The Heidelberg Tributary Loading Program: Nutrients, Sediment, and cHABs- Oh My!

The National Center for Water Quality Research has been monitoring major tributaries to Lake Erie for nearly 50 years as a part of its Heidelberg Tributary Loading Program (HTLP). Up to three samples a day are analyzed for all major nutrients and suspended sediment from six major tributaries to Lake Erie (Maumee, Sandusky, Portage, Huron, Raisin, and Cuyahoga). Long-term trends in loads and concentrations indicate that total phosphorus (TP) has decreased since the mid-1970s in the agricultural watersheds, whereas dissolved reactive P (DRP) has been increasing drastically since the mid-1990s corresponding to the recurrence of cyanobacterial Harmful Algal Blooms (cHABs) in Lake Erie. Increased DRP and cHABs appear to be associated with increased discharge in the past decade as well as recent patterns in agriculture, specifically the build-up of P at the soil surface combined with preferential flow of water to tile drainage. This high frequency water quality monitoring has allowed us to detect dominant sources and dynamics of nutrient runoff from watersheds. Further, we recently have begun using a Fluoroprobe to determine spatial and temporal dynamics of potamoplankton in the Sandusky River and have conducted investigations into the effect of sample holding time on algal community composition.