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Euendolithic marine fungi are ubiquitous bioeroders of calcareous skeletal substrates, even under the extreme environmental conditions of the polar regions. The new bioerosion trace fossil Saccomorpha guttulata isp. nov. is presumably produced by a marine fungus that is interpreted to be well adapted to low temperatures, based on the provenance of the studied fossil and recent material. Its trace may thus serve as indicator for cool- to cold-water (palaeo) environments. The microboring is diagnosed by a radiating and ramifying system of club-shaped segments that gradually widen from a thin filament into a distal node. Below the initial point of entry, a stalked central cavity of slightly larger dimension and depth of penetration is developed, from which several segments emerge. The segments are interpreted to reflect a regular temporal sequence in the formation of hyphal filaments that widen into sporangial cavities. While all Saccomorpha ichnospecies share this composition of presumed sporangial cavities and hyphal filaments, with a varying degree of segmentation and gradation between these two elements, different strategies with regards to the temporal pattern in the formation of the different functional elements have evolved.

For the first time, a combined genotype-phenotype diversity analysis of endolithic microorganisms by pyrosequencing and microscopy was carried out across the intertidal and supratidal ranges of the Adriatic limestone coast. The coastal profiles represent ecotones between the sea and land, which express gradients of water supply, solar illumination, and salinity. The use of scanning electron microscopy imagery of resin casts showed that euendolith penetration remained shallow in the uppermost zones and was progressively deeper in the lower ranges where the water supply was more frequent. Microbial genotypes and phenotypes along the coastal profile showed large differences in dominance of taxa, but less in their diversity. The linkage between morphotypes observed along the profile and sequences was achieved by sequencing single cells/filaments, which were morphologically identified prior to their amplification. Molecular signatures of Hormathonema spp., Hyella caespitosa, Scytonema endolithicum, Sol...

Stylasterids are azooxanthellate lace corals, which may show an unusual colouration in coral reef ecosystems, ranging from red to purple on the light-exposed side of their colonies. In the present study, it was discovered that the calcareous skeletons of such corals are actually invaded and eroded by cryptic carbonate boring algae that represent Conchocelis phases in the life cycle of bangialean rhodophytes. For the first time, the shape, organisation and distribution of Conchocelis filaments within the skeletons of two different genera of lace corals are reported and documented by light and electron microscopy. Such description and characterisation of Conchocelis can help to distinguish between morphologically and taxonomically different endolithic microorganisms penetrating coral skeletons, including their recognition in fossil borings as indicators of depositional depth, i.e. of the extent of the photic zone and light conditions in ancient marine environments. The results are discussed in the light of a possible symbiotic or parasitic relationship between Conchocelis phases and their stylasterid host corals.

The participation of microorganisms in construction and destruction of sedimentary structures is widely recognized, and so is the importance of studying such geological processes in modern systems, where the conditions, participating forces, and the results can be observed and recorded. This information is important for understanding and interpreting corresponding processes if their effects were preserved as part of the fossil record. The present contribution refers to topics discussed during the 9th International Bioerosion Workshop in Rome on Oct. 23–27, 2017, dedicated to the evaluation of microbial traces as paleoecological and paleobathymetric indicators. The paper reviews the habitats, methods of collection, and preparation of samples, followed by observation of extracted microbial euendoliths. This approach is complemented by producing images of three-dimensional display of inhabited microborings in their original positions using resin-casting and double embedding of the microbially invaded substrates. This contribution stresses the value of recognizing the microboring organisms’ identities as a key aspect of the interpretation of their traces. It discusses different and complementary ways of how to achieve such parallel assessments. It reports on the importance of photo-documentation and morphometric evaluation of microbial populations, while avoiding possible artefacts caused by the methods used. The study also briefly summarizes the distribution patterns of microboring organisms and their boring and etching traces along depth profiles. Problems arising in the naming of complex traces and the relation to biological nomenclature are discussed.

International audience; The marine benthic cyanobacteria on coral reefs of Moorea Island (French Polynesia) show significant changes in species diversity in response to environmental impacts. To study these changes in cyanobacterial diversity, we examined pristine and degraded coral reefs by combining microscopy of morphological properties of the taxa with characterization of each by 16S rRNA gene sequences. A total of 30 cyanobacterial species have been recorded, of which 10 (33%) of them represent a new record for Moorea Island. The majority of morpho-species we identified could be distinguished by phylogenetic analyses of 61 sequences. Our survey results showed a sharp distinction in the composition of benthic cyanobacterial assemblages from healthy (high living coral cover) versus degraded habitats (low live coral cover due to anthropogenic activities). Finally, 21 bloom-forming species were identified, occurring mostly in environmentally impacted area (north coast). Blooms were dominated by three species: Anabaena sp.1, Hydrocoleum majus-B, Lyngbya majuscula. This study provides novel insights into the taxonomy of tropical benthic cyanobacteria as important environmental indicators and advocates the use of new bioevaluative tools for the management of coral reef environments.

Traces of microboring microbial endoliths (euendoliths) conform closely to the outlines of their makers as they are made. This habit evolved among prokaryotic cyanobacteria and eukaryotic rhodophytes, chlorophytes, and fungi. Among eukaryotic microborers, the endolithic mode of life is often limited to a phase in the course of their development, which alternates with an epilithic leafy phase. These endolithic phases are sometimes independently described as separate genera and species. This was the case with Conchocelis rosea Batters, 1891, later identified as the endolithic phase of Porphyra and Bangia that helped in identification of fossil bangialean rhodophytes of Silurian age: Palaeoconchocelis starmachii Campbell, Kazmierczak et Golubic, 1979. However, the traces of Conchocelis phases, although conspicuous and used to characterize the resident body fossil, were never formally described. We present here the formal ichnotaxonomic description of the complex and variable Conchocelis trace as Conc...

Traces of microbial euendoliths have been recognized as convenient indicators of ancient depositional depths, particularly in ranges that lack physical evidence of actions of waves and currents. The paleobathymetric indication value is sought in recognizing the distinction between traces made by phototrophic microorganisms, which are expected to be restricted to the illuminated portions of the ocean, and organotrophic ones, which are light-independent and may occur at any depth. Our findings show that unrelated organisms often use similar solutions to solve similar problems, resulting in convergent evolution of body shapes and their functions, also expressed in the traces of phototrophic and organotrophic, which limits their recognition and indication value. The relationship between microboring organisms and their traces can only be studied in modern environmental settings, followed by comparisons with traces in the fossil record. Examples of convergent evolution between phototrophic and organotrophic euendoliths that resulted in similar morphological features of their trace morphologies are illustrated ways to improve the distinction between light-independent and light-dependent microboring forms are discussed.

The marine benthic cyanobacteria of the Iles Eparses, Mozambique Channel, were surveyed for the first time. A total of 39 species are reported: 29 from Europa, 17 from Glorioso and 23 from Juan de Nova Islands. The higher biodiversity in Europa is explained by greater habitat diversity on this Island with unique ecosystems (mangroves, fossil reefs, pools). Average species richness varied between the geomorphological habitat types with higher diversity in shallow environments (fossil reef pools, mangroves, reef flats), which are characterized by high temperatures and high irradiances. The most common species observed on the three islands were Hydrocoleum coccineum , Hydrocoleum glutinosum , Hydrocoleum lyngbyaceum , Phormidium laysanense , Lyngbya sordida , and Symploca hydnoides ; which are also the dominant species observed in the Southwest Indian Ocean region. The most frequent species was Phormidium laysanense with extensive cover observed in the northwest of Juan de Nova Island. Our study provided a comparison between the cyanobacterial flora of Iles Eparses and the recorded surveys in the Southwest Indian Ocean region. The low similarity observed between these species lists could be explained by differences in sampling strategies and efforts, as well as by different taxonomic approaches employed in past regional studies.

Ostreobium sp. (Bryopsidales, Ulvophyceae) is a major microboring alga involved in tropical reef dissolution, with a proposed symbiotic lifestyle in living corals. However, its diversity and colonization dynamics in host’s early life stages remained unknown. Here, we mapped microborer distribution and abundance in skeletons of the branching coral Pocillopora damicornis from the onset of calcification in primary polyps (7 days) to budding juvenile colonies (1 and 3 months) growing on carbonate and non-carbonate substrates pre-colonized by natural biofilms, and compared them to adult colonies (in aquarium settings). Primary polyps were surprisingly already colonized by microboring filaments and their level of invasion depended on the nature of settlement substrate and the extent of its pre-colonization by microborers. Growth of early coral recruits was unaffected even when microborers were in close vicinity to the polyp tissue. In addition to morphotype observations, chloroplast-encoded rbcL gene sequence analyses revealed nine new Ostreobium clades (OTU99%) in Pocillopora coral. Recruits and adults shared one dominant rbcL clade, undetected in larvae, but also present in aquarium seawater, carbonate and non-carbonate settlement substrates, and in corals from reef settings. Our results show a substratum-dependent colonization by Ostreobium clades, and indicate horizontal transmission of Ostreobium-coral associations.

Recent volcanic lava flows extending into the ocean represent an ideal opportunity to study the long-term successional development of marine floral assemblages on the bare new substratum. We describe the floral assemblages of nine lava flows of different ages (prehistoric to 2007) at Piton de la Fournaise (Reunion Island, Indian Ocean) based on a survey of 37 stations. We identified 159 species including 148 macroalgae, 1 seagrass, and 10 cyanobacteria. Fifty-one of those represent new records for Reunion Island, and at least 9 taxa were identified as new to science. Recent lava flows were characterized by the dominance of ephemeral, opportunistic species, such as Pseudobryopsis hainanensis and Acrocladus dotyanus, while prehistoric lava flows were mainly characterized by perennial species, particularly Sargassum portierianum and Turbinaria ornata. A canonical correspondence analysis revealed that the environmental factor that most significantly correlated to the variation in floral assemblages was the distance to the most recent lava flow (2007). This factor was also highly correlated to coral cover. The composition of the different floral assemblages is discussed in relation to abiotic and biotic factors to explain ecological succession in a tropical environment.

Extracellular UV-screening pigments gloeocapsin and scytonemin present in the exopolysaccharide (EPS) envelopes of extremophilic cyanobacteria of freshwater and marine environments were studied by Raman spectroscopy and compared to their intracellular photosynthetic pigments. This Raman spectral analysis of the extracellular pigment gloeocapsin showed that it shared Raman spectral signatures with parietin, a radiation-protective pigment known in lichens. The UV-light spectra also show similarities. Gloeocapsin occurs in some cyanobacterial species, mostly with exclusion of scytonemin, indicating that these pigments have evolved in cyanobacteria as separate protective strategies. Both gloeocapsin and scytonemin are widely and species-specifically distributed in different cyanobacterial genera and families. The widespread occurrence of these pigments may suggest an early origin, while their detection by Raman spectroscopy makes them potential biosignatures for cyanobacteria in the fossil record and demonstrates the usefulness of nondestructive Raman spectroscopy analyses for the search for complex organics, including possible photosynthetic pigments, if preservable in early Earth and extraterrestrial samples.

The Pyramid of Caius Cestius in Rome is a funerary architecture erected between 272 and 279 AD. The Pyramid is composed by a nucleus in opus caementicium covered by Luni marble slabs. The marble surface has been colonized by a biocoenosis of microorganisms. The most frequent alteration found on the surface of the stone is the grey-black microbial crust, consisting of three different systematic groups: coccoid and filamentous Cyanobacteria, belonging mainly to the genera Chroococccus , Gloeocapsa and Tolypothrix , and green algae often associated with microscopic fungi or lichenized. The present work is aimed to establish which taxa present in the black crust are epilithic and which ones are endolithic. The cyanobacterium Chroococcus lithophilus is the most abundant and frequent taxon in all the samples collected; its growth is epilithic, chasmoendolithic, cryptoendolithic and euendolithic. The resin embedding-casting technique allowed to define the traces produced by this cyanobacterium highlighting its ability to actively dig tunnels into the marble. The present paper is a significant contribution to the knowledge of the important role of C. lithophilus in the biodeterioration of stone monuments.

Populations of the benthic diazotrophic cyanobacterium Hydrocoleum Kutzing (1843) are widely distributed in coral reefs and lagoons of tropical oceans, where they contribute to benthic nitrogen fixation. We compared the morphological, molecular and physiological features of 31 freshwater and marine Hydrocoleum populations from geographically different localities and five specimens from herbaria. Our aims were to compare the features of Hydrocoleum with the morphologically and phylogenetically related genera Trichodesmium Ehrenberg ex Gomont 1892 and Blennothrix Kutzing 1843, and to provide the basis for the validity of the genus Hydrocoleum. The Hydrocoleum populations were distributed over a wide range of sizes, showing no consistent inter-population grouping and leaving no gaps between groups that were traditionally attributed to different species. Transmission electron microscopy showed regular cell division rhythms in all Hydrocoleum populations with each cell division completed before the nex...

A number of coated grains (spherical to elongated ones in shape) were collected from a small stream, Dijon, France. They were characterized by typical concentric lamination surrounding broken twigs, and were thus identified as concentric precipitation on plant twigs. Within carbonate coatings of the plant twigs, two morphological groups including, eukaryotic green algae (Vaucheria sp.) and cyanobacteria (Scytonema sp. and Rivularia sp.) were detected, which form carbonate crystals that are surrounding their filaments. The filaments could have triggered carbonate precipitation by photosynthetic removal of CO2 causing the increase of alkalinity of the water, and by supporting their sheaths as nucleation sites. Such encrusted twigs were found from 70 meters downstream, in which temperature and pH were measured as 11.1oC and 8.18, respectively. These water chemistries (11.1oC and pH 8.18), with the aid of microbial photosynthesis, were likely to provide a suitable condition for carbonate precipitation on the twigs.

A complex microboring trace of fungal affinity is described in shells as a new ichnotaxon Saccomorpha stereodiktyon isp. nov. and compared with the earlier established ichnotaxon Saccomorpha terminalis Radtke, 1991. The new trace is characterized by a three-dimensional network of tunnels composed of a bifurcate horizontal (parallel to substrate surface) network with an upright (perpendicular to surface) system of tunnels and by the formation of cylindrical to multilobate terminal sporangial swellings. The new trace shares with Saccomorpha terminalis Radtke, 1991 the terminal position of sporangial swellings but differs from this ichnotaxon by its complexity in spatial arrangement, segmented construction, and ramification of tunnels. The horizontal parts of the network in the new taxon adhere to the substrate surface and regularly produce thinner tunnels that explore the interior of the substrate, allowing the producer to participate in digestion of organic lamellae incorporated in the shell. Microborings ...

Microbial mats are often the dominant benthic biotype in desert streams, however information on such mats is very scarce. We investigated the gross morphology of microbial mats and their cyanobacterial species composition in a perennially flowing wadi in Northern Oman, in relation to current flow and other biotic and abiotic variables. Physical and chemical parameters at the six sites were generally similar with low concentrations of soluble phosphorus and nitrogen; however, flow rates varied greatly with the highest velocity being 50 cm/s. The mats varied greatly in their gross morphology with the four sites with the highest current velocities forming low laminated structures attached to cobbles, and the two sites with minimal or no flow forming complex three-dimensional structures or free floating balls 1 to 3 cm in diameter. The concentration of chlorophyll a varied between 2.6 (±0.02) and 1.4 (±0.11) mg chlorophyll a g -1 mat fresh weight, with the highest concentration detected in the free floating balls. Twenty one cyanobacterial morphotypes belonging to 14 genera (5 unicellular and 9 filamentous) were identified with Calothrix and Leptolyngbya spp. as the most abundant. Cluster analysis of the cyanobacterial species composition showed that mats could have very different morphologies despite similar species compositions suggesting a high degree of plasticity of mat form. We conclude that microbial mats are important elements in Wadi ecosystems and have great variety of structure and community composition.

Travertine deposition is a landscape-forming process, usually building a series of calcareous barriers differentiating the river flow into a series of cascades and ponds. The process of carbonate precipitation is a complex relationship between biogenic and abiotic causative agents, involving adapted microbial assemblages but also requiring high levels of carbonate saturation, spontaneous degassing of carbon dioxide and slightly alkaline pH. We have analysed calcareous crusts and water chemistry from four sampling sites along the Hoyoux River and its Triffoy tributary (Belgium) in winter, spring, summer and autumn 2014. Different surface textures of travertine deposits correlated with particular microenvironments and were influenced by the local water flow. In all microenvironments, we have identified the cyanobacterium Phormidium incrustatum (Nageli) Gomont as the organism primarily responsible for carbonate precipitation and travertine fabric by combining morphological analysis with molecular sequencing (16S rRNA gene and ITS, the Internal Transcribed Spacer fragments), targeting both field populations and cultures to exclude opportunistic microorganisms responding favourably to culture conditions. Several closely related cyanobacterial strains were cultured; however, only one proved identical with the sequences obtained from the field population by direct PCR. This strain was the dominant primary producer in the calcareous deposits under study and in similar streams in Europe. The dominance of one organism that had a demonstrated association with carbonate precipitation presented a valuable opportunity to study its function in construction, preservation and fossilisation potential of ambient temperature travertine deposits. These relationships were examined using scanning electron microscopy and Raman microspectroscopy.

Microboring or euendolithic microorganisms, which colonize and penetrate various carbonate substrates, are abundant in coral reef ecosystems and play a major role in reef carbonate dissolution. A few studies reported the presence of euendoliths in stylasterid coral skeletons but the biological identity, distribution and abundance of these microorganisms remain largely unknown. Observations of over 100 stylasterid colonies, collected in the Indo-Pacific area, revealed for the first time that the association between these corals and euendolith organisms appears to be quite common in shallow tropical waters. The most abundant euendolith was identified as a cryptic stage in the development of the rhodophyte Porphyra (Conchocelis stage). The euendoliths were observed in the skeletons of seven species of three genera (four Stylaster, two Distichopora and one Lepidotheca). The presence of euendoliths inside skeletons conferred a particular colour to the studied stylasterid corals. Distribution and abundance of microborings varied significantly among stylasterid species and among branches of a single colony and so did the colour of their skeletons. Colonization of skeletons and the associated colour distribution were almost uniform in some stylasterids, forming an upward gradually diminishing or sharply limited gradient. This study shows that patterns of euendolith colonization and growth in stylasterid skeletons may depend on the stage of the euendolith development as well as on their environmental requirements such as light exposure.

Cages and fertilizers were used at Glover's Atoll, Belize to test the relative importance of nitrogen (N) and phosphorus (P) to microbial euendolithic communities (bacteria, algae and fungi) and their bioerosion rates of Strombus gigas shells after 56-days of exposure. By the end of the experiment, the abundance of green algae was higher than cyanobacteria and fungi in N and N+P treatments, although green algae did not increase proportionally with increasing N concentrations, suggesting that green algae were co-limited by P and N. In contrast, cyanobacteria abundance increased with increasing P concentration, suggesting that cyanobacteria were P-limited. Fungi were not significantly affected by the addition of nutrients. Microbioerosion rates in the N and N+P treatments were 2-times greater than rates in the P treatment and 15-times greater than the control treatment. Results demonstrate that increased nutrient concentrations on coral reefs may increase microbioerosion rates, and variations in nutrient ratios can modify microborers community composition.

Fourty-two high-rank syntaxa and seven associations of the thallophyte system of syntaxa are either described as new or validated in this paper. Among those, there are the following nine classes: Aspicilietea candidae , Caulerpetea racemosae, Desmococcetea olivacei , Entophysalidetea deustae, Gloeocapsetea sanguineae , Mesotaenietea berggrenii , Naviculetea gregariae , Porpidietea zeoroidis , Roccelletea phycopsis . Eleven orders and ten alliances as well as three associations are described or validated: the Aspicilietalia verruculosae (incl. Aspicilion mashiginensis and Teloschistion contortuplicati ) , the Caulerpetalia racemosae (incl. Caulerpion racemosae ) , the Desmococcetalia olivacei (incl. Desmococcion olivacei ) , the Dirinetalia massiliensis , the Fucetalia vesiculosi (incl. Ascophyllion nodosi ) , the Gloeocapsetalia sanguineae, the Lecideetalia confluescentis (incl. Lecideion confluescentis ) , the Mesotaenietalia berggrenii (incl. Mesotaenion berggrenii, Mesotaenietum berggrenii and Chloromonadetum nivalis ) , the Naviculetalia gregariae (incl. Oscillatorion limosae and Oscillatorietum limosae ) , the Porpidietalia zeoroidis (incl. Porpidion zeoroidis ) , and the Roccelletalia fuciformis (incl. Paralecanographion grumulosae ). Further, five orders, seven alliances and four associations, classified in known classes, were described as well. These include: the Bacidinetalia phacodis, the Agonimion octosporae and the Dendrographetalia decolorantis (all in the Arthonio radiatae-Lecidelletea elaeochromae ), the Staurothelion solventis (in the Aspicilietea lacustris ), the Pediastro duplicis-Scenedesmion quadricaudae and the Pediastro duplicis-Scenedesmetum quadricaudae (both in the Asterionelletea formosae ), the Peccanion coralloidis and the Peltuletalia euplocae (both in the Collematetea cristati ), the Laminarion hyperboreae, the Saccorhizo polyschidi-Laminarietum and the Alario esculenti-Himanthalietum elongatae (all in the Cystoseiretea crinitae ) , the Delesserietalia sanguinei, the Delesserion sanguinei and the Delesserietum sanguineae (all in the Lithophylletea soluti ), as well as the the Rinodino confragosae-Rusavskietalia elegantis and the Rhizocarpo geographici-Rusavskion elegantis (both in the Rhizocarpetea geographici ).

In the temperate Azores carbonate factory, a substantial fraction of the calcareous skeletal components is recycled by a remarkable biodiversity of biota producing bioerosion traces (incipient trace fossils). To study this biodiversity, experimental carbonate substrates were exposed to colonisation by epilithic and endolithic organisms along a bathymetrical gradient from 0 to 500 m depth, during 1 and 2 years of exposure. The overall bioerosion ichnodiversity is very high and comprises 56 ichnotaxa and ichnoforms attributed to cyanobacteria, chlorophytes, fungi, other micro-chemotrophs, macroborers, grazers and epilithic attachment scars. In the intertidal, hydrodynamic force, partial emersion and strong temperature fluctuations lead to the lowest ichnospecies richness. This contrasts with the highest ichnodiversity found at 15 m under the most favourable environmental conditions. Towards aphotic depths, a gradual depletion in ichnodiversity is observed, most probably because of the restricted light availability and a slowdown in ichnocoenosis development. Analysis of similarity (ANOSIM), in combination with non-metrical multidimensional scaling (NMDS), was used to highlight variability in the relative abundance of traces among depths, substrate orientations and exposure times. Ichnodiversity and abundance of traces decrease significantly with depth and are higher on up-facing versus down-facing substrates, whereas differences between years were not as pronounced. This study demonstrates that statistical methods of biodiversity analysis are not per se restricted to biotaxa but may well be applied also to ichnotaxa. In the analysis of trace fossil assemblages, this approach supports the recognition of diversity patterns and their relation to environmental gradients.

The diversity within the genus Nostoc is still controversial and more studies are needed to clarify its heterogeneity. Macroscopic species have been extensively studied and discussed; however, the microscopic forms of the genus, especially those from running waters, are poorly known and likely represented by many more species than currently described. Nostoc isolates from biofilms of two Spanish calcareous rivers were characterized comparing the morphology and life cycle in two culture media with different levels of nutrients and also comparing the 16S rRNA gene sequences. The results showed that trichome shape and cellular dimensions varied considerably depending on the culture media used, whereas the characteristics expressed in the course of the life cycle remained stable for each strain independent of the culture conditions. Molecular phylogenetic analysis confirmed the distinction between the studied strains established on morphological grounds. A balanced approach to the evaluation of diversity of Nostoc in the service of autecological studies requires both genotypic information and the evaluation of stable traits. The results of this study show that 16S rRNA gene sequence similarity serves as an important criterion for characterizing Nostoc strains and is consistent with stable attributes, such as the life cycle.

We report the first identification of homoanatoxin-a from benthic marine cyanobacteria (Hydrocoleum lyngbyaceum) samples collected in Lifou (Loyalty Islands, New Caledonia), where cases of giant clams (Tridacna maxima) intoxications were recorded during a severe ciguatera fish poisoning outbreak. Homoanatoxin-a was also detected in extracts of giant clams harvested in the surroundings of the contaminated area suggesting the possible link between these poisoning events and the occurrence of potentially neurotoxic Hydrocoleum.

Cluster-forming boring traces in carbonate substrates, characterized by regular dichotomous ramifications, are described as a new ichnospecies of Abeliella Magdefrau 1937: A. bellafurca isp. nov. The new trace differs from A. riccioides Magdefrau by a three- rather than two-dimensional display of tunnels and branchings and by penetrating carbonatic rather than phosphatic substrates. These boring traces occur in bivalve shells from the Oligocene to the Recent in shallow, illuminated marine settings. Two distinct morphotypes of A. bellafurca were observed, both originating from a single point of entry: one produces prostrate boring system in early developmental stages followed by deeper penetration, and the other, which forms only deep penetrating three-dimensional boring systems. Tunnels with dichotomous ramifications in modern marine environments are produced by the cyanobacterium Hyella stella Al-Thukair et Golubic. The organism penetrates the shells and shell fragments, whereby the apical cell divides a...

Microboring endoliths were studied in dead modern corals collected at various depths and in growth position on La Surprise atoll in New Caledonia. Eight taxa of microborers were regularly observed: three cyanobacteria (Hyella caespitosa, Mastigocoleus testarum, and Plectonema terebrans), two chlorophytes (Ostreobium quekettii and Phaeophila dendroides) and three fungal forms (Dodgella priscus, and two unidentified fungi). The relative abundance of each taxon was determined in the modern corals throughout the studied sampling interval (from 0 down to 40 m water depth). This allowed us to propose for the first time a bathymetric model based on microendolith assemblages colonizing in situ hard-substrates of corals. In this model, the occurrence of the cyanobacteria Hyella and Mastigocoleus indicates a bathymetric range from 0 down to a water depth of 3 and 6 m respectively. The chlorophyta O. quekettii, associated with the cyanobacterium P. terebrans and fungi, is dominant from 10 to 40 m depth, which is the lower limit of our sampling. The distribution ranges of individual taxa observed in the dead coral substrates from New Caledonia are much narrower than those reported in the literature for other substrates. The bathymetric model based on distribution of microborers in modern corals was then applied to interpret the trace assemblages of microborers observed in Holocene corals collected by drilling on two reef sites of New Caledonia : La Surprise islet, in the vicinity of the sampling sites of the modern corals, and the barrier reef of Bayes, on the NE coast of Grande Terre. The paleodepth interpretations performed at various levels along the cores allow identification of several shallowing-upward sequences during the last 7000 years of reef growth in New Caledonia. Differences in the thickness of these sequences between La Surprise and Bayes sites were interpreted as differences in the space available for accommodation between the two sites, in turn related to the differential subsidence that affected New Caledonia during Holocene times. The use of the microendolith trace assemblages in paleodepth reconstructions of Holocene reefs from New Caledonia allowed detection of relative sea level variations finer than those deduced from changes in coralgal assemblages.

Dinitrogen-fixing organisms in cyanobacterial mats were studied in two shallow coral reef ecosystems: La Reunion Island, southwestern Indian Ocean, Sesoko (Okinawa) Island, and northwestern Pacific Ocean. Rapidly expanding benthic miniblooms, frequently dominated by a single cyanobacterial taxon, were identified by microscopy and molecular tools. In addition, nitrogenase activity by these blooms was measured in situ. Dinitrogen fixation and its contribution to mat primary production were calculated using (15)N(2) and (13)C methods. Dinitrogen-fixing cyanobacteria from mats in La Reunion and Sesoko showed few differences in taxonomic composition. Anabaena sp. among heterocystous and Hydrocoleum majus and Symploca hydnoides among nonheterocystous cyanobacteria occurred in microbial mats of both sites. Oscillatoria bonnemaisonii and Leptolyngbya spp. occurred only in La Reunion, whereas Hydrocoleum coccineum dominated in Sesoko. Other mats dominated by Hydrocoleum lyngbyaceum, Phormidium laysanense, and Trichocoleus tenerrimus occurred at lower frequencies. The 24-h nitrogenase activity, as measured by acetylene reduction, varied between 11 and 324 nmoles C(2)H(2) reduced microg(-1) Chl a. The highest values were achieved by heterocystous Anabaena sp. performed mostly during the day. Highest values for nonheterocystous cyanobacteria were achieved by H. coccineum mostly during the night. Daily nitrogen fixation varied from nine (Leptolyngbya) to 238 nmoles N(2) microg(-1) Chl day(-1) (H. coccineum). Primary production rates ranged from 1,321 (S. hydnoides) to 9,933 nmoles C microg(-1) Chl day(-1) (H. coccineum). Dinitrogen fixation satisfied between 5% and 21% of the nitrogen required for primary production.

Tropical rainfall patterns control the subsistence lifestyle of more than one billion people. Seasonal changes in these rainfall patterns are associated with changes in the position of the intertropical convergence zone, which is characterized by deep convection causing heavy rainfall near 10 ! N in boreal summer and 3 ! N in boreal winter. Dynamic controls on the position of the intertropical convergence zone are debated, but palaeoclimatic evidence from continental Asia, Africa and the Americas suggests that it has shifted substantially during the past millennium, reaching its southernmost position some time during the Little Ice Age (AD1400‐1850). However, without records from the meteorological core of the intertropical convergence zone in the Pacific Ocean, quantitative constraints on its position are lacking. Here we report microbiological, molecular and hydrogen isotopic evidence from lake sediments in the Northern Line Islands, Galapagos and Palau indicating that the Pacific intertropical convergence zone was south of its modern position for most of the past millennium, by as much as 500km during the Little Ice Age. A colder Northern Hemisphere at that time, possibly resulting from lower solar irradiance, may have driven the intertropical convergence zone south. We conclude that small changes in Earth’s radiation budget may profoundly affect tropical rainfall.

Stromatolites are sedimentary deposits that are the direct result of interactions between microbes and their surrounding environment. Once dominant on ancient Earth, actively forming stromatolites now occur in just a few remote locations around the globe, such as the island of Highborne Cay, Bahamas. Although the stromatolites of Highborne Cay contain a wide range of metabolically diverse organisms, photosynthetic cyanobacteria are the driving force for stromatolite development. In this study, we complement previous morphological data by examining the cyanobacterial phylogenetic and physiological diversity of Highborne Cay stromatolites. Molecular analysis of both clone and culture libraries identified 33 distinct phylotypes within the stromatolites. Culture libraries exhibited several morphologically similar but genetically distinct ecotypes, which may contribute to ecosystem stability within the stromatolites. Several of the cultured isolates exhibited both a positive phototactic response and light-dependent extracellular polymeric secretions production, both of which are critical phenotypes for stromatolite accretion and development. The results of this study reveal that the genetic diversity of the cyanobacterial populations within the Highborne Cay stromatolites is far greater than previous estimates, indicating that the mechanisms of stromatolite formation and accretion may be more complex than had been previously assumed.

Travertines and calcareous tufa are porous deposits formed by interactions between ambient precipitation of calcium carbonate and resident organisms under different temperature regimes. The distinctions between travertine as thermal spring deposits and calcareous tufa (Kalktuff) as deposits in the springs and rivers at ambient temperatures are fluid. Both represent end points in bio- and physico-chemical calcification processes across a broad gradient of temperature, mineral composition and ion saturation levels. Ecological preferences of micro- and macroorganisms in travertine depositional systems result in the re-distribution of water flow, modification of the landscape and its ecology. The resulting sedimentary structures include new environmental settings with different and diversified biota. They also include different microenvironments of diagenesis with different timings of the processes involved. Conditions in modern ambient temperature travertines of the Plitvice system of lakes and waterfalls are compared with the similar, ancient system of Rocchetta a Volturno, in the central Apennines. Diagenetic alterations are described and illustrated starting with biologically identified primary deposits.

From 2001 to 2005, numerous cases of seafood poisonings were reported in a tribe from Lifou (Loyalty Islands Province, New Caledonia) of which 35 were thoroughly examined. Observations outlined by the epidemiological and clinical data (including severity and rapid onset of certain symptoms following consumption of either giant clams ( Tridacna spp.) or grazing and molluscivorous fish together with the apparent inefficacy of traditional remedies, were not in favour of a classical Ciguatera Fish Poisoning (CFP) outbreak. From 2005 onwards, an environmental offshore survey of the affected area was conducted. Screening of the damaged coral area revealed the presence of large populations of cyanobacteria identified as Hydrocoleum Kutzing, but the absence of Gambierdiscus spp., the well-known dinoflagellate causative agent of CFP. In vivo and in vitro toxicological studies of extracts obtained from cyanobacteria and giant clams, strongly suggested the co-occurrence of ciguatoxin-like, anatoxin-like and paralytic shellfish toxins in these samples. These new findings shed new light on the complexity of the CFP symptomatology and treatment and also on the diversity and origin of the CFP toxins. Furthermore they provide new evidence of the overall variability of seafood poisonings following the ingestion of different sea products living in a marine environment where significant harmful populations of microalgae and cyanobacteria coexist. This is the first report on the involvement of cyanobacteria in CFP-like outbreaks following the consumption of giant clams or fish specimens. Consequently, it is recommended that CFP risk assessment programs now include monitoring of cyanobacteria besides the obvious screening of CFP-promoting dinoflagellates.

Variations in morphology, fatty acids, pigments and cyanobacterial community composition were studied in microbial mats across intertidal flats of the arid Arabian Gulf coast. These mats experience combined extreme conditions of salinity, temperature, UV radiation and desiccation depending on their tidal position. Different mat forms were observed depending on the topology of the coast and location. The mats contained 63 fatty acids in different proportions. The increased amounts of unsaturated fatty acids (12–39%) and the trans/cis ratio (0.6–1.6%) of the cyanobacterial fatty acid n-18:1ω9 in the higher tidal mats suggested an adaptation of the mat microorganisms to environmental stress. Chlorophyll a concentrations suggested lower cyanobacterial abundance in the higher than in the lower intertidal mats. Scytonemin concentrations were dependent on the increase in solar irradiation, salinity and desiccation. The mats showed richness in cyanobacterial species, with Microcoleus chthonoplastes and Lyngbya aestuarii morphotypes as the dominant cyanobacteria. Denaturing gradient gel electrophoresis patterns suggested shifts in the cyanobacterial community dependent on drainage efficiency and salinity from lower to higher tidal zones. We conclude that the topology of the coast and the variable extreme environmental conditions across the tidal flat determine the distribution of microbial mats as well as the presence or absence of different microorganisms.

Various types of microbial mats are widespread in the SW New Caledonia lagoon. Both heterocystous (Nodularia harveyana) and non-heterocystous (Hydrocoleum cantharidosmum, H. lyngbyaceum) cyanobacteria dominate these mats. Using the acetylene reduction technique, nitrogenase activity was observed at all sites. Heterocystous cyanobacteria fix N-2 during the daytime, whereas non-heterocystous cyanobacteria fix N-2 during the night. The intensity of nitrogenase activity depended on the level of light energy received during daylight. An estimation of nitrogen fixation by benthic cyanobacteria (16.4 +/- 5.4 mg N-2 m(-2) d(-1)) at 21 m depth (average depth of the lagoon) represented 19% of the nitrogen requirement for benthic primary production.

The age and shell growth patterns in populations of Patella rustica of the Adriatic Sea were determined by analyzing the inner growth lines visible in shell sections. Marginal increment analysis showed annual periodicity with annual growth line being deposited in May. The growth analysis of 120 individual shells showed that 90.8 % of collected individuals were less than 4 years of age and only two individuals (1.6 %) were older than 6 years. Population structure was described and the generalized von Bertalanffy growth parameters were calculated: asymptotic length (L ∞ ) was 38.22 mm and the growth constant (K) was 0.30 year -1 . Growth performance index value of P. rustica (O’) was 2.64 and is among the lowest ranges reported for limpet species. Patella rustica shells were degraded to different degrees by microbial bioerosion. Microboring organisms identified were pseudofilamentous and filamentous cyanobacteria Hormathonema paulocellulare , Hyella caespitosa, Mastigocoleus testarum and Leptolyngbya sp. The overall intensity of infestation was relatively low, but increased in severity with shell length. The damage was most often restricted to the oldest parts of the shell, i.e. apex of the shell, posing difficulties in determining the exact position of the first growth line. The present study is first to introduce the use of inner growth lines in Patella rustica shell sections as a reliable method for age determination and it provides the first insight into the growth patterns of this keystone species while taking the interference of microbial shell bioerosion in consideration.

WOS:000356545300009; Pronounced differences with respect to the extent of infestation and the degree of Lithophaga lithophaga shell damage inflicted by euendolithic taxa at two sites in the Adriatic Sea representing different productivity conditions, are described. Shells collected from the eastern part of Kastela Bay, which is characterized by higher primary productivity, have significantly more shell damage then the shell collected from a site on the outer coast of the island of Ciovo exposed to the oligotrophic Adriatic Sea. The presence of endoliths and their perforations were detected in different layers of the shell, including solidly mineralized parts of the skeleton and within the organic lamellae incorporated into the shell. Phototrophic endoliths were not observed in the specimens. The most serious damage to L. lithophaga shells was the boring clionaid sponge Pione vastifica, which was more common in shells collected from Kastela.

Hardly any molecular studies have been done on euendoliths of marine coastal environments, especially along the supratidal ranges of carbonate coasts. In our study, we provide a comparative sequence analysis using 454 pyrosequencing of the 16S ribosomal RNA (rRNA) gene combined with extensive microscopy of the endolithic community from rock pools of the Croatian Adria. Molecular diversity indices and richness estimates showed high level of diversity, particularly in high-salinity samples. The most common cyanobacteria belong to the order Pleurocapsales, similar to observations on limestone coasts in other parts of the world. Using single-cell amplification sequences of Hormathonema spp., Hyella caespitosa, and Kyrtuthrix dalmatica was for the first time introduced to the public GenBank. Microscopic investigations did not show qualitative variances in diversity among sites with different salinity but clear differences in prevalent organisms from similar environments suggesting that most of them are adapted to inhabit extreme, marine endolithic habitats and that similar species inhabit geographically separated but ecologically similar environments. This is a remarkable concordance rather seldom seen in molecular community studies in support of the hypothesis that endolithic ecosystems are seeded from a global meta-community. The relative diversity of the community is greater than those described from harsh endolithic habitats of cold and hot deserts. The maximum likelihood phylogenetic tree consisting of 166 operational taxonomic units (OTUs) at 96 % sequence similarity revealed 11 distinct clusters. Three clusters contained only epilithic or endolithic taxa, and five clusters contained mixed epilithic and endolithic taxa. Organisms clustered according to their taxonomic affiliations and not to their preferences to salt concentrations.

International audience; Cyanobacteria-dominated microbial mat communities thrive widely and year round in coral reefs and tropical lagoons, with periodic massive development of benthic blooms. We studied the diversity and spatiotemporal variation of the cyanobacterial dominance in mats of the shallow lagoon of La Réunion Island in the Indian Ocean by means of dena-turing gradient gel electrophoresis and cloning-sequencing approaches targeting the 16S rRNA gene, combined with macromorphological and micromorphological characterization of corresponding phenotypes. The mat-forming cyanobacteria were highly diversified with at least 67 distinct operational taxonomic units identified in the lagoon, encompassing the entire morphological spectrum of the phy-lum Cyanobacteria, but with striking dominance of Oscillatoriales and Nostocales. It appeared also that selective pressures acting at different geographical scales have an influence on the structure and composition of these mats dominated by cyanobacteria. First, large changes were observed in their diversity and composition in relation to local changes occurring in their environment. Second, from the data obtained on the richness and composition of the mats and from the comparison with similar studies in the world, tropical mats seem to display wider cyanobacterial richness than in temperate and cold areas. Moreover, these tropical mats share more species with mats in other tropical regions than with those in temperate and cold climatic regions, suggesting that marine cyanobacteria in biofilms and mats display a biogeo-graphic structure.

Dried herbarium specimens of cyanobacteria (exsiccata) deposited over 100 years ago were analysed and characterized using combined morphological and molecular approaches. Six representative coccoid and filamentous cyanobacteria from two historic collections and a 15-year-old air-dried environmental sample were studied. Morphological features observed by light and electron microscopy were correlated with the results of 16S rRNA gene sequencing. Historic identifications achieved by means of classical morphology could thus be confirmed by extracted, amplified and sequenced 16S rRNA gene fragments. The results of this study open the possibility of providing genotypic characterizations to botanical type specimens, thus reconciling the botanical and bacteriological approaches to the taxonomic treatment of these micro-organisms.

Cyanobacterial populations, the primary producers and builders of 'kopara' microbial mats were studied in four selected ponds along the rim of the Rangiroa Atoll, French Polynesia using a polyphasic approach. Seven isolates were maintained in uni-cyanobacterial cultures, characterized morphotypically and phylogenetically by evaluating sequences of the 16S rRNA gene of about 620 base pairs in length. Cyanobacteria in natural populations were analyzed microscopically, characterized morphotypically, and compared with cultured strains. Three of the isolates were identified in the field samples: Lyngbya aestuarii, Johannesbaptistia pellucida and Chroococcus submarinus were present in the mats only as minor components, whereas the species of Schizothrix that dominated the mat community could not be cultured. The sequence of Johannesbaptistia pellucida is published for the first time. The phylogenetic and taxonomic relations are discussed on the basis of a reconstructed phylogenetic tree in relation to morphotypic characters. Sequences of Kopara isolates plot separately from those cultured from the lagoon of the neighbouring atoll Tikehau, indicating a narrow niche differentiation of benthic cyanobacterial taxa. The results support the application of a polyphasic approach to characterization, ecology and diversity of cyanobacteria.

The filamentous cyanobacteria belonging to the genus Hydrocoleum (Blennothrix) are among the most common mat-forming cyanobacteria in tropical oceans. We present here the evidence that these benthic cyanobacteria are morphologically and phylogenetically very close to the planktonic species of Trichodesmium. Genetic relationship was established independently with regard to sequences of the 16S rRNA gene, nifH gene, and phycocyanin and phycoerythrin intergenic spacers. The species of both genera formed a common distinct branch in phylogenetically reconstructed cyanobacterial trees, suggesting that the main constituents of cyanobacterial benthos and plankton have an early common origin and both represent major contributors to nitrogen budget of tropical oceans today as in the distant geological past.

To quantify the contribution of endolithic phototrophs to primary production of dead carbonate substrates, experimental blocks of cleaned Porites lobata Dana skeleton were placed at three different sites in Kaneohe Bay, Hawaii: inshore, lagoonal, and oceanic. After 6 months of exposure, experimental blocks were colonized by communities characteristic of their estuarine (inshore, lagoonal) and oceanic (ocean) environments. Blocks were subsampled; net photosynthesis (NP) and chl a concentrations of the whole blocks (epi- and endoliths) and scrapped blocks (only endoliths) were quantified. Green turf algae colonized predominantly inshore and lagoonal blocks, while encrusting corallines were the dominant epiliths colonizing oceanic blocks. Four main species of endolithic phototrophs were identified in all blocks: Mastigocoleus testarum Lagerheim, Plectonema terebrans Bornet and Flahault (cyanobacteria), Phaeophila dendroides Crouan and Crouan, and Ostreobium quekettii Bornet and Flahault (Chlorophytes). While epiliths were very different between sites, NP rates and chl a concentration of endoliths did not vary significantly and were positively correlated (191 ± 25 mmol C·m -2 ·day -1 and 590 ± 150 mg chl a · m 2 of reef, respectively). Assimilation numbers for whole communities, including both epilithic and endolithic communities, were similar to those measured for endolithic communities alone (average of 0.3 g C-g chl a·h -1 ). Under experimental conditions, the contribution of endolithic phototrophs to community NP rates of blocks ranged from 56% to 81%, and under natural conditions, we estimated that this contribution ranged between 32% and 46%. Thus, we showed that the endolithic phototrophs are one of the major primary producers in dead coral substrates in a wide range of coral reef environments.

Benthic cyanobacteria of the genus Lyngbya can form prominent mats and blooms in tropical and subtropical coral reef and seagrass habitats worldwide. A Lyngbya bloom on the reef tract offshore of Broward County, Florida, was first noted in 2002, and although it is seasonally variable in its distribution and abundance, it has persisted and spread over the past 3 years. In this study, the most abundant species of Lyngbya found in the blooms have been identified and compared to other species of Lyngbya by morphological and molecular methods. The most common species of Lyngbya is consistent with the properties of Lyngbya confervoides C. Agardh. The 16S ribosomal DNA sequence shares 88–92% identity with other known Lyngbya sequences, suggesting that this bloom consists primarily of a new, previously unsequenced species of Lyngbya. The second most common Lyngbya in the bloom is consistent with Lyngbya polychroa. This persistent bloom is a concern because it smothers octocorals and other invertebrates and negatively impacts these southeastern Florida reefs.

Boring patterns of microbial endoliths were analyzed in bivalve shells collected from different environments in the Northern Bay of Safaga on the Red Sea, Egypt. A total of 20 ichnotaxa have been recognized within 64 samples and evaluated on the basis of 250 scanning electron micrographs. The analysis of microorganisms in shells from the same depth profile has been performed separately. Morphological properties of selected ichnotaxa were studied in detail, morphometric parameters established, measured, and statistically evaluated. This method was applied to determine the variability of dominant traces in view of their ichnotaxonomic treatment. Ichnogenus Rhopalia was discussed and a new ichnospecies Rhopalia spinosa was described. Formal change of name for cyanobacterial traces of Hyella and Solentia from Fasciculus to Fascichnus, and for the traces of the green alga Ostreobium from Reticulina to Ichnoreticulina were proposed on the ground of the priority rights in compliance with rules of the International Code of Zoological Nomenclature.

Natural populations of benthic cyanobacteria in the lagoon of Tikehau Atoll in French Polynesia were studied using a polyphasic approach that combined field observations, LM, culturing, and molecular sequencing. The approach assessed their phenotypic (morphotypic and ecological) and genotypic diversity. Partial sequences (approximately 450 bp long) of the PCR-amplified 16S rRNA gene were obtained from both natural and cultured populations using cyanobacteria-specific primers. The sequences obtained clustered into six separate phylogenetic clusters in relation to the complete set of 16S rRNA sequences available in public databases. Phylogenetic clustering correlated in many cases with some morphological characteristics. For example, Spirulina subsalsa could be identified to the morphospecies level using both molecular and microscopic approaches. Morphotypes identified as Symploca hydnoides (Kutz. ex Gomont) TK22, Phormidium sp. TK1, and P. laysanense (Lemmerman) TK14 formed a distinct cluster. The morphogenus Hydrocoleum (Blennothrix) clustered interestingly close to the morphologically similar, but planktonic, marine cyanobacterium Trichodesmium, suggesting a relationship. Other sequences belonging to morphotaxa with very narrow trichomes were found to be polyphyletic. Enrichment cultures, with inoculum obtained from field populations, were followed over a period of 18 months. Dominance in all cultures shifted over time in favor of a set of cyanobacterial strains with narrow trichomes, which were phenotypically and phylogenetically different from natural populations dominating the original samples. Sequences from strains enriched by cultivation clustered into two well-defined phylogenetic groups, possibly identifying new taxa. These clusters may represent a niche of opportunistic species, evolved to exploit short-term nutrient spikes in the environment.