Acoustics reveals the presence of a macrozooplankton biocline in the Bay of Biscay in response to hydrological conditions and predator-prey relationships.

Ainhoa Lezama-Ochoa, Xabier Irigoien, Alexis Chaigneau, Zaida Quiroz, Anne Lebourges-Dhaussy, Arnaud Bertrand

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12 Scopus citations


Bifrequency acoustic data, hydrological measurements and satellite data were used to study the vertical distribution of macrozooplankton in the Bay of Biscay in relation to the hydrological conditions and fish distribution during spring 2009. The most noticeable result was the observation of a 'biocline' during the day i.e., the interface where zooplankton biomass changes more rapidly with depth than it does in the layers above or below. The biocline separated the surface layer, almost devoid of macrozooplankton, from the macrozooplankton-rich deeper layers. It is a specific vertical feature which ties in with the classic diel vertical migration pattern. Spatiotemporal correlations between macrozooplankton and environmental variables (photic depth, thermohaline vertical structure, stratification index and chlorophyll-a) indicate that no single factor explains the macrozooplankton vertical distribution. Rather a set of factors, the respective influence of which varies from region to region depending on the habitat characteristics and the progress of the spring stratification, jointly influence the distribution. In this context, the macrozooplankton biocline is potentially a biophysical response to the search for a particular depth range where light attenuation, thermohaline vertical structure and stratification conditions together provide a suitable alternative to the need for expending energy in reaching deeper water without the risk of being eaten.
Original languageEnglish (US)
Pages (from-to)e88054
JournalPLoS ONE
Issue number2
StatePublished - Feb 4 2014

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by the ECOANCHOA project funded by the Department of Agriculture and Fisheries of the Basque Government and the Ministry of Agriculture, Fishery and Food (MAPA), of the Spanish Government and a grant to AL-O (Technological Centre Foundation). This work has also benefited from the cooperation agreement between the Institut de Recherche pour le Développement and the Instituto del Mar del Perú and from the International Joint Laboratory Dynamics of the Humboldt Current System (LMI DISCOH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.


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