Prediction of reference phosphorus concentrations in Swedish lakes

Area of Science:

• Environmental Science
• Limnology
• Water Quality Assessment

Background:

• Total phosphorus (TP) is a key indicator of lake water quality.
• Predicting TP concentrations is crucial for managing aquatic ecosystems, especially in lakes with varying turbidity.
• Existing models may not adequately capture TP dynamics in naturally turbid lakes.

Purpose of the Study:

• To examine the relationship between total phosphorus (TP) and various environmental variables in Swedish reference lakes.
• To develop a predictive model for TP concentrations that accounts for natural factors.
• To establish a method for identifying culturally eutrophic lakes based on reference TP levels.

Main Methods:

• Analysis of TP concentrations against chemical, climatic, morphological, and geographic variables in over a thousand Swedish lakes.
• Development of a natural particulate matter factor (PM(n)) to account for suspended matter.
• Validation of a three-parameter model using lakes with known anthropogenic phosphorus loads.

Main Results:

• Significant relationships were found between TP and absorbance of irradiance (420 nm) and altitude.
• The addition of PM(n) significantly improved TP prediction accuracy (R(2) = 0.71).
• The developed model successfully identified culturally eutrophic lakes.

Conclusions:

• A robust three-parameter model can accurately estimate reference TP concentrations in diverse lake types.
• The model aids in distinguishing natural TP levels from anthropogenic impacts.
• It provides a target for phosphorus reduction to restore natural trophic states in lakes.