Evaluation of Natural Tracers in Optical Flow Measurements: Part I

   There has been a few requests for more information about the research project that I worked on over the summer. The research that I worked on was a preliminary project for an up-scaled research experiment that will take place around June of next year. Since I have to present the research problem for my Independent Research class tomorrow morning, I figured that now is the perfect time to give everyone a more extensive discourse. 

http://www.vims.edu/newsandevents/topstories/archives/2011/oyster_reef_global.php

  Since 1980, the world's oyster reefs have witnessed a decrease in functionality by 85%. The Chesapeake Bay reef is considered functionally extinct. There are three basic reasons why: over-harvesting, disease, and habitat destruction. 

  But why are oysters important? They are filter feeders. They ingest phytoplankton, including algae. This reduces the incidence of unwanted algal blooms, keeps dissolved chemicals in the bay in check, and fixes nitrogen. They also provide habitat for bay life and serve an important role in the food web. 

ian.umces.edu/imagelibrary/displayimage-70-7044.html

     In response to human consumption, oyster aquaculture farms were introduced. There is quite a bit of controversy over their environmental impact versus their ability for economic sustainability. 

    However, the restoration of the Chesapeake Bay and other oyster reefs have taken a more central role in environmental sustainability. The two challenges facing natural restoration efforts have been engineering an alternative substrate to repair the habitat and the fact that we do not have a clear understanding of how larvae transport themselves. 

    Here, I will address the transport issue. We do know that oyster larvae respond to light, chemical cues, and fluid motion. We also know that larvae transport are controlled by the flow. Flow can be defined as currents, waves, or turbulence. Turbulence is the chaotic and rotational flow of a fluid. The only control that oyster larvae have in the umbonal stage of development is through a body part called the vellum. The vellum allows the larvae to float when open and can be withdrawn to allow the larvae to sink. The vellum, in the picture below, is the hair-like projection.

http://www.marinrodandgunclub.com/Oyster%20Habitat01.htm

el.erdc.usace.army.mil

      

   We want to measure fluid flow accurately without impacting oyster larvae behavior during the experiment. However, the standard seeding particle we use for particle image velocimetry measurements are glass hollow spheres which are not natural in reefs. The idea here is to see if we can use an algae, found in aquaculture farming, to feed oysters as a natural or biotic tracer. More information about the Isochrysis galbana can be found here. In the next post, I will talk about the equipment and the flow measurement technique used to capture the images.