NUTRIENT LIMITATION AND PHOSPHATE REGENERATION IN ARTIFICIAL CUTAWAY PEATLAND LAKES

Abstract

Abstract:Increasingly large areas of Ireland's emerging cutaway peatlands are being flooded to create a linked network of lakes and wetlands designed for conservation and amenity purposes. The current study examined water quality in four artificial cutaway peatland lakes over three years (2001-2004), with particular focus on nutrient dynamics and the potential for phosphate to be regenerated from the organic phosphorus pool via biotic and abiotic processes. The cutaway lakes contrasted strongly in both their physico-chemical characteristics, trophic statuses and limiting nutrient states. Two of the alkaline mesotrophic study lakes were annually N-limited in summer, while the acidic eutrophichypertrophic study lake underwent a transition to more sustained N-limitation. Laboratory experiments indicated a considerable potential for soluble reactive phosphorus (SRP) to be regenerated from the dissolved organic phosphorus pool by phosphatase enzyme hydrolysis (mean 2.6µg 1⁻¹). UV-induced SRP regeneration was found to play a lesser role (mean 0.9µg 1⁻¹), particularly in the dystrophic study lake, while combined UV and enzymatic hydrolysis produced an intermediate response (mean 2.3µg 1⁻¹). With all three mechanisms, the quantity of SRP regenerated appeared to be independent of lake trophic status. The current data provide some evidence that the regeneration of SRP from the large organic phosphorus pool in cutaway peatland lakes can help maintain a constant supply of bioavailable phosphorus, potentially contributing to the prevalence of N-limiting conditions in these systems.