Abstract
<p> <p id="x-x-sp0090"> Widespread and persistent Ecosystem Disruptive Algal Blooms dominated by marine picocyanobacteria ( <em> Synechococcus </em> ) commonly occur in the subtropical lagoonal <a title="Learn more about estuary from ScienceDirect's AI-generated Topic Pages"> estuary </a> of Florida Bay (U.S.A). These blooms have been linked to a decline in natural sheet flow over the past century from upstream Everglades National Park. <a title="Learn more about Remote sensing from ScienceDirect's AI-generated Topic Pages"> Remote sensing </a> algorithms for monitoring cyanobacteria blooms are highly desired but have been mainly developed for freshwater and coastal systems with minimal bottom reflectance contributions in the past. Examination of in situ <a title="Learn more about optical properties from ScienceDirect's AI-generated Topic Pages"> optical properties </a> revealed that <em> Synechococcus </em> blooms in Florida Bay exhibit unique <a title="Learn more about spectral absorption from ScienceDirect's AI-generated Topic Pages"> spectral absorption </a> and reflectance features that form the basis for algorithm development. Using a large, multi-year match-up dataset (2002–2012; n = 682) consisting of in situ pigment concentrations and <a title="Learn more about Moderate Resolution Imaging Spectroradiometer from ScienceDirect's AI-generated Topic Pages"> Moderate Resolution Imaging Spectroradiometer </a> (MODIS) Rayleigh-corrected reflectance (R <sub> rc </sub> (λ)), classification criteria for detecting cyanobacteria blooms with chlorophyll- <em> a </em> concentrations (Chl- <em> a </em> ) ~5–40 mg m <sup> −3 </sup> were determined based on a new approach to combine the MODIS Cyanobacteria Index, CI <sub> MODIS </sub> , and spectral shape around 488 nm, SS(488). The inclusion of SS(488) was required to prevent false positive classifications in seagrass-rich, non-bloom waters with high bottom reflectance contributions. 75% of cyanobacteria blooms were classified accurately based on this modified CI approach with <1% false positives. A strong correlation observed between cyanobacteria bloom in situ Chl- <em> a </em> and CI <sub> MODIS </sub> (r <sup> 2 </sup> = 0.80, n = 32) then allowed cyanobacterial chlorophyll- <em> a </em> concentrations (Chl <sub> CI </sub> ) to be estimated. Model simulations and image-based analyses showed that this technique was insensitive to variable <a title="Learn more about aerosol properties from ScienceDirect's AI-generated Topic Pages"> aerosol properties </a> and sensor viewing geometry. Application of the approach to the entire MODIS time-series (2000–present) may help identify factors controlling blooms and system responses to ongoing management efforts aimed at restoring flow to pre-drainage conditions. The method may also provide insights for algorithm development for other lagoonal estuaries that experience similar blooms. </p></p>
Original language | American English |
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Journal | Remote Sensing of Environment |
Volume | 231 |
DOIs | |
State | Published - Jan 1 2019 |
Keywords
- Algal bloom
- Ocean color
- Remote sensing
- MODIS
- Chlorophyll
- Cyanobacteria
- Synechococcus
- Florida Bay
Disciplines
- Life Sciences