4 research outputs found
Distribution and diel vertical movements of mesopelagic scattering layers in the Red Sea
© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Biology 159 (2012): 1833-1841, doi:10.1007/s00227-012-1973-y.The mesopelagic zone of the Red Sea represents
an extreme environment due to low food concentrations,
high temperatures and low oxygen waters. Nevertheless, a
38 kHz echosounder identified at least four distinct scattering
layers during the daytime, of which the 2 deepest
layers resided entirely within the mesopelagic zone. Two of
the acoustic layers were found above a mesopelagic oxygen
minimum zone (OMZ), one layer overlapped with the
OMZ, and one layer was found below the OMZ. Almost all
organisms in the deep layers migrated to the near-surface
waters during the night. Backscatter from a 300 kHz lowered
Acoustic Doppler Current Profiler indicated a layer of
zooplankton within the OMZ. They carried out DVM, yet a
portion remained at mesopelagic depths during the night.
Our acoustic measurements showed that the bulk of the
acoustic backscatter was restricted to waters shallower than
800 m, suggesting that most of the biomass in the Red Sea
resides above this depth.This research is based in part on work
supported by Award Nos. USA 00002, KSA 00011 and KSA 00011/02
made by KAUST to the Woods Hole Oceanographic Institution