Table 23-3. New Nutrient Input Versus Oceanic Advection 
from the Southeast Sector (+ is in) (thousands of moles/day) 
Process 
Nutrient 
Sewage 
Streams 
Advection 
Imbalance 
Fixed inorg. N 
+ 15.8 
+2.0 
-0.6 
Dissolved org. N 
+13.5 
+1.0 
-3.6 
Particulate N 
+ 1.2 
+1.2 
-4.5 
Total N 
+30.5 
+4.2 
-8.7 
+26.0 
Inorg. P 
+ 2.6 
+0.2 
-1.0 
Dissolved org. P 
+ 0.7 
+0.1 
i 
o 
CJ 
Particulate P 
+ 0.1 
+.01 
-0.5 
Total P 
+ 3.4 
+0.4 
-1.8 
+ 2.0 
low-density plume which flows northwestward from the sewer outfall. 
Nevertheless, either this simple mixing model underestimates advective losses 
by two-three fold, or there are additional budgetary terms to be considered. 
The budget can be further amplified. There is uptake of nutrients by 
planktonic and benthic algae, and subsequent cycling of these particulate 
materials within the food web. There is fallout of particulate organic material 
to the lagoon floor and nutrient release from the lagoon floor back into the 
water column. We have obtained nutrient release rates, gathered over one year 
by using 1-meter diameter Plexiglas hemispheres as in situ incubation 
chambers, and we can solve for fallout by difference between nutrient inputs 
and outputs (Table 23-4). The advective flux of nutrients from the southeast 
sector equals 30-50 percent of the nutrient inputs from terrigenous sources. 
The fallout of particulate nitrogen substantially exceeds terrigenous nitrogen 
inputs to the southeast sector. The high nitrogen fallout is maintained by rapid 
nitrogen release from the sediments. Particulate phosphorus fallout is also high, 
although it does not quite exceed terrigenous inputs. As with nitrogen, the 
rapid phosphorus fallout is maintained in large part by nutrient release from 
the sediments. The steps from stream plus sewage input to particulate fallout 
to release from the sediments show a progressive increase in the N:P ratio 
(9-*14->18). Material advected from the southeast sector is proportionally low 
in nitrogen (N:P « 5), largely reflecting the virtually complete uptake of 
dissolved inorganic nitrogen from the water. 
353 
