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Detection of Seagrass Cover and Water Clarity in Florida Bay and the Keys

Richard P. Stumpf, Michael J. Durako, James W. Fourqurean, Varis Ransibrahmanakul, and Megan L. Frayer

Remote sensing of changes in water clarity and seagrass cover in Florida Bay.

Previously we have reported on turbid water and benthic cover changes in Florida Bay from 1985 to 1997 using Advanced Very High Resolution Radiometer (AVHRR) imagery. The imagery confirmed the increase in turbidity starting in late 1987, as well as a decrease in the extent of bottom cover in the Bay. The bay continued to show decreased cover and increased turbidity through 1997.

In 1997, the imagery indicated reduced turbidity and increased bottom cover in the northwest Bay southwest of Flamingo. We found extensive Halodule along Dave Foy Bank in winter 1998. Field sampling from 1998 showed some recovery of seagrass in the NW region.

In late 1997, the SeaWiFS (Sea Wide Field-of-View) instrument was launched. SeaWiFS provides the same resolution as AVHRR (1 km pixel), with coverage about every two days. It offers a key improvement over AVHRR, as it was designed to monitor ocean chlorophyll as well as water clarity. With optical remote sensing, there is no fundamental distinction between seagrass chlorophyll and phytoplankton chlorophyll. Areas of dense seagrass in shallow water show relatively high chlorophyll, areas of sparse seagrass show low chlorophyll. SeaWiFS offers an additional data set for refinement of the methods applied to AVHRR for monitoring of seagrass. Using depth information and field data from 1998 and 1999, we are able to determine the sensitivity of the SeaWiFS method for monitoring seagrass in Florida Bay and the Keys, and monitor for seagrass in shallow water.


(This abstract was taken from "Programs and Abstracts - 1999 Florida Bay and Adjacent Marine Systems Science Conference". (PDF, 1 MB))

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