Abstracts

Detection and mapping of cyanobacterial harmful algal blooms using satellite data in one Louisiana lake and four Mississippi lakes

Author(s): Dash, P.

Cyanobacteria represent the major harmful algal group in fresh to brackish water environments. Cyanobacterial blooms are aesthetically undesirable since they discolor the water, cause turbidity in recreational facilities and synthesize a large number of low molecular weight compounds which cause taste and odor problems. Of particular concern are a diverse range of toxins produced by cyanobacteria, termed cyanotoxins, which are hazardous to human, animal and aquatic ecosystem health. Recently, a procedure was developed to estimate cyanobacterial concentrations by quantifying chlorophyll a (Chl a) and the primary cyanobacterial pigment phycocyanin (PC) using OCM satellite data over a small lake- Lac des Allemands in Louisiana, USA. This required the development of an atmospheric correction and vicarious calibration methodology for satellite data. Empirical inversion algorithms were developed to convert the OCM Rrs at bands centered at 510.6 and 556.4 nm to concentrations of PC. For the algorithms to be uniformly valid over all areas (or all bio-optical regimes) of the lake, a holistic approach was developed to minimize the influence of other optically active constituents. Similarly, empirical algorithms to estimate Chl a concentrations were developed using OCM bands centered at 556.4 and 669 nm. The best PC algorithm (R2=0.7450, p<0.0001, n=72) yielded a root mean square error (RMSE) of 36.92 µ g/L (PC from 2.75 to 363.5 µg/L, n=48). The best algorithm for Chl a (R2=0.7510, p<0.0001) produced an RMSE of 31.19 µ g/L (Chl a from 9.46 to 212.7 µ g/L, n=48). The results demonstrated the preliminary success of using OCM satellite data to map cyanobacterial blooms in a small lake in Louisiana. In the summer of 2012, five field campaigns were undertaken to four large Mississippi lakes- Lakes Sardis, Enid, Grenada, and the Ross Barnett reservoir in order to obtain a database of photosynthetic pigment concentrations and phytoplankton composition. The objective of this project is to combine multiple satellite data from several sensors such as VIIRS, MODIS AQUA and OCM-2, and developed techniques to quantify cyanobacteria in these four large Mississippi lakes and make the mapped images available through a website for use by water quality managers and general public to rapidly obtain synoptic information on cyanobacterial blooms. Time-series of true color satellite images clearly show the presence of algal blooms. Preliminary analyses of the field data analyzed thus far demonstrate the presence of numerous toxic species of cyanobacteria in these lakes. Preliminary results from this project will be presented.

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