An evaluation of a handheld spectroradiometer for the near real-time measurement of cyanobacteria for bloom management purposes.

A commercially available handheld spectroradiometer, the WISP-3, was assessed as a tool for monitoring freshwater cyanobacterial blooms for management purposes. Three small eutrophic urban ponds which displayed considerable within-pond and between-pond variability in water quality and cyanobacterial community composition were used as trial sites. On-board algorithms provide field measurements of phycocyanin (CPC) and chlorophyll-a (Chl-a) from surface reflectance spectra measured by the instrument. These were compared with laboratory measurements. Although significant but weak relationships were found between WISP-3 measured CPC and cyanobacterial biovolume measurements and WISP-3 and laboratory Chl-a measurements, there was considerable scatter in the data due likely to error in both WISP-3 and laboratory measurements. The relationships generally differed only slightly between ponds, indicating that different cyanobacterial communities had little effect on the pigment retrievals of the WISP-3. The on-board algorithms need appropriate modification for local conditions, posing a problem if it is to be used extensively across water bodies with differing optical properties. Although suffering a range of other limitations, the WISP-3 has a potential as a rapid screening tool for preliminary risk assessment of cyanobacterial blooms. However, such field assessment would still require adequate support by sampling and laboratory-based analysis.