but greater concentrations are found upstream closer to point source 
discharges. 
WATER QUALITY SUMMARY 
Tampa Bay Tributaries 
Overall, tributaries to Tampa Bay contain high levels of 
nutrients. Mean total phosphorus values for the tributaries listed in 
Table 2 ranged from .30 to .77 mg/1, with the exception of the Alafia 
River and Delaney Creek which had mean values of 2.4 and 2.7 mg/1. For 
the remaining tributaries, phosphorus values were highest for those 
systems which have been impacted by urban runoff or point source 
discharges. Although affected by varying degrees of pollution, three 
river stations --Hillsborough at Fowler Avenue, Little Manatee, and upper 
Manatee-- probably represent the three least impacted sites listed in 
Table 2. Mean total phosphorus concentrations for these three stations 
ranged from .29 to .38 mg/1. 
The concentration of nitrogen species in tributaries to Tampa Bay 
is particularly important because evidence indicates that algal 
production in the bay is primarily nitrogen limited. With the exception 
of Delaney Creek, mean ammonia concentrations in Table 2 ranged from .05 
to .40 mg/1, with the highest values reported from tributaries receiving 
point source discharges (Rocky, Sweetwater) or large quantities of'urban 
runoff. As with total phosphorus, mean nitrate concentrations for the 
Alafia River (1.23 mg/1) and Delaney Creek (9.7 mg/1) were exceptionally 
high compared to other stations, which ranged from .06 to .63mg/l. 
Organic nitrogen values listed in Table 2 ranged from .34 to 2.1 
mg/1, with the highest values reported from Delaney Creek and two of the 
small urban creeks studied by Lopez and Giovannelli (1984). Mean organic 
nitrogen concentrations for the remaining non-tidal stations were less 
than 1.0 mg/1. Total nitrogen values were similarly highest for two of 
the urban creeks and Delaney Creek, but were also high for the Alafia 
River. With the exception of Delaney Creek and the Alafia and Little 
Manatee Rivers, organic nitrogen comprised the majority of mean total 
nitrogen, ranging from 56 to 87 percent. For Delaney Creek and the 
Alafia River, total nitrogen concentrations were strongly influenced by 
high nitrate concentrations, and organic nitrogen averaged 16 and 26 
percent of total nitrogen, respectively. 
Nutrient Loading Estimates 
Nutrient loading estimates can be calculated for tributaries where 
streamflow and water quality data are available. These estimates are 
valuable for they quantify nutrient loading to various portions of the 
bay and provide a measure against which to assess the impacts from 
stormwater runoff or point source discharges. However, due to the 
inadequacies of limited available data, nutrient loading estimates are 
42 
