Publications

Selected recent publicaitons

Discovery and chemical composition of the eastmost deep-sea anoxic brine pools in the Eastern Mediterranean Sea

We discovered the eastmost brine pools in the Mediterranean Sea, 60 km offshore Israel at 1150 m water depth. These Palmahim brine pools are located directly above Messinian evaporites, which were up thrust to ~350 m below the seafloor. We found a bunch of small, anoxic, methanic and warm (21.6°C) brine pools, with salinity 1.5 times the ambient. This paper discusses their chemical properties and compares them with other deep saline basins.

Cold seeps alter the near-bottom biogeochemistry in the ultraoligotrophic Southeastern Mediterranean Sea

Gas seeps at Palmahim Disturbance offshore Israel potentially affect the functionality of the deep oligotrophic Southeastern Mediterranean Sea. This study is truly a multidisciplinary effort, combining chemists (including the leading author Dr. Guy Sisma-Ventura), physical oceanographers, geologists and biologists. We show that gas seepage may lower the pH of water as low as 6.8 tens of meters above the seep site, and alter the N to P ratio to 30:1–53:1. Bioturbated sediments near the Palmahim Disturbance seeps catalyze rapid nutrient cycling. We show high microbial activity and changes in microbial communities near the seabed, even in seeps with low activity. 

These sites export C and N into the water column, changing the deep hydrosphere.

Diversity, activity and abundance of benthic microbes in the Southeastern Mediterranean Sea

Microbes are great for biomonitoring! We sampled marine sediments from various depths (6-2000 m), offshore the Levant basin, within the framework of the National Monitoring Program of the Israeli Mediterranean Waters, in years 2018-2020. We show how the bacteria, archaea and fungi are distributed offshore, over coastal, shelf, slope and bathyal stations. One of the main findings indicates that microbial indices are affected by the downslope transport of organic matter. 

The worm affair: fidelity and environmental adaptation in symbiont species that co-occur in vestimentiferan tubeworms

This paper is led by Tal Zvi Kedem. We investigate the fascinating symbiosis between deep-sea tubeworms and chemosynthetic bacteria.  Two closely-related symbiont species often co-occur in one tubeworm host. We used this natural experimental system to ask how the fidelity of these associations is maintained.

We collaborated with the laboratory of Prof. Orit Sivan, using metagenomics to look for microbes that mediate iron cycling and methane oxidation in anoxic lake sediments.

We used mesocosm experiments to investigate the response of microbial communities to crude oil pollution in the Eastern Mediterranean.

Metagenomes of Red Sea subpopulations challenge the use of marker genes and morphology to assess Trichodesmium diversity

Trichodesmium is a globally-important, nitrogen-fixing, bloom-forming cyanobacterium. Coco Koedooder investigated the genotypes of the Red Sea Trichodesmium that form distinct colony morphotypes - two types of spherical "puffs" and raft-like "tufts". Puffs were shaped by Trichodesmium thiebautii and tufts by Trichodesmium erythraeum. Coco also identified genotypes of Trichodesmium that do not fix nitrogen. Previous attempts to look at the Red Sea Trichodesmium population structure using the hetR marker gene revealed a higher diversity. They found other species such as Trichodesmium aureum. Still, this metagenomics study suggests that the presence of hetR gene paralogs in Trichodesmium thiebautii genomes may account for the inflation in diversity. Great collaboration with Yeala Shaked's laboratory!