Environmental Science & Technology (MODIS), Medium Resolution Imaging Spectrometer (MERIS), possibly the Visible Infrared Imager Radiometer Suite (VIIRS), Pre-ACE, aerosols, clouds, and ecosystem (PACE) satellite, and the Ocean and Land Color Instrument (OLCI) on Sentinel-3. Multimission ocean color satellites are necessary to provide the future climate data record30 to continue the assessment process. Newer algorithms, such as the OC5,31 may perform better in coastal areas where turbidity is a major concern, such as within estuaries or near sediment-laden rivers. However, rivers in Florida were typically sediment starved such that chlorophyll-a along the WFS explained 87% of particulate backscatter.32 The OC5 may minimize effects of turbidity and bottom reflectance, but was not tested since it was not included in the SeaDAS l2gen program. Merging new missions, reprocessing events,33 newer algorithms,31,34 ad- vanced atmospheric corrections, and the stability between ChlRS-a and Chl-a require further discussion, and could be considered during criteria triannual reviews. It is recommended that compliance with ChlRS-a reference condition criteria values be assessed using similar satellite data and algorithms. This will mitigate problems associated with using the OC4 close to the coast, as interferences and overestimations are expected to be constant. Coastal segments could be considered impaired if a ChlRS-a assessment was identified as a statistically significant exceedance of the criteria value for either the medians or 75th percentiles. The exceedance could trigger appropriate actions under the Clean Water Act for remediation of impaired waters. The approach for developing numeric water quality criteria evaluated in this study could potentially be used to compute criteria for any coastal waters of similar scale. Large field sampling programs, such as ECOHAB and NEGOM, only provided a limited validation data set that was coincident with the SeaWiFS mission and within the 3NM limit. Preliminary analysis of field stations coincident with MODIS and MERIS suggested even less field data was available for validation within the 3NM limit due to later launch dates starting in 2002. There was less evidence of similar large field sampling programs looking into the future. Continued validation with field observations of existing satellites and new missions will be important.35 SeaWiFS ChlRS-a quantified a water quality baseline associated with use attainment and assessment data that could reveal changes that may cause loss of use. It would be necessary to have data and information available to demonstrate that water quality, during the reference period, was supportive of designated uses. Although coastal chlorophyll does change due to factors other than anthropogenic nutrient enrichment, such as coastal upwelling, we suggest a fixed quantitative baseline and an efficient procedure for detecting change as a valuable first step toward identifying water quality impairments resulting from nutrient pollution. Data quantifying nutrient fluxes to the coastal ocean would improve the prospects for relating ChlRS-a responses to anthropogenic nutrient pollution. ASSOCIATED CONTENT *S Supporting Information Additional information is provided on region of interest coastal segment data extraction, KdRSPAR validation regressions, optical penetration depth and bottom depth, K. brevis flagging, and river discharge. This material is available free of charge via the Internet at http://pubs.acs.org. ■ ■ ■ ■ Article AUTHOR INFORMATION Corresponding Author *Phone: 850-934-9205; fax: 850-934-2401; e-mail: schaeffer. blake@epa.gov. ACKNOWLEDGMENTS The information in this document has been funded in part by the U.S. Environmental Protection Agency. It has been subjected to review by the National Health and Environmental Effects Research Laboratory and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of the U.S. Environ- mental Protection Agency. This is contribution number 1425 from the Gulf Ecology Division. Jeff Jackson provided extensive GIS support. Tetra Tech, Inc. queried in situ data for satellite match-ups. Mario R. Sengco assisted in the compilation of ECOHAB data and FWRI counts, and provided comments on available K. brevis research. We thank Dr. Zhong Ping Lee at the Mississippi State University for his comments and suggestions. Finally, we thank the three anonymous reviewers for their critical comments. 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