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Ocean Science An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/os-2018-10
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
13 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Ocean Science (OS).
ADCP observations of migration patterns of zooplankton in the Cretan Sea
Emmanuel Potiris1,2, Constantin Frangoulis1, Alkiviadis Kalampokis1, Manolis Ntoumas1, Manos Pettas1, George Petihakis1, and Vassilis Zervakis2 1Institute of Oceanography, Hellenic Centre for Marine Research, Heraklion, Crete, 72100, Greece
2Department of Marine Sciences, School of the Environment, University of the Aegean, Mytilene, 81132, Greece
Abstract. The lack of knowledge of the mesopelagic layer inhabitants, especially of those performing strong vertical migration, is an acknowledged challenge as its incomplete representation leads to the exclusion of an active carbon and nutrient pathway from the surface to the deeper layers and reversely. The vertical migration of mesopelagic inhabitants (macro-planktonic and micro-nektonic) was observed by acoustical means in the epi- and mesopelagic layer of the open oligotrophic Cretan Sea (Eastern Mediterranean) for almost 2.5 years at the site of an operational fixed-point observatory located at 1500 m depth. The observed organisms were categorized in four groups according to their migration patterns. The variability of the migration patterns was inspected in relation to the physical and biological environmental conditions of the study area. The stratification of the water column does not act as a barrier for the vertical motion of the strongest migrants, moving up to 400 m every day. Instead, changes of light intensity (lunar cycle, daylight duration, cloudiness) and the presence of prey and predators seem to explain the observed daily, monthly and seasonal variability. The continuous presence of these organisms, yet capable of vertical motion and despite the profound seasonal circulation variability at the site of the observatory, implies their presence in the broader study area. The fundamental implications of the above for biogeochemical processing in oligotrophic seas due to the intimate link of the C and nutrient cycles, are discussed.
Citation: Potiris, E., Frangoulis, C., Kalampokis, A., Ntoumas, M., Pettas, M., Petihakis, G., and Zervakis, V.: ADCP observations of migration patterns of zooplankton in the Cretan Sea, Ocean Sci. Discuss., https://doi.org/10.5194/os-2018-10, in review, 2018.
Emmanuel Potiris et al.
Emmanuel Potiris et al.
Emmanuel Potiris et al.

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Short summary
Zooplankton and fishes living deeper than 200 m, may perform a vertical migration to the surface waters. The migration patterns, from 400 m depth to the surface, of four groups of organisms were studied in the deep (1500 m) Eastern Mediterranean (Cretan Sea) for 2.5 years. The lunar cycle, daylight duration, cloudiness, the presence of prey and predators explains their migration variability. This phenomenon is important as it constitutes an active transport of organic matter over large distances.
Zooplankton and fishes living deeper than 200 m, may perform a vertical migration to the surface...
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