NOAA PROFESSIONAL PAPER 11 



(1976) reported that inorganic nitrogen drops to very low 

 levels between 20 and 50 km from New York Harbor. 

 However, Garside et al. (1976) indicated that inorganic 

 nitrogen probably does not limit chlorophyll-specific 

 growth rates of phytoplankton within the Bight Apex. 

 Therefore, the effect of additional large inputs of DON 

 would be to enlarge the area of high phytoplankton pro- 

 ductivity and biomass. 



During our survey, eutrophic concentrations of DIN 

 decreased from 33 jjlM/1 in Lower Bay to just above de- 

 tection at the outer perimeter of the Apex (50 km from 

 station 69). This means that by the Apex and beyond most 

 of the nitrogen in the water column is bound organically, 

 as autotrophic and heterotrophic biomass and as DON. 

 Despite the low euphotic DIN concentrations between 50 

 and 200 km from Lower Bay, we observed high rates of 

 organic carbon production. Although average chlorophyll- 

 a and POC concentrations decreased considerably (15:1, 

 8:1) from the estuary to the 50-m isobath, integral eu- 

 photic zone concentrations (per square meter) of chlo- 

 rophyll a and DOC decreased only slightly (table 10-1). 

 The total water column P/R ratios (fig. 10-13) decreased 

 from 3.5 in the Apex to 1.3 off Barnegat Inlet to 0.2 to 

 0.9 east of there and south offshore to Cape May. Thus 

 active regeneration of nutrients and recycling of carbon 

 had to occur to sustain the system as described above. 



Organic loading from the New York metropolitan area 

 during 1976 was superimposed on and may have aggra- 

 vated natural conditions leading to oxygen depletion (Se- 

 gar and Berberian 1976). Future research should evaluate 

 the stimulation of both production and decomposition 

 processes in the water column and on the seabed by DIN 

 and DON compounds in sewage wastes. One hypothesis 

 to evaluate is that the initial effects of sewage-derived 

 inorganic nitrogen is the stimulation of autotrophy in the 

 Bight Apex. The "unused" Apex DON compounds plus 

 the organic compounds photosynthesized in the Apex 

 stimulate heterotrophy. However, the full effect of this 

 heterotrophic stimulation (P/R<<1, and reduced oxygen 

 concentrations) is delayed in time and occurs down the 

 plume of the estuary, seaward of the Apex along the New 

 Jersey coast. 



SUMMARY 



Between August 24 and September 9, 1976, about 2 

 months after the onset of oxygen depletion, data con- 

 cerning primary production, water-column and seabed 

 oxygen consumption, nutrients, organic carbon, phyto- 

 plankton identification and abundance, chlorophyll ci, and 

 bacteria were collected to document conditions. Our find- 

 ings follow. 



1. A strong, deep (12-20 m) pycnocline was present. 



2. A subpycnocline low D.O. area with sulfide existed. 



3. Nutrients generally were low above the pycnocline 

 and were plentiful below except for nitrate and nitrite. 



4. Nutrient regeneration supplied most of the nutrients 

 required by phytoplankton, but the estuary appeared to 

 be the major nutrient source for the Apex while in-situ 

 nutrient regeneration appeared to be the major source for 

 primary production offshore. 



5. In the oxygen-depleted area the subpycnocline water 

 had high concentrations of sulfide, ammonium, silicate, 

 and phosphate. The highest concentrations were associ- 

 ated with the pycnocline and not with the seabed. 



6. Based on sulfide to phosphorus ratios measured in 

 other anoxic systems, apparently more sulfide was pro- 

 duced than was measured. The presence of sulfide suggests 

 very active anaerobic metabolism during the oxygen de- 

 pletion episode. 



7. DOC concentrations were unusually high throughout 

 the region, relative to other coastal/shelf areas. 



8. Highest DOC concentrations were in the middle and 

 outer Apex. 



9. DOC was the largest organic carbon pool in New 

 York Bight — 3 to 25 times more abundant than the POC 

 present. 



10. DOC concentrations appeared to counteract sea- 

 ward dilution when compared to other forms of organic 

 carbon. This suggested that significant additions to the 

 DOC pool took place. 



1 1 . Beyond the Apex, adjacent to the New Jersey coast, 

 and in the oxygen-depleted area, large increases in chlo- 

 rophyll-a and POC concentrations were observed in the 

 pycnocline and directly above the seabed, suggesting or- 

 ganic loading to the subpycnocline layer. 



12. Most chlorophyll a was attributable to nannoplank- 

 ton (<20 |xm). 



13. The most abundant phytoplankton species present 

 was a small (1.5-3m), spherical, unicellular green form, 

 probably Nannochloris atonms. 



14. Chain-forming diatom species dominated pycnocline 

 and near-bottom waters; flagellated (motile) species dom- 

 inated surface waters. 



15. No Ceratium tripos, a large dinoflagellate, were ob- 

 served in samples during the August-September 1976 



cruise. 



16. Integral daily rates of total phytoplankton primary 

 productivity were high. Daily productivity exceeded 1 g 

 C/m=/d at 11 of 21 stations surveyed and exceeded 3 g C/ 

 m=/d at 5 of the stations. At many stations phytoplankton 

 growth rates exceeded two divisions per day. 



17. Comparison of our August-September 1976 and 

 June 1977 data for the same area shows that total primary 

 productivity was about the same both years for the entire 

 area studied, but was slightly higher in June 1977 than in 

 August-September 1976 for the oxygen-depleted area. 



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