CHAPTER 4 



in segment A is the data distribution good enough for the 

 non-1976 years to fulfill conditions for drawing a regres- 

 sion line. Depletion rates listed for 1976 all appear statis- 

 tically significant (P<0.05) and are up to 10 times more 

 rapid than non-1976 mean values; however, except for 

 segment A, none of the non-1976 rates have correlation 

 coefficients high enough to be considered significant at 

 the P<0.05 level. 



The 1976 depletion rates shown in table 4-6 for 1976 

 compare very well with those determined by Han et al. 

 (ch. 8). Note that the actual oxygen utilization rates, which 

 consider advection, are about double the depletion rates 

 (chapter 8, table 8-2). 



Recovery rates (J.D. 250 to 365) also are more rapid 

 in 1976, but we consider this a natural result of the 1976 

 oxygen deficiency; that is, once stratification was broken 

 up, equilibrium with the atmosphere was rapid, and re- 

 covery rates in the depleted system were high. 



NUTRIENT DISTRIBUTION 



Nutrient distributions control productivity and its sub- 

 sequent input of oxidizable carbon, thus reducing oxygen 

 concentrations in bottom waters. The distribution of nu- 

 trients in time and space in New York Bight has been 

 examined in some detail during the last 3 or 4 years by 

 several agencies and institutions. However, only late in 

 1976 did specific studies focus on the low oxygen condition 

 which existed during that summer. The MESA New York 

 Bight Project sponsored a series of extended water-col- 

 umn characterization (XWCC) cruises throughout 1975 

 and during 1976. The following is a comparison of data 

 from the early XWCC cruise with data collected by MESA 

 and Brookhaven National Laboratory (BNL) during the 

 severe oxygen-depletion event. 



All nutrient data reported here resulted from analysis 

 of frozen or fresh samples, using Technicon AutoAnalyzer 

 systems. Atlantic Oceanographic and Meteorological Lab- 



oratories (AOML) analyzed samples using standard 

 Technicon techniques described in their manuals. These 

 methods were checked against accepted methods of analy- 

 sis (Strickland and Parsons 1968; Fanning and Pilson 

 1973). The results of this comparison are available in an 

 AOML data report (Berberian and Barcelona 1978). 

 Methods used by BNL are given in Walsh et al. (1977). 



Nutrient samples collected in most of the studies were 

 frozen for later analysis in the laboratory because labo- 

 ratory space aboard research vessels and analytical equip- 

 ment availability were limited. Exceptions were the 

 AOML cruise in September 1976 and BNLs Atlantic 

 Coastal Ecosystem (ACE) cruises where nutrients were 

 run aboard ship. Some changes can be expected from fro- 

 zen samples, but previous studies have shown that the 

 mean change between fresh and frozen samples is only 

 about 10 percent (Thayer 1970) for orthophosphate, dis- 

 solved silicon, nitrate, and nitrite. Changes in ammonium 

 concentrations between fresh and frozen samples are 

 sometimes very large and contamination is a problem, so 

 ammonium was determined only in samples analyzed at 

 sea. On the September 1976 cruise, samples were drawn 

 in triplicate. One aliquot was analyzed aboard ship for 

 nitrate plus nitrite. The other two aliquots were frozen 

 and later analyzed at BNL and AOML to check whether 

 or not differences occurred as a result of such storage. 

 Those run fresh had a mean difference of -0.05 [xg-at/I for 

 BNL frozen samples (table 4-7). AOML frozen samples 

 were generally lower than the BNL frozen samples, with 

 a mean difference of about 1.0 ^J.g-at/l. Since bottom sam- 

 ples analyzed by the two laboratories showed essentially 

 the same differences, it was concluded that differences are 

 not related to the concentration of nitrogen but resulted 

 from a systematic difference in handling and analysis. As 

 a result, the values shown in the figure of this paper may 

 have a <1 (xg-at/1 difference between data sets and this 

 should be considered when making comparisons. 



AOML's nitrate samples with concentrations of 0.5 p.g- 

 at/1 or less were recorded as zero on the figures herein, 

 since AOML considers that the detection limit for the 



Tabi 1 4-7 — Comparison of concenlralions of nitrate plus nitrite measured in fresh or frozen samples on XWCC cruise 11. September 1976 



' Compared samples are from same water sampling bottles and were either run fresh or were frozen m polyethylene bottles. 

 - A = fresh samples run by BNL B = frozen samples run by BNL C = frozen samples run by AOML, 



97 



