Nutrient Budgets in Lakes

Abstract

This chapter discusses the sources and ultimate fate of nutrients into downstream lakes. It includes processes such as microbial denitrification, internal nutrient loading derived both from in situ measurements and from a mass-balance approach, and the loss of nutrients by flushing. Net and gross internal loads can be estimated using mass-balance equations. While the gross load is of interest because it contributes to the total load that drives algal growth, usually a large part of the gross load ends up sequestered in the sediment. Lake restoration efforts to reduce nutrients available to phytoplankton can focus on reducing both the inputs of nutrients and the cycling of nutrients within the lake. Various in-lake restoration techniques exist to target different fluxes within lake nutrient cycles. Therefore, understanding nutrient dynamics in the lake and sources and sinks of nutrients in lakes helps identify restoration approaches that are most likely to successfully reduce nutrient availability, phytoplankton blooms, and other related problems.