Seasonal modulation of mesoscale processes alters nutrient availability and plankton communities in the Red Sea
Devassy, Reny P.
El-Sherbiny, Mohsen M.
Capone, Douglas G.
Schulz, Isabelle Katharina
Al-Aidaroos, Ali M.
KAUST DepartmentRed Sea Research Center (RSRC)
Biological and Environmental Sciences and Engineering (BESE) Division
Marine Science Program
Online Publication Date2019-02-10
Print Publication Date2019-04
Permanent link to this recordhttp://hdl.handle.net/10754/631053
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AbstractHydrographic and atmospheric forcing set fundamental constraints on the biogeochemistry of aquatic ecosystems and manifest in patterns of resource (nutrient) availability and recycling, species composition of communities, trophic dynamics, and ecosystem metabolism. In the Red Sea, gradients in environmental conditions and primary production have been ascribed to fluctuations in Gulf of Aden Water inflow, upwelling/mixing, and regenerated nutrient utilization i.e. rapidly recycled nitrogen in upper layers. However, the understanding of upper layer dynamics and related changes in plankton communities, metabolism and carbon and nitrogen export is limited. We surmised that stratification and mesoscale eddies modulate the nutrient availability and taxonomic identity of plankton communities in the central Red Sea. Based on remote-sensing data of sea level anomalies and high resolution in situ profiling (ScanFish) we selected stations for hydrographic CTD profiles, water sampling (nutrients, seawater stable oxygen isotopes [δ18OSW]), phytoplankton and zooplankton collections. In fall 2014, strong stratification subjected the plankton community to an overall nitrogen and phosphorus shortage. The nutrient deficiency increased numbers of heterotrophic dinoflagellates, microzooplankton, and diazotrophs (Trichodesmium, diatom-diazotroph associations [DDAs]), albeit largely decreased phytoplankton and mesozooplankton abundances. In spring 2015, mesoscale eddies increased the nutrient availability, and the thermohaline characteristics and low δ18OSW point to the interaction of eddies with Gulf of Aden Surface Water (GASW). Cyclonic eddies and, most likely, the availability of nutrients associated with the GASW, increased the abundances of autotrophs (diatoms, Prasinophytes) and supported larger numbers of zooplankton and their larvae. We demonstrate that the interplay of stratification, advection of Gulf of Aden water and mesoscale eddies are key to better understand changes in plankton community composition, ecosystem metabolism, and macronutrient export in the Red Sea in space and time.
CitationKürten B, Zarokanellos ND, Devassy RP, El-Sherbiny MM, Struck U, et al. (2019) Seasonal modulation of mesoscale processes alters nutrient availability and plankton communities in the Red Sea. Progress in Oceanography. Available: http://dx.doi.org/10.1016/j.pocean.2019.02.007.
SponsorsWe thank the captains and crew of RV Thuwal, cruise participants, and the Coastal and Marine Resources Core Laboratories (CMOR). We are indebted to T. Gunderson, M. Tiahlo and M. Morando (USC) for providing ammonia data. We are thankful for the support from S. Kürten and P. Compean in the laboratory, S. Tiwari for providing HyperPro data, and S. Steinke for remote-sensing data visualization (all KAUST). This study used E.U. Copernicus Marine Service Information. Research reported in this publication was supported by the King Abdullah University of Science and Technology (KAUST) through the Competitive Center Funding program. We acknowledge E. Raes and one anonymous reviewer for their constructive feedback which helped to greatly improve the manuscript.
JournalProgress in Oceanography