Lab on a Secchi disk: A prototype open-source profiling package for low-cost monitoring in aquatic environments

Owing to the high cost of commercial optical sensors, there is a need to develop low-cost optical sensing packages to expand monitoring of aquatic environments, particularly in under-resourced regions. Visual methods to monitor the optical properties of water, like the Secchi disk and Forel-Ule color scale, remain in use in the modern era owing to their simplicity, low-cost and long history of use. Yet, recent years have seen advances in low-cost, electronic-based optical sensing. Here, the designs of a miniaturized hand-held device (mini-Secchi disk) that measures the Secchi depth and Forel-Ule color are updated. We then extend the device by integrating a small electronic sensing package (Arduino-based) into the Secchi disk, for vertical profiling, combining historic and modern methods for monitoring the optical properties of water into a single, low-cost sensing device, that measures positioning (GPS), light spectra, temperature, and pressure. It is charged and transfers data wireles...