Prof. Ilana Berman-Frank, of the Mina and Everard Goodman Faculty of Life Sciences, is researching the ecophysiology of phytoplankton and processes that are important in controlling aquatic primary productivity and nitrogen fixation, a biological transformation carried out by a small group of organisms that introduce atmospheric nitrogen (N2) into nitrogen limited oceanic waters and convert it into a usable form.
Berman-Frank and her research team explore how these organisms influence bio-geochemical cycling of carbon and nitrogen in the face of climatic changes. These changes include global warming and ocean acidification due to increased dissolution of atmospheric CO2 in the oceans.
Berman-Frank’s team has examined the globally important model N2 fixing organisms such as Trichodesmium, the dominant cyanobacterium of the tropical oceans with blooms extending over thousands of kilometers.
They have demonstrated that the future projections of high CO2 in the oceans can enhance nitrogen fixation and growth of this marine cyanobacterium. Their conclusions indicate thatTrichodesmium will thrive in the future warmer and more acidified oceans.
They have also examined changes in natural populations of nitrogen fixers from differing habitats (Red-Sea, Atlantic, Mediterranean Sea) under the combined effects of elevated CO2and higher temperatures as well as changes in essential nutrients such as phosphate and Fe that are expected to influence phytoplankton including nitrogen fixers in the future surface oceans. Thus strategies enabling more efficient nutrient uptake are important. Collaboration with colleagues on the iron uptake of Red Sea populations of Trichodesmiumhas illustrated that the colonies actively take up and shuttle Fe along the filaments to the center of the colony where it is dissolved and assimilated into the cells.
Trichodesmium undergoes an autocatalytic, genetically programmed cell death – a process that has been studied extensively by Berman-Frank and her colleagues and occurs in response to environmental stressors such as high irradiance and Fe limitation.
Their research attempts to link this form of death, which occurs in blooms ofTrichodesmium, to increased carbon export to the deep ocean. Carbon export is essential in biogeochemical cycling, and results in an increased capacity of the oceans to sequester CO2. If autocatalytic PCD enhances sinking of the blooms this could increase the flux of carbon to the deep ocean rather than recycling of organic matter within the surface layers.
The eastern Mediterranean Sea is known as a “blue desert”, poor in nutrients with subsequently low primary production. Berman-Frank’s team
studies the role of nitrogen fixers in the Levantine basin and eastern Mediterranean and the environmental controls on these organisms and other primary producers. They have elucidated the organisms responsible for nitrogen fixation and calculated their contribution to primary productivity and new production in the eastern Mediterranean.
In other collaborative studies, Berman-Frank’s group is examining the effects of nutrient enrichment on phytoplankton including harmful algal bloom forming species, and on N2fixers in coastal areas.
Working with the desalination industries, they are involved in characterizing and reducing the formation of natural biofilms that clog reverse osmosis membranes, decreasing efficiency and increasing costs of the desalination process.