estuary was a net sink for Chloro- 

 phyll a though the reasons for this 

 were different in each case. During 

 high flow when advection from ad- 

 jacent coastal water was the main 

 source of Chlorophyll a, only a small 

 percentage of the input was lost in 

 the lower estuary (4%) (probably as a 

 result of sinking) . The rest was re- 

 cycled back into coastal waters (89%) 

 or further upstream (7%) . The lower 

 estuary was a sink with respect to 

 both the upper estuary and offshore 

 waters during low flow. The loss was 

 17 percent of total input. However, 

 the loss was the net result of the 

 active processes of growth (mean for 

 lower estuary low .Jilow by above cal- 

 culations 192 x 10 mg ChL a d~ ) and 

 grazing (mean 239 x 10 mg Chi a 

 d ). Thus phytoplankton dynamics 

 changed from a passive system of 

 advection and sinking during high 

 flow to an active system of growth 

 and grazing during low flow. 



ACKNOWLEDGEMENTS 



This research was supported by 

 NSF Grant OCE 76-80883 and OCE 80- 

 00677. Lamont-Doherty Geological 

 Observatory Contribution No. 3160. 



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