3-34 



cycle was very similar. At this station, the lowest salinities occurred 

 in March and April and the highest in July, August, and September. 

 Lowest near-surface temperatures were observed in January and February 

 whereas the highest occurred in July. Month-to-month temperatures 

 between flood and ebb have been quite similar, but ebb-tidal salinities 

 were 2 to 6 ppt fresher than flood-tidal conditions (Figure 3-8) . 



The waters of the outer harbor at the periphery of Long Island 

 Sound (Station 20) are much less variable from near-surface to near- 

 bottom and flood tide to ebb tide (Figure 3-8) . The annual cycle start- 

 ing in November showed relatively constant salinities and decreasing 

 temperatures through February. Temperatures then rose through July, 

 while salinities dropped to the lowest levels of the year in May and 

 August. Temperatures were relatively stable July through September, 

 then decreased with relatively constant salinity through October. Ebb- 

 tidal salinities tended to be about 1 to 2 ppt lower than flood-tidal 

 values . 



These data show that runoff from land drainage plays a major 

 role in driving circulation by establishing salinity gradients within 

 the New Haven Harbor estuary. The more saline, colder Long Island Sound 

 waters tend to intrude landward at depth. Some of this water mixes with 

 the near-surface waters at the head of the estuary and returns seaward 

 to complete the cycle. 



Dissolved Oxygen Distribution 



Dissolved oxygen (DO) is a critical factor affecting the 

 distribution and abundance of aquatic organisms in New Haven Harbor. 

 Variability of conditions within the Harbor is caused by the combined 

 influence of ambient temperatures and biological fluctuations, indus- 

 trial discharges, and sewage effluents. 



The physical/chemical studies for the New Haven Harbor Station 

 Ecological Monitoring Studies program have shown a pronounced annual 



