Oxygen Depletion and Associated Benthic Mortalities 

 in New York Bight, 1976 



Chapter 11. Impact on Clams and Scallops 



Part 2. Low Dissolved Oxygen Concentrations and 

 Surf Clams — A Laboratory Study 



Frederick P. Thurberg and Randolph O. Goodlett' 



CONTENTS 



Page 



211 Introduction 



277 Methods 



278 Results 



279 Discussion 



280 Summary 



' Milford Laboratory, Northeast Fisheries Center, 

 National Marine Fisheries Service, NOAA, Milford, CT 

 06460 



INTRODUCTION 



Most aquatic organisms can use several aerobic or an- 

 aerobic metabolic pathways to obtain energy (Davis 1975). 

 Oysters become facultative anaerobes under low dissolved 

 oxygen (D.O.) conditions and are thus able to withstand 

 low D.O. for extended periods of time. (Hochachka and 

 Mustafa 1972). Modiolus demissus. Mytilus editlis, and 

 Rangia ciineata are other bivalves capable of sustaining 

 energy production during low oxygen conditions by shift- 

 ing away from oxygen-dependent pathways (Hammen 

 1969; Rossi and Reish 1976). The tolerance of bivalves to 

 low D.O. conditions varies with other environmental fac- 

 tors, however, and temperature seems to be very critical 

 to some species' survival (Theede et al. 1969; Vernberg 

 1972). 



The surf clam (Spisula solidissima) is able to endure low 

 levels of oxygen in the environment for extended periods, 

 because these conditions persisted for months along the 

 New Jersey coast without a complete loss of the surf clam 

 population (an estimated 25% of the offshore stocks were 

 lost). Our study was designed to test the range of this 

 animal's tolerance to low oxygen conditions. We also de- 

 termined the effect of such conditions on metabolic activ- 

 ity by measuring whole-animal oxygen-consumption rates 

 after exposure to various low concentrations of D.O. This 

 report, therefore, provides experimental confirmation of 

 several aspects of surf clam physiology that previously 

 could only be assumed or extrapolated from published 

 information on other species. 



METHODS 



The large surf clams (6-12 cm long) used in this study 

 were collected by hand from shallow beds in coastal waters 

 near Point Judith, R.I. The small clams used in this study 



277 



