KAPLAN, WELKER, and KRAUS; EFFECTS OF DREDGING 



GOOSE CREIKN.Y. 



Figure 9.— Isopleths of NO3 concentration in ug at. NOg-N/liter, 

 wind coming from the southern quarter. (Redrawn from Hair, 

 1968). 



GOOSf CREEK NY. 



Figure 10. — Depths of sediment below mean low water in 

 meters. Data taken from Suffolk County map dated 4/5/67. 



necessary to overcome the inertia of the sediment 

 particles as well as associated bacteria. 



Further substantiation of the hypothesis that 

 sediment distribution in Goose Creek was affected 

 by wind-driven currents can be obtained from 

 an examination of Figure 10. Depth of the sedi- 

 ment increases in a north-south direction, irre- 

 spective of the probable contour of the basin. 



Table 6 tabulates the number of 3-hourly 

 records of winds at or above 15 mph for 1967. 



Suspension of fine sediments during dredging 

 occurred during the months of least occurrence of 

 high winds (July- August). The absence of strong 

 winds would tend to minimize the distribution of 

 suspended sediment but it also prevents the re- 

 moval of the canopy of flocculent material 

 observed covering the Enteromorpha and Ruppia 

 stipes and leaves during and after dredging. 



Flemer et al. (1968) suggest that late fall is 

 the season which would be most desirable for 

 dredging, since benthic animal populations are 

 lowest then. On the other hand, the months of 

 November and December are characterized by 

 frequent windy days and any disturbance of the 

 sediment would be accentuated by wind-driven 

 currents. Saila, Polgar, and Rogers (1968) 

 describe summer surface and bottom current pat- 

 terns which caused maximum harmful effects of 

 dumped dredged sediment. Such factors as water 

 depth, contour of basin, and wind- and water- 

 driven currents must be studied further to deter- 

 mine the optimal season for dredging. 



Mercenaria Survey 



Mercenaria mercenaria is exploited commer- 

 cially in Goose Creek and it supports a substantial 

 sport fishery. Both before and after dredging, 

 from two to four commercial clammers regularly 

 visited the creek. In 1968, less than a year after 

 the dredging, two clammers were interviewed 

 regarding changes in the productivity of clams 

 over the interval of the dredging operation. They 

 reported that there was no substantial difference 

 in the size of their catch which, according to the 

 local conservation officer, was 4-5 bushels of clams 

 per day. 



Apparently there was no mass mortality of 

 clams resulting from the release of flocculent and 

 suspended material into the water as a result 

 of dredging. 



Four major clam producing areas of the bay 

 were sampled before and after dredging, on 8 

 July 1967 and 4 July 1968 (dredging was com- 

 pleted on 2 August 1967 (see Figure 11)). 



Table 6. — Number of days of at least two recordings of winds 

 over 15 mph by months (recordings taken at 3 h intervals), 1967. 



457 



