Temporal variability in dissolved organic matter composition export in streams

Area of Science:

• Environmental Science
• Ecology
• Biogeochemistry

Background:

• Dissolved organic carbon (DOC) export from freshwater systems is crucial for global carbon cycles and ecosystem function.
• Understanding the flux and composition of dissolved organic matter (DOM) is vital for assessing ecological impacts.
• Limited data exists on the composition of DOM export fluxes.

Purpose of the Study:

• To investigate how water temperature and discharge interact to affect DOC and DOM composition export fluxes.
• To compare DOM export fluxes between agricultural and forested watersheds in southern Ontario.
• To analyze seasonal variations in DOM export.

Main Methods:

• Utilized Generalized Additive Models to analyze data from two contrasting streams.
• Monitored DOC and DOM composition fluxes across different seasons.
• Examined the relationship between discharge, temperature, and DOM composition.

Main Results:

• Both stream discharge and water temperature significantly influenced DOM composition.
• Terrestrial humic-like DOM showed a strong positive correlation with discharge.
• While DOC loads were similar, DOM composition fluxes (fluorescent loads and fluxes) differed significantly between streams.
• Export loads and fluxes were higher in spring and winter, and at medium to high flows.

Conclusions:

• Watershed characteristics and nutrient availability are primary drivers of DOM dynamics and export.
• Seasonal factors like discharge and temperature modulate these patterns.
• Climate change and extreme events may alter DOM processing and delivery to downstream ecosystems.