Welcome to the Rahav lab
The impact of nutrient loads on bacterial and primary productivity at the Israeli Mediterranean coastline
The Eastern Mediterranean Sea is one of the most oligotrophic regions in the world's oceans and thus extremely sensitive to nutrients loads and potentially to climate changes. To date, nearly nothing is known about the bacteria-phytoplankton dynamics in this habitat (bottom of the food chain), especially along its coastline. Further, the coastal areas are constantly exposed to varying sources of nutrient inputs, including desalination effluents, ground waters discharges, sewage effluents, river outlets and tourism that significantly affect the ecology of these habitats. For that, we routinely monitor the Israeli coast and study how nutrient inputs affect bacteria and phytoplankton production and diversity. We conduct field and laboratory bioassay experiments in mesocosms, enabling us to better understand the current state and potential impact of nutrient inputs into the coastal environment. We characterize the dominant bacterial organisms using molecular tools (i.e. 16S and 18S), flow-cytometry (i.e. pico-phytoplankton characterization and bacterial counts), epi-fluorescence microscopic, analyses, and pigment analyses using HPLC
The impact of airborne microbes transported by desert dust into the southeastern Mediterranean Sea
Deposition of atmospheric dust is widely recognized as an important source of nutrients to surface seawater. Yet, it can also supply a high diversity of microorganisms, including bacteria, fungi, spores and virus originating form land and ocean areas throughout the world. We examine the role of airborne microorganisms in the oligotrophic southeastern Mediterranean Sea, an area receiving high levels of atmospheric input from diverse origins. We study specific bacterial groups of interest introduced with the dust and study how the 'biological' component interacts with surface marine ambient populations. The work here involves both laboratory (controlled micro and mesocosms) and field approaches (aboard the R/V Shiqmona and R/V Bat-Galim).
Influence of brine discharge on the benthonic microbial communities
Seawater desalination facilities continuously discharge hypersaline brine (up to 80 ppt) into the coastal environment. Brine waste is often denser than ambient seawater and therefore sink and flow along the seafloor. We study how this accumulation of brine within the sediment, alter microbial diversity, activity and growth rates. We conduct controlled laboratory experiments in specifically designed cores system aimed to study short and long effects of different salinities on benthic communities (both in pore waters and attached to sediment). Our work also involves field measurements aboard the R/V Etziona.
Response of oligotrophic microbial populations in the SE Mediterranean Sea to crude oil and condensate pollution
Anthropogenically-induced oil spills release large amounts of organic pollutants into the marine environment (both the water column and the sediments). We investigate the response of microbial populations (biomass, activity and diversity) to crude oil pollution and/or condensate in the coastal and offshore waters at the Israeli EEZ.