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FUTURE DIRECTIONS IN OCEAN SCIENCES 105 



Acoustics 



Sound is an extremely useful tool in biological and fisheries 

 oceanography. The scattering of sound by organisms at many 

 different trophic levels can be used for a variety of purposes. Schools 

 of fish and patches of plankton can be located and tracked acous- 

 tically. It may eventually be possible to distinguish living from 

 nonliving scatterers and to identify the biological scatterers by spe- 

 cies. It may soon be possible to estimate biomass acoustically as a 

 function of trophic level in the ocean. Sound scattering has been 

 used commercially since the 1930s to locate fish schools, but only 

 recently have multifrequency systems been available for quantita- 

 tive study of animal plankton. The Multi-Frequency Acoustic Pro- 

 filing System is capable of profiling zooplankton in the size range of 

 0.2 to 10 millimeters. General application of acoustical technology 

 will require the development of inexpensive equipment and tech- 

 niques to analyze and use the large volumes of data generated. 



Bio-optics 



Fluorometers, transmissometers, and spectroradiometers are 

 used to measure phytoplankton populations, the turbidity of the 

 water column, and the amount and wavelength of light that pen- 

 etrate beneath the ocean surface at a given site. Correlating site 

 measurements with measurements from satellite ocean color sen- 

 sors provides the means to extrapolate phytoplankton measure- 

 ments to a global scale. Mooring optical instruments together 

 with current meters and temperature and salinity sensors pro- 

 vides a technique for collecting long (months) and highly resolved 

 (minutes to hours) time-series measurements, permitting biologi- 

 cal oceanographers to study what physical factors control phy- 

 toplankton populations. Moorings contribute data on variation 

 over time and depth, whereas satellite sensors provide informa- 

 tion on variation over the global ocean surface. Flow cytometry 

 is another optically based technology that is extremely useful for 

 characterizing the size and pigment composition of phytoplank- 

 ton and bacteria and for sorting populations based on these and 

 other criteria. 



Imaging for Organism Enumeration 



New techniques for imaging organisms in situ, now available, 

 show promise for widespread application in the 1990s. These 



