Estimation of cyanobacteria biovolume in water reservoirs by MERIS sensor

Planktonic cyanobacteria primarily develop in lentic water bodies, such as lakes and water
reservoirs. In certain instances, toxin-producing cyanobacterial populations might dominate
the phytoplankton community. Satellite remote sensing is a useful tool for large
spatial scale monitoring of cyanobacteria, and the MERIS sensor from the Envisat satellite
has taken worldwide images at a high frequency for over 10 years. This short time lapse
image collection has provided an extensive record of images for the analysis of variation in
the cyanobacterial communities in water reservoirs for management and scientific purposes.
The objective of this work is to determine the relationship between measured
cyanobacterial biomass as biovolume and the estimations derived from MERIS imagery.
This study encompasses two independent studies relying on data from 23 water reservoirs.
First, a long-term global limnological research study was conducted that provided a field
data collection that included cyanobacterial biovolume, among other variables. Second, a
survey was conducted that applied the processed images derived from the Envisat MERIS
sensor. The chlorophyll-a (Chl a) content and phycocyanin concentration (PC) were estimated
from the MERIS images. The PC estimated by remote sensing and total cyanobacterial
biovolume measured from the field samples were found to be significantly
correlated (R2 = 0.6219; p < 0.001). No relevant differences were found among the taxonomical
groups, which indicated that this tool provides accurate estimations irrespective
of the cyanobacterial group. For validation, the algorithm derived from the entire dataset
was applied to the MERIS image dataset of the Rosarito reservoir. An estimated cyanobacterial
biovolume time series was performed and compared to the biovolume data
collected in an extensive sampling schedule spanning 4 years. The results indicated a
strong correlation (R2 = 0.72; p < 0.001) between the measured and estimated data acquired
on the same day