Inter-Annual Variability in Phytoplankton and Nutrients in the Gulf of Elat/Aqaba

Hadar Berman*, Hezi Gildor, Erick Fredj

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The Gulf of Elat/Aqaba exhibits high inter-annual variability in mixed layer depth. Observations from the northern Gulf show differences of hundreds of meters in winter mixing depth, which ranges between 300 m in years with shallow mixing and up to 700 m in years with deep mixing. Deep mixing events can occur in two consecutive years or after four consecutive years of shallow mixing. The mixing depth has an effect on the concentration of nutrients and chlorophyll (and other tracers) in the surface and deep water. Using a 3D coupled physical-ecological model, we studied the effect of shallow versus deep mixing on the processes controlling the phytoplankton bloom and on nutrient accumulation in the deep water. We found that years with deep mixing are characterized by larger spatial variability in surface and integrated chlorophyll concentration during the mixing season. We found that horizontal advection is a dominant contributor for integrated phytoplankton concentration in years with deep mixing in the northern Gulf. Even when mixing was deep and nutrient limitation decreased, light limitation on phytoplankton integrated growth was enhanced in the north compared with the south. In addition, we showed that the nutrient accumulation in the deep water after a year with deep mixing in the northern Gulf was initially affected mostly by physical processes (such as advection and vertical mixing), and less from ecological regeneration, and switched to be dominated by ecological processes alone during the third year after mixing.

Original languageAmerican English
Article numbere2022JC019431
JournalJournal of Geophysical Research: Oceans
Volume128
Issue number6
DOIs
StatePublished - Jun 2023

Bibliographical note

Publisher Copyright:
© 2023. The Authors.

Keywords

  • deep mixing
  • horizontal advection
  • inter-annual variability
  • nutrient accumulation
  • physical-biological interactions
  • phytoplankton

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