KAPLAN, WELKER. and KRAUS: EFFECTS OF DREDGING 



maximum values for the dye and, therefore, a 

 comparatively low exchange rate. 



Dissolved Nutrients 



Fazio (1969) and Hair (1968) studied the dis- 

 tribution of certain nutrients in Goose Creek 

 before and after the dredging operation. The 

 results of their investigations are summarized 

 in Table 3 and fluctuations in pre- and post- 

 dredging concentrations of chlorophyll a, silicate, 

 dissolved organic phosphate, and nitrite are 

 depicted in Figure 6. 



Fazio reported that there were significant 

 changes in the values of particulate phosphorus, 

 silicates, and chlorophyll a as a result of the 

 dredging. He demonstrates high correlations 

 between particulate phosphorus and chlorophyll 

 a {r = 0.83), but is unwilling to suggest a direct 

 relationship between this nutrient and phy- 

 toplankton productivity. 



Instead, he explains the congruent increases in 

 particulate phosphates and chlorophyll a as either 

 a suspension of living benthic organisms intro- 

 duced into the water by the disturbance of the 

 sediment, or resuspension of detrital material 

 and/or land runoff. Analysis of the water near 

 a leaking spoil area revealed great amounts of 

 particulate phosphorus and chlorophyll a were 

 being added to the water column. 



The distribution of silicates was shown to be 

 related to the dredging process since highest 

 readings were associated with stations in the 

 vicinity of the dredge pipe and spoil areas; these 

 high readings shifted down the bay following the 

 movements of the dredge. There was, however, a 

 low positive correlation between silicates and 

 chlorophyll. Coupling high concentrations of 

 chlorophyll a with extreme turbidity and very 

 low light penetration in the vicinity of the dredge, 

 Fazio (1969) concludes that the chlorophyll is not 

 necessarily an indicator of the presence of 

 phytoplankton, since the opacity of the sediment- 

 laden water would prevent photosynthesis and 

 limit phytoplankton production. Instead, he sug- 

 gests that plant detritus in the spoil runoff is the 

 main source of the high chlorophyll a readings 

 and that phytoplankton populations might be 

 very low. 



Examination of Figure 6 reveals a second high 

 in chlorophyll a readings in December 1967- 



GOOSE CREEK, NY. 



Figure 5. — Rhodamine B residues in ppm on day of adminis- 

 tration and after 6 weeks. Figures in parentheses represent the 

 later readings. (Drawn from data from Black, pers. comm.) 



January 1968. This corresponds with a second 

 dredging which occurred from 22 December 1967 

 to 12 April 1968 in the western quarter of the 

 bay. The picture is very much like that of the 

 first dredging. A similar peak chlorophyll a read- 

 ing occurred at the onset of dredging followed by 

 a sustained high yield throughout the late 

 winter and early spring. Mean chlorophyll a 

 readings for the months of December 1967 to June 

 1968 are consistently two to five times those of 

 the comparable 1966-1967 period. Resolution of 

 the problem of whether the chlorophyll readings 

 represent an increase in phytoplankton or are 

 artifacts resulting from runoff will be decided 

 when Cassin publishes his analysis of the phy- 

 toplankton cycle 1967-1968. 



Table 3. — The fluctuations in certain dissolved and particulate 

 nutrients in Goose Creek, 1966-1968. 



Nutrients 



Mean concentration 

 1966 (Hair) 



Mean concentration 

 1967 (Fazio) 



453 



