32 



3.2.6.1 Active Mounds 



Within the CLIS survey area, median OSI values ranged from 0.5 to 10. Lower 

 values predominate in the area of the two active mounds, CLIS-90 and CS-90-1 (Figure 

 3-18). OSI values were also less than +6 south of CLIS-89 and in the northwest area of the 

 survey. Where the median OSI value is +0.5, (southwest of CLIS-89) there appeared to 

 have been recent trawling or other physical disturbance. Between the original sixty-six- 

 station grid over the active mounds, and the reference areas, the OSI values were 

 significantly different (Figure 3-19; Mann- Whitney U-test, p< 0.001). 



3.2.6.2 Inactive Mounds and Reference Areas 



On the inactive mounds, FVP, MQR, and NHAV74, the OSI values were not 

 significantly different from the main REMOTS® survey area (Mann- Whitney U-test, 

 p=0.374, 0.512, and 0.513, respectively). At NHAV-74 and FVP, the OSI values were 

 greater than +6 for most stations. On the MQR mound, most OSI values fell between +1 

 and +3 cm. On CLIS-88 and CLIS-89, OSI values ranged from 4 to 11. The median OSI 

 values for the three reference areas were predominantly greater than OSI =+6 (Figure 3-20). 



3.3 Sediment Analysis 



3.3.1 Grain Size and Total Organic Carbon 



Grain size analyses were conducted on samples retrieved from the center of 2500W- 

 REF, 4500E-REF, and CLIS-REF (Table 3-1). All samples were dark grey clay-silt with 

 shell fragments. The percentage of sand versus silt/clay was similar for all the reference 

 areas. Of the silt/clay fraction, silt dominated at all three areas. Grain size results were 

 87% silt/clay and 13% sand for 2500W-REF and CLIS-REF. The sample from 4500E-REF 

 was 12% sand and 88% silt/clay. These results corresponded with the grain size major mode 

 determined by REMOTS® for 4500E-REF and CLIS-REF. The REMOTS® grain size 

 determination at the center of 2500E-REF, very fine sand (4-3 phi), was coarser than the 

 silt/clay determined by grain size analysis. REMOTS® stations 100 m away from the center 

 were consistent with the laboratory grain size analysis. The average percent TOC was 

 highest at 2500W-REF (1.05%), followed by 0.89% at CLIS-REF, and 0.83% at 4500E- 

 REF. 



3.3.2 Metals 



Cadmium (Cd), lead (Pb), and zinc (Zn) were detected at all three reference areas. 

 Values for cadmium ranged from 0.15 to 0.28 ppm; lead 51 to 76 ppm; and zinc 130 to 

 210 ppm. Replicate values were within approximately one standard deviation of the mean 

 (Table 3-2). The average values for Cd, Pb, and Zn were slightly higher at 2500W than at 



Monitoring Cruise at the Central Long Island Sound Disposal Site, June 1991 



