bay, but they are not undertaken as ongoing routine monitoring. These 

 measurements are being made before diversion and, to the extent necessary, 

 will be repeated after the diversion. Tlie sampling design is modified to answer 

 specific questions. For example: What are the relationships among variables 

 obviously related to water clarity? Wliile an answer can, to some extent, be 

 extracted from routine sampling, ft is more satisfactorily addressed by sampling 

 along strong water clarity gradients which may or may not coincide with the 

 routine sampling stations. 



3. Laboratory experiments, also designed to answer specific questions 

 about the ecosystem. Particular responses of communities within Kaneohe Bay 

 are best addressed by controlled laboratory experiments. These experiments 

 vary in volumetric scale from batch phytoplankton cultures in 500 ml flasks, to 

 flow-thro ugli microcosm tanks which are 500 liters or larger in volume. The 

 questions addressed in these simplified, but controlled laboratory experiments, 

 cannot be easily answered under natural, and largely uncontrolled field 

 conditions. Of course, the largest of the controlled experiments is the bay 

 itself, a "reaction vessel" with a water volume in excess of 200 million m . The 

 time scales of these experiments vary from a few days in the flasks, to months 

 in the microcosms, and several years in the field. 



In this presentation, I do not explicitly separate these various research 

 components. Rather, I synthesize the components into our present view of 

 total ecosystem characteristics and predicted responses to sewage diversion. 

 This exercise is, of necessity, a preliminary analysis of our ongoing study. 



MAJOR ECOSYSTEM CHANGES IN THE 

 PAST TWO DECADES 



The impact of runoff on Kaneohe Bay is largely in the form of short-term 

 "catastrophic events." In the past 17 years, there have been three years with 

 monthly rainfall in excess of 75 centimeters within the Kaneohe watershed 

 (Figure 23-2). In terms of water deHvery to the bay, May 1965 represented an 

 extreme: most of the rain fell in a 2-day period and was followed by rapid 

 runoff. A freshwater lens from that storm killed corals and other reef 

 organisms on the fringing reef and nearshore patch reefs to a depth of up to 1 .5 

 meters (1). The reef flats are less than 1 meter deep, so such a destructive 

 "freshwater kill" virtually decimated the stenohaline marine organisms of the 

 reef flats and upper portion of tlie reef slopes. Below about 2 meters the 

 organisms were relatively unaffected. 



Sediment loading associated vsdth runoff has two general effects on the 

 ecosystem, one as the material is deposited, the other as the material is in the 

 water column. Deposition smothers reef organisms and lowers the availability 



349 



