Organic matter cycling in a model restored wetland receiving complex effluent

Area of Science:

• Environmental Science
• Biogeochemistry
• Wetland Ecology

Background:

• Wetlands naturally process nutrients, organic matter, and toxins from anthropogenic effluents.
• Generalizable knowledge of effluent-derived dissolved organic matter (DOM) cycling in wetlands remains limited.
• Frank Lake, Alberta, a restored wetland complex, receives urban and agro-industrial effluents.

Purpose of the Study:

• To quantify the cycling of effluent-derived DOM in Frank Lake.
• To understand the compositional changes and processing of DOM within the wetland.
• To assess the net export of DOM from the wetland under varying hydrological conditions.

Main Methods:

• Optical analyses and parallel factor analysis (PARAFAC) modelling to characterize DOM composition.
• Microbial incubations to determine DOM consumption rates and half-lives.
• Mass balance calculations to quantify long-term dissolved organic carbon (DOC) export and net DOM flux.

Main Results:

• DOM composition shifted from bioavailable and protein-like at input sites to aromatic and humic-like at the outflow.
• Effluent DOM was rapidly consumed, with half-lives increasing significantly from input to outflow.
• Long-term DOC export was relatively low, but Frank Lake acted as a net DOM source, influenced by water residence time.

Conclusions:

• Frank Lake effectively processes and transforms effluent DOM, increasing its stability.
• The wetland's role as a DOM source or sink fluctuates with hydrological conditions (wet vs. drought years).
• Understanding DOM cycling in restored wetlands is crucial for managing water quality and downstream ecosystems.