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Drivers of declining P and rising DOC; Role of wetlands/beaver ponds

Catherine Eimers (PI/Trent University) and
Shaun Watmough (co-PI/Trent University)
Kieran Pinder (MSc/Trent University)

Total phosphorus (TP) levels have declined and dissolved organic carbon (DOC) concentrations have increased in many lakes and streams across the Muskoka River Watershed over the past three decades. The reasons for these changes are unknown, and this lack of knowledge limits watershed model development and management decisions.

Previous studies in the region have identified wetlands as the primary source of both TP and DOC, and we hypothesize that change in wetland coverage and/or shifts in wetland hydrology may be contributing to changes in surface water quality.

Kieran's project will investigate TP dynamics in four catchments that have very different wetland coverage. All four streams drain into Dickie Lake, and have very different TP and DOC levels. Dickie Lake has shown particularly large changes in TP and DOC over the past thirty years as well as changes in wetland coverage (including beaver ponds) in its watershed. It is hoped that by determining the cause(s) of differences in TP and DOC export across the Dickie Lake watershed we can gain insight into the drivers of long-term changes in surface water quality that have been observed in the region.

Update - November 2013

 
Total phosphorus (TP) levels have declined in many lakes and streams across the Muskoka River Watershed over the past three decades. These declines have occurred despite increasing shoreline development on many lakes, which presents challenges to management and modeling efforts toward predicting future TP levels.

Kieran's research is focused on solving this problem by investigating the influence of past wetland disturbance on TP declines. He has assessed trends in long-term TP export at four streams in the Dickie Lake Watershed as well as patterns in lake TP and atmospheric deposition loads.

In addition, he has collected data on trees within wetlands in the four sub-catchments and has estimated the pools of P in biomass. He has found that disturbance in wetland-dominated sub-catchments at Dickie Lake may explain the high TP concentrations that occurred there in the early 1980s and 1990s, whereas declines in TP thereafter may due to recovery from that disturbance.