IX. MARINE BIOLOGICAL SAMPLING 

 John R. DePalma 



A. INTRODUCTION 



The complex problems of population dynamics demand, a great 

 variety of biological instruments for locating, observing, and collect- 

 ing organisms varying in size, habitat, and motility. Emphasis on 

 biological measurements is becoming more and more evident today 

 in the consideration of the overall aspects of submarine and mine 

 warfare. 



On the basis of size, plankton have been classified into three kinds: 

 (1) macroplankton, the large units of plankton, visible to the unaided 

 eye, (2) ( net plankton, plankton secured by a plankton net equipped with 

 No. 25 silk bolting cloth (mesh, 0.03 to 0.04 mm.), and (3) nannoplank- 

 ton, very minute plankton not secured by a plankton net with No. 25 silk 

 bolting cloth. 



Plankton yield is a function of such aspects as distribution, produc- 

 tivity, and size, which in turn are influenced by wind action, currents, 

 upwelling, predators, nutrient content of the water, diurnal migration, 

 and physiochemical stratification. Plankton samples may include 

 organisms that are contributing to fouling, light and sound scattering, 

 and bioluminescence. Larger marine organisms may produce noises 

 or otherwise interfere with underwater sound transmission. Fouling 

 communities must be studied with particular reference to species 

 distribution, growth rate, and ecological succession in order to 

 predict accurately fouling conditions for any given area. 



Plankton sampling instruments are evaluated according to how well 

 they accomplish the following: collect from all depths, collect both 

 horizontally and vertically, capture large and small specimens, capture 

 the more active swimmers, secure undamaged specimens, record 

 exactly the amount of water sampled and at what depth, sample over 

 long distances, and sample several depths simultaneously. 



B. INSTRUMENTATION AND EQUIPMENT 



1. Meter (or half- meter) plankton sampler 



A meter (or half- meter) plankton sampler consists essentially 

 of three parts: a metal ring, one or one-half meter in diameter, provided 

 with rope bridles for attaching to a tow line; a conical bag or net made 



IX- 1 



