Periphyton monitoring using stationary and aerial red-green-blue and multispectral imagery

Session: Harmful Algal Blooms and Their Toxicity: Remote Sensing and Modeling Approaches (1)

Anika Kuczynski, National Institute of Water and Atmospheric Research, [email protected]
Jochen Bind, National Institute of Water and Atmospheric Research, [email protected]
Cathy Kilroy, National Institute of Water and Atmospheric Research, [email protected]

Abstract

Periphyton form the base of the food web in streams, but nuisance biomass levels can cause a variety of problems, especially in the case of toxin-producing Microcoleus. New Zealand’s National Policy Statement for Freshwater Management mandates monthly monitoring of chlorophyll a, the chosen metric for stream periphyton biomass. Sample collections for chlorophyll a analysis and visual cover estimates are low resolution, time- and cost-intensive monitoring methods. Our objective is to test whether imagery-based monitoring is an effective alternative. We conducted 1) stationary camera monitoring, which provides a high sampling frequency (daily), and 2) aerial monitoring using drones, which provides broad spatial cover. We obtained a time series of daily red-green-blue (RGB) and multispectral imagery from stationary sites on two streams and covering a ~1 km reach of the Opihi River in Canterbury, New Zealand on two occasions. Alongside the imagery, we collected ground-truth data of chlorophyll a and visual cover estimates divided into different groups of periphyton (weekly at the stationary sites and from five patches on the Opihi River). Although stream characteristics and weather conditions are limiting factors, preliminary image analysis results indicate that RGB and multispectral imagery can be used for high resolution periphyton monitoring in shallow streams.