The Deep Sea
There are four major zones with regards to light within the ocean; Epipelagic zone, Mesopelagic zone, Bathypelagic zone and the Abyssopelagic zone.
Photosynthetically active radiation (PAR) within the Epipelagic zone is great enough to support light dependent reactions in Photosynthesis and Photomorphogenesis, thus this zone, and smaller zones in shallower waters, are called the Euphotic zone.
In zones deeper than the Epipelagic zone light intensity is too low to support any light dependent reactions, thus these zones are named Aphotic. As you can see in the image regarding light; blue light and some dark purples are able to penetrate the furthest in depths of water, to around 250 m. This is due to these lights having a larger amounts of frequency, in comparison to the rest of the visible electromagnetic radiation, allowing them to transmit further through water. This fact is relevant later when discussing organism’s adaptations to the stresses of low light intensity within this environment.
The only visible light present within the Bathypelagic zone is that which is created by organisms occupying this zone in a processes known as Bioluminescence.
Photosynthetically active radiation (PAR) within the Epipelagic zone is great enough to support light dependent reactions in Photosynthesis and Photomorphogenesis, thus this zone, and smaller zones in shallower waters, are called the Euphotic zone.
In zones deeper than the Epipelagic zone light intensity is too low to support any light dependent reactions, thus these zones are named Aphotic. As you can see in the image regarding light; blue light and some dark purples are able to penetrate the furthest in depths of water, to around 250 m. This is due to these lights having a larger amounts of frequency, in comparison to the rest of the visible electromagnetic radiation, allowing them to transmit further through water. This fact is relevant later when discussing organism’s adaptations to the stresses of low light intensity within this environment.
The only visible light present within the Bathypelagic zone is that which is created by organisms occupying this zone in a processes known as Bioluminescence.
Bioluminescence:
Bioluminescence is a form of Chemiluminescence which occurs within a living organism; such as M. niger, in this example the organism is able to independently synthesis light as the main responsible substrate and enzyme needed for bioluminescence, Luciferin and Luciferase, are present. The Bioluminescence reaction is as followed; |
However some organisms have to use alternative methods of producing light within the aphotic zones, as they are unable to undergo the reaction above. Species of Anglerfish such as the female Melanocetus johnsonii rely on a symbiotic relationship with bioluminescent bacteria to produce their light for them. Without this symbiotic relations M. johnsonii, which mainly uses bioluminescence as a lure to aid predatory behaviours, would not be as effected at competing within certain trophic levels within its environment.
Bioluminescence is used for many reasons, many organisms utilize a combination of functions, here are a few examples; avoiding/defending against predation via crypsis; as well as some other methods, Aiding predation and communication. Some organisms may also have other beneficial adaptations that can function in conjugation with bioluminescence; allowing certain anatomical adaptations to work in more of a system.