Environmental Science & Technology Article Figure 1. Station data and coastal segments used in satellite remote sensing analysis of ChlRS-a and KdRSPAR. Coastal segments were delineations proposed in this approach to develop numeric chlorophyll criteria for the (A) Florida Panhandle, (B) West Florida Shelf, and (C) Atlantic Coast. Open circles indicate the station data used to compare Chl-a to satellite remote sensing observations of ChlRS-a. Filled triangles indicate station data used to compare KdPAR to satellite remote sensing observations of KdRSPAR. Numbers are coastal segment numbers ranging from 1 through 76. phosphorus pollution (comparative reference condition). The State of Florida CWA section 303(d) listings did not include any coastal segments described as impaired for nutrients under Florida’s narrative standard. Therefore the historical reference condition could be based on existing water quality. Karenia brevis is a harmful algal bloom dinoflagellate that frequently occurs within the coastal waters of Florida.5 However, nutrients from land have not been strongly implicated in bloom initiation.6 Nutrient export from land has been implicated in the maintenance phase of blooms when advected to near-shore waters. Acknowledging the potential for K. brevis blooms to increase coastal chlorophyll concentrations, we also evaluate an approach for addressing K. brevis blooms within the context of a reference condition approach to numeric water quality criteria development. Water quality in Florida’s coastal waters has not been extensively monitored, potentially limiting application of a reference condition approach for criteria development. One possible solution is the use of remote sensing technologies. Satellite remote sensing currently uses low earth orbiting satellites to derive ocean color products on a global scale7 and at frequent revisit intervals. Remote sensing has most commonly been used for open ocean applications. However, these satellites are useful for applications in near-coastal waters.8,9 In addition, satellite remote sensing has been previously applied in water quality management (i.e., NOAA Harmful Algal Bloom Operation Forecast System).10,11 The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) became operational in September 1997 and is used in this study to quantify an indicator of chlorophyll-a (ChlRS-a) between 1997 and 2010. We evaluate potential interferences, specifically colored dissolved organic matter (CDOM) and bottom reflectance affecting the derivation of ChlRS-a in coastal waters. ■ EXPERIMENTAL SECTION Coastal waters were subdivided into 76 coastal segments based on the Florida Department of Environmental Protection’s Water Body Identification System (WBIDs), which start at the land margin and extend seaward to 3 NM. Segment distance along the coast was typically between 6 and 14 NM depending on the State’s contour at a particular location. Coastal WBIDs located near an estuary pass were typically centered at the pass. This study included 17 coastal segments in the Florida Panhandle (FP) between the Alabama border and St. Joseph Bay, 20 segments on the West Florida Shelf (WFS) from Anclote Bay to Rookery Bay, and 39 Atlantic Coast (AC) segments from Biscayne Bay to the Georgia border (Figure 1). Areas within south Florida, including the Florida Keys, were omitted because comprehensive in situ monitoring of the area rendered a remote-sensing approach unnecessary, and signifi- cant bottom reflectance confound derivation of ChlRS-a. The area between St. Joseph Bay and Anclote Bay were also omitted because coastal seagrass coverage12 and extremely high colored dissolved organic carbon exports from rivers13 were expected to confound derivation of ChlRS-a. Satellite ocean color data were obtained from the National Aeronautics and Space Administration’s (NASA) Ocean Color Web.14 SeaWiFS provided daily images with pixels having a nominal 1.1 km spatial resolution. SeaWiFS data (reprocessing R2009) temporally spanned between September 14, 1997 and January 1, 2010. Imagery spatially covered between 31.0 to 23.0° N and 88.0 to 79.0° W. The SeaWiFS Data Analysis System (SeaDAS) version 6.115 was used to process data that 917 dx.doi.org/10.1021/es2014105 | Environ. Sci. Technol. 2012, 46, 916−922