region as a result of an overabundance of dissolved nutrients. This 
process of eutrophication can have serious implications for the quality 
of production in the bay. 
Through a cooperative study, the U.S. Fish and Wildlife Service 
(USFWS) and the Florida Department of Natural Resources (FDNR) estimated 
habitat changes in the Tampa Bay area from the 1950’s to 1982. The data, 
housed in digital form on the DNR Marine Resource Geographic Information 
System (MRGIS) are photo-interpreted aerial photographs that have been 
computer digitized in a 1:24000 scale using the National Wetlands 
Inventory standard classification system. Over 600 separate categories 
are detailed in this hierarchical classification for the Tampa Bay 
region. Two 7.5-minute USGS topographic quadrangles (approximately 
36,000 ha, northwest and southwest portion of Figure 1) have been 
interpreted and digitized into the MRGIS in addition to the data 
developed in conjunction with USFWS. The data have been synthesized on 
the MRGIS into general categories for ease of discussion (Table 1). 
Table 1. Summary of major habitat trends, in hectares, for the Tampa Bay 
region. 
Habitat 
1950 
1982 
Percent Chanqe 
Mangrove 
8,629 
8,032 
- 7 
Saltmarsh 
2,063 
1,432 
- 30 
Seagrass 
25,801 
12,968 
- 50 
Mudflats 
6,812 
9,389 
+ 37 
Freshwater wetland 
18,335 
14,440 
- 21 
Agriculture 
25,347 
45,193 
+ 78 
Range/forest 
124,630 
42,997 
- 65 
Urban 
32,730 
95,586 
+192 
Lewis et al. (1985) estimated that 44% of the saltmarsh and 
mangrove and 81% of the seagrass meadows have been lost in Tampa Bay 
since the late 1800’s. The recent calculations (Table 1) are not readily 
comparable because of differences in time, methodology, vegetation 
classification, and aerial coverage. However, the results confirm that 
significant losses of habitat have occurred. Perhaps the most 
significant deviation from other published results is the seemingly small 
loss of mangroves (7%) in the bay. This is an artifact of the USFWS 
classification system which underestimates change for this particular 
category and is being addressed in the MRGIS database. 
Significant loss of fishery habitat has occurred in the Tampa Bay 
area. Loss of marsh and mangrove has been the result of dredge and fill 
activities. Dredge and fill has caused direct loss of seagrasses and 
indirect impacts have been hypothesized, primarily from changes in water 
quality which preclude seagrass growth. Dredge and fill activities are 
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