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Open AccessArticle

Picoplankton Distribution and Activity in the Deep Waters of the Southern Adriatic Sea

1
Institute of Oceanography and Fisheries, Šetalište Ivana Meštrovića 63, POB 500, 21000 Split, Croatia
2
National Institute of Oceanography and Applied Geophysics, Borgo Grotta Gigante 42/c, 34010 Sgonico (Ts), Italy
3
University of Split, University Department of Marine Studies, Ruđera Boškovića 37, 21000 Split, Croatia
*
Author to whom correspondence should be addressed.
Water 2019, 11(8), 1655; https://doi.org/10.3390/w11081655
Received: 19 July 2019 / Revised: 7 August 2019 / Accepted: 8 August 2019 / Published: 10 August 2019
(This article belongs to the Special Issue Ocean Exchange and Circulation)
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Abstract

Southern Adriatic (Eastern Mediterranean Sea) is a region strongly dominated by large-scale oceanographic processes and local open-ocean dense water formation. In this study, picoplankton biomass, distribution, and activity were examined during two oceanographic cruises and analyzed in relation to environmental parameters and hydrographic conditions comparing pre and post-winter phases (December 2015, April 2016). Picoplankton density with the domination of autotrophic biomasses was higher in the pre-winter phase when significant amounts of picoaoutotrophs were also found in the meso-and bathy-pelagic layers, while Synechococcus dominated the picoautotrophic group. Higher values of bacterial production and domination of High Nucleic Acid content bacteria (HNA bacteria) were found in deep waters, especially during the post-winter phase, suggesting that bacteria can have an active role in the deep-sea environment. Aerobic anoxygenic phototrophic bacteria accounted for a small proportion of total heterotrophic bacteria but contributed up to 4% of bacterial carbon content. Changes in the picoplankton community were mainly driven by nutrient availability, heterotrophic nanoflagellates abundance, and water mass movements and mixing. Our results suggest that autotrophic and heterotrophic members of the picoplankton community are an important carbon source in the food web in the deep-sea, as well as in the epipelagic layer. Besides, viral lysis may affect the activity of the picoplankton community and enrich the water column with dissolved organic carbon. View Full-Text
Keywords: picoplankton community; deep-sea; Southern Adriatic; Mediterranean Sea picoplankton community; deep-sea; Southern Adriatic; Mediterranean Sea
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Šantić, D.; Kovačević, V.; Bensi, M.; Giani, M.; Vrdoljak Tomaš, A.; Ordulj, M.; Santinelli, C.; Šestanović, S.; Šolić, M.; Grbec, B. Picoplankton Distribution and Activity in the Deep Waters of the Southern Adriatic Sea. Water 2019, 11, 1655.

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