 0.460 mg TN/L and 1.7 μg Chl a/L; for the mesotrophic: 0.030 mg TP/L, 0.820 mg TN/L and 9.0 μg Chl a/L). Through an example with a different dataset (from the Itupararanga Reservoir, Brazil), we encouraged the use of frequency curves to compare data from individual monitoring efforts with the expected concentrations in oligotrophic, mesotrophic and eutrophic regional systems. Such analysis might help designing recovery programs to reach targeted concentrations and mitigate the undesirable eutrophication symptoms in subtropical freshwaters.
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ISSN:0273-1223
1996-9732
DOI:10.2166/wst.2012.035