3-35 



cycle (Figure 3-9) . Peak levels occurred in January and February (up to 

 14.0 to 15.0 mg/1) ; values then declined to minimum levels in July, 

 August, and September and returned to peak values by December. The most 

 unfavorable dissolved oxygen conditions occurred at the confluence of 

 the Mill and Quinnipiac Rivers, but all three of the innermost stations 

 (Stations 1, 2 and 3) had numerous dissolved oxygen readings in the 

 unacceptable (<4.0 mg/1) range. 



pH Distribution 



Average pH in New Haven Harbor was 7.6, with a maximum of 9.7 

 and a minimum of 6.0 (Figure 3-10). There are no indications that 

 fluctuations of pH are correlated with depth, tidal phase, or station 

 location. Because of the considerable neutralizing potential of the 

 saline waters, pH is generally an insignificant factor in the ecology of 



New Haven Harbor. 



\ 



Summary data from Station 3 , representing conditions in the 

 inner harbor from 1971 through 1911 , show mean values between 6 and 9 

 (Figure 3-10) . Flood-tidal conditions have tended to be quite uniform 

 with slightly lower values near the surface than near the bottom. Ebb 

 tidal conditions showed more variability, with readings in July 1975 as 

 low as 6.0. 



Waters in the outer harbor at Station 20 showed average pH 

 values between 7 and 9 (Figure 3-10) . At this location, there is little 

 variation between flood-tidal and ebb-tidal conditions, but near-surface 

 values tend to be slightly higher than near-bottom values. 



Continuous measurements from the Honeywell Water Quality 

 Monitor located on the pier off the New Haven Harbor Station showed 

 little variation in pH on both a daily and seasonal basis. Because of 

 its uniformity, pH does not appear to have been an important controlling 

 parameter in New Haven Harbor. 



(Text continued on page 3-41) 



