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The biomass surrogate
Owing to the fact that a large fraction of marine organisms of
widely distributed species are luminescent, biomass is often a
good measure of the light emission potential of an oceanic region.
An estimate of biomass is possible by satellite measurements of
PAR (photosynthetically available light) and chlorophyll concentration
in seawater. This is logical because these measurements lead to
an estimate of total productivity of marine plants, principally
dinoflagellates, and these are the base of the marine food chain,
just as terrestrial plants are the basis of the terrestrial food
chain from grazers upon plants through various levels of predation.
The highest biomass values are found in coastal regions. This
is because these regions are typically rich in plant nutrients
from upwelling and, in some instances, from rivers or coastal rain
runoff.
The figure above illustrates some of these points. It shows temperature, salinity, and bioluminescence in the upper 30 meters as measured by an autonomous underwater vehicle (AUV). Beginning near shore (on the right) we see high levels of bioluminescence, which reach a maximum at about 12 km before falling off.
The AUV can also be used to map high-resolution, three-dimensional bioluminescence distributions, as shown in the one-km square, 30-meter deep cube reconstructed above.
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