18. BIOLOGICAL INSTRUMENTATION 



Charles S. Yentsch 



Woods Hole Oceanographic Institution 

 Woods Hole, Massachusetts 



In the short time that I have this afternoon I cannot possibly 

 describe all existing problems of sampling in the field of biolog- 

 ical oceanography. Any attempt to do so would only result in worth- 

 less overgeneralization. Therefore, I shall confine my discus- 

 sion to a nnajor field in biological oceanography, the study of 

 plankton, and discuss some of the sannpling problems associated 

 with it. 



"Plankton" is an aggregation of plant and animal organisms 

 which is moved about by ocean currents. Plant plankton is 

 phytoplankton and the ajiimal, zooplankton. In open oceans these 

 organisms make up the bulk of living matter and are respons- 

 ible for many of the chemical, physical, and biological changes 

 in the sea. 



Figure 18. 1 is a microphotograph of a collection of 

 PHYTOPLANKTON. Notice the great diversity in the shapes of 

 these organisms as well as their size. Most of these are dia- 

 toms, one-celled plants which contain chloroplastic pigments 

 and are capable of photosynthesis. The cell-wall material in 

 these organisms is silica and the organisms may be found as 

 solitary cells or in long chains as shown. In the open ocean 

 these organisnns are responsible for the initial production of 

 organic matter. Through their activities, inorganic matter 

 changes to organic in the presence of light. Figure 18.2 is a 

 microphotograph of ZOOPLANKTON. Notice the bizarre shapes 

 of these organisms and the wide diversity of size. Much zoo- 

 plankton is made up of "primary herbivores"; these organisms 

 graze on the phytoplankton and thus provide the second step in 

 the transfer of organic matter in the food chain. Not all species 

 of zooplankton remain such for their entire life histories. For 

 instance, the organism with the big eye ajid spine in the center 

 of the lower photograph (fig. 18. 2) is a zoeal stage of a crab. 

 It will eventually develop into an adult similar to the well-known 

 coastal blue crab. Exemriples of species which remain as plankton 

 throughout life are illustrated by the shrimp-like forms in the 



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