Total phosphorus Owing to the well-established fact that phosphorus is im- 



portant to phytoplankton growth, field observations of this nutrient were con- 

 tinued. The major features of phosphorus distribution were (1) the maximum 

 zone in upper Tampa Bay and (2) rapidly diminishing seaward concentrations. 



The monthly changes in total phosphorus show higher concentrations 

 (21. l->29.0 p.g. at. /L) in upper Tampa Bay during September and October after 

 hurricanes "Brenda" and "Donna" passed through Florida. Extremely high 

 total phosphorus concentrations (33. 3->33. 3 ^ig.at. /i) were recorded in March 

 throughout the waters of upper Tampa Bay. These high values were observed 

 during relatively strong onshore winds (20-25 m.p.h.), suggesting phosphorus 

 enrichment from stirring of bottom sediments. This supposition was verified 

 by phosphorus analysis of bottom sediments and supernatant water containing 

 bottom sediment. 



Total phosphorus was more than adequate for phytoplankton growth 

 in the waters of Tampa Bay and up to 10 miles offshore. Seaward from 10 

 miles offshore phosphorus concentrations rarely exceeded 1.0 |jig.at. /Land in 

 three instances were recorded as low as 0. 1 jig. at. /I. 



Nitrogen There w^as no apparent relationship between the incidence of G. 



breve and nitrate-nitrites. Comparatively low concentrations (0. 0-2. |ig.at./l) 

 of nitrate-nitrite nitrogen continued to persist in Tampa Bay and adjacent waters. 

 The concentrations of nitrate-nitrites during 1959, a year with heavy rainfalls, 

 were higher than during the period of this report. During this latter period 

 nitrogen varied from 0. 1 to 0. 5 fig. at. /l.in 87. 2% of the samples; in 6. 1% of 

 the samples the concentrations varied from 0. 6 to 2. |j.g. at. /I,, while in 6. 8% 

 of the samples there were no measurable quantities. Atypical of the nitrate- 

 nitrites distribution usually observed in an estuary, there were no maxima 

 near the fresh-water end of Tampa Bay. Although some higher concentrations 

 of nitrate-nitrites were noted during the fall, winter, and early spring months, 

 the seasonal distribution pattern continued to be very irregular. The greatest 

 depletion occurred during July, when in 20. 8% of the samples the nitrate- 

 nitrites were completely exhausted. 



Concentrations of ammonia ranged from 0.0 to 30.0 jxg.at. /I. Dur- 

 ing the first 11 months (April I960 - March 1961) the spatial distribution of 

 ammonia shows concentrations in upper and central Tampa Bay two to three 

 tinnes higher than in the offshore waters. 



From April I960 to the present, 241 inorganic nitrogen and organic 

 nitrogen determinations have been performed on filtered sea water. In Decem- 

 ber I960, experiments showed that the HA millipore filters used in micro- 

 filtration were adding erratic amounts of a substance which reacted with the 

 sodium phenate reagent to give an erroneous color development. Since January 

 1961, all determinations have been made on unfiltered sea water. Total inor- 

 ganic nitrogen in unfiltered samples varied from 0. to 6. 7 |j.g.at. /I. while total 

 organic nitrogen ranged from 3.7 to 30.9 H-g*^t. /I. Total organic nitrogen ex- 

 ceeded total inorganic as a rule and represented 87.4% of the total. The lon- 

 gitudinal distribution of total nitrogen indicates existence of maximum values 

 in Tampa Bay with a decreasing trend seaward. In contrast to the low levels 

 of nitrate-nitrite nitrogen, the observed concentrations of ammonia and total 

 nitrogen are comparable to those of other marine areas of the world. 



67 



