Comparison Between Bay Areas 



Differences in nitrogen concentration be- 

 tween bay areas in each habitat were highly 

 significant (Table 6). Concentrations of nitro- 

 gen were highest in all habitats of Upper and 

 mid-Galveston Bays except in 1965 when the 

 concentrations in the channel habitat of East 

 Bay exceeded that in mid-Galveston Bay. 



Table 6.— Comparisons of annual mean concentrations 

 of dissolved organic nitrogen between bay areas 

 within each habitat in the Galveston Bay system, 

 1964-66. 



Areal distributions of nitrogen concentration 

 in the bay system are shown in Figure 9. An 

 isopleth was not drawn for 1966 because nitro- 

 gen was sampled at only 16 stations. The 

 greatest concentration of nitrogen was in the 

 Houston Ship Channel, and concentrations 

 decreased from Upper Galveston to Lower 

 Galveston Bay. The second major source of 

 nitrogen was the Intracoastal Waterway where 

 concentrations decreased from the eastern to 

 the western part of East Bay. The isopleths also 

 indicate the relative contribution of nitrogen 



ORGANIC NITROGEN 

 (/iG AT, /L) 



Figure 9. Isopleths (annual average) for dissolved 

 organic nitrogen in the Galveston Bay system, 

 1964-65. 



from the creeks snA bayous. The influence of 

 Gulf waters low in nitrogen was apparent in 

 Lower Galveston and East Bays. 



Comparison Between Years 



In general, nitrogen values were similar be- 

 tween years within each habitat of the 

 Galveston Bay system (Figure 10). Greatest 

 variations between years in the peripheral and 

 open-water habitats were in the spring and fall, 

 whereas the variations between years in the 

 channel were erratic. 



to 20 10 20 10 20 10,20 10 20 10 20 10 20 10 20 10 20 10 20 10 20 10 20 



JAN Ffe MAR APR MflV JUN JUL AUG SEP OCT NOV DEC 



Figure 10. Mean values of dissolved organic nitrogen 

 by date, habitat, and year in the Galveston Bay 

 system, 1964-66. 



Relation to River Discharge 



Nitrogen levels in the lower bays were more 

 closely correlated with river discharge from the 

 Trinity and San Jacinto watersheds than those 

 in the upper bays (Table 7). This may be 

 related to a rapid transport of upper bay water 

 high in nitrogen content into the lower bays 

 during the periods of high river flow. 



Table 7.— Correlation coefficients (r) between average 

 weekly stream flow and concentrations of dissolved 

 organic nitrogen, 1964-66. 



Nitrogen versus Trimly discharge Nitrogen ver 

 ^^^^ ^"""^^ Peripheral Open wai 



Channel Peripheral Open v 



East 37C* 



d._f. 67 



Trimiy -0 06 



d.i, 67 



iignidtance le\ el = h%. 



> Signilicance level = 1 



