declines in the Alafia River Basin. Even so, the north prong of the 
Alafia River had an annual average phosphorus concentration of 7.68 mg/1 
in 1984 (Boler 1986). 
Nitrate-nitrite-nitrogen concentrations were relatively low in 
1984, as in most years, with highest levels in Hillsborough Bay. Total 
Kjeldahl nitrogen concentrations were more uniform throughout the bay in 
the same year, with all but gulf stations with geometric means greater 
than 0.5 mg/1. (Ten-year trend analyses for nitrogen are unavailable 
because analytical methods changed in 1980.) 
Dissolved Oxygen 
In 1984 all mean annual bottom concentrations of dissolved oxygen 
were greater than 5.0 mg/1, except for McKay Bay, an arm of Hillsborough 
Bay. In the subsequent, wetter year of 1985, mean annual concentrations 
of dissolved oxygen at the bottom were less than 5.0 mg/1 along the 
western shore of Hillsborough Bay and the shallow waters of middle Tampa 
Bay. In general, bottom dissolved oxygen minima were greater than 
3.5 mg/1 throughout all of Tampa Bay except Hillsborough Bay (Figure 12), 
although conditions in Hillsborough Bay are improving (Figure 13). 
Table 2 summarizes extreme dissolved oxygen conditions in Tampa Bay and 
accentuates Hillsborough Bay as the area of greatest fluctuation. 
Table 1. Frequency {% total samples) of violations (<4.0 mg/1) and 
supersaturation of dissolved oxygen (adapted from Palmer 
and McClelland 1988). 
Area 
N 
% Violations 
% SuDersaturated 
Hillsborough Bay 
surface 
1421 
5 
61 
bottom 
1408 
20 
33 
Old Tampa BayZ 
surface 
1478 
0 
56 
bottom 
1479 
2 
45 
Middle Tampa Bay 
surface 
1126 
0 
66 
bottom 
1123 
3 
39 
Lower Tampa Bay 
surface 
946 
0 
72 
bottom 
945 
0 
59 
80 
