Seasonal trends in phosphorus export from three major Canadian Lake Erie tributaries

Abstract

The re-appearance of algal blooms in Lake Erie in recent decades has been attributed to increased loading of bioavailable phosphorus (soluble reactive phosphorus; SRP) in US tributaries, a trend linked to agricultural practices, tile drainage, and climate change. Here, we explore P-loading trends for three major Canadian tributaries of the Canadian Lake Erie Basin (CLEB) and investigate if increased loading can be related to increased use of tile drainage. Our results confirm that SRP loading from the Canadian tributaries has been increasing over the past decade in the late winter early spring, and that tile drainage is a significant driver of SRP across all seasons. However, the effects of tile drainage are not consistent across all regions where climate conditions, soil characteristics and agricultural management practices vary. This study highlights the complexity of P transport via tile drains and underscores why no single solution should be applied to manage P across the CLEB.