Influence of glacial landform hydrology on phosphorus budgets of shallow lakes on the Boreal Plain, Canada

•Hydrogeological influence on lake phosphorus concentrations on Boreal Plain.•High phosphorus concentrations in lakes located on fine-textured landforms.•Low phosphorus concentrations in lakes located on coarse-textured landform.•Wetland groundwater phosphorus concentrations greater than mineral groundwater.•Lake phosphorus budgets reflect lake connectivity to surrounding source waters.

SummaryA comparative study of three shallow lake catchments in contrasting glacial landscapes (coarse-textured outwash, fine-textured-till hummocky moraines and glacio-lacustrine clay-till plains) demonstrated a distinct landform control on the proportion and type of surface and groundwater sources influencing total phosphorus ([P]) and total dissolved phosphorus ([DP]) concentrations, and P budgets of lakes on the Boreal Plain of the Western Boreal Forest, Alberta, Canada. Lakes located on fine-textured landforms had high [P] and [DP] (median 148 and 148 μg L−1 glacio-lacustrine plains; 99 and 63 μg L−1 moraine, respectively) linked to shallow groundwater loadings from near-surface peat with high [P] from adjacent wetlands. In contrast, the lowest lake [P] and [DP] (median 50 and 11 μg L−1, respectively) occurred on the coarse-textured landform, reflecting greater inputs of deep mineral-groundwater with low [P] from quartz-rich substrates. Annual lake P budgets reflected lake connectivity to the surrounding landform and relative contributions of P by surface versus groundwater. They also reflected distinct scales of groundwater (larger-scale versus short, shallow-flow paths) with differing [P] between landform types and occurrence of internal biogeochemical P cycling within landforms. A regional lake survey reflected trends from the catchment-scale, linking landform type to potential P sources as well as topographic position to potential trophic status across the Boreal Plain. Together, the results provide a conceptual framework for the scale of interactions between lakes and surrounding source waters influencing P loadings in differing hydrogeological landscapes, important to management strategies and predicting impacts of land-use disturbances on productivity of Boreal Plain lakes.