Nutrient availability reduced in older rural impoundments in coastal Bay of Fundy, Canada

The Cumberland Marsh Region (CMR), located at the head of the Bay of Fundy, is an important area for waterbird foraging, and wetland restoration and creation. Wetland managers in the CMR have observed that waterbird usage is high when wetlands (impoundments) are newly created, but can decline upon impoundment aging-a phenomenon called wetland senescence that is not well understood. We examined surface water chemistry among newly created and older impoundments in the CMR during the summer months (when waterbird breeding and staging are important), and hypothesized that nutrient availability would be reduced in older impoundments if nutrient loadings were primarily of internal origin. Despite ample rainwater and proximate agricultural sources, macro and micronutrient concentrations in impoundment surface water were significantly higher in newly created impoundments (< 1 year), and reduced in older impoundments (> 30 years) and impoundments 5-7 years in age. We suspect that impoundment creation has potential to generate high productivity levels, and older impoundments lack land-derived nutrients and may not sustain long-term nutrient availability when waterfowl brood foraging is important. More research is required to better understand wetland rehabilitation strategies that can help sustain nutrient availability, and inputs and pathways in impoundments.