NOAA PROFESSIONAL PAPER 11 



Table 16-1 — Major benlhic mortalities and poteimally important associated environmental factors. 1966-76 



Environmental factor 



1966 



1967 1968 1969 1971) 1971 



1972 



1973 1974 1975 1976 



High Hudson River discharge' . . . . 



Early formation of density 



stratification- . . . . 



Late breakdown of density 



stratification- x 



Persistent southerly winds' . . . . 



Large ocean dumping inputs'' . . . . 



Reversals of summer bottom currents' ? 



Extensive C. tripos bloom'' ? 



Total number per year: 1 



Major benthic mortalities observed . . 



.... X X X 



X 



X X 



X X X X 



.... X X X X X 



' Years when the mean flow for February, March, and April exceeds the mean of record for these months by 1 standard error. Data from U.S. 

 Geological Survey 



- From Armstrong (ch. 6 ). 



' Years when the southerly component of wmds from April through September exceeded the resultant mean for April through September 1966-75. 

 Data from National Oceanic and Atmospheric Administration, Environmental Data and Information Service, National Climatic Center. 



' Years when ocean dumping (sewage sludge, dredge material, and acid waste) input in terms of BOD, exceeded the mean for the 1965-76 period. 

 Data from U.S. Environmental Protection Agency, Region II. 



* Years when major current reversals below the pycnocline were observed on ihe continental shelf during summer. Negative inferences from sources 

 as follow: Bumpus 1969. Patchen et al. 1976, NOAA 1976. 



" Information from Walsh et al (in preparation). 



A relation between the persistent southerly and 

 southwesterly winds and the interruption of the expected 

 southwestward flow of bottom water over the New Jersey 

 shelf is noted (Mayer et al. ch. 7). In 1976 the spring 

 southward flow at 100 km offshore was considerably less 

 than in 1975, whereas the alongshore component on the 

 inner shelf (50 km offshore) was reversed, flowing north- 

 ward from mid-May through July. 



During most of June the net flow near the bottom was 

 to the northwest along the New Jersey coast into the Bight 

 Apex, with strong onshore components, associated up- 

 welling (ch. 8), and intensified flow up the Hudson Shelf 

 Valley. This flow, particularly in the latter half of June, 

 transported oxygen into the oxygen-depleted area. The 

 same flow would, in all likelihood, also have transported 

 C. tripos into the area and perhaps led to accumulation 

 of this organism in coastal waters, despite its low doubling 

 rate (ch. 9, pt. 1). The overall effect of the inferred ac- 

 cumulation of C. tripos would be to provide the high net 

 utilization of oxygen calculated by the model — calculated 

 to be 3 to 10 times larger in the Apex and New Jersey 

 coastal segment than in other segments of the Bight. 



C. tripos were observed to accumulate at the base of 

 the pycnocline, which was below the photic zone (1% to 



3% light level). Because photosynthetic processes were 

 reduced at these depths, the C. tripos organisms possibly 

 were living heterotrophically (depending upon external 

 sources of organic substances for food and energy), 

 thereby using oxygen through respiration (ch. 9. pt. 1). 

 This bloom in May and early June could have been main- 

 tained by the large concentration of particulate organic 

 material in the nearshore waters from the large Hudson- 

 Raritan estuary discharge during spring, which may ex- 

 plain the absence of elevated nutrients and carbon con- 

 centrations in the water column (ch. 4). The stratiflcation 

 of nearshore waters and possible reduction of particulate 

 organic material with the concomitant reduction in Hud- 

 son River discharge may have limited the availability of 

 nourishment for continued growth of C. tripos below the 

 pycnocline during late June. As a result, the bloom de- 

 clined rapidly during July and created an area of organic 

 floe at the bottom, corresponding to the area of depressed 

 D.O. in bottom waters. 



Respiration of C. tripos (ch. 9, pt. 1) plus benthic res- 

 piration (Thomas et al. 1976) can be determined and com- 

 pared with the net utilization of oxygen as calculated by 

 Han et al. (ch. 8) for segments of the Bight. The respi- 

 ration rate of a single cell of C. tripos is given as 1,4 x 



340 



