APPENDIX A 



DEVELOPMENT OF A QUANTITATIVE SAMPLING PLAN 



I. INTRODUCTION 



Generally, it is not possible to study the sampling problems involved with 

 a particular environment and set of research objectives before the initiation 

 of benthic surveys. As a result, development of a sampling plan often de- 

 pends upon information generated from other studies and the experience of the 

 investigators. This is to be expected since one of the primary objectives of 

 many surveys is the identification of the fauna. 



The objectives of this study were more specific and required a prior 

 understanding and reduction of the variations due to sampling error. 

 Sampling was restricted to a few permanent stations that were maintained and 

 sampled by divers within a locally defined area. 



Three major problems should to be solved to develop a quantitative sampl- 

 ing plan for the study area: 



(a) Does the sampling device catch all or most of the organisms 

 found in a given volume of sediment? 



(b) How many replicates must be taken to be confident, within 

 certain statistical limits, that the parameters used to describe a 

 fauna are adequately estimated? 



(c) How should the replicates be distributed over the environ- 

 ment? 



II. THE SAMPLING DEVICE 



The sampling device is a standard 1.4-kilogram coffee can with both ends 

 removed. Careful placement of corers by divers minimizes bottom disturbance 

 and snap-on plastic lids create a watertight seal that allows transportation 

 of intact sediment cores both in water and air. Depth of penetration can be 

 adjusted by diver operation so the constant surface area (0.018 square meter) 

 is associated with the same volume of sediment. Corers were inserted to 

 maximum penetration which produced an average core height of 15 centimeters. 



Quantitative measurements of biomass were not made since they require a 

 sampler that covers a large surface area and penetrates deeper than 15 centi- 

 meters into fine sand (Masse, 1968; Oliver, 1973). This is primarily due to 

 the effect of sparsely distributed large animals on the biomass. 



A recent comparison of benthic samples taken with the 1.4-kilogram 

 coffee can corer, a diver-operated suction dredge, and a Smith-Mclntyre 

 grab at Moss Landing indicated that all three techniques produce similar 

 estimates of the number of species per unit area, number of individuals 



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