Oxygen Depletion and Associated Benthic Mortalities 

 in New York Bight, 1976 



Chapter 10. Biological Processes: Productivity 



and Respiration 



James P. Thomas, Jay E. O'Reilly, Andrew F.J. Dra.xler. John A. Babinchak, 

 Craig N. Robertson, William C. Phoel, Ruth 1. Waldhauer, Christine A. Evans, 

 Albert Matte, Myra S. Cohn, Maureen F. Nitkowski, and Shearon Dudley^ 



CONTENTS 



Page 



231 Introduction 



231 Methods 



233 Hydrographic and Nlitrient 



Conditions 



239 Organic Carbon and Ph-itoplankton 



244 Phytoplankton Productivity 



247 Contributions to the DOC Pool 



247 Oxygen Consumption 

 247 In the Water Column 



249 By the Seabed 



252 Net Oxygen Depletion and 



Utilization Rates 



252 Anaerobic Metabolism 



255 Probable Organic Carbon Sources 



257 Expanded Apex Hypothesis 



258 Summary 



260 Acknowledgments 



260 References 



' Sandy Hook Laboratory, Northeast Fisheries Cen- 

 ter, National Marine Fisheries Service, NOAA, High- 

 lands, NJ 07732 



INTRODUCTION 



This chapter describes the distribution and magnitude 

 of biological processes in the water column and on the 

 seabed in the New York Bight in August-September 1976. 

 Whereas most previous chapters dealt with the establish- 

 ment of oxygen depletion, this chapter discusses processes 

 occurring about 2 months after the onset of the peak an- 

 oxic condition. Major emphasis is placed on primary pro- 

 ductivity and dissolved oxygen (D.O.) utilization in the 

 water column and on the seabed. 



METHODS 



From August 24 to September 9, 1976, measurements 

 were made of primary production, rates of oxygen con- 

 sumption in the water-column and on the seabed, and of 

 concentrations of nutrients, organic carbon, phytoplank- 

 ton, chlorophyll a, and bacteria (fig. 10-1). Most of the 

 data are presented in Thomas et al. (in press). 



Large-volume (20-30 1) Niskin bottles were used to 

 collect all water samples. Five to nine depths in the water 

 column were sampled, based on profiles of temperature, 

 chlorophyll-fl fluorescence, and photosynthetically active 

 radiation (PAR; 400-700 nm). A bottom-tripping Niskin 

 bottle collected water 20 to 50 cm above the bottom. Ex- 

 pendable bathythermographs (XBTs) and reversing ther- 

 mometers were used simultaneously to measure temper- 

 ature at all stations. A submersible pump was used to 

 obtain vertical profiles of in vivo chlorophyll-a fluores- 

 cence. A Lambda submersible quantum photometer was 

 used to determine extinction of PAR. 



Salinity was measured with a Beckman RS 7-C induction 

 salinometer. Alkalinity, sulfide, pH, ammonium, and par- 

 ticulate organic carbon were determined using methods 

 described by Strickland and Parsons (1972). Seawater 



231 



