Publications by authors named "Vona Meleder"

11 Publications

  • Page 1 of 1

Extensive spatial impacts of oyster reefs on an intertidal mudflat community via predator facilitation.

Commun Biol 2022 03 22;5(1):250. Epub 2022 Mar 22.

Université de Nantes, Département des Sciences de la Vie, EA 2160 Mer - Molécules - Santé 2, Rue de la Houssinière, 44322, Nantes, France.

Habitat engineers make strong and far-reaching imprints on ecosystem processes. In intertidal mudflats, the dominant primary producer, microphytobenthos (MPB), often forms high biomass patches around oyster reefs. We evaluate multiple hypotheses linking MPB with oyster reefs, including oyster biodeposition, meiofaunal grazing, and abiotic factors, aiming to help predict effects of reef removal or proliferation. We quantify spatial patterns of an Atlantic mudflat community and its environment around two large Crassostrea reefs before experimentally sacrificing one reef via burning. MPB biomass was enriched surrounding living oyster reefs although infaunal biomass and individual sizes were low. Structural equation modelling best supported the hypothesis that crab predation intensity, which decayed with distance from the reefs, locally freed MPB from grazing. Our results suggest that Crassostrea reef expansion may enrich local MPB patches and redirect trophic energy flows away from mudflat infauna, with potential implications for the sustainability of local fisheries and bird conservation.
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http://dx.doi.org/10.1038/s42003-022-03192-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8940938PMC
March 2022

Marine and brackish D.G.Mann (Bacillariophyta) species from the Java Sea and South China Sea coasts with the description of three new species.

PhytoKeys 2021 22;183:115-142. Epub 2021 Oct 22.

Université de Nantes, EA 2160 Mer - Molécules - Santé 2, Rue de la Houssinière, 44322 Nantes, France.

In this study, samples were collected from the Java Sea coasts, from the South China Sea in Hainan Island coasts and Quảng Yên region and Rú Chá mangrove near Hue in Central Vietnam. In studied samples a total of eight species have been observed. Three of the taxa studied are described herein as species new to science - , and Under light microscopy (LM) and are similar with rhombic-lanceolate to rhombic/ elliptic-lanceolate to elliptic valve shapes and narrowly rounded apices. Both species can be easily distinguished by stria density (higher density in ). Under SEM is characterized by cribrate areola occlusions, a character thus far observed only in three established species. The remaining species of the whole genus known thus far are characterized by hymenate areola. Similar morphology species have been observed from tropical mangrove forests from Madagascar but they all can be easily distinguished based on the lack of grooves in the central area. The third species - has rhombic-elliptic to rhombic-lanceolate valves with broadly rounded to slightly protracted apices in larger specimens. This species has a relatively broad central area. Also unique among brackish-water is the small, rounded stigma positioned almost midway between the valve center and valve margin. In the habitats from which the new species are described we also identified five established taxa including, , , , and . For those species we provide detailed SEM characteristics of valve ultrastructure, as well as the range of environmental conditions and geographic distribution within the study area.
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http://dx.doi.org/10.3897/phytokeys.183.71049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8556211PMC
October 2021

, A Novel Cosmopolitan Species of Blue Diatoms.

Biology (Basel) 2021 Apr 14;10(4). Epub 2021 Apr 14.

Institute of Graduate Studies in Science, Department of Biotechnology, Mersin University, Ciftlikkoy, Mersin 33343, Turkey.

Specimens of a new species of blue diatoms from the genus Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by , as evidenced by UV-visible spectrophotometry and Raman spectrometry. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare pseudogene, but the number, nature, and positions of the group II introns inside its gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the and genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved.
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http://dx.doi.org/10.3390/biology10040328DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8070900PMC
April 2021

Effects of light and nitrogen availability on photosynthetic efficiency and fatty acid content of three original benthic diatom strains.

PLoS One 2019 6;14(11):e0224701. Epub 2019 Nov 6.

Université de Nantes, Laboratoire Mer Molécules Santé, Nantes, France.

Microalgal biotechnology has gained considerable importance in recent decades. Applications range from simple biomass production for food and animal feed to valuable products for fuel, pharmaceuticals, health, biomolecules and materials relevant to nanotechnology. There are few reports of the exploration of wider microalgae biodiversity in the literature on high value microalgal compounds, however, because it is believed that there is little to be gained in terms of biomass productivity by examining new strains. Still, without diversity, innovation in biotechnology applications is currently limited. Using microalgal diversity is a very promising way to match species and processes for a specific biotechnological application. In this context, three benthic marine diatom strains (Entomoneis paludosa NCC18.2, Nitzschia alexandrina NCC33, and Staurosira sp NCC182) were selected for their lipid production and growth capacities. Using PAM fluorometry and FTIR spectroscopy, this study investigated the impact of nitrogen repletion and depletion as well as light intensity (30, 100, and 400 μmol.photons.m-2.s-1) on their growth, photosynthetic performance and macromolecular content, with the aim of improving the quality of their lipid composition. Results suggest that under high light and nitrogen limitation, the photosynthetic machinery is negatively impacted, leading cells to reduce their growth and accumulate lipids and/or carbohydrates. However, increasing lipid content under stressful conditions does not increase the production of lipids of interest: PUFA, ARA and EPA production decreases. Culture conditions to optimize production of such fatty acids in these three original strains led to a balance between economic and ecophysiological constraints: low light and no nitrogen limitation led to better photosynthetic capacities associated with energy savings, and hence a more profitable approach.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0224701PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6834396PMC
March 2020

Microphytobenthos primary production estimated by hyperspectral reflectance.

PLoS One 2018 14;13(5):e0197093. Epub 2018 May 14.

Littoral Environnement et Sociétés (LIENSs)-UMR 7266, CNRS/Université de La Rochelle, Institut du Littoral et de l'Environnement, 2 rue Olympe de Gouges, La Rochelle, France.

The use of remote sensing techniques allows monitoring of photosynthesis at the ecosystem level and improves our knowledge of plant primary productivity. The main objective of the current study was to develop a remote sensing based method to measure microphytobenthos (MPB) primary production from intertidal mudflats. This was achieved by coupling hyperspectral radiometry (reflectance, ρ and second derivative, δδ) and PAM-fluorometry (non-sequential light curves, NSLC) measurements. The latter allowed the estimation of primary production using a light use efficiency parameter (LUE) and electron transport rates (ETR) whereas ρ allowed to estimate pigment composition and optical absorption cross-section (a*). Five MPB species representative of the main growth forms: epipelic (benthic motile), epipsammic (benthic motile and non motile) and tychoplanktonic (temporarily resuspended in the water column) were submitted to increasing light intensities from dark to 1950 μmol photons.m-2.s-1. Different fluorescence patterns were observed for the three growth-forms and were linked to their xanthophyll cycle (de-epoxydation state). After spectral reflectance measurements, a* was retrieved using a radiative transfer model and several radiometric indices were tested for their capacity to predict LUE and ETR measured by PAM-fluorometry. Only one radiometric index was not species or growth-form specific, i.e. δδ496/508. This index was named MPBLUE and could be used to predict LUE and ETR. The applicability of this index was tested with simulated bands of a wide variety of hyperspectral sensors at spectral resolutions between 3 and 15 nm of Full Width at Half Maximum (FWHM).
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0197093PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5951593PMC
July 2018

Photosynthetic epibionts and endobionts of Pacific oyster shells from oyster reefs in rocky versus mudflat shores.

PLoS One 2017 21;12(9):e0185187. Epub 2017 Sep 21.

Laboratoire Mer Molécules Santé (EA2160), Institut Universitaire Mer et Littoral (FR_C 3473), Université de Nantes, Nantes, France.

The Pacific oyster, Crassostrea gigas (Thunberg), is the main bivalve species cultivated in the world. With global warming enabling its reproduction and larval survival at higher latitudes, this species is now recognized as invasive and creates wild oyster reefs globally. In this study, the spatial distribution of photosynthetic assemblages colonizing the shells of wild C. gigas was investigated on both a large scale (two contrasting types of reefs found in mudflats and rocky areas) and a small scale (within individual shells) using a hyperspectral imager. The microspatial distribution of all phototrophs was obtained by mapping the Normalized Difference Vegetation Index (NDVI). Second derivative (δδ) analyses of hyperspectral images at 462, 524, 571 and 647 nm were subsequently applied to map diatoms, cyanobacteria, rhodophytes and chlorophytes, respectively. A concomitant pigment analysis was carried out by high performance liquid chromatography and completed by taxonomic observations. This study showed that there was high microalgal diversity associated with wild oyster shells and that there were differences in the structure of the phototropic assemblages depending on the type of reef. Namely, vertically-growing oysters in mudflat areas had a higher biomass of epizoic diatoms (hyperspectral proxy at δδ462 nm) and were mainly colonized by species of the genera Navicula, Nitzschia and Hippodonta, which are epipelic or motile epipsammic. The assemblages on the horizontal oysters contained more tychoplanktonic diatoms (e.g. Thalassiosira pseudonana, T. proschkinae and Plagiogrammopsis vanheurckii). Three species of boring cyanobacteria were observed for both types of reef: Mastigocoleus testarum, Leptolyngbya terrebrans, and Hyella caespistosa, but the second derivative analysis at 524 nm showed a significantly higher biomass for the horizontally-growing oysters. There was no biomass difference for the boring chlorophyte assemblages (δδ647 nm), with two species: Eugomontia testarum and Ostreobium quekettii observed for both types of reef. This study shows that oyster shells are an idiosyncratic but ubiquitous habitat for phototrophic assemblages. The contribution of these assemblages in terms of biomass and production to the functioning of coastal areas, and particularly to shellfish ecosystems, remains to be evaluated.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185187PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5608347PMC
October 2017

Functional xanthophyll cycle and pigment content of a kleptoplastic benthic foraminifer: Haynesina germanica.

PLoS One 2017 23;12(2):e0172678. Epub 2017 Feb 23.

UMR CNRS 6112 LPG-BIAF, Bio-Indicateurs Actuels et Fossiles, Université d'Angers, Angers, France.

Some shallow water benthic foraminifera are able to retain functional chloroplasts (kleptoplasts) from their food source, i.e. diatoms. Here we assessed the functionality of the kleptoplast xanthophyll cycle (XC, i.e. the main diatom short-term photo-regulation mechanism) and we surveyed Haynesina germanica kleptoplast pigment composition over time and at different light regimes. Six common diatom lipophilic pigments were detected, two chlorophylls (Chl a, Chl c) and four carotenoids (fucoxanthin and by-products, diadinoxanthin, diatoxanthin and β-carotene), the same pigment profile as the diatom species frequently isolated at the sampling site. The xanthophyll cycle (XC) was functional with kleptoplast diatoxanthin (DT) content increase with concomitant diadinoxanthin (DD) decrease after short term light exposure. DT/(DT+DD) and DT/DD ratios increased significantly in specimens exposed to low light and high light in comparison to specimens maintained in the dark. Specimens placed in very low light after the light treatments reverted to values close to the initial ones, suggesting that H. germanica XC is functional. A functional XC is an indication of H. germanica kleptoplasts capacity for short-term photo-protection from photo-oxidative damages caused by excess of light. Furthermore, the pigment survey suggests that H. germanica preserved some chloroplasts over a longer time than others and that pigment content is influenced by previous light history. Finally, the current study highlighted seasonal differences, with higher pigment contents in winter specimens (27.35 ± 1.30 ng cell-1) and lower in summer specimens (6.08 ± 1.21 ng cell-1), a quantitative and qualitative composition suggesting light acclimation to low or high light availability, according to the season.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0172678PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5322967PMC
August 2017

Response of intertidal benthic microalgal biofilms to a coupled light-temperature stress: evidence for latitudinal adaptation along the Atlantic coast of Southern Europe.

Environ Microbiol 2015 Oct 3;17(10):3662-77. Epub 2015 Feb 3.

UMRi7266 LIENSs 'Littoral, Environnement et Sociétés', CNRS/Université de La Rochelle, Institut du Littoral et de l'Environnement, La Rochelle, France.

Although estuarine microphytobenthos (MPB) is frequently exposed to excessive light and temperature conditions, little is known on their interactive effects on MPB primary productivity. Laboratory and in situ experiments were combined to investigate the short-term joint effects of high light (HL) and high temperature (37 °C versus 27 °C) on the operating efficiency of photoprotective processes [vertical migration versus non-photochemical quenching (NPQ)] exhibited by natural benthic diatom communities from two intertidal flats in France (FR) and Portugal (PT). A clear latitudinal pattern was observed, with PT biofilms being more resistant to HL stress, regardless the effect of temperature, and displaying a lower relative contribution of vertical migration to photoprotection and a stronger NPQ in situ. However, higher temperature leads to comparable effects, with photoinhibition increasing to about three times (i.e. from 3% to 10% and from 8% to 22% in PT and FR sites respectively). By using a number of methodological novelties in MPB research (lipid peroxidation quantification, Lhcx proteins immunodetection), this study brings a physiological basis to the previously reported depression of MPB photosynthetic productivity in summer. They emphasize the joint role of temperature and light in limiting, at least transiently (i.e. during emersion), MPB photosynthetic activity in situ.
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http://dx.doi.org/10.1111/1462-2920.12728DOI Listing
October 2015

Growth form defines physiological photoprotective capacity in intertidal benthic diatoms.

ISME J 2015 Jan 8;9(1):32-45. Epub 2014 Jul 8.

UMR7266 LIENSs 'Littoral, Environnement et Sociétés', CNRS/Université de La Rochelle, Institut du Littoral et de l'Environnement, La Rochelle, France.

In intertidal marine sediments, characterized by rapidly fluctuating and often extreme light conditions, primary production is frequently dominated by diatoms. We performed a comparative analysis of photophysiological traits in 15 marine benthic diatom species belonging to the four major morphological growth forms (epipelon (EPL), motile epipsammon (EPM-M) and non-motile epipsammon (EPM-NM) and tychoplankton (TYCHO)) found in these sediments. Our analyses revealed a clear relationship between growth form and photoprotective capacity, and identified fast regulatory physiological photoprotective traits (that is, non-photochemical quenching (NPQ) and the xanthophyll cycle (XC)) as key traits defining the functional light response of these diatoms. EPM-NM and motile EPL showed the highest and lowest NPQ, respectively, with EPM-M showing intermediate values. Like EPL, TYCHO had low NPQ, irrespective of whether they were grown in benthic or planktonic conditions, reflecting an adaptation to a low light environment. Our results thus provide the first experimental evidence for the existence of a trade-off between behavioural (motility) and physiological photoprotective mechanisms (NPQ and the XC) in the four major intertidal benthic diatoms growth forms using unialgal cultures. Remarkably, although motility is restricted to the raphid pennate diatom clade, raphid pennate species, which have adopted a non-motile epipsammic or a tychoplanktonic life style, display the physiological photoprotective response typical of these growth forms. This observation underscores the importance of growth form and not phylogenetic relatedness as the prime determinant shaping the physiological photoprotective capacity of benthic diatoms.
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http://dx.doi.org/10.1038/ismej.2014.105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4274417PMC
January 2015

In vivo estimation of pigment composition and optical absorption cross-section by spectroradiometry in four aquatic photosynthetic micro-organisms.

J Photochem Photobiol B 2013 Dec 22;129:115-24. Epub 2013 Oct 22.

LUNAM Université, Université de Nantes, MMS-EA 21 60, 2 rue de la Houssinière, BP 92 208, 44322 Nantes Cedex 3, France; UMR 7266 'LIENSs', CNRS/University of La Rochelle, Institute for Coastal Research and Environment (ILE), 2 rue Olympe de Gouges, 17000 La Rochelle Cedex, France. Electronic address:

The objective of the present study was to estimate in vivo pigment composition and to retrieve absorption cross-section values, a(∗), of photosynthetic micro-organisms using a non-invasive technique of reflectance spectrometry. To test the methodology, organisms from different taxonomical groups and different pigment composition were used (Spirulina platensis a Cyanophyta, Porphyridium cruentum a Rhodophyta, Dunaliella tertiolecta a Chlorophyta and Entomoneis paludosa a Bacillariophyta) and photoacclimated to two different irradiance levels: 25 μmol photonm(-2)s(-1) (Low Light, LL) and 500 μmol photonm(-2)s(-1) (High Light, HL). Second derivative spectra from reflectance were used to identify pigment in vivo absorption bands that were linked to specific pigments detected by high performance liquid chromatography. Whereas some absorption bands such as those induced by Chlorophyll (Chl) a (416, 440, 625 and around 675 nm) were ubiquous, others were taxonomically specific (e.g. 636 nm for Chl c in E. paludosa) and/or photo-physiological dependent (e.g. 489 nm for zeaxanthin in the HL-acclimated S. platensis). The optical absorption cross-section, a(∗), was retrieved from reflectance data using a radiative transfer model previously developed for microphytobenthos. Despite the cellular Chl a decrease observed from LL to HL (up to 88% for S. platensis), the a(∗) increased, except for P. cruentum. This was attributed to a 'package effect' and to a greater absorption by photoprotective carotenoids that did not contribute to the energy transfer to the core Chl a.
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http://dx.doi.org/10.1016/j.jphotobiol.2013.10.005DOI Listing
December 2013

[Microphytobenthos assemblage mapping by spatial visible-infrared remote sensing in a shellfish ecosystem].

C R Biol 2003 Apr;326(4):377-89

Laboratoire d'écophysiologie marine intégrée-ISOMer-UPRES EA 2663, Laboratoire de planétologie et géodynamique, UMR CNRS 6112, BP 92 208, 44322 Nantes, France.

The aim of this work is to assess the use of (SPOT) multispectral visible infrared remote sensing to study microphytobentos assemblages in a shellfish ecosystem (Bay of Bourgneuf, France). SPOT satellite images (acquired at low tide in spring or autumn between 1986 and 1998) were calibrated using in situ radiometric data, and the normalised vegetation index (NDVI) obtained from these images showed microphytobenthos on bay mudflats. Proliferation was mainly along a north-south strip, essentially localised around the +2 m isobath and covering a surface area of 19 to 25% of the total mudflat area studied (420 to 550 ha). Three factors seem to be responsible for the spatial structure of the assemblages: bathymetry, nutrient input from the Falleron River and its channel, and the location of oyster-farming areas. Although spatial and spectral resolutions of multispectral remote sensing data have certain limitations, this approach opens up a new field of application for hyperspectral remote sensing, particularly for synoptic mapping of biomass distribution.
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http://dx.doi.org/10.1016/s1631-0691(03)00125-2DOI Listing
April 2003
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