KANEOHE BAY: NUTRIENT MASS BALANCE, 
SEWAGE DIVERSION, AND 
ECOSYSTEM RESPONSES 
Stephen V. Smith 
Hawaii Institute of Marine Biology 
University of Hawaii 
P.O. Box 1346 
Kaneohe, Hawaii 96744 
ABSTRACT 
Kaneohe Bay, Hawaii, is a coral reef/estuary ecosystem presently subjected 
to stresses from sewage discharge and runoff. The sewage discharge is scheduled 
to be diverted from the bay. This “relaxation” of sewage stress will be a major 
ecosystem perturbation: the termination of a chronic stress which has been 
imposed, with increasing intensity, on the bay over the past two decades. We 
are treating this sewage diversion event as a controlled experiment designed to 
ascertain ecosystem responses to such environmental perturbation. The 
experiment is being performed by means of time-series field monitoring, 
discrete field studies, and laboratory experiments. 
The stream runoff imposes short-term, catastrophic stress from fresh water 
and sediment influx. The sewage accounts for about 90 percent of the 
land-derived nutrient delivery to the bay, thus imposing an influence which 
stimulates biological activity. 
The sediments in the bay have been a major repository for nutrients 
discharged into the bay; nutrient release from the sediments has been, and will 
continue to be, a significant process affecting the ecosystem. When the sewage 
stress is relaxed, planktonic responses to that event will be more rapid than 
benthic responses; both because the plankton are immediately responsive to 
the point-source sewage discharge, and because of characteristic high biomass, 
efficient nutrient cycling, and limited mobility of benthic organisms. 
INTRODUCTION 
Kaneohe Bay is a coral reef and estuary complex on the northeast 
(windward) coast of Oahu, Hawaii (Figure 23-1). The bay was once renowned 
as one of the most beautiful coral reef ecosystems in Hawaii. The reef 
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