ranging from 14 to 26 ppt in the dry season to 0 to 19 ppt in the wet 
season (E.D. Estevez, pers. comm.). 
Virtually all of the Manatee River below its reservoir is tidal 1y 
affected and brackish water (>1,000 umhos) comes within three miles of 
the dam during the dry season. The zone of maximum mixing of fresh and 
salt water occurs from 9 to more than 18 river miles above the bay 
depending on seasonal flow. The river below the dam is characterized by 
moderately high nutrient levels, periodic algal blooms and seasonal 
problems with low dissolved oxygen. A study of this portion of the river 
by Manatee County and Camp, Dresser, and McKee, Inc. (1984) examined 
water quality in four ecological zones of the lower river. The zone 
nearest the mouth had the lowest concentrations of nutrients, 
chlorophyll, and coliform bacteria due to the flushing action of lower 
Tampa Bay, a region of the bay with good water quality. In the nine mile 
zone nearest the reservoir, average nutrient concentrations were 
moderately high, but maximum recorded levels of TKN (8.0 mg/1), ammonia 
(.33 mg/1), pH (9.1) and chlorophyll (60 ug/1) were very high, indicating 
occasionally poor water quality conditions. Instantaneous dissolved 
oxygen concentrations in this zone were periodically below state water 
quality standards (4.0 mg/1). 
Another area of the lower river that has periodic water quality 
problems is from the mouth of the Braden River downstream to the main 
bridge between the towns of Palmetto and Bradenton. The City of 
Bradenton’s wastewater treatment plant and a citrus processing plant 
discharge into this portion of the river, and these effluents may be also 
transported up the Braden River on flooding tides. Violations of state 
water quality standards were most numerous in this portion of the river 
with violations for dissolved oxygen concentrations being most common. 
Mean nutrient concentrations were moderately high (Table 2), but maximum 
concentrations of TKN (5.99 mg/1), ammonia (.54 mg/1), chlorophyll (182 
ug/1), and pH (9.37) were very high indicating periodic water quality 
problems. In general, water quality in the lower Manatee River is 
appreciably degraded and suffers from the effects of point source 
discharges, agricultural and urban runoff, and seasonally important 
streamflow reductions. 
Sarasota Bay 
To various degrees, all tributaries to Sarasota Bay have been 
channelized or otherwise modified to facilitate stormwater drainage. 
Water quality data are available for three of these tributaries including 
the two largest drainage systems, Whitaker Bayou and Phillippi Creek. 
Nutrient concentrations are very high near the mouth of Whitaker Bayou 
due to discharges from the City of Sarasota’s wastewater treatment plant 
(Table 2). The plant discharged an average of 8.3 mgd of secondarily 
treated effluent during 1987, but all discharge to the bayou is scheduled 
to be discontinued in late 1988. Phillippi Creek, which is highly 
channelized, similarly receives domestic wastewater discharges in 
addition to stormwater runoff. Nutrient concentrations, particularly 
those for nitrogen species, are high for the station listed in Table 2, 
41 
