Variability of sedimentary phosphorus composition across Canadian lakes.

Area of Science:

• Environmental Chemistry
• Limnology
• Geochemistry

Background:

• Phosphorus (P) in lake sediments exists in various forms, influencing its potential release into the water column.
• The balance between P retention and release is governed by sediment chemistry and the specific P fractions present.

Purpose of the Study:

• To assess the composition of P-fractions in surficial lake sediments across Canadian ecozones.
• To identify watershed and lake-specific variables that predict sediment P speciation and its vulnerability to release.

Main Methods:

• Utilized sequential fractionation to analyze six P-fractions in surficial sediments from 236 Canadian lakes.
• Correlated sediment P composition with watershed soil types and lake/sediment chemical characteristics.

Main Results:

• Significant variation in sediment P composition was observed across Canadian ecozones, with residual-P and labile organic P being dominant.
• Sediment P speciation was strongly influenced by watershed soil types (e.g., podzols, chernozems) and lake water/sediment chemistry (e.g., Ca, Al, Fe, SO4, pH, salinity).
• Distinct regional differences in P composition were noted between Western/Mid-West and Eastern/Western coastal ecozones.

Conclusions:

• Sediment P composition is highly variable and predictable based on watershed and lake characteristics.
• Understanding P-fraction dynamics is crucial for predicting internal P loading and managing lake ecosystems.
• This research advances knowledge of P cycling in millions of unstudied lakes.