Rovira-Peña, Wilson
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Publication Characterizing zooplankton and micronekton diel vertical migration at the western Puerto Rican shelf/slope break(2006) Rovira-Peña, Wilson; García-Saís, Jorge R.; College of Arts and Sciences - Sciences; Capella, Jorge E.; Armstrong, Roy A.; Aponte, Nilda E.; Department of Marine Sciences; Alfaro, MónicaDiscrete zooplankton/micronekton samples from three plankton cruises were collected over a moored Bluewater Broadband ADCP in Mona Passage, west of Puerto Rico to: describe the taxonomic composition, vertical distribution, and diel vertical migrations of the zooplankton/micronekton community, and calibrate ADCP echo intensity data (relative backscatter strength, RBS) versus zooplankton/micronekton biomass and density. A Tucker trawl system (mesh size: 0.2, 0.3, 0.5, 1.0 mm) sampling in vertically stratified step-oblique net tows was used to collect, quantify, and identify zooplankton/micronekton taxa. Three 24-hour net tow stations were occupied over the insonified cone of the 76.8 kHz Acoustic Doppler Current Profiler (ADCP). Echo intensity and current velocity data were acquired from the ADCP. Relative backscatter strength (RBS) time-series contours revealed persistent DVM layers in Mona Passage and La Parguera at depths of 150 and 400 m. Diel vertical migrator (DVM) layers were observed to migrate with maximum vertical velocity ranging from 4 to 12 cm/s. Copepods were the dominant taxon collected in all events, presenting a relative abundance (RA) of approximately 89% of the total zooplankton. The copepod assemblage included Candacia pachydactila, Undinula vulgaris, Euchaeta marina, and Scolecithrix danae. Euphausiids, generally strong migrators, were represented by several species of the genus Stylocheiron, Nematoscelis and Euphausia. Statistically significant differences of zooplankton abundance with depth and time of day were detected for several taxonomic groups. Positive linear regressions between RBS and zooplankton/micronekton biomass and densities were statistically significant for several taxonomic groups in the Mona Challenge and Abril La Sierra 2004 cruises. These findings confirmed the existence of a deep scattering layer comprised of zooplankton and micronekton in Caribbean waters, and confirmed the effectiveness of indirect approaches such as the RBS produced by ADCPs to detect such phenomena.