By any method, it is surprisingly difficult to determine in a volume of water the number of particles in a size range from micrometers to several millimeters. Imaging systems are especially suitable to demonstrate this problem as the particle numbers greatly depend on the sensitivity threshold of the combined optomechanical - image analysis protocols. The ill-defined particle numbers can be largely attributed to gels that are orders of magnitude more abundant than denser particles. Standard optical tools are calibrated to render suitable images of plankton and other dense particles but are ill-equipped to record the abundance of gels that come in a variety of densities depending on factors such as sediment entrapment and microbial colonization. This problem is magnified in the deep sea where amorphous particles far exceed the abundance of live plankton. Here we suggest methods of tying particle numbers to objectively determined optical densities. We also explore techniques that accurately capture a group of enigmatic particles forming a large portion of the total particle volume in the deep ocean. 

Primary Presenter: Alexander Bochdansky, Old Dominion University (abochdan@odu.edu)

Authors:

Huanqing Huang, Old Dominion University  (hhuan006@odu.edu)

Maureen Conte, Bermuda Institute of Ocean Sciences  (mconte@mbl.edu)