Real-time monitoring of harmful algal blooms in the southern Benguela

Abstract

The southern Benguela Current region off South Africa is subject to frequent harmful algal blooms (HABs), which can have serious impacts — both through the introduction of toxins into the ecosystem and the collapse of high-biomass blooms leading to anoxia. As part of the Benguela Current Large Marine Ecosystem Programme, a bio-optical buoy has been developed for monitoring HABs in the region, providing both real-time and time-series data. Considerations in developing the buoy were that it should be small, cost effective and robust, allowing for field calibration of the sensors and servicing from a small boat. The instrument package on the buoy consists of two hyperspectral radiometers (providing remote sensing reflectance), a thermistor chain, a fluorometer and an Acoustic Doppler Current Profiler. A half-hourly acquisition regime collects data from the instruments, which are transmitted in real time using cellular phone telemetry. A website is updated with these data, when available, along with satellite data and shellfish warnings, to provide near real-time information on conditions in the area. Demonstration data from the buoy, related to observed blooms of dinoflagellates and the ciliate Mesodinium rubrum, are presented.