Following sewage abatement, the pattern remained essentially the same, and was 

 reflected in the physical condition of the benthic surface, as well as in species 

 distribution (Dollar, 1979). In the acute impact zone the reef platform was re- 

 duced to a pitted flat limestone pavement by biological/chemical erosional activity. 

 The dense aggregations of polycheate worms were totally absent. Termination of the 

 heavy fallout of particulate organic material emanating from the outfall resulted 

 in a complete change in trophic community structure in the acute impact zone. 

 Apparently qualitative alteration of the limestone surface affected the recon- 

 ditioning process that is a precursor to hermatypic coral colonization. 

 Deep Outfall 



Preliminary observations revealed that diversion of sewage to the deep water 

 discharge resulted in none of the severe community structure alterations that were 

 apparent at the shallow site. No changes occurred either by removal of organisms 

 from adverse environmental conditions or additions of new species in response to 

 increased nutritional loading. In addition, there were no apparent changes in 

 water column productivity and nutrient characteristics in the vicinity of the out- 

 fall (Laws and Terry, 1983). 



However, results of benthic nutrient flux experiments performed with the Hawaii 

 Undersea Research Laboratory Submersible Makali ' i showed a very distinct pattern 

 of metabolic community response to nutrient subsidy from sewage loading. 



Table 1 summarizes the results of the deep Sand Island outfall study and includes 

 for purposes of comparison similar data from a Hawaiian estuary, Kaneohe Bay 

 (Harrison, 1981) and a deep ocean site underlying an area of intense upwelling off 

 the coast of California known as the Patton Escarpment (Smith, et a_l_. 1979). 

 Results of oxygen uptake experiments indicate that within a horizontal distance 

 of 25 meters from the diffuser, metabolic oxygen uptake varies from levels of the 

 deep ocean (3800 m) to an estuary subjected to high levels of terrigenous input 

 from stream runoff and recycled sewage-derived nutrients. 



NUTRIENT FLUX 

 (uM M- 2 day- 1 ) 



STATION DEPTH DISTANCE 

 (M) FROM 



OUTFALL (M) 



O.FLUX 



(mM K _2 day- 1 ) 



NH+ 

 4 



PO/. 



SEDIMENTATION 

 RATE-ORGANIC C 

 (grams M~ 2 day _1 ) 



% ORGANIC C 

 IN BOTTOM 

 SEDIMENT 



X SEDIMENTED ORG. 

 CARBON OXIDIZED 



TABLE 1. Summary of results of Sand Island nutrient flux and sedimentation rate studies. Positive fluxes indicate efflux 

 from sediments; negative fluxe6 indicate uptake by sediments. Kaneohe Bay data is from Harrison (1981) 

 Patton Escarpment, North Pacific data is from Smith et. al. (1979). 



142 



