D. Some ConsIDERATIONS ON THE Errects or NATURAL AND MAn- 
Mapr Anoxic ConpDITIONS ON THE SURROUNDING ENVIRONMENT 
(By Kenneth Mopper, Woods Hole Oceanographic Institution) 
INTRODUCTION 
Nature has a tremendous capacity to recover from the abuses of domestic 
pollution so long as the rate of addition does not exceed the rate of recovery of 
the environment. When this limit is exceeded, however, the deterioration of the 
environment is rapid and sometimes irreversible—B. H. Kercuum. 
An anoxic condition in the marine environment occurs when the 
concentration of dissolved oxygen has diminished to zero. Processes 
leading to anoxic environments have been initiated either by nature or 
by man. This paper discusses these processes and also with the con- 
sequences of anoxic conditions on the surrounding environment. Stress 
is placed on ecological effects of the New York Bight waste and sewage 
sludge disposal area. The water directly above the sludge is rapidly 
becoming anoxic and no bottom life, with the exception of anaerobic 
bacteria, has been found. Possible dangers of heavy metals in the 
sludge to the surrounding environment are explained. 
PROCESSES LEADING TO ANOXIC CONDITIONS 
Natural 
Permanent natural anoxic conditions originate when the water circu- 
lation is restricted horizontally by a physical barrier (i.e., a sill) and 
vertically by either a strong halocline or pycnocline. Examples are: 
the Black Sea, the Cariaco Trench in the Caribbean, and Lake Nitinat 
on the coast of Vancouver Island, British Columbia. Figure 1 shows a 
plan view and a cross-section of Lake Nitinat. Although called a 
lake, it is in reality a fjord which has been cut off from the Pacific 
Ocean by a 2.7-kilometer long sill. Horizontal water circulation across 
the sill extends to depths of about 4 or 5 meters. Because the water 
circulation is restricted, the water in the lake below 30 meters is 
stagnant. Once the dissolved oxygen below this depth became con- 
sumed by biological processes, the water became anoxic. The anoxic 
zone is essentially abiotic; the only organisms capable of surviving are 
anaerobic bacteria (ZoBell, 1942). Photosynthetically produced organic 
debris rain down into the anoxic zone and collect on the bottom. Some 
of this organic matiter is oxidized by anaerobes via nitrate, sulfate, 
carbonate (or CO.), and phosphate reduction, in order of decreasing 
free energy (table 1). That is, most of the available dissolved nitrate is 
consumed before sulfate is reduced, and so on. Nitrate and sulfate 
reduction are the most important sources of oxygen for the anaerobic 
bacteria. Ammonia and molecular nitrogen are products of nitrate 
utilization, while hydrogen sulfide results from sulfate reduction. For 
details of these processes see: Richards (1965a, 1965b) ; Richards et al. 
(1965); Redfield, Ketchum, and Richards (1963); and Richards (1968). 
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