Tal Ben-Ezra, PhD student


Tal Ben-Ezra- Jointly supervised with Prof. Danny Tchernov and Prof. Michael D. Krom, Department of Marine Biology, Haifa University

Quantifying and Understanding the seasonality of nutrient limitation in the EMS

The Eastern Mediterranean Sea (EMS) is a unique body of water that was recently suggested to have a seasonal switch in the nutrient limiting primary productivity (PP). High nitrate+nitrite (N+N) in winter, while soluble reactive phosphate (SRP) below detection limits (BDL), and with the progression of summer, N+N decrease in the photic zone. Thus at the end of summer, the system was characterized as co-limited. Both the temporal and spatial resolution of this switch is in need of further investigation. Furthermore, the secondary limiting nutrient i.e. the access concentrations of the nutrient that is not currently limiting and is available in the photic zone is also an important parameter in order to evaluate the system’s plasticity and productive potential. In this study, firstly I intend to perform monthly nutrient measurements on EMS off-shore water. Secondly, I intend to perform seasonal bioassays based on Alkaline Phosphatase Activity (APA) and nutrient enrichment titrations as a tool to investigate how the microbial community responds to nutrient enrichments, how far is the system from one type of limitation or another, how it changes with season and how sharp the transition between the two limitations is according to the changing nutrient regimes during different seasons. This method allows us to ask questions about the limitation dynamic but from the organisms’ perspective i.e. what nutrients does the microbial community “see”? This fundamental understanding of the system is crucial in order to formulate science-based management decisions and sustainable usage of this valuable resource.