Oxygen Depletion and Associated Benthic Mortalities 

 in New York Bight, 1976 



Chapter 9. Plankton Dynamics and Nutrient 



Cycling 



Part 1. Water Column Processes 



Thomas C. Malone,^ Wayne Esaiasr and Paul Falkowski^ 



' Lamont-Doherty Geological Observatory, Palisades. 

 NY 10964 



^ Marine Sciences Research Center, State University 

 of New York, Stony Brook, NY 11794 



^ Oceanographic Sciences, Brookhaven National Lab- 

 oratory, Upton, NY 11973 



INTRODUCTION 



An extensive bloom of the dinoflagellate Ceratium tri- 

 pos (O. F. MiJller) Nitzsch developed throughout the 

 Middle Atlantic Bight (between 36° N, 41° N. and the 

 continental shelf break) from January through July 1976. 

 By late June-early July an oxygen minimum layer (<2.0 

 ppm) had developed below the thermocline between the 

 20- and 40-m isobaths off the New Jersey coast from At- 

 lantic City to Sandy Hook. (See chapter 2.) Local anoxic 

 conditions were most widespread east of Barnegat Inlet 

 (39° 45'N) in early July and east of Great Bay (39° 30'N) 

 by late July. Presence of this subthermocline oxygen min- 

 mum layer and associated sulfide production apparently 

 resulted in mass mortalities of demersal fishes and benthic 

 invertebrates. (See chapter 12.) 



The occurrence of the C. tripos bloom and the subse- 

 quent development of the oxygen minimum layer led to 

 the hypothesis that C. tripos was involved in generating 

 the biological oxygen demand (BOD) required to produce 

 the oxygen minimum. In an effort to clarify the role of C. 

 tripos, this paper addresses these questions: 



1. What was the areal extent of the bloom and the 

 time course of its development? 



2. What were the most likely causes of the bloom and 

 its collapse? 



3. What were the effects of the bloom on the distri- 

 bution of organic matter and dissolved oxygen? 



For this discussion, the New York Bight was divided 

 into five regions (fig. 9.1-1); 1) Long Island coastal area, 

 2) New Jersey coastal area (<20 m deep within 5 km of 

 the coastline), 3) lower Hudson estuary (including Upper 

 and Lower Bays of New York Harbor), 4) the Apex 

 (bounded by 40° lO'N and 73° 30'W), and 5) the outer 

 Bight (south and east of the Apex to the shelf break be- 

 tween Montauk Point and Cape May). 



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