Growth-in-motion Creates Phytoplankton Biomass Patterns in a Great Plains River

Abstract

Phytoplankton populations can grow in river water during downstream transport, and the combination of net growth and transport dynamics produces spatial patterns of phytoplankton biomass. High phytoplankton biomass at a location along a river will impact essential ecosystem processes, including river metabolism and foodweb energetics. High phytoplankton also presents a potential management issue because high algal biomass can negatively impact water resources, particularly drinking water quality. Phytoplankton spatial patterns and their dynamics in time, however, remain poorly characterized, and we do not have a clear mechanistic account that can explain what controls phytoplankton biomass magnitude at a specific location along the length of rivers. This dissertation seeks to address that gap, first characterizing phytoplankton spatial patterns through time and then answering the question: what controls phytoplankton biomass at a specific location along a river? I found that low biomass values are controlled by variations in growth conditions and residence time, but total nutrient loading sets an upper boundary on phytoplankton biomass.