Abstract
The Eastern Mediterranean Sea (EMS) is a poorly studied ultra-oligotrophic marine environment, dominated by small-size phyto- and bacterioplankton. Here, we describe the dynamics of a single annual cycle (2018–19) of phyto- and bacterioplankton (abundances, pigments and productivity) in relation to the physical and chemical conditions in the photic water column at an offshore EMS site (Station THEMO-2, ∼1,500 m depth, 50 km offshore). We show that phytoplankton biomass (as chlorophyll a), primary and bacterial productivity differed between the mixed winter (January–April) and the thermally stratified (May–December) periods. Prochlorococcus and Synechococcus numerically dominated the picophytoplankton populations, with each clade revealing different temporal and depth changes indicative to them, while pico-eukaryotes (primarily haptophytes) were less abundant, yet likely contributed significant biomass. Estimated primary productivity (∼32 gC m−2 y−1) was lower compared with other well-studied oligotrophic locations, including the north Atlantic and Pacific (BATS and HOT observatories), the western Mediterranean (DYFAMED observatory) and the Red Sea, and was on-par with the ultra-oligotrophic South Pacific Gyre. In contrast, integrated bacterial production (∼11 gC m−2 y−1) was similar to other oligotrophic locations. Phytoplankton seasonal dynamics were similar to those at BATS and the Red Sea, suggesting an observable effect of winter mixing in this ultra-oligotrophic location. These results highlight the ultra-oligotrophic conditions in the EMS and provide, for the first time in this region, a full-year baseline and context to ocean observatories in the region.
Original language | American English |
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Article number | 103720 |
Journal | Deep-Sea Research Part I: Oceanographic Research Papers |
Volume | 182 |
DOIs | |
State | Published - Apr 2022 |
Bibliographical note
Funding Information:We thank the captains and crew of the R/V Mediterranean Explorer (EcoOcean) and R/V Bat-Galim (IOLR), Oshra Yosef, Elad Rachmilovitz, Guy Sisma-Ventura for help with the sampling. The SoMMoS ship-time was funded by the Leon H. Charney School of Marine Sciences with help from EcoOcean and IOLR. This study was supported by grant RGP0020/2016 from the Human Frontiers Science Program (to DS), by grant number 1635070/2016532 from the NSF-BSF program in Oceanography (NSFOCE-BSF, to DS), and partly by the Israel Science Foundation (grants number 1211/17 to ER and BH and 996/08 to I. B–F and B.H). This study is in partial fulfilment of the M. Sc. thesis of Tom Reich (University of Haifa).
Funding Information:
We thank the captains and crew of the R/V Mediterranean Explorer (EcoOcean) and R/V Bat-Galim (IOLR), Oshra Yosef, Elad Rachmilovitz, Guy Sisma-Ventura for help with the sampling. The SoMMoS ship-time was funded by the Leon H. Charney School of Marine Sciences with help from EcoOcean and IOLR. This study was supported by grant RGP0020/2016 from the Human Frontiers Science Program (to DS), by grant number 1635070/2016532 from the NSF-BSF program in Oceanography (NSFOCE-BSF, to DS), and partly by the Israel Science Foundation (grants number 1211/17 to ER and BH and 996/08 to I. B?F and B.H). This study is in partial fulfilment of the M. Sc. thesis of Tom Reich (University of Haifa).
Publisher Copyright:
© 2022 Elsevier Ltd
Keywords
- Bacterial productivity
- Eastern mediterranean
- Levantine basin
- Phytoplankton
- Pico-eukaryotes
- Primary productivity
- Prochlorococcus
- Seasonal dynamics
- Synechococcus