Ronen Alkalay- Jointly supervised with Prof. Yishai Weinstein- Faculty of Geography and Environment, Bar Ilan University. Prof. Ilana Berman-Frank- Leon H. Charney School of Marine Sciences, University of Haifa, and Dr. Timor Katz- Israel Oceanographic and Limnological Research.

Title of PhD project: Particulate carbon export in the Levantine Basin (East Mediterranean Sea)

About 10-30% of the net primary production, produced in the oceans photic zone, is exported downwards by the biological pump. This pump is an important buffering agent of atmospheric CO2, and it forms significant foundation for most of the heterotrophic life in the deep-sea. It is commonly estimated that 80% of the export settles as particulate matter mainly via passive sinking of aggregates and fecal pellets aided by mineral ballast. Nevertheless, in oligotrophic areas, such as the Levantine Basin, observations and modelling suggest that of the exported carbon, usually only ca. 10% survives the travel through the oceanic Twilight Zone (TLZ, i.e. 200 to ~1,000 m depth) and reaches the deep, Dark Zone.

In this study, the first of its kind in this area, we have deployed and operated the “Deep-lev moored observatory”, which is located 50k of shore, at water depth of 1500m.

In this observatory we are using a variety of 16 sensors to collect physical and biological parameters,

The main components of the system are three sediment traps to study the flux of particulate matter.

The flux of particulate matter consists mainly on biogenic and lithogeny substances.

In the research I am involved with we are using two complementary methods –

1. Measurements of captured material by time series sediment traps.
2.  Radioisotope technique, based on a radioactive disequilibrium between 238U and 234Th.  Disequilibrium arises when 234Th adheres to particulate matter and sinks.

Due to the unique characteristic of the Levantine basin it may serve as a model for carbon fluxes  in a warming, oligotrophic regions in the ocean.

Publications

Alkalay, R., Pasternak, G., Zask, A., 2007. Clean-coast index-A new approach for beach cleanliness assessment. Ocean Coast. Manag. 50.

Alkalay, R., Zlatkin, O., Katz, T., Herut, B., Halicz, L., Berman-Frank, I., Weinstein, Y., 2020. Carbon export and drivers in the southeastern Levantine Basin. Deep. Res. Part II Top. Stud. Oceanogr. 171, 104713.

Avnaim-Katav, S., Herut, B., Rahav, E., Katz, T., Weinstein, Y., Alkalay, R., Berman-Frank, I., Zlatkin, O., Almogi-Labin, A., 2020. Sediment trap and deep sea coretop sediments as tracers of recent changes in planktonic foraminifera assemblages in the southeastern ultra-oligotrophic Levantine Basin. Deep. Res. Part II Top. Stud. Oceanogr. 171, 104669.

Katz, T., Weinstein, Y., Alkalay, R., Biton, E., Toledo, Y., Lazar, A., Zlatkin, O., Soffer, R., Rahav, E., Sisma-Ventura, G., Bar, T., Ozer, T., Gildor, H., Almogi-Labin, A., Kanari, M., Berman-Frank, I., Herut, B., 2020. The first deep-sea mooring station in the eastern Levantine basin (DeepLev), outline and insights into regional sedimentological processes. Deep. Res. Part II Top. Stud. Oceanogr. 171, 104663.

STERN, N., ALKALAY, R., LAZAR, A., KATZ, T., WEINSTEIN, Y., BERMAN-FRANK, I., & HERUT, B. (2020). Unexpected massive enmeshments of the Sharpchin barracudina Paralepis coregonoides Risso, 1820 in mesopelagic sediment traps in the Levantine Basin, SE Mediterranean Sea. Mediterranean Marine Science, 21(1), 47-51.