capacity. Here the endpoint is defined as an unacceptable disturbance to the 

 community of marine organisms. The waters of the Southern California Bight have 

 successfully accommodated the waste discharges from the highly industrialized and 

 populated (11 million people) adjacent land areas for the past 20 years without 

 unacceptable effects as determined by studies on the marine plant and animal com- 

 munities. The most important sources of pollutants are five large municipal waste- 

 water outfalls that discharge about 8 billion 1/day (2 billion gal/ day). Increased 

 amounts of metals and nutrients are evident in the Bight waters, as well as in the 

 sedimentary records. Amounts of organic particulates have also risen as a 

 consequence of sewage discharges. These organic phases appear to be incorporated 

 into the planktonic food web without impact. 



In two of the studied areas, Puget Sound and the New York Bight, there is evi- 

 dence that the assimilative capacities for some substances may have been reached or 

 exceeded. 



Twenty million persons live in the lands adjacent to the New York Bight. It is one 

 of the most intensively used coastal regions of the world. Its assimilative capacity for 

 dumped excavation dirt and construction debris was exceeded in the late 1800s and 

 shoaling of the channels interfered with the passage of ships. Four pollutants were 

 examined for their potential effects upon the Bight: microorganisms, nitrogen- 

 containing biostimulants, polychlorinated biphenyls, and cadmium. Of these, only 

 cadmium appeared to have reached unacceptable levels. For this metal, an endpoint 

 of 5.00 ppb in marine waters has been proposed on the basis that, at this 

 concentration, some oysters accumulate enough of the metal to nauseate human 

 oyster eaters. The highest estimates of cadmium now present in the waters are 

 substantially lower than this amount. Nevertheless, a model using reasonable 

 partition coefficients between shellfish and suspended sediments indicates that 

 organisms growing in heavily contaminated dredge spoils might exceed safe limits 

 for their body burdens of cadmium. 



Puget Sound receives about 25 percent of the wastewater from the municipal treat- 

 ment plant (METRO), which discharges between 470 and 1,279 nr (61 1 and 1,675 

 yd 3 )/ day. There is some evidence that the recent toxic dinoflagellate blooms in the 

 central basin may be related to these discharges as may one incident of oyster larvae 

 mortality. In previous years, pulp mill discharges caused depressions in oxygen 

 concentrations, changes in the structure of benthic communities, and toxic effects 

 upon marine organisms. Increased and effective treatment facilities, combined with 

 a leveling off in activity, has resulted in reduced environmental stresses. 



ENDPOINTS 



In pollution monitoring, the endpoints have usually involved a single substance or 

 a collective of similar substances such as the polychlorinated biphenyls or DDT and 

 its degradation products. Exposure levels in seawaters are generally determined 

 indirectly, primarily through the use of sentinel organisms, although concentrations 

 in waters have been directly determined. For a determination of the assimilative 

 capacity, often the material to be discharged contains a variety of pollutants, the 

 analyses of which would be extremely costly. It appears that impacts of such 

 materials upon the well-being of marine organisms can provide endpoints, especially 

 those upon animal health. Some biological effects are already well established, while 

 others will require further assessment. 



Bivalves, especially mussels, have several attributes for use as indicators of general 

 biological stress. First of all, they are cosmopolitan, and often a given species can be 

 found over a wide latitudinal spectrum. Secondly, they are sturdy creatures and can 

 endure considerable physiological or biological stress without mortality. Still, when 

 adaptive mechanisms fail to respond, a measurable impact may be found. A 

 sampling of such impacts taken from Bayne et al. (1980) will be cited in the following 

 paragraphs. 



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