Continuous <i>In Situ</i> Nutrient Analyzers Pinpoint the Onset and Rate of Internal P Loading under Anoxia in Lake Erie’s Central Basin
Hanna S Anderson, Thomas H. Johengen, Casey M. Godwin, H. Purcell, Peter J. Alsip, Steven A. Ruberg, Lacey A. Mason
Abstract
Lake Erie ’s central basin experiences seasonal anoxia, contributing to internal sediment phosphorus (P) loadingand exacerbating eutrophication. The precise conditions requiredfor internal loading are poorly understood. This study constrainsthe timing and rates of internal P loading using continuous in situ temperature, dissolved oxygen (DO), and soluble reactive P (SRP)observations from two sites. SRP concentrations remained lowduring normoxia (>2 mg of DO L −1) and hypoxia (0 −2m go fD O L−1) but increased abruptly after anoxia for 12 −42 h. SRP flux rate estimations varied, likely due to advection and hypolimnionthickness variation, but could still be reasonably quanti fied. Flux rates and standard errors during anoxia averaged 25.67 ±5.5 mg