Patterns in river color reveal flow dependent ecosystem patchiness in a Great Plains river

Keywords: river ecology, landscape ecology, ecosystem ecology, spatial ecology, remote sensing, landscape heterogeneity
Session Type: Virtual Paper Abstract
Day: Friday
Session Start / End Time: 2/25/2022 11:20 AM (Eastern Time (US & Canada)) - 2/25/2022 12:40 PM (Eastern Time (US & Canada))
Room: Virtual 19

Abstract

Ecosystems often have a patchy spatial structure at some scale, where similar contiguous areas are separated by sharp changes in physical or biological conditions. When patches are sufficiently different, they will favor different ecosystem processes. In river ecosystems, flow moves material from headwaters to oceans, through any ecosystem patchiness. Therefore understanding river ecosystem processes requires understanding river ecosystem structure. Patchiness has been characterized in smaller systems where most ecosystem processes occur in the river-bed, but not in larger rivers where the water column is an important ecosystem component. We assessed ecosystem patchiness in a highly managed Great Plains river (The Kansas) by analyzing spatial color profiles across flow conditions. River color is a robust metric derived from satellite imagery that reflects the combined state of several important habitat features, specifically suspended sediment, CDOM, and phytoplankton. We also compared color to in-situ chlorophyll a (chl-a) and turbidity measurements from a spatially distributed array of continuous sensors. We found that at flows beyond a certain threshold, the entire river was uniformly yellow. At flows below the threshold, the river was greener and characterized by patches of very green water upstream of run-of-river dams. Comparing color with in-situ data further indicated that the color patches had either elevated chl-a or reduced suspended sediment, which both impact river ecosystem processes. Flows exceeded the threshold flow on 20% of days during the period of record (1985-present), indicating the ecosystem regularly shifted between homogeneous and patchy states.