Learning Objectives

22.4.1 Describe the concept of nutrient spiraling in moving waters and summarize the factors that control the spiral lengths.

22.4.2 Differentiate between natural and anthropogenic causes of eutrophication.

22.4.3 Explain why seasonal lake turnover and upwelling are important to enhancing nutrient supply in lakes and oceans.

In freshwater and marine ecosystems, nutrient transformations and transfers have the added complexity of occurring in a moving aqueous medium. Inputs of nutrients from outside the ecosystem are much more important than in terrestrial ecosystems. Furthermore, oxygen concentrations are often lower than in terrestrial ecosystems, constraining biological activity and the biogeochemical processes associated with it.