Table 4. Mean annual 
(time weighted) 
flux rates (umoles m' 
V 1 ) of 
ammonia-nitrogen from selected U.S. 
sediments. 
east coast 
estuarine 
Water Bodv 
Temp 
SOD 
Source 
Hillsborough Bay 
111-573 
300 
COT, 1986b 
Patuxent Estuary 
0-1584 
295 
Boynton et al 
., 1980 
Neuse River Estuary 
71-454 
224* 
Fisher et al. 
, 1982 
South River Estuary, NC 
0-267 
113* 
Fisher et al. 
, 1982 
Narragansett Bay 
0-400 
100 
Nixon et al., 
1976 
Buzzards Bay 
2-124 
68 
Rowe et al., 
1975 
*Mean value (not an annual time-weighted average). 
The importance of Hillsborough Bay sediment nutrient fluxes can be 
assessed relative to the nutrient demands of water column primary 
production. Annual Hillsborough Bay phytoplankton production is 620 
gCm"2yr~l based on * 4 C measurements from 1978 to 1983 (Johansson, 
Steidinger and Carpenter 1985). Water column demands were estimated 
assuming that phytoplankton production accounts for nearly all primary 
production and that phytoplankton assimilate N and P in proportion to the 
Redfield C:N:P ratios of 106:16:1. Selected Hillsborough Bay ammonia and 
orthophosphate inputs expressed as a percent of N and P assimilated by 
phytoplankton are shown in Table 5. The sediments can support 34 and 140% 
of the phytoplankton N and P demand, respectively. The Alafia River, a 
major source of dissolved material to the bay, can only supply 0.3 and 
51% of N and P demand, respectively. The COT advanced wastewater 
treatment plant, often cited as a major point source of nutrients, can 
only supply a small fraction of the N demand and 25% of the P demand if 
no other sources were available. 
Table 5. Selected Hillsborough Bay nutrient inputs (NH 3 -N and PO 4 -P) 
expressed as a percent of N and P assimilated annually by 
phytoplankton. N and P assimilation by phytoplankton computed 
using the Redfield C:N:P ratios of 106:16:1. 
NH 3 -N PO 4 -P 
moles m^-yr 
% 
moles m^-yr 
% 
Phytoplankton 
7.8 
0.49 
Sediments 
2.68 
34 
0.67 
140 
Alafia River 
0.024 
0.30 
0.25 
51 
COT AWT Plant 
0.005 
0.06 
0.12 
25 
138 
