Roksana Majewska | publications

Journal Articles (total 42)

2021

J. Phycol.

On sea turtle-associated Craspedostauros (Bacillariophyta), with description of three novel species.

Majewska, Roksana, Ashworth, Matt P., Bosak, Sunčica, Goosen, William E., Nolte, Christopher, Filek, Klara, Vijver, Bart Van de, Taylor, Jonathan C., Manning, Schonna R., and Nel, Ronel

Journal of Phycology 57:199–218, 2021

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The current study focuses on four species from the primarily marine diatom genus Craspedostauros that were observed growing attached to numerous sea turtles and sea turtle-associated barnacles from Croatia and South Africa. Three of the examined taxa, C. danayanus sp. nov., C. legouvelloanus sp. nov., and C. macewanii sp. nov., are described based on morphological and, whenever possible, molecular characteristics. The new taxa exhibit characters not previously observed in other members of the genus, such as the presence of more than two rows of cribrate areolae on the girdle bands, shallow perforated septa, and a complete reduction of the stauros. The fourth species, C. alatus, itself recently described from museum sea turtle specimens, is reported for the first time from loggerhead sea turtles rescued in Europe. A 3-gene phylogenetic analysis including DNA sequence data for three sea turtle-associated Craspedostauros species and other marine and epizoic diatom taxa indicated that Craspedostauros is monophyletic and sister to Achnanthes. This study, being based on a large number of samples and animal specimens analyzed and using different preservation and processing methods, provides new insights into the ecology and biogeography of the genus and sheds light on the level of intimacy and permanency in the host–epibiont interaction within the epizoic Craspedostauros species.
J. Phycol.

Diatom type material in permanent slides does not need to be permanently unavailable for electron microscopy examination.

Majewska, Roksana, Taylor, Jonathan C., and Goosen, William E.

Journal of Phycology 57:698–701, 2021

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The inability to thoroughly examine diatom type material existing only in resin-mounted permanent slides is a common frustration for diatomologists. Here, we present an efficient, inexpensive, and straightforward technique to extract siliceous exoskeletons of diatoms from permanent slides prepared with commonly used mounting media. Van Heurck’s slide constituting an isotype duplicate of Proschkinia bulnheimii var. belgica, an entity with an uncertain taxonomic status, was deconstructed to allow thorough examination using scanning electron microscopy. Numerous specimens of the taxon, including intact frustules and specimens with complete areola occlusions, were recovered and documented. The extracted diatom material was sufficient to prepare two scanning electron microscopy specimens and reconstruct the permanent slide. The proposed approach may help overcome many of the taxonomic bottlenecks associated with the low resolution of information provided by older diatom descriptions and permanent slide observations.
Diatom Res.

Nagumoea hydrophicola sp. nov. (Bacillariophyta), the first diatom species described from sea snakes.

Majewska, Roksana

Diatom Research 36:49–59, 2021

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Although diatoms colonize a vast diversity of immersed hard-surfaced objects and organisms, many diatom species, and sometimes entire genera, show a clear preference towards a particular type of substratum. Studies of animal-associated diatoms indicate that some epizoic forms may require this specific habitat to thrive, and new diatom taxa are expected to be found on as yet unexplored animal hosts. The current study is the first to investigate the diatom flora of sea snakes. Three museum specimens of yellow-bellied sea snakes (Hydrophis platurus) collected over a period of 23 years from the south-eastern coast of South Africa were examined for their diatom flora. Diatoms were abundant on the sea snakes, but communities were composed of only a few species. A previously undescribed species of Nagumoea contributed over 99% of the total diatom assemblage on both the sea snake skin and sea-snake-associated barnacles (Octolasmis sp.). This diatom dominant is described here as Nagumoea hydrophicola sp. nov., based on detailed observations of its frustule ultrastructure using light and scanning electron microscopy. The species is most similar to N. serrata, sharing a similar valvocopula morphology with two rows of pores. However, it can be distinguished from all currently known congeners by its lanceolate central area, short distal raphe endings not reaching the valve mantle, and doubly perforated abvalvar girdle bands. Environmental preferences of the new species are discussed in the context of its host’s biology.
Protist

Diatom genus Hyalosira (Rhabdonematales emend.) and resolution of its polyphyly in Grammatophoraceae and Rhabdonemataceae with a new genus, Placosira, and five new Hyalosira species.

Lobban, Christopher S., Majewska, Roksana, Ashworth, Matt, Bizsel, Nihayet, Bosak, Sunčica, Kooistra, Wiebe H. C. F., Lam, Daryl W., Navarro, J. Nelson, Pennesi, Chiara, Sato, Shinya, Vijver, Bart, and Witkowski, Andrzej

Protist 172:125816, 2021

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Hyalosira gene sequences are divided into two clades within different families. We examined authentic material of Hyalosira (isotype material of H. obtusangula, synonymous with H. delicatula) and voucher specimens of published sequences, and pooled our observations of Hyalosira-like taxa from benthic and epizoic habitats in several parts of the globe. The two molecular clades corresponded to two morphological groups, with Hyalosira obtusangula associated with Grammatophoraceae. We emend the description and provide lectotypification for Hyalosira and propose Placosira to encompass the taxa in the other clade, associated with Rhabdonemataceae. We propose that Hyalosira has uniseriate to triseriate striae, sometimes different on valve face and mantle. Copulae in most species had shallow septa, though in one they were moderately deep. All species had girdle bands bearing two rows of areolae separated by a midrib. We name five new species of Hyalosira. Morphologies of taxa in the Placosira clade were superficially similar to Hyalosira but differed in having areolae with ricae, a single row of areolae on the girdle bands, and tubular rimoportulae on the valve-face-mantle junction. Hyalosira hustedtiana Patrick should revert to its original position in Striatella until the appropriate genus can be determined. We emend Rhabdonematales to encompass Rhabdonemataceae, Grammatophoraceae and Tabellariaceae.
New observations on the diatom genus Druehlago (Bacillariophyta) and description of two new species from South Africa

Majewska, Roksana, Mayombo, Ntambwe A. S., Smit, Albertus J., and Goosen, William E.

Phycologia 0:1–14, 2021

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Two new species of the previously monospecific diatom genus Druehlago were discovered during the ongoing studies exploring the epizoic and epiphytic diatom flora of the Southern African coasts. These species are formally described here as D. craspedostauriformis sp. nov. and D. lobbanii sp. nov. Detailed morphological examination using both light and scanning electron microscopy revealed wedge-shaped frustules with a central constriction containing multiple lenticular chloroplasts, as well as heteropolar valves with wider headpoles and biarcuate raphes, typical of Druehlago. A stauros narrower than the fascia, a feature not yet reported from Druehlago but typical of the morphologically similar genus Craspedostauros, was observed in D. craspedostauriformis. Apart from the presence of a stauros, the latter species can be easily distinguished from other Druehlago members by its large size, low stria density, externally raised raphe-sternum, and girdle bands with a crenate pars interior. Although the gross morphology of D. lobbanii strongly resembled that of D. cuneata, the two species can be distinguished based on clear differences in size and stria density. Moreover, whereas shallow septa run along the almost entire length of the girdle bands in D. cuneata, they are absent in D. lobbanii. Based on the new findings and observations, the taxonomic status of the genus Druehlago and its morphological and ecological similarity to Craspedostauros and Achnanthes are discussed and evaluated.

2020

PLoS One

Geographical variation in the diatom communities associated with loggerhead sea turtles (Caretta caretta).

Vijver, Bart Van de, Robert, Käthe, Majewska, Roksana, Frankovich, Thomas A., Panagopoulou, Aliki, and Bosak, Sunčica

PLOS ONE 15:, 2020

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Epizoic diatoms form an important part of micro-epibiota of marine vertebrates such as whales and sea turtles. The present study explores and compares the diversity and biogeography of diatom communities growing on the skin and shell of loggerhead sea turtles (Caretta caretta) from four different localities: Adriatic Sea (Croatia), Ionian Sea (Greece), South Africa and Florida Bay (USA) using both light and scanning electron microscopy. We observed almost 400 diatom taxa belonging to more than 100 genera. Diatom communities from Greece and Croatia showed the highest similarity and were statistically different from those recorded from South Africa and Florida. Part of this variation could be attributed to differences in sampling techniques; however, we believe that geography had an important role. In general, contrary to several previous observations from sea turtles, the presumably exclusively epizoic diatoms contributed less than common benthic taxa to the total diatom flora, which might have been related to the loggerhead feeding behavior. Moreover, skin samples differed from carapace samples in having a distinct diatom composition with a higher proportion of the putative true epizoonts. Our results indicate that epizoic diatom communities differ according to loggerhead geographical location and substrate (skin vs. carapace). The relative abundances of common benthic diatoms and putative exclusive epizoic taxa may inform about sea turtle habitat use or behavior though detailed comparisons among different host species have yet to be performed.
Bot. Lett.

A new species of Lucanicum (Cyclophorales, Bacillariophyta) associated with loggerhead sea turtles from South Africa.

Majewska, Roksana, Robert, Käthe, Vijver, Bart, and Nel, Ronel

Botany Letters 167:7–14, 2020

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A new Lucanicum species, L. ashworthianum Majewska, K.Robert & Van de Vijver sp. nov., was found in multiple samples of biofilm growing on loggerhead sea turtles Caretta caretta and their symbiotic barnacles Chelonibia testudinaria collected on the beaches of Kosi Bay, eastern coast of South Africa, during the two nesting seasons (the austral summers of 2017/2018 and 2018/2019). The new species possesses several features typical of the genus Lucanicum, including the uniseriate striae composed of one large macroareola, the presence of large apical slit fields and transapically elongated rimoportulae at both poles, and a cingulum composed of numerous open, doubly perforated copulae. It differs from the only other Lucanicum species known to date, the coral-associated L. concatenatum, in having considerably smaller cells with clearly rostrate or sub-capitate apices and internal rimoportula opening composed of a C-shaped inner lip and an oval, flap-like outer lip – a feature not observed previously in Lucanicum. Based on these new observations, an amendment of the genus description is proposed.
Phycologia

Diatoms on sea turtles and floating debris in the Persian Gulf (Western Asia).

Azari, Mahtab, Farjad, Yas, Nasrolahi, Ali, De Stefano, Mario, Ehsanpour, Maryam, Dobrestov, Sergey, and Majewska, Roksana

Phycologia 59:292–304, 2020

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The current study investigated diatom communities on juvenile green turtles foraging in neritic habitats around five Iranian islands. The primary objectives were to (1) compare species composition, growth form structure, and abundance of diatom communities associated with sea turtles foraging within the restricted boundaries of local feeding pastures, and (2) assess the level of uniqueness of the epizoic diatom flora in comparison with biofilms growing on floating debris. All observations and diatom counts were performed using scanning electron microscopy. The effect of the sampling location was apparent among sea turtle samples and reflected in significantly different cell densities. Diatom abundances were significantly higher on sea turtles (758–1836 cells mm−2) than on floating debris samples (9–189 cells mm−2). Epizoic diatom communities were composed of 20 diatom taxa and dominated by erect forms belonging to the so-called ‘marine gomphonemoids’, Chelonicola and Poulinea, previously reported on sea turtles from other geographical regions. The diatom flora found on floating debris was composed of 21 taxa. Only four taxa, Amphora cf. bigibba, Cocconeis cf. neothumensis var. marina, Psammodictyon constrictum, and Tabularia affinis, were recorded from both sea turtles and floating debris samples, and none of these exceeded 4% of the average relative abundance on the sea turtle carapaces. The study reveals a clear substratum preference in sea turtle-associated diatoms, with no evidence for species turnover across the investigated region over different sampling seasons, thus confirming previous speculations that sea turtle diatom communities would show a high level of uniqueness and stability.
J. Phycol.

For better, for worse: manatee-associated tursiocola (Bacillariophyta) remain faithful to their host.

Majewska, Roksana, and Goosen, William E.

Journal of Phycology 56:1019–1027, 2020

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With the advent of more comprehensive research into the microbiome and interactions between animals and their microbiota, new solutions can be applied to address conservation challenges such as husbandry and medical care of captive animals. Although studies on epizoic algae are relatively rare, and the function and role of those mainly photosynthetic organisms in the animal microbiome is not well understood, recent surveys on epizoic diatoms show that some of them exhibit traits of obligate epibionts. This study explores diatom communities on captive–born manatees from the Africarium in Wroclaw, Poland. Light and scanning electron microscopy analyses revealed that skin of all animals sampled was dominated by apochlorotic Tursiocola cf. ziemanii, an epizoic species described recently from Florida manatees, that reached 99,9% of the total diatom abundance. Despite using media with a wide range of salinity (0–34), the isolated Tursiocola cells did not grow, whereas the normally pigmented Planothidium sp., that was only occasionally found on the animal substratum, survived in all culture media tested. Our observations provide direct evidence that manatee–associated Tursiocola endure the dramatic salinity changes that occur regularly during their host life cycle, and can thrive in an artificial captive setting, if the manatee substratum is available. The impact of practices and routines used by the Africarium on manatee–associated diatoms, as well as ultrastructure of areolae in Tursiocola, are briefly discussed.
Phytotaxa

Tursiocola neliana sp. nov (Bacillariophyceae) epizoic on South African leatherback sea turtles (Dermochelys coriacea) and new observations on the genus Tursiocola.

Majewska, Roksana

Phytotaxa 453:1–15, 2020

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Tursiocola, a presumably exclusively epizoic diatom genus, comprises species found on various aquatic animals such as cetaceans, manatees, and marine and freshwater turtles. The genus is characterised by linear or lanceolate valves with well-developed pseudosepta at both poles, a valvocopula with three pairs of siliceous tabs, and a butterfly-like structure extending from the central nodule on the internal side of the valve. The current study describes a novel species of Tursiocola, T. neliana Majewska sp. nov. that grows epizoically on leatherback sea turtles from the Eastern Coast of South Africa based on detailed observations using light and scanning electron microscopy. The new taxon resembles the other currently known sea turtle-associated Tursiocola species in possessing relatively small, slightly heteropolar valves with acute apices and a strongly reduced butterfly structure on the internal side. However, T. neliana differs from all other members of the genus in being distinctly dorsiventral, with a clearly bowtie-shaped central area, unequal stria density on two sides of the raphe-sternum, and up to 8 areolae per stria. The description of the new taxon brings the total number of the sea turtle-associated Tursiocola species known so far up to four. An emended description of Tursiocola is proposed based on the new observations presented in this and other recent reports. Furthermore, the current understanding of the genus ecology is summarised.
Extremophiles

Microbiomics of Namib Desert habitats.

Cowan, D. A., Hopkins, D. W., Jones, B. E., Maggs-Kölling, G., Majewska, R., and Ramond, J.-B.

Extremophiles 24:17–29, 2020

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The Namib Desert is one of the world’s only truly coastal desert ecosystem. Until the end of the 1st decade of the twenty-first century, very little was known of the microbiology of this southwestern African desert, with the few reported studies being based solely on culture-dependent approaches. However, from 2010, an intense research program was undertaken by researchers from the University of the Western Cape Institute for Microbial Biotechnology and Metagenomics, and subsequently the University of Pretoria Centre for Microbial Ecology and Genomics, and their collaborators, led to a more detailed understanding of the ecology of the indigenous microbial communities in many Namib Desert biotopes. Namib Desert soils and the associated specialized niche communities are inhabited by a wide array of prokaryotic, lower eukaryotic and virus/phage taxa. These communities are highly heterogeneous on both small and large spatial scales, with community composition impacted by a range of macro- and micro-environmental factors, from water regime to soil particle size. Community functionality is also surprisingly non-homogeneous, with some taxa retaining functionality even under hyper-arid soil conditions, and with subtle changes in gene expression and phylotype abundances even on diel timescales. Despite the growing understanding of the structure and function of Namib Desert microbiomes, there remain enormous gaps in our knowledge. We have yet to quantify many of the processes in these soil communities, from regional nutrient cycling to community growth rates. Despite the progress that has been made, we still have little knowledge of either the role of phages in microbial community dynamics or inter-species interactions. Furthermore, the intense research efforts of the past decade have highlighted the immense scope for future microbiological research in this dynamic, enigmatic and charismatic region of Africa.
Fottea

Nagumoea serrata, a new diatom species (Bacillariophyceae) found on seagrass from the south-eastern coast of Africa (Indian Ocean).

Majewska, Roksana, and Vijver, Bart

Fottea 20:98–103, 2020

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A novel diatom species belonging to the genus Nagumoea is described based on detailed light and scanning electron microscopy observations. The new taxon was found abundantly in several samples collected from seagrass on the southernmost coasts of Mozambique, Southern Africa. While the new species shows characters (e.g. scalariform valvocopula, fibulae of complex shape and structure) consistent with the genus description, it differs distinctly from currently known members of Nagumoea. Differences include generally larger (7-29 µm) and more slender (1.0-1.5 µm) valves with acutely rounded apices and 4-5 areolae per stria, a doubly-perforated valvocopula, and the last-formed copula with a highly regular serrated margin. Based on the current knowledge and understanding of the diatom morphology and phylogeny, Anaulus vallus Nikolaev, previously included within the genus Denticula, is transferred to the genus Nagumoea. This brings the current number of the genus members to five. Ecological preferences of Nagumoea are briefly discussed.
Diversity

An assessment of the influence of host species, age, and thallus part on kelp-associated diatoms.

Mayombo, Ntambwe Albert Serge, Majewska, Roksana, and Smit, Albertus J.

Diversity 12:385, 2020

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Diatom community composition and abundances on different thallus parts of adult and juvenile specimens of Eckloniamaxima and Laminariapallida were examined in False Bay, South Africa, using light and scanning electron microscopy. Altogether, 288 thallus portions were analysed. Diatom abundances ranged from 0 to 404 cells mm−2 and were generally higher on E. maxima and juvenile thalli than L. pallida and adult specimens. Moreover, diatom abundances differed between the various thallus parts, being highest on the upper blade and lowest on the primary blade. A total of 48 diatom taxa belonging to 28 genera were found. Gomphoseptatum Medlin, Nagumoea Witkowski and Kociolek, Cocconeis Ehrenberg, and Navicula Bory were the most frequently occurring genera, being present in 84%, 65%, 62.5%, and 45% of the analysed samples, respectively. Among these, Cocconeis and Gomphoseptatum were the most abundant, contributing 50% and 27% of total diatom cells counted collectively across all samples. Permutational multivariate analysis of variance (PERMANOVA) revealed that all investigated main factors (kelp species and age and thallus part), as well as their two- and three-way interactions, except for the interaction between the host species and age, were significant. The high residual variance (72%) indicated that the sum of other unexamined factors contributed the largest component of the variation observed in the kelp-associated diatom communities, and grazing and possible defence strategies utilised by kelps are proposed as processes playing an important role in the structuring of epiphytic diatom communities. Possible endophytism of tissue-boring diatoms colonizing both kelp species is briefly discussed.
Diversity

Diatom diversity on the skin of frozen historic loggerhead sea turtle specimens.

Kanjer, Lucija, Majewska, Roksana, Vijver, Bart, Gračan, Romana, Lazar, Bojan, and Bosak, Sunčica

Diversity 12:383, 2020

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In recent years, biofilm-forming diatoms have received increased attention as sea turtle epibionts. However, most of the research has focused on carapace-associated taxa and communities, while less is known about diatoms growing on sea turtle skin. The current study investigated diatom diversity on the skin of loggerhead sea turtle heads detached from the carcasses found along the Adriatic coast between 1995 and 2004 and stored frozen for a prolonged period of time. By using both light and scanning electron microscopy we have found diatom frustules in 7 out of 14 analysed sea turtle samples. Altogether, 113 diatom taxa were recorded, with a minimum of seven and a maximum of 35 taxa per sample. Eight taxa, Achnanthes elongata, Berkeleya cf. fennica, Chelonicola sp., Licmophora hyalina, Nagumoea sp., Navicula sp., Nitzschia cf. lanceolata, and Poulinea lepidochelicola exceeded 5% of relative abundance in any one sample. The presumably obligately epizoic diatom taxa, A. elongata, Chelonicola sp., and P. lepidochelicola, dominated in six loggerhead samples, contributing up to 97.1% of the total diatom abundance. These observations suggest that on the sea turtle skin highly specialised taxa gain even greater ecological advantage and dominance over the co-occurring benthic forms than in the carapace biofilms. The suitability of frozen sea turtle skin specimens for diatom analysis and limitations of this approach are discussed.

2019

Eur. J. Phycol.

Six new epibiotic Proschkinia (Bacillariophyta) species and new insights into the genus phylogeny.

Majewska, Roksana, Bosak, Sunčica, Frankovich, Thomas A., Ashworth, Matt P., Sullivan, Michael J., Robinson, Nathan J., Lazo-Wasem, Eric A., Pinou, Theodora, Nel, Ronel, Manning, Schonna R., and Vijver, Bart

European Journal of Phycology 54:609–631, 2019

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The diatom genus Proschkinia is a common element of biofilms covering diverse substrata in saline inland or shallow coastal environments. It can be distinguished from other naviculoid taxa by its lanceolate valves with a fistula located within the central area and numerous open girdle bands with a U-shaped cross-section and a single row of perforations on the internal side of the fold. Despite this distinct morphology, frustules of Proschkinia are typically weakly silicified and often overlooked when cleaned diatom material is analysed. The current paper describes six new species of Proschkinia: P. browderiana sp. nov., P. lacrimula sp. nov., P. maluszekiana sp. nov., P. sulcata sp. nov., P. torquata sp. nov. and P. vergostriata sp. nov., found in numerous samples of marine organisms, such as sea turtles (including sea turtle museum specimens), sea turtle-associated barnacles and seagrass from across the three oceans. Some of the newly described taxa were found on multiple individuals belonging to different sea turtle species, whereas others were in samples collected from different continents. Molecular phylogenetic analysis indicated that examined Proschkinia strains formed a monophyletic clade, sister to Fistulifera.
Afr. J. Mar. Sci.

Diatoms associated with two South African kelp species: Ecklonia maxima and Laminaria pallida.

Mayombo, Ntambwe Albert Serge, Majewska, Roksana, and Smit, Albertus J.

African Journal of Marine Science 41:221–229, 2019

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Kelp forests are believed to host a large biomass of epiphytic fauna and flora, including diatoms, which constitute the base of aquatic food webs and play an important role in the transfer of energy to higher trophic levels. Epiphytic diatom assemblages associated with two common species of South African kelps, Ecklonia maxima and Laminaria pallida, were investigated in this study. Primary blades of adult and juvenile thalli of both kelp species were sampled at False Bay in July 2017 and analysed using scanning electron microscopy. Our findings showed that both kelp species hosted relatively low densities of diatoms (ranging from 7 [SD 5] cells mm−2 on adult specimens of L. pallida to 43 [SD 66] cells mm−2 on blades of juvenile E. maxima), with Amphora and Gomphoseptatum reaching the highest absolute abundances. Although non-metric multidimensional scaling showed overlapping and largely scattered sample sets, a significant relationship between the diatom communities and the species and age of the host macroalga was detected by two-way PERMANOVA. In general, more abundant and diverse diatom communities were observed on juvenile thalli than on adult thalli, with species belonging to Navicula and Rhoicosphenia contributing significantly to the observed dissimilarity. Due to a significant interaction between species and age effects, however, the overall ability of kelp species, their age, and their interaction to explain the variation in diatom community structure was limited. We suggest that the low densities of epiphytic diatoms were directly related to the sloughing of epithelial cells observed in both kelp species. We further speculate that on such unstable substrata some diatom taxa might adapt to an endophytic life to avoid the antifouling mechanisms developed by their hosts.
Micro Nano Eng.

Transforming diatomaceous earth into sensing devices by surface modification with gold nanoparticles.

Villani, M., Onesto, V., Coluccio, M. L., Valpapuram, I., Majewska, R., Alabastri, A., Battista, E., Schirato, A., Calestani, D., Coppedé, N., Zappettini, A., Amato, F., Di Fabrizio, E., and Gentile, F.

Micro and Nano Engineering 2:29–34, 2019

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Diatomaceous earth, or diatomite, is produced through the accumulation of diatom (Bacillariophyceae) skeletons (i.e. cell walls called frustules) made of amorphous silica. The porous, highly symmetrical structure and microscopic size of diatom cell walls make them ideal constituents of sensing devices and analytical chips. Here, we propose chemical methods to purify diatom frustules extracted from diatomaceous earth. Using photo deposition techniques, we grow gold nanoparticles on the surface of diatom skeletons and within the pores of the skeletons, where the size and density of nanoparticles can be controlled by changing the parameters of the synthesis. Resulting devices have an internal porous structure that can harvest molecules from a solution, and an external shell of gold nanoparticles that amplifies the electromagnetic field generated by the measurement laser in Raman or other spectroscopies. The combination of these effects enables the analysis of biological specimens, chemical analytes and pollutants in extremely low abundance ranges. The devices were demonstrated in the analysis of Bovine Serum Albumin in water with a concentration of 100 aM, and mineral oil with a concentration of 50 ppm.
Mar. Turtle Newsl.

Standardizing sea turtle epibiont sampling: outcomes of the Epibiont Workshop at the 37 th International Sea Turtle Symposium.

Pinou, Theodora, Domènech, Francesc, Lazo-Wasem, E, Majewska, Roksana, Pfaller, Joseph, Zardus, John, and Robinson, Nathan

Marine Turtle Newsletter 157:22–32, 2019

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A growing interest in the relationship between sea turtles and their epibionts (i.e., marine organisms that attach to, or dwell on the exterior shell or skin of sea turtles) resulted in a workshop focused on sea turtle epibiosis at the 37th International Sea Turtle Symposium, Las Vegas, Nevada (Pinou et al. 2017). The primary objectives of the workshop were to present the current state of knowledge on sea turtle epibiosis research to an interdisciplinary community and to collectively develop a standardized epibiont sampling methodology for improved data sharing among scientists. The talking points of the workshop discussion included: 1.) clarifying the utility of published epibiont lists, 2.) articulating a functional understanding of interspecies connections between sea turtles and epibionts, 3.) framing the need for an open-access, global epibiont database, 4.) developing a repository for collected material accessible to all workers in the field, and 5.) employing hypothesis testing in epibiont research, and 6.) envisioning long-term monitoring plans to advance the study of sea turtle epibiosis.
PSSA

Epizoic diatoms in zoological collections – what do they tell us about their hosts?

Majewska, Roksana

Newsletter of Phycological Society of Southern Africa 85:4, 2019

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2018

Nova Hedwig. Beih.

Labellicula lecohuiana, a new epizoic diatom species living on green turtles in Costa Rica.

Majewska, R., De Stefano, M., and Vijver, B.

Nova Hedwigia, Beihefte :23–31, 2018

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NPJ Precis. Oncol.

Superhydrophobic lab-on-chip measures secretome protonation state and provides a personalized risk assessment of sporadic tumour.

Malara, N., Gentile, F., Coppedè, N., Coluccio, M. L., Candeloro, P., Perozziello, G., Ferrara, L., Giannetto, M., Careri, M., Castellini, A., Mignogna, C., Presta, I., Pirrone, C. K., Maisano, D., Donato, A., Donato, G., Greco, M., Scumaci, D., Cuda, G., Casale, F., Ferraro, E., Bonacci, S., Trunzo, V., Mollace, V., Onesto, V., Majewska, R., Amato, F., Renne, M., Innaro, N., Sena, G., Sacco, R., Givigliano, F., Voci, C., Volpentesta, G., Guzzi, G., Lavano, A., Scali, E., Bottoni, U., and Di Fabrizio, E.

npj Precision Oncology 2:1–13, 2018

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Secretome of primary cultures is an accessible source of biological markers compared to more complex and less decipherable mixtures such as serum or plasma. The protonation state (PS) of secretome reflects the metabolism of cells and can be used for cancer early detection. Here, we demonstrate a superhydrophobic organic electrochemical device that measures PS in a drop of secretome derived from liquid biopsies. Using data from the sensor and principal component analysis (PCA), we developed algorithms able to efficiently discriminate tumour patients from non-tumour patients. We then validated the results using mass spectrometry and biochemical analysis of samples. For the 36 patients across three independent cohorts, the method identified tumour patients with high sensitivity and identification as high as 100% (no false positives) with declared subjects at-risk, for sporadic cancer onset, by intermediate values of PS. This assay could impact on cancer risk management, individual’s diagnosis and/or help clarify risk in healthy populations.
Chem. Sci.

Folding mechanisms steer the amyloid fibril formation propensity of highly homologous proteins.

Malgieri, Gaetano, D’Abrosca, Gianluca, Pirone, Luciano, Toto, Angelo, Palmieri, Maddalena, Russo, Luigi, Sciacca, Michele Francesco Maria, Tatè, Rosarita, Sivo, Valeria, Baglivo, Ilaria, Majewska, Roksana, Coletta, Massimo, Pedone, Paolo Vincenzo, Isernia, Carla, Stefano, Mario De, Gianni, Stefano, Pedone, Emilia Maria, Milardi, Danilo, and Fattorusso, Roberto

Chemical Science 9:3290–3298, 2018

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Significant advances in the understanding of the molecular determinants of fibrillogenesis can be expected from comparative studies of the aggregation propensities of proteins with highly homologous structures but different folding pathways. Here, we fully characterize, by means of stopped-flow, T-jump, CD and DSC experiments, the unfolding mechanisms of three highly homologous proteins, zinc binding Ros87 and Ml153–149 and zinc-lacking Ml452–151. The results indicate that the three proteins significantly differ in terms of stability and (un)folding mechanisms. Particularly, Ros87 and Ml153–149 appear to be much more stable to guanidine denaturation and are characterized by folding mechanisms including the presence of an intermediate. On the other hand, metal lacking Ml452–151 folds according to a classic two-state model. Successively, we have monitored the capabilities of Ros87, Ml452–151 and Ml153–149 to form amyloid fibrils under native conditions. Particularly, we show, by CD, fluorescence, DLS, TEM and SEM experiments, that after 168 hours, amyloid formation of Ros87 has started, while Ml153–149 has formed only amorphous aggregates and Ml452–151 is still monomeric in solution. This study shows how metal binding can influence protein folding pathways and thereby control conformational accessibility to aggregation-prone states, which in turn changes aggregation kinetics, shedding light on the role of metal ions in the development of protein deposition diseases.
Diatom Res.

Craspedostauros alatus sp. nov., a new diatom (Bacillariophyta) species found on museum sea turtle specimens.

Majewska, Roksana, Ashworth, Matt P., Lazo-Wasem, Eric, Robinson, Nathan J., Rojas, Lourdes, Vijver, Bart, and Pinou, Theodora

Diatom Research 33:229–240, 2018

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Several populations of a new Craspedostauros species were observed on museum specimens of juvenile green turtle and Kemp’s ridleys collected from Long Island Beach, New York, USA. The new taxon, Craspedostauros alatus Majewska & Ashworth sp. nov., exhibits a distinctive set of morphological features typical of the genus, including cribrate areolae, a stauros narrower than the fascia, multiple doubly perforated girdle bands, and two fore and aft chloroplasts, but clearly differs from all known Craspedostauros species in possessing partially fused proximal helictoglossae forming an internal thickening with a shallow central cavity, distinctive external wing-like silica flaps near the apices, and a combination of valve dimensions and stria density not observed in other taxa. The same taxon was identified in the NCMA culture collection (strain CCMP120), isolated in 1967 from a sample collected from the equatorial upwelling zone in the Pacific Ocean. Nine samples from three sea turtle species were collected from the same location (Long Island Beach). Statistical analyses suggested that the epizoic diatom flora composition was not affected by the collection season but differed among sea turtle species. The most significant difference was observed between the samples with and without C. alatus. Samples with C. alatus were always dominated by Achnanthes elongata and Berkeleya cf. rutilans, while those lacking the new taxon were characterized by remarkably higher contributions of epizoic Poulinea species. This observation suggests that the microhabitat provided by each sea turtle differs among specimens, which may be related to the different stages of biofilm development on the host sea turtle. Additionally, the value of zoological museum collections for epizoic diatom surveys is briefly discussed.
Nanoscale Res. Lett.

Silica diatom shells tailored with Au nanoparticles enable sensitive analysis of molecules for biological, safety and environment applications.

Onesto, V., Villani, M., Coluccio, M. L., Majewska, R., Alabastri, A., Battista, E., Schirato, A., Calestani, D., Coppedé, N., Cesarelli, M., Amato, F., Di Fabrizio, E., and Gentile, F.

Nanoscale Research Letters 13:94, 2018

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Diatom shells are a natural, theoretically unlimited material composed of silicon dioxide, with regular patterns of pores penetrating through their surface. For their characteristics, diatom shells show promise to be used as low cost, highly efficient drug carriers, sensor devices or other micro-devices. Here, we demonstrate diatom shells functionalized with gold nanoparticles for the harvesting and detection of biological analytes (bovine serum albumin—BSA) and chemical pollutants (mineral oil) in low abundance ranges, for applications in bioengineering, medicine, safety, and pollution monitoring.
Phytotaxa

Taxonomic revision and morphological cladistics analysis of the diatom genus Anorthoneis (Cocconeidaceae), with description of Anorthoneis arthus - bertrandii sp. nov.

Pennesi, Chiara, Majewska, Roksana, Sterrenburg, Frithjof A. S., Totti, Cecilia, and Stefano, Mario De

Phytotaxa 336:201–238, 2018

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We present here an ultrastructure-based revision of the diatom genus Anorthoneis using both light (LM) and electron microscopy (SEM). The original slides and type material of all known Anorthoneis species were analysed and new, previously unseen, morphological features of the frustules, such as rota-like vela and ligulate structures around the valve margin, were revealed. The phylogenetic relationships among Anorthoneis taxa were investigated based on morphological characters using a maximum parsimony method. This analysis indicated a large, well-supported clade that included taxa that exhibited similarities in external and internal details of the central areas in both raphe-sternum and sternum valves. Revealed synapomorphies within the genus include externally and internally transversely dilated central area on both sides of the raphe-sternum valve, externally transversely dilated central area on both sides of the sternum valve, sternum valve striae parallel at the center and radiate at the apices, and areolae with hymenes in both valves. During a survey a new species Anorthoneis arthus-bertrandii sp. nov., was found on seagrass leaves collected from Siladen Island (Indonesia). This taxon is sister to A. hyalina, but can be easily differentiated from the latter by smaller valve dimensions, central area size and shape, and rota-like vela occluding sternum valve areolae - a feature that has never been observed in other Anorthoneis taxa.

2017

Microb. Ecol.

Shared epizoic taxa and differences in diatom community structure between green turtles (Chelonia mydas) from distant habitats.

Majewska, Roksana, Vijver, Bart Van, Nasrolahi, Ali, Ehsanpour, Maryam, Afkhami, Majid, Bolaños, Federico, Iamunno, Franco, Santoro, Mario, and De Stefano, Mario

Microbial Ecology 74:969–978, 2017

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The first reports of diatoms growing on marine mammals date back to the early 1900s. However, only recently has direct evidence been provided for similar associations between diatoms and sea turtles. We present a comparison of diatom communities inhabiting carapaces of green turtles Chelonia mydas sampled at two remote sites located within the Indian (Iran) and Atlantic (Costa Rica) Ocean basins. Diatom observations and counts were carried out using scanning electron microscopy. Techniques involving critical point drying enabled observations of diatoms and other microepibionts still attached to sea turtle carapace and revealed specific aspects of the epizoic community structure. Species-poor, well-developed diatom communities were found on all examined sea turtles. Significant differences between the two host sea turtle populations were observed in terms of diatom abundance and their community structure (including growth form structure). A total of 12 and 22 diatom taxa were found from sea turtles in Iran and Costa Rica, respectively, and eight of these species belonging to Amphora, Chelonicola, Cocconeis, Navicula, Nitzschia and Poulinea genera were observed in samples from both locations. Potential mechanisms of diatom dispersal and the influence of the external environment, sea turtle behaviour, its life stage, and foraging and breeding habitats, as well as epibiotic bacterial flora on epizoic communities, are discussed.
Bot. Mar

Two new epizoic Achnanthes species (Bacillariophyta) living on marine turtles from Costa Rica.

Majewska, Roksana, Stefano, Mario De, Ector, Luc, Bolaños, Federico, Frankovich, Thomas A., Sullivan, Michael J., Ashworth, Matt P., and Vijver, Bart Van de

Botanica Marina 60:303–318, 2017

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It has been known for a long time that marine mammals, such as whales and dolphins, host a very specific epizoic community on their skin. Whether or not a similar community exists on the carapaces of sea turtles is less studied. The present paper describes two new epizoic diatoms from the genus Achnanthes sensu stricto , Achnanthes elongata and Achnanthes squaliformis , found on the carapaces of nesting olive ridley sea turtles ( Lepidochelys olivacea ) in Ostional Beach on the Pacific coast of Costa Rica, based upon detailed scanning electron microscopy and comparison with the type material of Achnanthes groenlandica var. phinneyi and Achnanthes pseudogroenlandica . The two taxa appear to be closely related on the basis of their morphological features including long, slender valves, absence of terminal orbiculi, large cribrate areolae and absence of typical costae on the internal virgae of both valves. They can, however, be differentiated from each other by the number of areolae per stria, the position of the rapheless sternum and differences in their length/width ratio.
Trop. Ecol.

Spatio-temporal variation in phytoplankton communities along a salinity and pH gradient in a tropical estuary (Brunei, Borneo, South East Asia).

Majewska, Roksana, Adam, Aimimuliani, Mohammad-Noor, Normawaty, Convey, Peter, De Stefano, Mario, and Marshall, David J.

Tropical Ecology 58:251–269, 2017

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Tropical estuaries often have a low buffering capacity and may experience acidification, both naturally through microbial degradation and run-off from acid sulphate soils (ASS), or from various anthropogenic sources. Here, we describe phytoplankton communities from the turbid, acidified, and eutrophic Sungai Brunei and Brunei Bay estuarine system. Four sampling stations were selected, representing the full spectrum of the salinity (0.4-28.5 PSU) and pH (5.87-8.06) gradients associated with this system. A total of 25 microalgal families of phytoplankton (including 22 diatom and seven dinoflagellate genera) and one of ciliates were recorded in the survey, which was carried out between August 2011 and June 2012. Phytoplankton density ranged from 7 to 9107 cells ml(-1). Diatoms were a dominant component of the communities, with Nitzschia spp., Rhizosolenia spp., and Leptocylindrus sp. reaching the highest abundances. Phytoplankton communities present at the four sampling stations differed significantly in terms of both algal abundance and composition and were strongly influenced by the effect of season (30% of the total variance). The interactive effects of pH and salinity, and of pH and temperature, explained 16.7% and 17.5% of the total observed variation, respectively. A positive correlation between pH and the number of taxa found was detected. The functional diversity observed in phytoplankton from the Brunei River estuary was generally low with few taxa adapted well to the chronically low pH conditions. This study provides baseline data about structural and compositional changes in a tropical estuarine phytoplankton community associated with various levels of acidification of both natural and anthropogenic origins.
Polar Biol.

Diatom communities in the High Arctic aquatic habitats of northern Spitsbergen (Svalbard).

Zgrundo, Aleksandra, Wojtasik, Barbara, Convey, Peter, and Majewska, Roksana

Polar Biology 40:873–890, 2017

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As High Arctic environments are particularly sensitive to global and regional climate changes, a growing number of studies have focused on that region. It has been shown that living and fossil diatoms can be successfully used to track environmental changes in polar habitats. Nevertheless, the diatom flora of many Arctic areas remains unknown. The present study set out to examine the diatom flora in the rarely visited and near-pristine zone of northern Spitsbergen. Examination by light and scanning electron microscopy of 25 sediment samples, collected in fjords, tidal plains and lakes, indicated significant differences between the diatom assemblages identified in lakes located within different fjord watersheds. Altogether, 96 diatom taxa (46 genera) were found. The most abundant species (Achnanthidium minutissimum, Staurosirella pinnata and Nitzschia alpina) occurred in at least eight of the 11 investigated lakes. Assemblages from the Woodfjorden region were characterized by the presence of Cavinula pseudoscutiformis and Encyonema reichardtii, along with Navicula spp., which coincided with relatively low conductivity (34–58.7 µS cm−1) and near-neutral pH (7.2–7.5). Diatom assemblages found in the Wijdefjorden area were typically characterized by Denticula kuetzingii and Nitzschia inconspicua, with these lakes generally having higher water conductivity (\textgreater184 µS cm−1) and pH (7.5–8.1) conditions. Conductivity, biogenic silica concentration and water temperature were indicated as significant predictors of diatom community species composition and structure. No diatom frustules were found in fjord and tidal plain sediments. The effects of selected environmental factors on diatom assemblage formation are discussed.
Microelectron. Eng.

Surface enhanced thermo lithography.

Coluccio, Maria Laura, Alabastri, Alessandro, Bonanni, Simon, Majewska, Roksana, Dattola, Elisabetta, Barberio, Marianna, Candeloro, Patrizio, Perozziello, Gerardo, Mollace, Vincenzo, Di Fabrizio, Enzo, and Gentile, Francesco

Microelectronic Engineering 174:52–58, 2017

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We used electroless deposition to fabricate clusters of silver nanoparticles (NPs) on a silicon substrate. These clusters are plasmonics devices that induce giant electromagnetic (EM) field increments. When those EM field are absorbed by the metal NPs clusters generate, in turn, severe temperature increases. Here, we used the laser radiation of a conventional Raman set-up to transfer geometrical patterns from a template of metal NPs clusters into a layer of thermo sensitive Polyphthalaldehyde (PPA) polymer. Temperature profile on the devices depends on specific arrangements of silver nanoparticles. In plane temperature variations may be controlled with (i) high nano-meter spatial precision and (ii) single Kelvin temperature resolution on varying the shape, size and spacing of metal nanostructures. This scheme can be used to generate strongly localized heat amplifications for applications in nanotechnology, surface enhanced thermo-lithography (SETL), biology and medicine (for space resolved cell ablation and treatment), nano-chemistry.

2016

PLoS One

Summer epiphytic diatoms from Terra Nova Bay and Cape Evans (Ross Sea, Antarctica) - a synthesis and final conclusions?

Majewska, Roksana, Convey, Peter, and De Stefano, Mario

PLOS ONE 11:, 2016

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Despite recent advances in polar marine biology and related fields, many aspects of the ecological interactions that are crucial for the functioning of Antarctic shallow water habitats remain poorly understood. Although epiphytic diatoms play an essential role in the Antarctic marine food web, basic information regarding their ecology, biodiversity and biogeography is largely unavailable. Here, we synthesise studies on Ross Sea epiphytic diatoms collected during 11 summer Antarctic expeditions between the years 1989/90 and 2011/12, presenting a full list of diatom taxa associated with three macroalgal species (Iridaea cordata, Phyllophora antarctica, and Plocamium cartilagineum) and their epiphytic sessile fauna. Diatom communities found during the three summer months at various depths and sampling stations differed significantly in terms of species composition, growth form structure and abundances. Densities ranged from 21 to \textgreater8000 cells mm-2, and were significantly higher on the surface of epiphytic micro-fauna than on any of the macroalgal species examined. Generally, host organisms characterized by higher morphological heterogeneity (sessile microfauna, ramified Plocamium) supported richer diatom communities than those with more uniform surfaces (Iridaea). Differences between epiphytic communities associated with different macroalgae were reflected better in species composition than in growth form structure. The latter changed significantly with season, which was related strongly to the changing ice conditions. A general trend towards an increasing number of erect forms in deeper waters and tube-dwelling diatoms in the shallowest sites (2–5 m) was also observed. This study explores further important and largely previously unknown aspects of relationships and interactions between Antarctic epiphytic diatoms and their micro- and macro-environments.
PLoS One

Epibiotic diatoms are universally present on all sea turtle species.

Robinson, Nathan J., Majewska, Roksana, Lazo-Wasem, Eric A., Nel, Ronel, Paladino, Frank V., Rojas, Lourdes, Zardus, John D., and Pinou, Theodora

PLOS ONE 11:e0157011, 2016

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The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals.

2015

PLoS One

Diatoms and other epibionts associated with olive ridley (Lepidochelys olivacea) sea turtles from the Pacific Coast of Costa Rica.

Majewska, Roksana, Santoro, Mario, Bolaños, Federico, Chaves, Gerardo, and De Stefano, Mario

PLOS ONE 10:e0130351, 2015

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Although the sea turtles have long been familiar and even iconic to marine biologists, many aspects of their ecology remain unaddressed. The present study is the first of the epizoic diatom community covering the olive ridley turtle’s (Lepidochelys olivacea) carapace and the first describing diatoms living on sea turtles in general, with the primary objective of providing detailed information on turtle epibiotic associations. Samples of turtle carapace including the associated diatom biofilm and epizoic macro-fauna were collected from Ostional beach (9° 59´ 23.7´´ N 85° 41´ 52.6´´ W), Costa Rica, during the arribada event in October 2013. A complex diatom community was present in every sample. In total, 11 macro-faunal and 21 diatom taxa were recorded. Amongst diatoms, the most numerous were erect (Achnanthes spp., Tripterion spp.) and motile (Haslea sp., Navicula spp., Nitzschia spp., Proschkinia sp.) forms, followed by adnate Amphora spp., while the most common macro-faunal species was Stomatolepas elegans (Cirripedia). Diatom densities ranged from 8179 ± 750 to 27685 ± 4885 cells mm-2. Epizoic microalgae were either partly immersed or entirely encapsulated within an exopolymeric coat. The relatively low diatom species number, stable species composition and low inter-sample dissimilarities (14.4% on average) may indicate a mutualistic relationship between the epibiont and the basibiont. Dispersal of sea turtle diatoms is probably highly restricted and similar studies will help to understand both diatom diversity, evolution and biogeography, and sea turtle ecology and foraging strategies.
Phytotaxa

Chelonicola and Poulinea, two new gomphonemoid diatom genera (Bacillariophyta) living on marine turtles from Costa Rica.

Majewska, Roksana, Kociolek, J. P., Thomas, Evan W., Stefano, Mario De, Santoro, Mario, Bolanos, Federico, and Vijver, Bart Van de

Phytotaxa 233:236–250–236–250, 2015

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Marine mammals such as whales and dolphins have been known for a long time to host a very specific epizoic community on their skin. Less known however is the presence of a similar community on the carapaces of sea turtles. The present study is the first describing new taxa inhabiting sea turtle carapaces. Samples, collected from nesting olive ridley sea turtles (Lepidochelys olivacea) on Ostional Beach (Costa Rica), were studied using light and scanning electron microscopy. Two unknown small-celled gomphonemoid taxa were analysed in more detail and are described as two new genera, closely related to other gomphonemoid genera with septate girdle bands, such as Tripterion, Cuneolus and Gomphoseptatum. Chelonicola Majewska, De Stefano & Van de Vijver gen. nov. has a flat valve face, uniseriate striae composed of more than three areolae, simple external raphe endings, internally a siliceous flap over the proximal raphe endings and lives on mucilaginous stalks. Poulinea Majewska, De Stefano & Van de Vijver gen. nov. has at least one concave valve, uniseriate striae composed of only two elongated areolae, external distal raphe endings covered by thickened siliceous flaps and lives attached to the substrate by a mucilaginous pad. Chelonicola costaricensis Majewska, De Stefano & Van de Vijver sp. nov. and Poulinea lepidochelicola Majewska, De Stefano & Van de Vijver sp. nov. can be separated based on stria structure, girdle structure composed of more than 10 copulae, raphe structure and general valve outline. A cladistics analysis of putative members of the Rhoicospheniaceae indicates that the family is polyphyletic. Chelonicola and Poulinea are sister taxa, and form a monophyletic group with Cuneolus and Tripterion, but are not closely related to Rhoicosphenia, or other genera previously assigned to this family. Features used to help diagnose the family such as symmetry and presence of septa and pseudosepta are homoplastic across the raphid diatom tree of life.
Polar Biol.

A comparison of epiphytic diatom communities on Plocamium cartilagineum (Plocamiales, Florideophyceae) from two Antarctic areas.

Majewska, Roksana, Kuklinski, Piotr, Balazy, Piotr, Yokoya, Nair Sumie, Paternostro Martins, Aline, and De Stefano, Mario

Polar Biology 38:189–205, 2015

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Our understanding of diatoms, one of the most important Antarctic primary producers, is based mostly on investigations of plankton, sea-ice, and sediment samples. Herein, we contribute to the limited research devoted to benthic Antarctic diatoms by presenting a study on epiphytic diatom communities sampled in two remote Antarctic regions: Admiralty Bay (maritime Antarctica, Antarctic Peninsula) and Terra Nova Bay (Ross Sea). Recent studies have demonstrated that the most critical factor for the local epiphytic diatom communities was the nature of the substrate. In order to eliminate this factor so we could evaluate other potential controls, we sampled epiphytic diatoms from only one substrate that is common to both regions: the macroalgae Plocamium cartilagineum (L.) Dixon. Thalli of P. cartilagineum and their associated microalgal community was collected in January 2011 (Admiralty Bay) and 2012 (Terra Nova Bay) from a water depth of 5–25 m. Dehydrated macroalgal pieces were placed on stubs and sputter-coated, which allowed observation of diatoms attached to the substrate in their original position using scanning electron microscopy. A total of 72 taxa were observed, of which 31 taxa were common to both regions. Cell abundance and diatom growth form dominance were significantly different in Admiralty Bay and Terra Nova Bay samples. Total diatom abundance was higher in Admiralty Bay samples, dominated by adnate diatoms (Cocconeis spp.), but the number of taxa found as well as the values of ecological indices were higher for samples from the Ross Sea, where motile forms were dominant (Navicula spp.). Our results suggest that Antarctic shallow-water benthic habitats may present a high degree of microniche heterogeneity and highlight the need of fine-scale analyses in microbial studies. We also suggest grazers as a factor that contributes greatly to the observed differences.
Antarct. Sci.

Epiphytic diatom communities on Phyllophora antarctica from the Ross Sea.

Majewska, Roksana, and Stefano, Mario De

Antarctic Science 27:44–56, 2015

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Antarctic seaweeds play an important ecological role, but the vast macroalgal beds, typical of the shallow-water zone, are not efficiently grazed. However, macroalgal thalli are covered by epiphytic diatoms which represent a rich food source for higher trophic levels. We describe the abundances, growth form structure, species composition and distribution patterns in the diatom communities associated with Phyllophora antarctica from selected sites within the Ross Sea. The goal of this work was to learn more about the relationships between various components of the epiphytic community and its habitat. To examine diatoms at the microscale, four relatively well described sampling sites were chosen and analyses were performed on a large number of diatoms. All observations and counts were made with the scanning electron microscope. Samples collected in the same season but from different sites and under different sea and ice conditions differed significantly in terms of species composition, but all represented abundant and well-developed diatom communities. A list of species associated with P. antarctica from the investigated area is provided and the influence of the sampling effort on the observed diatom diversity is assessed.

2014

Aquatic Botany

Cocconeis Ehrenberg (Bacillariophyta), a genus dominating diatom communities associated with Posidonia oceanica Delile (monocotyledons) in the Mediterranean Sea.

Majewska, Roksana, D’Alelio, Domenico, and De Stefano, Mario

Aquatic Botany 112:48–56, 2014

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A fine-scale analysis of diatoms associated with Posidonia oceanica in selected locations was carried out along a longitudinal gradient in the Mediterranean Sea (00°21′W–27°07′E) to investigate the composition and diversity of epipthytic communities and to determine the distribution and relative importance of their components with special reference to the most common and abundant genus, Cocconeis. Posidonia oceanica was sampled twice (once per year for two years) at 19 sites. At each site, forty samples of P. oceanica shoots separated by several metres were taken. Epiphytic diatom communities were studied with SEM (scanning electron microscopy) and TEM (transmission electron microscopy). Fifty-two diatom genera were identified. In every studied case, adnate Cocconeis spp. cells dominated the community. Among 32 Cocconeis species and varieties found, recently described C. neothumensis var. marina and C. scutellum var. posidoniae were almost always the most numerous. The structure of Cocconeis assemblages changed across the various geographic regions both in terms of the species’ presence–absence and their relative abundance. In general, the most abundant species appeared to be broadly distributed, while less abundant species had a more distinct biogeographic pattern. In the course of this study, several Cocconeis species described as Indo-Pacific were found in the Mediterranean Sea for the first time. Potential relationships between different Cocconeis species and genetically distinct P. oceanica populations are discussed.
Diatom Res.

4th Polar Marine Diatom Taxonomy and Ecology Workshop, Cardiff University, UK, 4–9 August 2013.

Stroynowski, Zuzia, Minzoni, Rebecca, and Majewska, Roksana

Diatom Research 29:223–224, 2014

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2013

Polar Biol.

Growth form analysis of epiphytic diatom communities of Terra Nova Bay (Ross Sea, Antarctica).

Majewska, Roksana, Gambi, Maria Cristina, Totti, Cecilia Maria, Pennesi, Chiara, and De Stefano, Mario

Polar Biology 36:73–86, 2013

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Diatoms have been long collected from the Southern Ocean but almost no data exist for epiphytic communities, despite their high ecological significance as an important food source in Antarctic coastal food chains. Here, we present a first growth form analysis of diatoms associated with rhodophyte hosts from Terra Nova Bay, Ross Sea, Antarctica. We performed this study to gather baseline information on the species composition of epiphytic diatom communities, determine the influence of some environmental variables on the diatom distribution patterns, and assess the caveats that must be taken into account in terms of sampling design. Macroalgal material was collected during the Italian Antarctic expeditions between 1990 and 2004. Epiphytic diatoms were studied by means of scanning electron microscopy. In terms of growth forms, there were no significant differences between the diatom communities on the different macroalgal host species. Motile (mainly small-celled Naviculaperminuta and other Navicula spp.) and adnate (Cocconeis spp.) diatoms dominated the community throughout the study period. Many of the macroalgal blades examined were also covered by epiphytic animals (calcareous bryozoans, hydroids) over most of their surface, with a significant effect on the associated diatom community structure. Our findings suggest that the bio-physicochemical characteristics of each sampling site affected the epiphytic diatom communities more than the substrate type provided by the macroalgal host or the sampling depth.
Antarct. Sci.

Epiphytic diatom communities of Terra Nova Bay, Ross Sea, Antarctica: structural analysis and relations to algal host.

Majewska, Roksana, Gambi, Maria Cristina, Totti, Cecilia Maria, and Stefano, Mario De

Antarctic Science 25:501–513, 2013

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Epiphytic diatoms are important constituents of the Southern Ocean coastal water ecosystem, being a key element in many of the Antarctic trophic chains. However, only limited information exists relating to these microalgal communities. Here we describe our findings of a study on epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica) based on material collected during the summer campaigns spanning from 1990–2004. Observations of diatoms associated with three rhodophyte species (Iridaea cordata (Turner) Bory, Phyllophora antarctica Gepp & Gepp, and Plocamium cartilagineum (L.) Dixon) were carried out with the use of a scanning electron microscope. A total of 73 diatom taxa (32 genera) were distinguished, of which 20 taxa exceeded 3% of total abundance. Cocconeis fasciolata (Ehrenberg) Brown, Navicula perminuta Grunow, and Fragilariopsis nana (Steemann Nielsen) Paasche appeared in every sample. The analysis of similarities (ANOSIM) test as well as non-metric multidimensional scaling analysis indicated the nature of host organism as a major factor influencing associated diatom community structure, whereas depth, site, and time of sampling seemed to be less important. The epizooic communities associated with sessile fauna epiphytic on macroalgae differed significantly from those associated with macroalgal surface. A pronounced difference between the communities epiphytic on various host macroalgae species was also observed, although most of the dissimilarities occurred between diatom taxa of the same growth form.

2012

Phycol. Res.

Benthic diatoms of the Vistula River estuary (Northern Poland): Seasonality, substrata preferences, and the influence of water chemistry.

Majewska, Roksana, Zgrundo, Aleksandra, Lemke, Paulina, and Stefano, Mario De

Phycological Research 60:1–19, 2012

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Seasonal studies of water bodies in separate branches of the Vistula River estuary in Northern Poland were conducted over 30 months from May 2005 to October 2007. Diatom samples were collected from different substrata from two sites located in the river mouth, which has physical characteristics as a result of a complex interplay of natural and human influences that have taken place over the last 100+ years. The diatom flora growing on hard surfaces near the river banks such as sand, muddy sand, rocks, macroscopic green algae and/or vascular aquatic plants was recorded. All diatom taxa collected were distinguished based on their morphological features using light (LM) and scanning electron microscopy (SEM). A total of 187 species belonging to 61 genera were identified. A canonical correspondence analysis indicated that the diatom assemblages were definitely associated with salinity as well as nutrient concentrations and substratum type. During the study, malformations of diatom valves were observed in 48% of the microphytobenthos samples. Abnormal outline morphology and ornamentation deformities in several individuals of nine different species were recorded, which were mainly in epilithic and epiphytic communities collected from spring to autumn.

2011

Eur. J. Phycol.

Patterns in taxonomic composition of epiphytic diatom assemblages from Terra Nova Bay (Antarctica).

Majewska, Roksana, Totti, Cecilia, and De Stefano, Mario

European Journal of Phycology 46:109–194, 2011

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Epiphytic diatoms are one of the key biotic elements of the Antarctic marine ecosystem. Their unusually high metabolic flexibility gives them a crucial role in the Antarctic trophic chain. Despite being fundamental to the ecosystem functioning, diatom communities associated with marine macroalgae are frequently ignored in the floristic studies of the area. Few attempts to investigate substrate preferences have been reported. The present study provides the first examination and description of the epiphytic diatom flora from Terra Nova Bay (Ross Sea, Antarctica). Material was collected during Italian Antarctic campaigns in the years 1989–2005. Samples of thalli of Iridaea cordata, Phyllophora Antarctica, and Plocamium cartilagineum were taken from different depths at five sampling sites localized along the shore. All observations have been carried out under the scanning electron microscope. The genus Cocconeis was the most common. Two identified, previously described and well known from the Antarctic waters species – Cocconeis antiqua and C. fasciolata, as well as small naviculoid species (most likely Navicula perminuta), appeared in abundance. The Cocconeis component of the assemblage was estimated to approach 105 cells per cm2 on foliose hosts such as Iridaea. Melosira adelie was the only non-pennate diatom to achieve any degree of dominance, although Paralia sol and Trigonium arcticum were common on some of the filamentous parts of host macroalgae. Our results indicate a strong relation between the diatom assemblages and the sampling site. There is no clear evidence of diatoms host specificity. However, the filamentous forms as well as topographic anomalies (e.g. colonies of hydroids or bryozoans) can provide a point of attachment for a wider range of taxa.