bottom nitrite, 3.55; surface orthophosphate, 6.90; bot- 

 tom orthophosphate, 6.14. 



In April 1973, ammonium concentrations (Figs. 22, 23) 

 were much lower at Throgs Neck than during the pre- 

 vious summer, and the decrease moving eastward was 

 much less marked, with values at the eastern end slightly 

 higher than for Cruise 1. Nitrate levels (Figs. 24, 25) were 

 somewhat above those measured on Cruise 1, with ex- 

 tremely high concentrations (to 41.6 jigat/liter) at the 

 mouth of the Connecticut River during this period of 

 high runoff. Orthophosphorus (Figs. 26, 27) was low and 

 uniform, varying between 0.4 and 1.0 Mgat/liter except for 

 values of 1.0 to 2.7 from Hempstead Harbor west. Ni- 

 trite (Figs. 28, 29) was lower than the previous summer; 

 large portions of central and eastern LIS contained <0.1 

 Mgat/liter. 



On Cruise 2 we added urea determinations to our nu- 

 trient measurements in tm effort to better determine the 

 effects of sewage additions on LIS's nutrient patterns. 

 Urea concentrations in April 1973 (Figs. 30, 31) were 

 found to be < 1 ^gat/liter for most of LIS. As expected, 

 the higher values were found in the western end, again 

 most noticeably from Stamford and Hempstead Harbor 

 west. The maximum concentration was 3.24 ^gat/liter at 

 Throgs Neck. This was somewhat higher than that 

 measured by Hardy (1972b) in this area in April 1971. 

 Hardy found that urea concentrations continued to in- 

 crease in the East River, with a maximum of >6 

 /igat/liter in the lower river. 



The Connecticut River and its plume into LIS had ele- 

 vated urea concentrations as did a large area roughly be- 

 tween Bridgeport, New Haven, and Port Jefferson. 



Dissolved Oxygen 



Dissolved oxygen (DO) levels showed a strong inverse 

 relationship to nutrient concentrations in summer 1972. 

 Surface DO's (Fig. 32) were depressed, and bottom 

 concentrations (Fig. 33) markedly so, in extreme west- 

 em LIS. Surface values were >7 mg/liter through most of 

 eastern and central LIS. DO declined sharply from 

 approximately Hempstead Harbor west, falling from 8 to 

 <3 mg/liter within 7 n.mi. Lesser DO depressions were 

 evident off the Saugatuck River and in the areas of 

 Bridgeport, New Haven, New London, and Huntington 

 Bay (stations 22, 26). A significant feature of surface DO 

 distributions was the appearance of supersaturated areas 

 off Hempstead Harbor, Stamford, and between Bridge- 

 port and Port Jefferson. Hardy and Weyl (1971) reported 

 similar findings for August 1970. They attributed the 

 observed pattern to phytoplankton blooming in re- 

 sponse to the high nutrient levels in this area. West of the 

 DO maxima, phytoplankton standing crops may be 

 reduced by inhibition from East River sewage effluents 

 (Hardy 1972b), or perhaps by light limitation or a neces- 

 sary incubation period prior to blooming. 



Bottom DO's (Fig. 33) were above 5 mg/liter for most 

 of the central basin, and >7 in the eastern sector. They 

 fell below 5 mg/liter in deep waters west of New Haven, 

 <4 mg/liter west of Stamford, and <3 mg/liter past 



Hempstead Harbor. There were scattered areas of still 

 greater depletion, with 1.7 and 1.8 mg/liter at two sta- 

 tions (9 and 10) in the Hempstead Harbor area, and 1.7 

 near the mouth of the Saugatuck River (station 27). Low 

 oxygen levels in western LIS bottom waters during sum- 

 mer have been reported previously (Hardy and Weyl 

 1971). An earlier survey of this area (National Marine 

 Fisheries Service") revealed the entire western end to 

 have its lowest bottom DO's (1.0 mg/liter at Throgs 

 Neck; 0.7 at Hempstead Harbor's mouth) coincident 

 with highest summer temperatures. In the present sur- 

 vey, the Connecticut shoreline in the Bridgeport-New 

 Haven region also showed somewhat depressed bottom 

 DO. 



The low DO's described above are of course a seasonal 

 phenomenon. In April 1973, after a lengthy period of cold 

 temperatures and wind-generated mixing, DO's had 

 risen above 10 mg/liter for the entire Sound (Figs. 34, 35). 

 Our September 1973 data (Figs. 36, 37) indicate the 

 rapidity with which oxygen levels in the western Sound 

 can change. Samples taken on 12 and 13 September 1973 

 again revealed the characteristically low values associ- 

 ated with western LIS during the warmer months. Two 

 weeks later, however, bottom DO's had increased to >5 

 mg/liter at Throgs Neck and >6 everywhere else. This 

 dramatic improvement was again probably related to 

 wind-generated mixing. Hardy and Weyl (1971) agreed 

 that winds can have a controlling effect on DO concen- 

 trations in western LIS. 



Sediments 



Figure 38 shows distribution of silts and clays ( <62 tim 

 diameter) in surface sediments for summer 1972, based 

 on means of two cores analyzed per station. Sediments 

 over large portions of central and western LIS, especially 

 in deeper waters but also along portions of the Connecti- 

 cut coast, consist predominantly of fine materials (50- 

 95% silt/clay). These soft-bottom areas are interrupted 

 by strips or patches of coarser sediments in several parts 

 of LIS, generally corresponding to shoaler areas. Coarser 

 materials (<5% silt/clay) are also found in shallow areas 

 for the entire length of the Long Island coast. The rela- 

 tively coarse sediments extend into deeper waters (17-26 

 m) atop Mattituck Sill, a submarine ridge separating 

 eastern LIS from the remaining two-thirds of the Sound 

 (Hardy 1972b). The well-flushed eastern basin has most- 

 ly coarse sediments. 



Sediment Heavy Metals, Microorganisms 



As mentioned earlier, distributions of sediment heavy 

 metals and fecal coliform bacteria have been described 

 elsewhere. To summarize: heavy metal and coliform dis- 

 tributions were in general agreement with the distribu- 

 tions of nutrients and dissolved oxygen described above. 



'National Marine Fisheries Service. 1972. Davids Island Phase I; A 

 short-term ecological survey of western Long Island Sound. Middle 

 Atlantic Coastal Fisheries Center, Informal Rep. 7, 29 p. 



