Sources of light in the deep ocean

Abstract

Abstract. Studies during recent decades have shown that the deep ocean (depths below where solar luminance plays a direct environmental role) is far from a dark, cold, lifeless region. Evidence obtained by utilizing a variety of photo-optical devices, providing spatial, temporal, and spectral information, has demonstrated that this portion of the Earth is a region rich in life and light. Findings to date have provided challenges for geologists, physicists, biologists, chemists, and oceanographers, and the sharing of techniques and expertise among these disciplines has demonstrated the rewards to be gained from interdisciplinary research. Bioluminescence has been found far below the depths at which it has received most attention historically. The study of this phenomenon is complicated by the fact that the measuring apparatus itself causes a stimulation of the luminescence so that a true background will be difficult to determine.Nuclear physics has played a role in that the electron resulting from the decay of an isotope of potassium (K 4ø) provides an ubiquitous background of light through a process known as Cerenkov radiation. The possibility of light generated by cosmic rays must also be taken into account. An intriguing source of light at the very bottom of the sea is found at hydrothermal vents. Here are found not only light but also abundant life. At the vent orifice, temperatures are found to be as high as 250ø-400øC. A large component of the light is due to thermal radiation. However, the light in the wavelengths 450-600 nm is significantly greater than the thermal flux at those wavelengths. Identifying the physical mechanisms that may account for this excess is important in providing insight into the processes occurring in the vents and plumes and in the accompanying ecosystem. INTRODUCTIONThe ocean covers over 70% of the Earth's surface.The average overall depth of the ocean is approximately 3900 m, and over 75% of the ocean is at a depth between 3000 and 6000 m. The volume of the ocean is more than 10 times the volume of land above sea level [Herring, 1971]. Sunlight is absorbed exponentially and is restricted to relatively very shallow depths, depending greatly on local conditions. It is sometimes stated that at depths below the limit of the continental shell (200 m) the ocean is "dark," and some authors take depths beyond 200 m to be "deep ocean." It is more reasonable to put 1000 rn as the beginning of the deep ocean (the limit of the mesopelagic zone), where only a few animals It has also been known for many years that low-level ambient light in the deep ocean is due to the passage of ionizing cosmic ray particles and ions from the decay of naturally occurring radioactive elements, primarily the isotope of potassium, 4øK.The relatively recent discovery of deep-sea hydrothermal vents, and that there is light at and near the orifice of many of them, has been an important development of interest to geologists, physicists, biologists, chemists, oceanographers, and Earth resource scientists. Each of the...

Low Energy Subsurface Environments as Extraterrestrial Analogs

“…Some characteristics are common to subsurface environments of Earth. Light is mostly absent ( Van Dover et al, 1996 ; Reynolds and Lutz, 2001 ; White et al, 2002 ; Beatty et al, 2005 ), generally eliminating phototrophy as a lifestyle. Chemical-based lithotrophic reactions support a large fraction of life in Earth’s subsurface environments, though transport of organic matter and oxidants of photosynthetic origin (i.e., oxygen) introduces influences from Earth’s surface.…”

Diel and lunar cycles of vertical migration extending to below 1000 m in the ocean and the vertical connectivity of depth‐tiered populations

“…In situ irradiance below the euphotic zone-Little information has been published about the diffuse attenuation coefficient (k d ) in the mesopelagic and bathypelagic ocean because it is difficult to separate the solar irradiance from internal light sources (i.e., bioluminescence and Cerenkov emission from either 40 K beta decay or Muons produced by Neutrino). At such depths, the contribution of internally produced irradiance has spectra with significant overlap with the residual daylight (Mobley 1994;Reynold and Lutz 2001) and comprises a significant portion of in situ irradiance (Denton 1990Amram et al 2000. At depths below 500 m, the wavelength dependence of light attenuation in the ocean leads to a narrow band irradiance centered on 480 nm (we follow the convention of using wavelengths in the vacuum).…”

“…At such depths, the contribution of internally produced irradiance has spectra with significant overlap with the residual daylight (Mobley 1994;Reynold and Lutz 2001) and comprises a significant portion of in situ irradiance (Denton 1990Amram et al 2000. At depths below 500 m, the wavelength dependence of light attenuation in the ocean leads to a narrow band irradiance centered on 480 nm (we follow the convention of using wavelengths in the vacuum).…”

Vision in the deep sea

“…Below 1000 m almost no daylight penetrates, certainly not enough to be seen by deep-sea animals (Denton, 1990). However, at the mouths of benthic hydrothermal vents the high water temperatures promote chemical processes that emit another (extremely weak) source of visible light (White et al, 2000 ;Reynolds & Lutz, 2001). The light these processes produce -chemiluminescence, sonoluminescence and triboluminescence -may even be bright enough to be seen.…”

“…Other possible sources of light include chemiluminescence, triboluminescence and sonoluminescence produced as the result of chemical interactions within the hot water plume gushing from the vent (White et al, 2000;Reynolds & Lutz, 2001). These processes have the potential to produce an extremely weak visible light.…”