The Ocean Technology – Hyperspectral and Conventional Imagers
To evade detection by predators, many organisms have evolved camouflage to blend into their visual surroundings. Discerning how organisms optically match their background requires an understanding of how light is reflected, scattered, absorbed, and even polarized in seawater. To measure these properties of light requires a range of technologies including conventional digital cameras that capture images in only a few spectral bands of light and more advanced imagers that capture the full spectrum of visible light. These imagers can also be outfit with filters that capture the amount and type of polarized light or the orientation of the photons.
Surface Optics Corporation 710 Hyperspectral Imager (left) and affordable GoPro high definition camera will provide images for analysis. |
The Teacher Technology Experience – Hiding in the Light
Dr. Heidi Dierssen’s laboratory led this Teacher Technology Experience (TTE) that quantified the optical properties of different habitats where fish and cephalopods camouflage, such as seagrass and seaweeds, and the biological response of vertebrate and invertebrate animals to the dynamic optical marine environment. The team recorded images of near-shore and near-surface marine environments and collected samples for evaluation and manipulation in a laboratory setting. The Tech Team also examined imagery that demonstrates the ability of animals to respond to changes in spectral and polarized reflectance to investigate their camouflaging capabilities.
Some of the most sophisticated examples of camouflage occur in earth’s ocean, where precise regulation of spectral and polarized reflectivity is known to occur in some fish and cephalopods. These animals have special cells (chromatophores, reflective structures and photophores) that allow them to change their color and reflective properties to match the background optical properties: spectral variability, intensity and polarization components. While some dynamic camouflage may be achieved passively by reflective structures, active camouflage requires perception of the background and perhaps the illuminant. However, our interpretations of the underwater world are confounded by the differences between our visual systems and those of other species. The use of optical technology allows us to move away from our own eyes to what the animals themselves might see.
For this professional development TTE three teachers and one informal educator received background instruction on the properties of light in water, the various technologies used to measure these properties and the software used to analyze the images. This included several experimental activities that demonstrated how light travels in the water, providing a good conceptual introduction to optics. Teachers spent the second day working as a team to collect a number of images in the field and in the laboratory using affordable underwater high-definition cameras, a variety of light sources, and light-polarizing filters.
The third and fourth days were spent analyzing the images using free, open source software such as ImageJ, and collectively drafting lesson plans and other educational resources to broaden the impact of the research.
For More Information:
Through a Fish Eye, Lightly [Internet]. Discover. 1996 Oct 1 [Cited 2011 May 14]. Available from: http://discovermagazine.com/1996/oct/throughafisheyel905.
Novales Flamarique I, Hawryshyn CW. 1997. Is the use of underwater polarized light by fish restricted to crepuscular time periods? Vision Res. 37(8):975-89.
