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Temporal variations of zooplankton biomass in the Ligurian Sea inferred from long time series of ADCP data

August 24, 2013

Three years of 300 kHz ADCP data collected in the central Ligurian Sea are analyzed to investigate the variability of the zooplankton biomass and the Diel Vertical Migrations (DVM) in the upper thermocline. After a pre-processing aimed at avoiding the slant range attenuation, hourly volume backscattering strength time series are obtained. Despite the lack of concurrent net samples collection, different migration patterns are identified and their temporal variability examined by means of time-frequency analysis. The effect of changes in the environmental condition is also investigated. Highest zooplankton biomasses are observed in April–May just after the peak of surface primary production in March–April. The main migration pattern points to a “nocturnal” migration with zooplankton organisms occurring deeper in the water column during the day and shallower at night. Also twilight migration is highlighted during this study. The largest migrations are recorded in November–December, corresponding to lowest backscattering strength values and are likely attributable to larger and more active organisms (i.e. euphausiids and mesopelagic fish). The results suggest further applications of the historical ADCP time series available.

Bozzano R, Fanelli E, Pensieri S, Picco P, Schiano M E, 2013, Temporal variations of zooplankton biomass in the Ligurian Sea inferred from long time series of ADCP data,Ocean Science Discussions, 10, 1367-1404, doi:10.5194/osd-10-1367-2013. Article (subscription required).

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