Zooplankton diel vertical migration in the Corsica Channel (north-western Mediterranean Sea) detected by a moored acoustic Doppler current profiler

Abstract

Abstract. Diel vertical migration (DVM) is a survival strategy adopted by zooplankton that we investigated in the Corsica Channel using acoustic Doppler current profiler (ADCP) data from April 2014 to November 2016. The principal aim of the study is to characterize migration patterns and biomass temporal evolution of zooplankton along the water column. The ADCP measured vertical velocity and echo intensity in the water column range between about 70 and 390 m (the bottom depth is 443 m). During the investigated period, zooplanktonic biomass had a well-defined daily and seasonal cycle, with peaks occurring in late winter to spring (2015 and 2016) when the stratification of the water column is weaker. Zooplanktonic biomass temporal distribution in the whole water column is well correlated with biomass of primary producers, estimated with satellite data. Zooplanktonic blooming and non-blooming periods have been identified and studied separately. During the non-blooming period zooplanktonic biomass was most abundant in the upper and the deep layers, while during the blooming period the upper-layer maximum in zooplanktonic biomass disappeared and the deep layer with high zooplanktonic biomass became thicker. These two layers are likely to correspond to two different zooplanktonic communities. The evolution of zooplanktonic biomass is well correlated with chlorophyll, with phytoplankton biomass peaks preceding the upper-layer secondary production by a lag of about 3.5 weeks. Nocturnal DVM appears to be the main pattern during both periods, but reverse and twilight migration are also detected. Nocturnal DVM was more evident at mid-water than in the deep and the upper layers. DVM occurred with different intensities during blooming and non-blooming periods. One of the main outcomes is that the principal drivers for DVM are light intensity and stratification, but other factors, like the moon cycle and primary production, are also taken in consideration.

Impact of tidal dynamics on diel vertical migration of zooplankton in Hudson Bay

“…However, there has been a recent success in using data obtained by an Acoustic Doppler Current Profiler (ADCP), which is a modern oceanographic instrument commonly used to measure the vertical profile of current velocities. Because the velocity profiling by an ADCP is based on processing the measured intensity of acoustic pings backscattered by suspended particles in the water column, further processing of the measured acoustic backscatter to volume backscatter strength (Deines, 1999) has been successful in quantifying zooplankton abundance (Bozzano et al, 2014;Brierley et al, 2006;Cisewski et al, 2010;Cisewski and Strass, 2016;Fielding et al, 2004;Guerra et al, 2019;Hobbs et al, 2018;Last et al, 2016;Lemon et al, 2008;Petrusevich et al, 2016;Potiris et al, 2018, etc.). ADCP backscatter data, validated using a time-series of zooplankton samples collected from sediment traps, provides a particularly useful tool for understanding the effects of physical oceanographic processes on zooplankton DVM, changes in zooplankton community composition throughout the year, and an overall better understanding of the marine ecosystem function and carbon cycling (Berge et al, 2009;Willis et al, 2006Willis et al, , 2008.…”

Thin layers in the coastal zone of Ubatuba, Brazil: Mechanisms of formation and dissipation

“…The RVBS (in dB), obtained from ADCP acoustic backscatter data, is a measure that can be used to estimate the relative amount of particles suspended in the water (such as sediments, organisms or bubbles) (Guerra et al 2019). On February 20 th , the RVBS distribution revealed higher values (> 65 dB) in the upper mixed layer (~ 3–6 m) and near‐bottom (24–25 m; Fig.…”

“…7c). As zooplankton swarms tend to aggregate at specific depths (Guerra et al 2019), the higher intensity of RVBS may indicate the detection of a zooplankton layer in this region. Mesozooplankton organisms such as appendicularians, cnidarians and chaetognaths, were detected by the imaging system in this depth range.…”

Daily vertical distribution of zooplankton in two oligo-mesotrophic north Patagonian lakes (39° S, Chile).

“…Typically, descending at dawn reduces the risk of predation, whereas ascending at dusk allows species to feed on zooplankton. In contrast, "twilight" and "reverse" DVM patterns are less common (Guerra et al, 2019).…”