using standard automated techniques. 



Incubations at depths down to 35 meters were performed by use of 

 SCUBA. At depths in excess of 35 m, the submersible, Makali'i was 

 used to emplace and sample the domes. Oxygen data were normalized to 

 a half-sine wave model of diurnal production and integrated to esta- 

 blish net production (Marsh and Smith, 1978). For lack of a more 

 accurate estimate, nighttime respiration measurements were extrapol- 

 ated throughout the day. A summary of the data is given in Tables 1 

 and 2. Due to equipment failures, reliable CO2 data were obtained 

 only for two of the six sampled depth intervals, yet the close cor- 

 respondence between these figures suggests a uniformity of RQ and PQ 

 values throughout the sampled depth range. 



Table 1. Summary of Enewetak lagoon sediment metabolic data. 

 Depth in meters; respiration and gross production means ± standard 



deviation. Units: mmoles O2 m' 



DEPTH n RESPIRATION PRODUCTION 



4 10 60 ± 12.5 64 ± 16.7 



7 26 58 ± 34.9 64 ± 36 



10 12 54 ± 8.6 50 ± 7.8 



16 32 36 ± 14.2 36 ± 13.2 



27 9 30 ± 7.9 27 ± 9.8 



55 5 12 ± 19.8 13 ± 21.5 



day 



_ 1 



RQ 



1.5 ± 0.6 



(n = 21) 



1.5 ± 0.6 



(n = 23) 



NET PQ 



1.0 ± 0.7 



(n = 22) 



1.0 ± 0.5 



(n = 24) 



TRUE PQ 



0.8 



0.8 



Table 2 

 meters ; 

 theses. 

 Units : 



DEPTH 



4 



7 



10 



16 



27 



55 



Enewetak lagoon sediment nutrient fluxes. Depth in 

 mean fluxes ± standard deviation. Sample size in paren- 

 Negative sign denotes uptake by the sediments, 

 micromoles 



P0 4 



m 2 day 



- 1 



-47 ± 62.3 

 (7) 



46 ± 352.7 

 (22) 



7 ± 16.0 

 (7) 



-54 ± 190.8 

 (25) 



-2 ± 21.2 

 (5) 



-18 ± 88.9 

 (9) 



N0 2 + N0 3 



-7 ± 24.5 

 (7) 



38 ± 111.7 

 (23) 



-10 ± 48.4 

 (7) 



-7 ± 94.2 

 (24) 



-11 ± 61.6 

 (5) 



-40 + 53.9 

 (9) 



NH, 



131 ± 174.9 

 (6) 



206 ± 523.2 

 (23) 



306 ± 563.8 

 (7) 



132 ± 536.3 

 (25) 



86 ± 1132.8 

 (5) 



-45 ± 113.2 

 (9) 



Oxygen data are depicted in the histogram (Figure 1) by depth. 

 The evident depth trends of both respiration and gross production are 

 not found in the sediment nutrient fluxes (Table 2). In general, 

 nutrient fluxes, particularly phosphate and nitrite + nitrate, are 

 barely above limits of detection. However, as noted in previously 

 studied lagoon floors (Harrison, 1981), both oxygen and dissolved 



146 



