Biology subjects

Tchernov, D.

Publications and source records attributed to Tchernov, D..

9 recordsLinked to original sources

bioRxiv2025

Microbiota Dynamics in Lionfish (Pterois): Insights into Invasion and Establishment in the Mediterranean Sea

Lionfishes (Pterois spp.), originally native to the Indo-Pacific and Red Sea, have become one of the most invasive marine species globally, including the recent establishment in the Mediterranean Sea. This study investigates the microbiota of lionfish to explore its potential role in their invasion success and establishment. Using high-throughput sequencing and microbiota analyses, we characterized the species-specific core microbiome and identified habitat-specific markers across different regions (Red Sea, Mediterranean Sea, Caribbean, and aquarium populations) and organs. Focusing on the Mediterranean invasion, we tracked lionfish distribution and population dynamics along the Israeli coastline from 2017 to 2023, monitoring size, seasonal trends, and depth preferences. Our findings reveal that lionfish initially established themselves in deeper waters before expanding to shallower habitats, with a gradual increase in population size and body length over time. From a microbial aspect, we compared the microbiota of lionfish organs and identified a similar pattern (Photobacterium), to Earlier Lessepsian migrants fish species. This study provides novel insights into the interactions between microbiota and host ecology, shedding light on the mechanisms that may support the successful invasion. This study contributes to the understanding of lionfish invasion dynamics in the Mediterranean. It highlights the microbiota as an integral component for studying the ecological and biological mechanisms underpinning invasive species success and establishment of lionfish.

ecology↗

bioRxiv2024

Interannual changes in nutrient and phytoplankton dynamics in the Eastern Mediterranean Sea (EMS) predict the consequences of climate change; results from the Sdot-Yam Time-series station 2018-2022

Global climate change is predicted to reduce nutrient fluxes into the photic zone, particularly in tropical and subtropical ocean gyres, while the occasional major storms will result in increased nutrient pulses. In this study the nutrient and phytoplankton dynamics have been determined at a new time-series station in the southeastern Levantine basin of the Eastern Mediterranean Sea (EMS) over 4.5 years (2017-2022). In 2018 and 2019, there was a moderate concentration of residual nitrate and nitrite (N+N) in the photic zone (280-410nM) in winter, resulting in phytoplankton dynamics dominated by cyanobacteria with relatively few picoeukaryotes (280{+/-} 90 gC m-2). Winter storm driven mixing was much reduced in 2020 and particularly in 2021, resulting in a lower concentration of N+N in the photic zone, which decreased during summer stratification, such that by August 2021, the N+N was highly depleted (<60 nM) resulting in an integrated phytoplankton biomass of 23 gC m-2. A major storm in December 2021 (Storm Carmel) injected high N+N (750 nM; max = 1090 nM) in the upper 100 m, which stimulated pico and nanophytoplankton biomass ([~]2400 gC m-2) and probably increased eukaryotes (diatoms). The pattern of measured silica reinforced our conclusion that we sampled 3 different nutrient and ecosystem states. Phosphate was always at or close to LoD because of rapid uptake by cyanobacteria into their periplasm. These results predict that climate change in the EMS will result in periods of nutrient and phytoplankton depletion (Famine) interrupted by short periods of Mesotrophy (Feast) caused by major storms. Highlights- Nutrient dynamics from 4 years of Time-series station in the S.E. Levantine basin - Defined ecosystem status of normal, depleted and temporarily mesotrophic which are predicted status caused by climate change - Winters with low deep mixing resulted in severely nutrient depleted conditions subsequently - Major storm and relatively shallow nutricline resulted in temporary mesotrophic status

ecology↗

bioRxiv2023

New record of Dendronephthya hemprichi (Family: Nephtheidae) fromMediterranean, Israel- an evidence for tropicalization?

Bioinvasions have the potential to provoke cascade effects that can disrupt natural ecosystems, and cause ecological regime shifts. The Mediterranean Sea is particularly prone to bioinvasions as the changing water conditions, evoked by climate change, are creating advantageous conditions for Lessepsian migrants from the Red Sea. Recently, in May 2023, a new alien species was documented in the Mediterranean Sea - a soft coral of the genus Dendronephthya. This discovery was made by divers conducting Long Term Ecological Research surveys, along the coast of Israel, at a depth of 42 m. Genetic and morphological testing were utilized to confirm the species identity as Dendronepthya hemprichi, an Indo-Pacific coral, common in the Red Sea. According to life history traits of this species such as accelerated attachment to available surfaces and fast growth, we expect it to rapidly expand its distribution and abundance across the Mediterranean. HighlightsO_LIPotential Tropicalization of the Mediterranean Sea C_LIO_LIIncreasing water temperatures are an important vector for marine bioinvasion C_LIO_LIA second soft coral species, associated with Lessepsian migration, was identified in the Mediterranean C_LIO_LIThe importance of a long-term ecological monitoring program for identifying ecosystem changes C_LI

ecology↗

bioRxiv2023

Metabolic handoffs between multiple symbionts may benefit the deep-sea bathymodioline mussels

Bathymodioline mussels rely on thiotrophic and methanotrophic chemosynthetic symbionts for nutrition, yet, secondary heterotrophic symbionts are often present and play an unknown role in the fitness of the organism. The bathymodioline Idas mussels that thrive in gas seeps and on sunken wood in the Mediterranean Sea and the Atlantic Ocean, host at least six symbiont lineages that often co-occur, including the primary, chemosynthetic methane- and sulfur-oxidizing gammaproteobacteria, and the secondary Methylophagaceae, Nitrincolaceae and Flavobacteraceae symbionts, whose physiology and metabolism are obscure. Little is known about whether and how these symbionts interact or exchange metabolites. Here we curated metagenome-assembled genomes of Idas modiolaeformis symbionts and used genomecentered metatranscriptomics and metaproteomics to assess key symbiont functions. The Methylophagaceae symbiont is a methylotrophic autotroph, as it encoded and expressed the ribulose monophosphate and Calvin-Benson-Bassham cycle enzymes, particularly RuBisCO. The Nitrincolaceae ASP10-02a symbiont likely fuels its metabolism with nitrogen-rich macromolecules and may provide the holobiont with vitamin B12. The Flavobacteriaceae Urechidicola symbionts likely degrade glycans and may remove NO. Our findings indicate that these flexible associations allow for expanding the range of substrates and environmental niches, via new metabolic functions and handoffs.

microbiology↗

bioRxiv2022

3D Imaging Reveals Resilience: Storm Impact on Coral Reef Structural Complexity

Extreme weather events are increasing in frequency and magnitude. Consequently, it is important to understand their effects and remediation. Resilience reflects the ability of an ecosystem to absorb change, which is important for understanding ecological dynamics and trajectories. To describe the impact of a powerful storm on coral reef structural complexity, we used novel computational tools and detailed 3D reconstructions captured at three time points over three years. Our data-set Reefs4D of 21 co-registered image-based models enabled us to calculate the differences at seven sites over time and is released with the paper. We employed six geometrical metrics, two of which are new algorithms for calculating fractal dimension of reefs in full 3D. We conducted a multivariate analysis to reveal which sites were affected the most and their relative recovery. We also explored the changes in fractal dimension per size category using our cube-counting algorithm. Three metrics showed a signicant difference between time points, i.e., decline and subsequent recovery in structural complexity. The multivariate analysis and the results per size category showed a similar trend. Coral reef resilience has been the subject of seminal studies in ecology. We add important information to the discussion by focusing on 3D structure through image-based modeling. The full picture shows resilience in structural complexity, suggesting that the reef has not gone through a catastrophic phase shift. Our novel analysis framework is widely transferable and useful for research, monitoring, and management. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/519015v3_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@888999org.highwire.dtl.DTLVardef@1c51dorg.highwire.dtl.DTLVardef@340d97org.highwire.dtl.DTLVardef@16865d8_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIThe effect of storms on coral reef 3D structure is poorly understood. C_LIO_LIWe studied the impact of a storm on coral reefs using a novel 3D imaging framework. C_LIO_LIWe used geometrical metrics including new methods for calculating fractal dimension. C_LIO_LIThe reefs recovered in two years with regards to structural complexity. C_LIO_LIBased on 3D analysis the reefs exhibit structural resilience. C_LI

ecology↗

bioRxiv2022

Phenotyping technology for assessing protein content in seaweed by field spectroscopy and a machine learning algorithm

Determining seaweed protein concentration and the associated phenotype is critical for food industries that require precise tools to moderate concentration fluctuations and attenuate risks. Algal protein extraction and profiling have been widely investigated, but content determination involves a costly, time-consuming, and high-energy, laboratory-based fractionation technique. The present study examines the potential of field spectroscopy technology as a precise, high-throughput, non-destructive tool for on-site detection of red seaweed protein concentration. By using information from a large dataset of 144 Gracilaria sp. specimens, studied in a land-based cultivation set-up, under six treatment regimes during two cultivation seasons, and an artificial neural network, machine learning algorithm and diffuse visible-near infrared reflectance spectroscopy, predicted protein concentrations in the algae were obtained. The prediction results were highly accurate (R2 = 0.95; RMSE = 0.84), exhibiting a high correlation with the analytically determined values. External validation of the model derived from a separate trial, exhibited even better results (R2 = 0.99; RMSE = 0.45). This model, trained to convert phenotypic spectral measurements and pigment intensity into accurate protein content predictions, can be adapted to include diversified algae species and usages. HighlightNon-destructive determination of protein content in the edible red seaweed Gracilaria sp. by in-situ, VIS-NIR spectroscopy and a machine learning algorithm.

biochemistry↗

bioRxiv2021

Physiological and transcriptomic variability indicative of differences in key functions within a single coral colony

Polyps in different locations on individual stony coral colonies experience variation in numerous environmental conditions including flow and light, potentially leading to transcriptional and physiological differences across the colony. Here, we describe high-resolution physiological measurements and differential gene expression from multiple locations within a single colony of Stylophora pistillata, aiming to relate these to environmental gradients across the coral colony. We observed broad transcriptional responses in both the host and photosymbiont in response to height above the substrate, cardinal direction, and, most strongly, location along the branch axis. Specifically, several key physiological processes in the host appear more active toward branch tips including several metabolic pathways, toxin production for prey capture or defense, and biomolecular mechanisms of biomineralization. Further, the increase in gene expression related to these processes toward branch tips is conserved between S. pistillata and Acropora spp. The photosymbiont appears to respond transcriptionally to relative light intensity along the branch and due to cardinal direction. These differential responses were observed across the colony despite its genetic homogeneity and likely inter-polyp communication. While not a classical division of labor, each part of the colony appears to have distinct functional roles related to polyps differential exposure to environmental conditions.

genomics↗

bioRxiv2021

The worm affair: Genetic diversity in two species of symbionts that co-occur in tubeworms from the Mediterranean Sea

The symbioses between the vestimentiferan tubeworms and their chemosynthetic partners (Gammaproteobacteria, Chromatiales, Sedimenticolaceae) hallmark the success of these organisms in hydrothermal vent and hydrocarbon seep deep-sea habitats. The fidelity of these associations varies, as both the hosts and the symbionts can be loose in partner choice. Some tubeworms may host distinct symbiont phylotypes, which often co-occur in a single host individual. To better understand the genetic basis for the promiscuity of tubeworm symbioses, we curated and investigated metagenome-assembled genomes of two symbiont phylotypes (species, based on the average nucleotide identity <95%) in Lamellibrachia anaximandri, a vestimentiferan endemic to the Mediterranean Sea, in individuals collected from Palinuro hydrothermal vents (Italy) and hydrocarbon seeps (Eratosthenes seamount and Palmahim disturbance). Using comparative genomics, we show that mainly mobilome and defense mechanism-related features distinguish the symbiont genotypes. While many central metabolic functions are conserved in the tubeworm symbionts, nitrate respiration (Nar, Nap and Nas proteins) is modular, yet this modularity is not linked to speciation, but rather to local adaptation. Our results hint that variation in a single moonlighting protein may be responsible for the host-symbiont fidelity.

microbiology↗

bioRxiv2020

Effect of different derivatization protocols on the calculation of trophic position using amino acids compound-specific stable isotopes

Amino acids compound-specific nitrogen stable isotope (AA-CSIA) is an emerging tool in ecology for understanding trophic system dynamics. While it has been successfully used for several independent studies across a range of environments and study locations, researchers have encountered calculation issues for determining trophic position values. Most studies introduce modifications to the constants of trophic position equation calculations, but then fail to account for the equation variations when comparing the results of separate research studies. The acceptance of this approach is related to the underlying presumption that no addition of the exogenous nitrogen atom occurs in the different methods and, therefore, such variations should not affect the outcome. In this paper, we evaluate the use of the EZfaast amino acid derivatization kit (chloroformate) and compare it to the isotopic results of two other derivatization methods. We highlight new considerations for working with AA-CSIA that might account for some of the variations in the results and lead researchers to modify constants in the equation. This likely requires developing the unique constants per derivatization method in order to be able to compare the trophic position results across different studies.

ecology↗