CHAPTER 15 



below the pycnocline, as is indicated by the vertical dis- 

 tributions of ammonium found by O'Connors and Duedali 

 (1975) and the rapid convective descent (sslO cm/s) of 

 sewage sludge material through the pycnocline (Proni et 

 al. 1977). That unknown fraction of the ammonium re- 

 leased below the pycnocline is probably almost completely 

 unavailable to phytoplankton until it is advected out of 

 the Bight or is mixed within the photic zone after the 

 autumnal breakdown of the pycnocline. 



As with sewage sludge, most of the ammonium from 

 dredged materials is probably released to the water col- 

 umn soon after dumping, with an unknown percentage 

 released beneath the pycnocline. Some of the organic ni- 

 trogen in dredged material will no doubt be released to 

 the water column through mineralization before reaching 

 the bottom (Bremner 1965; Austin and Lee 1973; Blom 

 et al. 1976). The same is true of sewage sludge, because 

 many of the particles remain in the water column for long 

 periods (Proni et al. 1977). 



It seems probable that most of the nitrogen dumped in 

 the Bight as dredged material and sewage sludge gets into 

 the water column in dissolved inorganic forms. Given the 

 findings outlined above, I assume here, conservatively, 

 that roughly 70 percent of the dumped nitrogen in all 

 forms becomes dissolved inorganic nitrogen within days 

 after dumping. An unknown fraction of this amount is 

 released below the pycnocline where it would not con- 

 tribute to phytoplankton production until the autumnal 

 breakdown of density stratification. 



The atmosphere is also an important source of nitrogen 

 for Bight waters. Mueller et al. (1976b) estimated a mass 

 load of 66 t total N/d from the atmosphere; that is 13 

 percent of all nitrogenous inputs to New York harbors 

 and the Bight. However, the atmospheric nitrogen input 

 to the outer Bight almost certainly does not contribute to 

 oxygen depletion farther inshore. The nitrogen falling on 

 surface waters of the outer Bight (i.e.. more than 90 km 

 from shore) would tend to be carried to the southwest by 

 surface currents during all seasons, although current speed 

 and direction are extremely variable (Hansen 1977; Wil- 

 liams et al. 1977). Hence, my estimate of atmospheric 

 nitrogen input considers the Bight sea surface within 90 

 km of shore. 



Uttormark et al. (1974) summarized the atmospheric 

 contribution of nitrogen to 60 locations in North America, 

 on both land and water. These measurements give some 

 indication of nitrogen fallout contours in the Bight region. 

 Frizzola and Baier (1975a, 1975b) measured total nitrogen 

 fallout at three points on Long Island from 1969 through 

 1974. Available nitrogen fallout values in the New York 

 Bight region known to me are shown in figure 15-2; the 

 contours are consistent with Uttormark et al. (1974). In- 

 tegrating over the inner 34,300 knr of the Bight sea sur- 

 face, the estimated fallout of total nitrogen is 71 t/d. There 



is some evidence that nitrogenous fallout during June and 

 July is somewhat higher than the daily average over a 

 year, and somewhat lower than average during late sum- 

 mer (Likens 1972; Likens and Bormann 1972). This tend- 

 ency, together with the increasing concentrations of at- 

 mospheric nitrogen over recent years, makes this estimate 

 of 71 t/d during summer a conservative one. Further, the 

 above authors treat organic nitrogen in atmospheric fall- 

 out as a contaminant and eliminate it from consideration. 

 Hence, any additional contribution of organic nitrogen 

 fallout is assumed to be negligible, although supporting 

 evidence is lacking. 



Unfortunately, estimates are not yet available for ni- 

 trogenous inputs from sediments and from onwelling over 

 the continental shelf. Both contributions could be sub- 

 stantial, relative to other sources. 



Carbon Loadings 



In addition to nitrogen loading, unusually large car- 

 bonaceous inputs to the Bight contribute to oxygen de- 

 pletion problems. Recently. Walsh et al. (1976). Ketchum 

 (1976), and others discussed the significance of carbon 

 loads relative to oxygen sags in the Bight. Work on the 

 implications of BOD (biological oxygen demand) loads 

 to the Hudson-Raritan estuary (with consequences for the 

 Bight) dates from O'Connor (1960. 1962). 



The total carbon loading to the Bight from the atmos- 

 phere is adjusted from Mueller et al. (1976a) in table 15-2. 

 The conservative assumption is made that atmospheric 

 fallout of carbon is evenly distributed over the entire 

 Bight. Thus, about 67 percent of the atmospheric carbon 

 is assumed to fall within the 34.300 km- area east of New 

 Jersey. 



Reliable estimates of spring/summer loadings to the 

 Bight proper (seaward of the Sandy Hook/Rockaway 

 Point transect) cannot be made simply from estimated 

 contributions from rivers and harbors. The several proc- 

 esses that are important in determining how much of the 

 estuarine inputs reach the Bight are not well understood. 

 Perhaps the principal difficulty is the differential deposi- 

 tion of particulates from the estuarine water column and 

 their short-term, large-scale resuspension and advection. 

 These and other difficulties have led to alternative esti- 

 mates of carbon inputs by different workers (Segar and 

 Berberian 1976; Garside and Malone 1978). 



The substantial quantities of oxidizable carbon (includ- 

 ing plankton) from the estuary and from dumping (see 

 table 15-2) have been estimated to be from 30 percent of 

 phytoplankton production in the Apex (Garside and Ma- 

 lone 1978) to about 80 percent of Apex production (Segar 

 and Berberian 1976). Both carbon sources originate above 

 the pycnocline for the most part. Their influence and that 

 of in-situ phytoplankton production upon the 1976 anoxic 

 event, and upon bottom waters every year, depends on 



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