Use of satellite imagery for water quality studies in New York Harbor

The utility of satellite imagery for water quality studies in New York Harbor is investigated. Ground data from a routine sampling program (New York Harbor Water Quality Survey) are compared to imagery from the Landsat Thematic Mapper (TM) and Terra Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. New York Harbor is a challenging environment for remote sensing because of the complex hydrography and strong tidal influence. Using a time-averaged spatial analysis it is shown that turbidity as determined from Secchi depth correlates with Landsat TM red reflectance in regions affected by the Hudson River sediments (N=21, R2=0.85). Based on this correlation the estuarine turbidity maximum of the Hudson River is mapped. Landsat TM red reflectance is also used to identify and map plumes of increased turbidity caused by rainfall runoff and/or spring tide resuspension in Newark Bay. Chlorophyll a concentration correlates with the ratio of Landsat TM green to red reflectance in the eutrophic East River and Long Island Sound (N=16, R2=0.78). Terra MODIS estimates of chlorophyll a show no correlation with ground observations, are biased towards low values and are therefore not directly useable for New York Harbor.