Interuniversity Institute for Marine science in Eilat

Eilat, Israel

Interuniversity Institute for Marine science in Eilat

Eilat, Israel
Time filter
Source Type

Tremblay P.,Center Scientifique Of Monaco | Tremblay P.,University of Quebec at Rimouski | Fine M.,Interuniversity Institute for Marine Science in Eilat | Fine M.,Bar - Ilan University | And 3 more authors.
Biogeosciences | Year: 2013

This study has examined the effect of low seawater pH values (induced by an increased CO2 partial pressure) on the rates of photosynthesis, as well as on the carbon budget and carbon translocation in the scleractinian coral species Stylophora pistillata, using a new model based on 13C labelling of the photosynthetic products. Symbiont photosynthesis contributes to a large part of the carbon acquisition in tropical coral species, and it is thus important to know how environmental changes affect this carbon acquisition and allocation. For this purpose, nubbins of S. pistillata were maintained for six months at two pHTs (8.1 and 7.2, by bubbling seawater with CO2). The lowest pH value was used to tackle how seawater pH impacts the carbon budget of a scleractinian coral. Rates of photosynthesis and respiration of the symbiotic association and of isolated symbionts were assessed at each pH. The fate of 13C photosynthates was then followed in the symbionts and the coral host for 48 h. Nubbins maintained at pHT 7.2 presented a lower areal symbiont concentration, and lower areal rates of gross photosynthesis and carbon incorporation compared to nubbins maintained at pHT 8.1. The total carbon acquisition was thus lower under low pH. However, the total percentage of carbon translocated to the host as well as the amount of carbon translocated per symbiont cell were significantly higher under pHT 7.2 than under pHT 8.1 (70% at pHT 7.2 vs. 60% at pHT 8.1), such that the total amount of photosynthetic carbon received by the coral host was equivalent under both pHs (5.5 to 6.1 μg C cm-2 h-1). Although the carbon budget of the host was unchanged, symbionts acquired less carbon for their own needs (0.6 compared to 1.8 μg C cm-2 h-1), explaining the overall decrease in symbiont concentration at low pH. In the long term, such decrease in symbiont concentration might severely affect the carbon budget of the symbiotic association. © Author(s) 2013.

Nir O.,Interuniversity Institute for Marine science in Eilat | Nir O.,Hebrew University of Jerusalem | Gruber D.F.,City University of New York | Einbinder S.,Interuniversity Institute for Marine science in Eilat | And 4 more authors.
Coral Reefs | Year: 2011

The algae living endosymbiotically within coral are thought to increase algal pigmentation with increasing depth to capture the diminishing light. Here, we follow distribution of the hermatypic coral Seriatopora hystrix along a 60-m bathymetric gradient in the Gulf of Eilat, Red Sea, to study coral ecophysiology and response to light regimes. Combining work on coral morphology, pigment content and genotyping of the photosymbiont, we found that total chlorophyll concentration per zooxanthellae cell and the dark- and light-acclimated quantum yield of photosystem II did not vary significantly along the 60-m gradient. However, the chlorophyll a/c ratio increased with depth. This suggests that the symbiotic algae in S. hystrix possess a mechanism for acclimatization or adaptation that differs from previously described pathways. The accepted photoacclimatory process involves an increase in chlorophyll content per alga as light intensity decreases. Based on corallite and branch morphology, this research suggests that S. hystrix has two depth-dependent ecophenotypes. Above 10 m depth, S. hystrix exhibits sturdier colony configurations with thick branches, while below 30 m depth, colonies are characterized by thin branches and the presence of a larger polyp area. Between 10 and 30 m depth, both ecophenotypes are present, suggesting that corallite morphology may act as another axis of photoacclimation with depth. © 2011 Springer-Verlag.

Kranzler C.,Hebrew University of Jerusalem | Kranzler C.,Interuniversity Institute for Marine science in Eilat | Lis H.,Interuniversity Institute for Marine science in Eilat | Lis H.,Hebrew University of Jerusalem | And 5 more authors.
ISME Journal | Year: 2014

Iron bioavailability limits biological activity in many aquatic and terrestrial environments. Broad scale genomic meta-analyses indicated that within a single organism, multiple iron transporters may contribute to iron acquisition. Here, we present a functional characterization of a cyanobacterial iron transport pathway that utilizes concerted transporter activities. Cyanobacteria are significant contributors to global primary productivity with high iron demands. Certain cyanobacterial species employ a siderophore-mediated uptake strategy; however, many strains possess neither siderophore biosynthesis nor siderophore transport genes. The unicellular, planktonic, freshwater cyanobacterium, Synechocystis sp. PCC 6803, employs an alternative to siderophore-based uptake-reduction of Fe(III) species before transport through the plasma membrane. In this study, we combine short-term radioactive iron uptake and reduction assays with a range of disruption mutants to generate a working model for iron reduction and uptake in Synechocystis sp. PCC 6803. We found that the Fe(II) transporter, FeoB, is the major iron transporter in this organism. In addition, we uncovered a link between a respiratory terminal oxidase (Alternate Respiratory Terminal Oxidase) and iron reduction - suggesting a coupling between these two electron transfer reactions. Furthermore, quantitative RNA transcript analysis identified a function for subunits of the Fe(III) transporter, FutABC, in modulating reductive iron uptake. Collectively, our results provide a molecular basis for a tightly coordinated, high-affinity iron transport system.

Kranzler C.,Hebrew University of Jerusalem | Kranzler C.,Interuniversity Institute for Marine science in Eilat | Lis H.,Interuniversity Institute for Marine science in Eilat | Lis H.,Hebrew University of Jerusalem | And 3 more authors.
Environmental Microbiology | Year: 2011

In many aquatic environments the essential micronutrient iron is predominantly complexed by a heterogeneous pool of strong organic chelators. Research on iron uptake mechanisms of cyanobacteria inhabiting these environments has focused on endogenous siderophore production and internalization. However, as many cyanobacterial species do not produce siderophores, alternative Fe acquisition mechanisms must exist. Here we present a study of the iron uptake pathways in the unicellular, planktonic, non-siderophore producing strain Synechocystis sp. PCC 6803. By applying trace metal clean techniques and a chemically controlled growth medium we obtained reliable and reproducible short-term (radioactive assays) and long-term (growth experiments) iron uptake rates. We found that Synechocystis 6803 is capable of acquiring iron from exogenous ferrisiderophores (Ferrioxamine-B, FeAerobactin) and that unchelated, inorganic Fe is a highly available source of iron. Inhibition of iron uptake by the Fe(II)-specific ligand, ferrozine, indicated that reduction of both inorganic iron and ferrisiderophore complexes occurs before transport through the plasma membrane. Measurements of iron reduction rates and the inhibitory effect of ferrozine on growth supported this conclusion. The reduction-based uptake strategy is well suited for acquiring iron from multiple complexes in dilute aquatic environments and may play an important role in other cyanobacterial strains. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

Shaked Y.,Interuniversity Institute for Marine science in Eilat | Shaked Y.,Hebrew University of Jerusalem | Lis H.,Interuniversity Institute for Marine science in Eilat | Lis H.,Hebrew University of Jerusalem
Frontiers in Microbiology | Year: 2012

The bioavailability of iron to microorganisms and its underlying mechanisms have far reaching repercussions to many natural systems and diverse fields of research, including ocean biogeochemistry, carbon cycling and climate, harmful algal blooms, soil and plant research, bioremediation, pathogenesis, and medicine. Within the framework of ocean sciences, short supply and restricted bioavailability of Fe to phytoplankton is thought to limit primary production and curtail atmospheric CO2 drawdown in vast ocean regions. Yet a clear-cut definition of bioavailability remains elusive, with elements of iron speciation and kinetics, phytoplankton physiology, light, temperature, and microbial interactions, to name a few, all intricately intertwined into this concept. Here, in a synthesis of published and new data, we attempt to disassemble the complex concept of iron bioavailability to phytoplankton by individually exploring some of its facets. We distinguish between the fundamentals of bioavailability - the acquisition of Fe-substrate by phytoplankton - and added levels of complexity involving interactions among organisms, iron, and ecosystem processes. We first examine how phytoplankton acquire free and organically bound iron, drawing attention to the pervasiveness of the reductive uptake pathway in both prokaryotic and eukaryotic autotrophs. Turning to acquisition rates, we propose to view the availability of various Fesubstrates to phytoplankton as a spectrum rather than an absolute "all or nothing." We then demonstrate the use of uptake rate constants to make comparisons across different studies, organisms, Fe-compounds, and environments, and for gaging the contribution of various Fe-substrates to phytoplankton growth in situ. Last, we describe the influence of aquatic microorganisms on iron chemistry and fate by way of organic complexation and bio-mediated redox transformations and examine the bioavailability of these bio-modified Fe species.

Ben-Tzvi O.,Interuniversity Institute for Marine science in Eilat | Ben-Tzvi O.,Ben - Gurion University of the Negev | Tchernov D.,Interuniversity Institute for Marine science in Eilat | Tchernov D.,Hebrew University of Jerusalem | And 3 more authors.
Marine Ecology Progress Series | Year: 2010

Insight into the mechanisms that underlie settlement and recruitment is important for our understanding of the demography and ecology of coral reef fish and the biology of their coral host. Current knowledge of larval behaviour leading up to settlement is rather meager, and is mostly derived from controlled experiments under artificial conditions. However, it has been shown that presettlement juvenile fishes use acoustic and olfactory cues to locate the reef and, together with visual cues, to choose their first habitat in the reef. Chromis viridis (Pomacentridae) also use chemical and physical cues to locate the coral colonies on which they settle. Moreover, they appear to consistently and preferentially utilize some, but not other, conspecific colonies. To further evaluate the cues involved in microhabitat choice at settlement, we used in situ manipulation in which water from Acropora spp. coral colonies with positive settlement histories (SH+) was transferred to colonies with negative settlement histories (SH-) and vice versa. By closely monitoring settlement to manipulated and non-manipulated colonies, we found that at least 2 different water-borne cues are informing micro-habitat selection by C. viridis. Water transferred from SH- to SH+ A. hyacintus colonies was found to discourage settlement in the SH+ colonies. On the other hand, water transferred from SH+ to SH-A. eurystoma colonies encouraged settlement in the SH-colonies. These findings show that dissolved coral-derived cues dictate the fishes' settlement decisions, which raises an intriguing question as to the information content of these cues and their evolutionary context. © Inter-Research 2010.

Schoffman H.,Hebrew University of Jerusalem | Lis H.,Hebrew University of Jerusalem | Shaked Y.,Hebrew University of Jerusalem | Shaked Y.,Interuniversity Institute for Marine science in Eilat | Keren N.,Hebrew University of Jerusalem
Frontiers in Plant Science | Year: 2016

Iron limits photosynthetic activity in up to one third of the world’s oceans and in many fresh water environments. When studying the effects of Fe limitation on phytoplankton or their adaptation to low Fe environments, we must take into account the numerous cellular processes within which this micronutrient plays a central role. Due to its flexible redox chemistry, Fe is indispensable in enzymatic catalysis and electron transfer reactions and is therefore closely linked to the acquisition, assimilation and utilization of essential resources. Iron limitation will therefore influence a wide range of metabolic pathways within phytoplankton, most prominently photosynthesis. In this review, we map out four well-studied interactions between Fe and essential resources: nitrogen, manganese, copper and light. Data was compiled from both field and laboratory studies to shed light on larger scale questions such as the connection between metabolic pathways and ambient iron levels and the biogeographical distribution of phytoplankton species. © 2016 Schoffman, Lis, Shaked and Keren.

PubMed | Hebrew University of Jerusalem and Interuniversity Institute for Marine science in Eilat
Type: | Journal: Environmental microbiology | Year: 2016

Iron (Fe) bioavailability, as determined by its sources, sinks, solubility and speciation, places severe environmental constraints on microorganisms in aquatic environments. Cyanobacteria are a widespread group of aquatic, photosynthetic microorganisms with especially high iron requirements. While iron exists predominantly in particulate form, little is known about its bioavailability to cyanobacteria. Some cyanobacteria secrete iron solubilizing ligands called siderophores, yet many environmentally relevant strains do not have this ability. This work explores the bioavailability of amorphous synthetic Fe-oxides (ferrihydrite) to the non-siderophore producing, unicellular cyanobacterium, Synechocystis sp PCC 6803. Iron uptake assays with

Meron D.,Bar - Ilan University | Atias E.,Bar - Ilan University | Iasur Kruh L.,Institute of Soil, Water and Environmental Sciences | Elifantz H.,Institute of Soil, Water and Environmental Sciences | And 4 more authors.
ISME Journal | Year: 2011

Rising concentrations of atmospheric carbon dioxide are acidifying the world's oceans. Surface seawater pH is 0.1 units lower than pre-industrial values and is predicted to decrease by up to 0.4 units by the end of the century. This change in pH may result in changes in the physiology of ocean organisms, in particular, organisms that build their skeletons/shells from calcium carbonate, such as corals. This physiological change may also affect other members of the coral holobiont, for example, the microbial communities associated with the coral, which in turn may affect the coral physiology and health. In the present study, we examined changes in bacterial communities in the coral mucus, tissue and skeleton following exposure of the coral Acropora eurystoma to two different pH conditions: 7.3 and 8.2 (ambient seawater). The microbial community was different at the two pH values, as determined by denaturing gradient gel electrophoresis and 16S rRNA gene sequence analysis. Further analysis of the community in the corals maintained at the lower pH revealed an increase in bacteria associated with diseased and stressed corals, such as Vibrionaceae and Alteromonadaceae. In addition, an increase in the number of potential antibacterial activity was recorded among the bacteria isolated from the coral maintained at pH 7.3. Taken together, our findings highlight the impact that changes in the pH may have on the coral-associated bacterial community and their potential contribution to the coral host.

Meron D.,Bar - Ilan University | Rodolfo-Metalpa R.,University of Plymouth | Cunning R.,University of Miami | Baker A.C.,University of Miami | And 3 more authors.
ISME Journal | Year: 2012

Surface seawater pH is currently 0.1 units lower than pre-industrial values and is projected to decrease by up to 0.4 units by the end of the century. This acidification has the potential to cause significant perturbations to the physiology of ocean organisms, particularly those such as corals that build their skeletons/shells from calcium carbonate. Reduced ocean pH could also have an impact on the coral microbial community, and thus may affect coral physiology and health. Most of the studies to date have examined the impact of ocean acidification on corals and/or associated microbiota under controlled laboratory conditions. Here we report the first study that examines the changes in coral microbial communities in response to a natural pH gradient (mean pHT 7.3-8.1) caused by volcanic CO2 vents off Ischia, Gulf of Naples, Italy. Two Mediterranean coral species, Balanophyllia europaea and Cladocora caespitosa, were examined. The microbial community diversity and the physiological parameters of the endosymbiotic dinoflagellates (Symbiodinium spp.) were monitored. We found that pH did not have a significant impact on the composition of associated microbial communities in both coral species. In contrast to some earlier studies, we found that corals present at the lower pH sites exhibited only minor physiological changes and no microbial pathogens were detected. Together, these results provide new insights into the impact of ocean acidification on the coral holobiont. © 2012 International Society for Microbial Ecology All rights reserved.

Loading Interuniversity Institute for Marine science in Eilat collaborators
Loading Interuniversity Institute for Marine science in Eilat collaborators