Bathyphotometry

A system that uses photodiodes to convert the optical signals into electrical signals which are sampled, integrated, and coupled to output terminals for transmission to a surface host vehicle.

• In recent years, advances in optical instrumentation have led to the development of more compact and more accurate photo-detectors.
• This has important implications in the measurement of bioluminescence, and it is important to know whether these technologies will increase the capabilities of bathyphotometers.
• A well-designed bathyphotometer not only will consist of an accurate photodetector but also will take into account issues of temporal and spatial variability of the bioluminescent phenomenon.
• Bathyphotometers are designed to discriminate between typical zooplankton flashes, dinoflagellate flashes, and planktonic bioluminescence; opening the possibility of identifying some zooplankton types directly from flash duration estimates.
• The strength of bioluminescence signals is related to seasonal planktonic biomass fluctuations, low in winter, higher in spring.
• A photomultiplier tube (PMT) records light from bioluminescent organisms after they are mechanically stimulated at the chamber entrance by a high-velocity impeller.
• Marine bioluminescent organisms occur at all accessible depths and domains, often in immense numbers.
• Although the sources and occurrence of oceanic bioluminescence (BL) have been extensively studied, poorly developed instruments have often been involved, raising questions regarding radiometric and excitational inter-calibration.
• Bathyphotometers have provided information about bioluminescent organisms, specifically the spatial and temporal location of bioluminescence as well as its relationship with other measured biological, physical, and chemical parameters in the ocean.
• With respect to the fine-scale organization of the bioluminescent coastal complexes, the distribution of bioluminescence remains poorly understood due to limitations of the instruments used, which were typically designed for open-ocean applications.
• Bathyphotometers were initially designed to ensure optimal capture efficiency in the open ocean where bioluminescent organisms vary widely in abundance and ability to avoid capture.
• In coastal waters, such high flow rates and large instruments might obscure the fine-scale distribution of bioluminescent organisms, and make it difficult to discriminate individual organisms within the bulk bioluminescent signals.
• Furthermore, the size of most large bathyphotometers requires large deployment vessels and dedicated winches, effectively barring them from use close inshore and on small mobile platforms or moorings.
• The outstanding characteristics of a bathyphotometer that affect bioluminescent stimulation efficiency are the extent of signal loss by premature excitation in the bioluminescent intake, and the duration and intensity of excitation.

Related "bathy-, meter-, photo-" units: bathy-; meter-; photo-.