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Actinocyclus ingens Rattray is a useful stratigraphic marker. It has been sub-divided into several 'forms' because of a presumed high degree of morphological variability: it is considered a 'polymorphic species'. The type specimens of Actinocyclus ingens, Coscinodiscus elegans Grev., Cosmiodiscus elegans Grev., and Coscinodiscus perikompsos var. curta Rattray are examined and commentary is made on the meaning of sub-specific categories. For nomenclatural reasons, detailed within, Actinocyclus ingens requires a new name. This paper primarily concerns names. [ABSTRACT FROM AUTHOR]

The complexity of the Kaikōura earthquake rupture and tsunami generation presented a unique opportunity to examine and learn from a modern event. This paper reviews how the five years of research following the Kaikōura tsunami have improved our understanding of the event and our knowledge of tsunami science across a range of disciplines. Teams of researchers and practitioners across disciplines of tsunami hazard modelling, palaeotsunami, risk and impact science, early warning, and emergency management learned from the event to calibrate models, enhance proxies for interpreting palaeotsunami deposits, and improve disaster risk readiness, reduction and response measures. While new scientific knowledge has been developed about the co-seismic hazard and risk facing Aotearoa-New Zealand, fundamental questions nonetheless remain about tsunami-generating sources and the likely return period for high impact events in Aotearoa-New Zealand. Further scientific endeavour is needed to investigate the onshore and offshore geological records to help improve understanding of tsunami hazard and history to underpin risk and impact assessments informing more effective disaster risk management. Lessons also emphasise a need for more effective partnership, participation, education, and engagement to increase local community capacity and capability to respond to local source tsunami events. [ABSTRACT FROM AUTHOR]

Diatom species identification with DNA metabarcoding is an economical, fast and reliable alternative to identification via light microscopy for river quality monitoring. Using a short DNA sequence of the rbcL gene and 'Diat.barcode', a reference barcode library, enables the identification of more than 90% of the environmental sequences to species level in French rivers. But the completeness of this library is much lower in other regions, such as the tropical French overseas departments. A barcode library completion method using high-throughput sequencing data combined with microscopy count data from natural samples (Rimet et al. 2018) was applied and tested in rivers of Martinique and Guadeloupe (West Indies), for which only 45% of the environmental sequences could be identified to species level using Diat.barcode v9. Assigning barcodes to the most abundant species in the islands by this method is illustrated with Ulnaria goulardii and two new species belonging to Nupela and Epithemia, which are also described in this paper. The more complex situation of morphologically similar species is illustrated by reference to Gomphonema designatum and G. bourbonense. Using a combination of molecular and morphological data, their conspecificity, as G. bourbonense, is demonstrated with their reference barcodes. However, when several morphologically similar species and several environmental sequences belonging to the same clade are present, it is not possible to relate the barcodes to corresponding morphological species. Applying this method enabled the Diat.barcode library (v.10) to be updated, with 84% of the environmental sequences from the West Indies now identifiable at the species level. However, many morphological species still lack barcodes. In these cases, more classical methods, such as cell isolation, Sanger sequencing and morphological observations of cultures, must be applied. [ABSTRACT FROM AUTHOR]

This paper describes a new diatom species (Orthoseira helvetica sp. nov.) found in the Swiss Alps at an elevation over 2600 m a.s.l. The diatom was recorded at the Macun plateau, Swiss National Park, from samples of terrestrial and wet semi-terrestrial mosses near the stream splash zone. The diatom has a unique set of features and is easily recognized under light and scanning electron microscopy. The most distinctive feature is the presence of a prominent silica collar in a 'rose flower' shape rounding each carinoportulae and an additional silica collar on the areolae (first 3–4 rows) bordering the hyaline area. The valve diameter of O. helvetica sp. nov. is 7.5–26.5 µm and possesses 2–3 (usually 3) carinoportulae. Linking spines at the valve face/mantle junction are present, having a simple basis and being triangular in shape. [ABSTRACT FROM AUTHOR]

Regions with high levels of biodiversity, which mostly correspond to tropical regions, can be treated as treasuries of endemism, even for single-celled life forms. Learning about these areas, and the species present in them, is key to understanding the processes that govern their emergence and sustainability. This paper is a contribution towards revealing the biodiversity of marine benthic diatom species of the world. The samples used in this paper were taken from East Java (Indonesia), Nosy Be (north-west Madagascar) and the Tagus River estuary (Portugal). We describe a new diatom genus, Catenulopsis, and propose the first species of the genus from Nosy Be, named Catenulopsis catenulafalsa. We also describe two new Catenula species, one from Java (Catenula javanica) and the other from Portugal (Catenula brotasiae). The paper also discusses the characteristics of Catenula adhaerens and variations in the species across geographic space. We characterize the morphological variation of C. adhaerens in samples from equatorial West Africa, South Africa, Portugal, Japan, Madagascar and Indonesia. [ABSTRACT FROM AUTHOR]

This paper evaluates diatom biomass as a biosorbent for removing Cr+6, Cd2+, and PO43- ions from water. The diatom was characterized by X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Scanning Electron Microscopy (SEM-EDS) for its crystallinity, functional groups, and morphology. A batch sorption study was conducted to evaluate the parameters influencing Cr+6, Cd2+, and PO43- ions adsorption, and the mechanisms were explored. The FTIR spectra revealed Si-O, O-H, N-H, and C-O as the main functional groups present on the surface of the adsorbent. The SEM showed a rough and irregular-shaped morphology, while the EDS indicated that the diatom biomass is an aluminosilicate material. The rate-limiting steps for Cr+6 and Cd2+ were pseudo-first order, and pseudo-second order sorption favored PO43- based on their R2 values. Moreover, the dominant adsorption model that best described the equilibrium data was the Freundlich isotherm. The maximum adsorption capacities obtained for Cr+6 was 5.66 (mg/g), and Cd2+ was 5.27 (mg/g) at 313 K while PO43- was 19.13 (mg/g) at 298 K. The thermodynamic data revealed that the reaction was endothermic for Cd2+ and exothermic for Cr+6 and PO43-, respectively. Diatom biomass was observed to be a promising bio-sorbent for removing Cr6+, Cd2+ and PO42- from wastewater. [ABSTRACT FROM AUTHOR]

The genus Shionodiscus (Thalassiosirales, Thalassiosiraceae) includes species that have strutted processes with long inward but reduced outward extensions, a labiate process typically located on the valve face, distant from the margin. Shionodiscus species inhabit the marine environment, and the genus includes both living and fossil species. In the course of our study of plankton samples from the Kara Sea, we found specimens belonging to Shionodiscus. Based on LM, SEM, and TEM investigations, a new species, Shionodiscus karianus sp. nov., is described. This species is distinguished from others in the genus based on areola densities, as well as the fine structure and location of the rimoportula and the central fultoportula and the ultrastructure of the areolae and cingulum. In this paper, we provide a morphological description of this taxon as well as a comparison with similar taxa. Previous records of Shionodiscus species in the Russian Arctic seas are discussed. Finally, we summarize and evaluate information on the important morphological characters, such as rimoportula position and fultoportula structure, for Shionodiscus. [ABSTRACT FROM AUTHOR]

Recent claims based on hydrodynamic modelling within a sequence stratigraphical perspective of incised valley fill sedimentation have argued that the Lower River Murray and its terminal lakes Alexandrina and Albert represented a marine–estuarine lake system, with marine salinities for some 200 km upstream from the Murray Mouth. These claims have encouraged proposals for the removal of barrages near the Murray Mouth to restore the 'original natural condition' of the lakes. It has also been suggested that fine-grained terrestrial sediments were trapped in this mega-lake, necessitating a re-assessment of the Holocene climatic history of southeastern Australia determined from the study of continental slope cores. We show that throughout Holocene time (the past 11.7 ka), the Lower River Murray remained a freshwater-dominated system, based on a range of mutually complementary sedimentary evidence. Radiocarbon dating of Aboriginal middens adjacent to the river and lakes comprising freshwater mussels (dominantly Velesunio ambiguous), crayfish (Euastacus armatus), turtles (Emydura macquarii) and otoliths of freshwater fish species, such as Murray cod (Maccullochella peelii), confirm freshwater riverine and lacustrine conditions throughout the Holocene. Lake Alexandrina also contains endemic obligate freshwater fishes, including a genetically divergent and locally adapted lineage of southern pygmy perch (Nannorpeca australis), revealing an evolutionary history linked to freshwater habitat in the lakes since the late Pleistocene. Freshwater diatoms from fine-grained fluvial clay successions at Riverglen Marina, and diatoms and lacustrine sediments, including sapropels in the lower lakes and their former embayments of Cooke Plains and Waltowa Swamp, also chronicle a history of freshwater deposition. Lakeshore ridges of terrestrially derived quartz sand formed during elevated freshwater lake levels 8.0 ± 1.2 ka ago, while consolidated masses of the freshwater clam Corbicula australis, radiocarbon dated at 2650 ± 90 year BP, also attest to long-term freshwater conditions. An open Murray Mouth is prima facie evidence for sustained river discharge, and the mouth remained open throughout the Holocene based on geomorphological evidence. The barrages that were built to retain freshwater within the lower lakes, in response to upstream water abstractions, which had reduced river flows, provide the closest analogue of the 'original' conditions of this environment. With increased automation, nuanced barrage operation could even better simulate the original environment, whereas removing the barrages and building a weir at Wellington would destroy the character of this internationally significant Ramsar Wetland, with detrimental impacts farther upstream. Paleoclimatic, geomorphological and modelling reconstructions, together with sedimentary records based on freshwater diatoms, molluscs, fish, turtles and lacustrine systems and evidence of genetically divergent and locally adapted obligate freshwater fishes, demonstrate that predominantly freshwater conditions were present in the Lower River Murray and its terminal lakes throughout Holocene time (11.7 ka). The empirical observations presented in this paper reveal that a large marine-dominated mid-Holocene estuary was not present in the Lower River Murray, Australia. Proposals to remove the barrages near the Murray Mouth would destroy the long-term freshwater environment of this Internationally Significant Wetland Site with negative ecological impacts. [ABSTRACT FROM AUTHOR]

This short paper discusses two new synonyms of Ulnaria vitrea: Synedra mesocampa Brébisson in Kützing and Synedra tenuis Kützing. The data generated herein are based on original material and form a contribution to the taxonomic clarification of species in the genus Ulnaria. Both names discussed have barely been noticed since their original description and then usually considered as synonyms of Ulnaria ulna. Some additional notes on other relevant names are included, such as Synedra putealis O'Meara and Synedra tenuis var. subtilis (Kützing) Brun. [ABSTRACT FROM AUTHOR]

Aulacoseira is a freshwater diatom genus found today in numerous lakes, ponds and rivers worldwide, and inhabiting a wide range of environmental conditions. The genus is one of the oldest diatom lineages known to colonize freshwater environments, dating to the late Cretaceous and radiating over much of the Cenozoic. The purpose of this paper is to describe a new species, Aulacoseira chockii, from an early Eocene locality situated near the Arctic Circle in northern Canada. The exquisitely preserved specimens have allowed for a detailed examination of frustule morphology of this early Cenozoic taxon. Three characteristics clearly separate A. chockii from all other known fossil and modern species in the genus. First, the spines of A. chockii are formed by coalescence of extensions from three to five mantle costae and multiple ribs that originate on the valve face. This type of spine design has never been reported and represents a potentially ancient trait in the Aulacoseiraceae lineage. Second, the valve has multiple sessile rimoportulae that are each connected to the end of a tube or canal that runs parallel to, and inside, the mantle wall. Rimoportulae with this structure are rare, and found primarily on extinct species of Aulacoseira. Third, the mantle striae are sinistrorse, and represent another rarely observed character within the genus. Because frustules of A. chockii possessed only separation spines, existed largely as single cells and not in long filaments, and were found in associated with remains of numerous heliozoans as well as testate euglyphids and sponges, it is believed this species grew in the littoral zone of a shallow waterbody. [ABSTRACT FROM AUTHOR]

The so-called Oamaru Diatomite dates from approximately the Eocene-Oligocene Transition (~34 million years ago), which is widely regarded as one of the most important climatic events of the entire Cenozoic era due to global cooling and the onset of continental-scale Antarctic glaciations. It also represents one of the richest fossil diatom deposits ever known and was first made famous owing to a series of diatom papers by Grove & Sturt. Based primarily on the collection of Sturt, supplemented by slides mounted by Grove, all curated in The Natural History Museum, we consider all 108 diatom taxa from the Oamaru Diatomite that were proposed in these seminal papers by Grove & Sturt and designate type specimens for 87 taxa that were not typified by previous workers, and for which nomenclatural types could be established. Light photomicrographs of all specimens interpreted as types are presented next to reproductions of the line drawings from Grove & Sturt publications to aid future workers on the Oamaru Diatomite, and on diatom evolution across this critical climatic phase of the Palaeogene period. [ABSTRACT FROM AUTHOR]

The aim of the present paper was to study the effect of zinc on the benthic diatom Halamphora luciae. Bioassays using the metal concentration corresponding to the ICzn50 were terminated in two selected endpoints: day 4 (acute phase) and day 9 (chronic phase). A 1.4- and 2.2-fold reduction in Zn2+ with respect to the initial cation concentration was estimated by atomic absorption at days 4 and 9, respectively and was attributed both to precipitation of insoluble carbonates and oxides at alkaline pH and to biosorption. Carrying capacity of Zn-exposed cultures diminished even when growth rate remained unchanged, suggesting some degree of acclimation of the strain to metal stress. Zn stimulated cell bleaching together with the shift into the lipogenic phase, denoted by total lipid quantification and bigger lipid bodies volumes. Lipid peroxidation and phenolic compounds dosage revealed no major metal-induced oxidative stress. On the other hand, metal exposure had an antagonistic effect on the activation of alkaline phosphatase activity after phosphorus starvation. Superoxide dismutase (SOD) activity, cell motility and mucilage secretion were enhanced only during acute exposure. Soluble extracellular polymeric substances (S-EPS) from Zn-exposed cultures denoted a higher heterogeneity in monosaccharide composition. Frustules from metal-exposed cells presented a reduction in areolae diameter together with a lower area:volume ratio of the cells due to the addition of cingular bands. [ABSTRACT FROM AUTHOR]

Minidiscus Hasle is a genus of small sized diatoms comprising about eight nanoplanktonic marine species. Renewed interest in this genus has arisen since recent investigations recorded a fairly high contribution of some species to the phytoplankton biomass on a global scale. In Brazil, very few studies have been performed, and only two species of Minidiscus have been reported over the 8500 Km coastline. In this paper, we report five species found in Southeast and South Brazilian waters: Minidiscus alphacrucis sp. nov., M. chilensis, M comicus, M. trioculatus, and M. variabilis (also the variety inornata). One of the tiniest diatom ever described, the new species M. alphacrucis has poroidal areolae, which are organized in radial striae with two rows of poroids, conspicuously limited by the interstriae. Minidiscus alphacrucis is compared with other morphologically similar species. In addition, the world distribution of the extant Minidiscus species is reviewed and discussed. [ABSTRACT FROM AUTHOR]

In approximately one decade, global temperatures will likely exceed a warming level that a United Nations Intergovernmental Panel on Climate Change report considers a "red alert for humanity". We propose exploring tidal flat diatoms to address climate change challenges. Tidal flats are extensive coastal ecosystems crucial to the provisioning and regulation of aquatic environments. Diatoms contribute to tidal flat biomass production and account for 20% of global primary productivity and 40% of annual marine biomass production, making them crucial for nutrient cycling and sediment stabilization. Potential CO2 removal from Korean tidal flats by diatoms is estimated to be 598,457–683,171 t CO2 equivalents (CO2e) annually, with the economic value of blue carbon (BC) resulting from diatom activity being approximately US$ 17.95–20.50 million. Dissemination of this potential could incentivize coastal wetland protection and climate change mitigation measures. The global estimated CO2e removal potential of tidal flat diatoms is 40,957,346–46,754,961 t CO2e, representing 0.11–0.13% of the annual global greenhouse gas emissions, even though tidal flats cover 0.0025% of the Earth's surface and diatoms represent less than 0.5% (by weight) of all photosynthetic plants. Researchers should combine ecology and economics to develop standardized approaches for carbon input monitoring and quantification. Further, spatiotemporal analyses of environmental threats to tidal flat diatoms are necessary for conserving their biodiversity and function as a critical BC source. Land-based cultivation for large-scale biomass production and biorefinery processes can contribute to a greener, more prosperous future for humanity and the marine ecosystems upon which we rely. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

It has been proposed that, within flood-pulse systems, seasonally dynamic conditions promote extremely high levels of biodiversity. In this paper, we aim to understand how variation in environmental conditions and habitat availability, across space and time, influences the structure and composition of plankton diatom communities within the Tonle-Sap Lake (Cambodia) during two flood-pulse cycles. We hypothesize that (i) communities vary considerably across space and time, (ii) environmental filtering accounts for a substantial portion of the variation in community composition, and (iii) shifts in meta-community structure occur seasonally, due to variation in both environmental conditions and habitat availability. A principal component analysis and a permutational multivariate analysis of variance were used to characterize spatio-temporal variations in environmental conditions, community structure and composition. Determinants of community variations across space were identified by redundancy analyses and variation partitioning, while seasonal changes in meta-community structure were assessed by investigating temporal changes in β-diversity. Our results indicate that (i) spatial variations in community structure and composition are largely influenced by the seasonal flood-pulse, (ii) environmental filtering is the most likely process driving the compositional changes, and (iii) changes in diatom life-form community provide insights into the hydrological functioning of the Tonle Sap. We conclude that the survey of diatom communities may constitute a relevant sensor of hydrological change in the system and could be used to derive regionally specific hypotheses about how global climate change is impacting the lake's functioning. [ABSTRACT FROM AUTHOR]

This paper is the first integrated account of the sedimentology, stratigraphy, and vertebrate paleontology for the marine strata of the Chilcatay Formation exposed at Ullujaya, Pisco basin (southern Peru). An allostratigraphic framework for the investigated strata was established using geological mapping (1:4000 scale) and conventional sedimentary facies analysis and resulted in recognition of two unconformity-bounded allomembers (designated Ct1 and Ct2 in ascending order). The chronostratigraphic framework is well constrained by integration of micropaleontological data and isotope geochronology and indicates deposition during the early Miocene. The marine vertebrate fossil assemblage is largely dominated by cetaceans (odontocetes), whereas isolated teeth and spines indicate a well-diversified elasmobranch assemblage. Our field surveys, conducted to evaluate the paleontological sensitivity of the investigated strata, indicate that vertebrate remains only came from a rather restricted stratigraphic interval of the Ct1 allomember and reveal the high potential for these sediments to yield abundant and scientifically significant fossil assemblages. [ABSTRACT FROM AUTHOR]

The Low Temperature Method (LTM) for sample stabilization in environmental scanning electron microscopy (ESEM) is a promising tool for observing diatom assemblages in vivo. Use of ESEM, in comparison to conventional scanning electron microscopy, enables fresh material to be studied without any chemical pretreatment or conductive coating. The newly developed LTM, introduced in this paper, offers higher resolution and better resistance of wet samples to radiation damage. We used natural epiphytic algal assemblages to image the 3D structure of: (i) biofilm/periphyton and its physical complexity, (ii) diatoms with their extracellular mucilaginous secretions attaching cells to the substratum, (iii) diatom colony formation, and (iv) intact diatom cells, rather than the separated empty valves observed under conventional scanning electron microscopy. This study demonstrates the potential of the LTM for ESEM in diatom biology and ecology compared to other imaging methods. [ABSTRACT FROM AUTHOR]

This paper presents a new species found in water and surface sediment samples from the Jáchal River, in San Juan Province, Argentina. This new species belongs to the group of species related to Cymbella helvetica Kützing, which do not have apical pore fields. It can be distinguished from known species of the group by its combination of morphometric and morphological features, such as the ventral deflection of the proximal raphe fissures, and the shape of the apex. [ABSTRACT FROM AUTHOR]

As an important indoor environment parameter, air humidity plays an important role in indoor health, thermal comfort and energy consumption of heating and air-conditioning. In this paper, the experimental study on the humidity control performance and the effect of humidity control in the practical application environment for diatom ooze were carried out. The micro - characterized of research object was carried out by low-temperature nitrogen adsorption-desorption, and the adsorption and desorption properties of diatomite and three kinds were studied, obtaining equilibrium moisture absorption and desorption curves, isothermal desorption and desorption rates, cyclic desorption and desorption properties. Based on the above results, it was concluded that the performance of diatom humidity control of three different construction processes. Then, the room temperature and humidity of three rooms were obtained by testing the indoor environment of diatom ooze room, latex paint room and wallpaper room in different seasons, compering and analyzing the effect of diatom ooze on the indoor thermal and humid environment. Results show that the pore structure characteristics and ambient temperature of diatom ooze have a great influence on its humidity control performance; the diatom ooze is more effective in winter and summer, and the transition season is weaker. [ABSTRACT FROM AUTHOR]

The genus Luticola is characterized mainly by valves with an internal longitudinal channel located at the valve face/mantle junction, rounded areolae and an isolated pore (stigma) near the central area. Studies on Luticola species that occur in Brazil are scarce. Therefore, this paper illustrates and describes the morphology of 18 species of Luticola under optical and scanning electron microscopy, from 15 rheophilic environments of an Atlantic Forest in southern Brazil. Two new species are proposed: Luticola moreirae Straube, Tremarin et T. Ludwig and Luticola papilioformis Straube, Tremarin et T. Ludwig, and are compared with morphologically similar species. Furthermore, the ultrastructure of Luticola camopiensis is revealed and described from SEM. Luticola beyensii, L. camopiensis and Luticola saprophila are recorded for the first time from Brazil. [ABSTRACT FROM AUTHOR]

A new centric diatom belonging to the genus Aulacoseira was found during a survey of the diatom community from peatbogs of Tierra del Fuego (southern Argentina). The present paper describes Aulacoseira frenguelliana sp. nov. based on detailed light and scanning electron microscopy and compares its morphological features with similar species. Aulacoseira frenguelliana is characterized by short chains joined by spatulate spines, one row of marginal areolae, a very narrow ringleist and only one rimoportula. The type material of Melosira laevis var. fuegiana Frenguelli, a species described from Tierra del Fuego showing some morphological resemblance to the new species, was studied using light microscopy to clarify the taxonomic position of this species. A transfer to Aulacoseira is proposed as A. fuegiana (Frenguelli) comb. et stat nov. [ABSTRACT FROM AUTHOR]

Chlorination, used as anti-fouling biocide in coastal power plants, has potential environmental consequences. Phytoplankton entrained into the cooling water circuit are subjected to chlorine stress. The paper reports a study on the effects of chlorination on phytoplankton entrained into the coolant system of a power plant operating on the East Coast of India. Field observations showed 1) a significant reduction (15-80%) in chlorophyll a as water passed from the intake point to the outfall and 2) partial restoration of chlorophyll a values as the discharged water mixed with the ambient sea. Laboratory experiments showed that growth rate, chlorophyll a and primary productivity of chlorine-treated diatoms decreased, depending on dosage. There were species-specific differences in tolerance levels and recovery pattern among the diatoms tested. Chaetoceros wighami and Amphiprora palludosa were sensitive, whereas Amphora coffeaeformis and Cocconeis scutellum were comparatively more tolerant. The paper discusses the impact of chlorine-induced effects on entrained diatoms in light of the available data. [ABSTRACT FROM AUTHOR]

Testing of fouling release (FR) technologies is of great relevance for discovery of the next generation of protective marine coatings. In this paper, an accumulation assay to test diatom interaction under laminar flow with the model organismNavicula perminutais introduced. Using time lapse microscopy with large area sampling allows determination of the accumulation kinetics of the diatom on three model surfaces with different surface properties at different wall shear stresses. The hydrodynamic conditions within the flow cell are described and a suitable shear stress range to perform accumulation experiments is identified at which statistically significant discrimination of surfaces is possible. The observed trends compare well to published adhesion preferences ofN. perminuta. Also, previously determined trends of critical wall shear stresses required for cell removal from the same set of functionalized interfaces shows consistent trends. Initial attachment mediated by extracellular polymeric substances (EPS) present outside the diatoms leads to the conclusion that the FR potential of the tested coating candidates can be deducted from dynamic accumulation experiments under well-defined hydrodynamic conditions. As well as testing new coating candidates for their FR properties, monitoring of the adhesion process under flow provides additional information on the mechanism and geometry of attachment and the population kinetics. [ABSTRACT FROM PUBLISHER]

Water quality and algal populations in the Vaal River Barrage Reservoir have been monitored extensively for many decades, because of its importance as a water source for the most densely populated area in South Africa. AlthoughAulacoseira granulata(Ehrenberg) Simonsen is frequently found and at it times dominates algal assemblages in the Barrage,Aulacoseira ambigua(F.Meister) Tuji & D.M.Williams has never before been recorded at this locality. During a countrywide proficiency-testing scheme for algae counting, coordinated by Rand Water, spiral-shaped diatom colonies with distinctly curved cells were detected during May 2015. Upon investigation, it was found that the spiral colonies wereAulacoseira ambiguaf.japonica, its presence in the fresh waters of South Africa being recorded for the first time. Since their first appearance during May 2015, colonies ofAulacoseira ambiguaf.japonicahave been constantly present in the surface waters of the Barrage. Their presence at this site can be linked to increasing eutrophication in the Vaal River, because the spiral form is known to prefer eutrophic conditions. Centric diatoms rarely form spiral colonies and there is some confusion in the literature as to the identity of this particular form, therefore in this paper we discuss this taxon, its nomenclature and ecological significance. [ABSTRACT FROM PUBLISHER]

The freshwater diatomDidymosphenia geminatahas emerged in recent years as a nuisance organism with invasive tendencies in some areas. Knowledge of the biological and ecological intricacies ofD. geminatais limited, in part due to the absence of a suitable culture medium for the maintenance of the diatom. This paper describes the development of a chemically defined synthetic medium for the short-term culture ofD. geminatacells. A range of combinations and concentrations of macronutrients were tested andD. geminatasurvival and attachment monitored. This development provides the potential to explore unexplained aspects ofD. geminatabiology and physiology through robust culture-based laboratory studies. [ABSTRACT FROM PUBLISHER]

The genusAmphorotiaWilliams & Reid (2006) was established to accommodate a group of diatoms formerly allocated toEunotiaEhrenberg. The new genus was shown to display a distinct biogeographical distribution. To increase the knowledge of this genus, especially in China, a taxonomic investigation ofAmphorotiain the Pearl River delta area was undertaken using borehole materials. This paper reports and describes specimens of an uncommon species ofAmphorotiaextracted from sediment samples using a special concentration technique. Morphological data derived from both light (LM) and scanning electron microscopy (SEM) are used to characterise the specimens. Based on these observations, an emended description of a species formerly reported from the same region,Amphorotia curvataWilliams & Reid, is provided and its neotype is established. The new Pearl River specimens are all attributed toA. curvataand this species is compared to otherAmphorotiaspecies from China, Southeast Asia and Lake Baikal. It is similar to the Siberian taxonAmphorotia lacusbaikali(Skvortzov) Williams & Reid when observed with LM, but can be distinguished by ultrastructural details (SEM).Amphorotiais clearly monophyletic and the new features ofA. curvataare used to suggest links withAmphorotiaspecies from East Asian regions. [ABSTRACT FROM PUBLISHER]

Harvesting is one of the key challenges to determine the feasibility of producing biodiesel from algae. This paper presents experimental results for a cost-effective system to harvestChaetoceros calcitrans, using natural sedimentation, flocculation, and inducing pH. No efficient sedimentation of microalgal cells was observed only by gravity. By alkalinity-induced flocculation, at a pH value of 9.51, 86% recovery of the cells was achieved with a sedimentation rate of 125 cm/h and a concentration factor (CF) of 4 (volume/volume (v/v)) in 10 min. The maximum photochemical quantum yield of photosystem II (Fv/Fm) of concentrated cells was almost the same as fresh culture (0.621). Commercial flocculants, aluminium sulphate and poly-aluminium chloride (PAC), were also successful in harvesting the studied algal cells. Optimum concentration of aluminium sulphate (AS) could be concluded as 10 ppm with 87.6% recovery and 7.10 CF (v/v) in 30 min for cost-efficient harvesting, whereas for PAC it was 20 ppm with 74% recovery and 6.6 CF (v/v).Fv/Fmyields of concentrated cells with AS and PAC showed a 1% reduction compared to fresh culture. Mg+2was the triggering ion for alkalinity-induced flocculation in the conditions studied. The rheology behaviour of the concentrated cells was Newtonian with values between 2.2 × 10−3and 2.3 × 10−3 Pa s at 30°C. [ABSTRACT FROM PUBLISHER]

Fouling release (FR) coatings are increasingly applied as an environmentally benign alternative for controlling marine biofouling. As the technology relies on removing fouling by water currents created by the motion of ships, weakening of adhesion of adherent organisms is the key design goal for improved coatings. In this paper, a microfluidic shear force assay is used to quantify how easily diatoms can be removed from surfaces. The experimental setup and the optimization of the experimental parameters to study the adhesion of the diatomNavicula perminutaare described. As examples of how varying the physico-chemical surface properties affects the ability of diatoms to bind to surfaces, a range of hydrophilic and hydrophobic self-assembled monolayers was compared. While the number of cells that attached (adhered) was barely affected by the coatings, the critical shear stress required for their removal from the surface varied significantly. [ABSTRACT FROM PUBLISHER]

We speculate that heterotrophic and/or silica-rich eukaryotic microorganisms maybe an important part of the lichen symbiosis. None of the very few studies of heterotrophic protists associated with lichens have considered the possibility that they may be of functional significance in the lichen symbiosis. Here we start to develop, currently speculative, theoretical ideas about their potential significance. For example, all the protist taxa identified in lichens we sampled in Ohio USA depend on silica for growth and construction of their cell walls, this could suggest that silica-rich lichen symbionts may be significant in the biogeochemistry of the lichen symbiosis. We also present arguments suggesting a role for protists in nitrogen cycling within lichen thalli and a potential role in controlling bacterial populations associated with lichens. In this necessarily speculative paper we highlight areas for future research and how newer technologies may be useful for understanding the full suite of organisms involved in the lichen symbiosis. [ABSTRACT FROM AUTHOR]

Several studies regarding the effects of excess nutrients and metals as possible causes of deformities found in diatom cells have been conducted in Europe, North America and Australia. This is the first study in South Africa which catalogued and analysed diatom deformities in detail. We assessed diatom deformities in response to a large water chemistry dataset, including pH, electrical conductivity, alkalinity, hardness, nutrients, heavy metals and radioactive elements. The freshwaters of the Karoo exhibited wide ranges in many of their environmental variables. Diatom deformities were categorised into four types (outline, raphe, striation and mixed/other), and each cell measured and photographed. Correlations and multivariate analyses between environmental variables and deformity type, as well as diatom species, were performed. A cumulative criterion unit (CCU) ratio, using South African aquatic ecosystem limits, was calculated for Al, Cd, Cu, Mn, Pb, Se and Zn to determine if the combined effect of these metals exerted any influence on the cause of deformities. No single stressor could be linked to the deformities. Instead, variables showing to be most probable to exert an influence are electrical conductivity, oxidised nitrogen, sulphate and lithium, with selenium and strontium having a lesser influence. The CCU application did not yield expected results. This could be due to the naturally highly mineralised water found in the Karoo. [ABSTRACT FROM AUTHOR]

Nutrients are important determinants of diatom growth in lakes, and diatoms are considered reliable indicators of changing lake nutrient concentrations and eutrophication. However, diatom ecologies are not static, nor are they linked to single environmental variables, leading to imprecise diatom nutrient inferences. Anthropogenic nutrient enrichment is the principal issue facing New Zealand's lakes. Thus, knowledge of diatom responses to nutrients in New Zealand lakes will be important for understanding contemporary and past changes in nutrient availability. Using a nutrient amendment experiment and diatom communities from dune lakes, here we show that the response of specific diatom species is not universal among lakes and is partly determined by lake nutrient concentrations and limitation status. The response of focal diatom species to nutrient additions differed from previously reported nutrient requirements, and did not align with published, assigned trophic statuses. This study highlights that the response of diatoms to nutrient enrichment is context-dependent, and that intraspecific generalisations of diatom ecologies between geographic locations or through time should be made with caution. To apply diatoms to making nutrient inferences, more work focusing on how physiochemical and biological factors influence diatom nutrient requirements is required. [ABSTRACT FROM AUTHOR]

In this paper we examine the aspects of phytoplankton communities along a riverine-estuarine continuum in the Kowie system, Eastern Cape (South Africa). This study aims to relate the phytoplankton population community structure to physicochemical parameters and estimate the different chlorophyll-a concentrations for the Kowie system. Eight sampling sites along a 70 km reach of the Kowie system were sampled over a one-year period. One hundred and seventy-eight species belonging to 78 genera were recorded within the riverine-estuarine continuum. Diatoms were predominant, accounting for 81.9% of the total abundance. The estuary had 98 species (55 genera) recorded whereas the river had 141 species (67 genera). Using a two-way analysis of variance (ANOVA), species richness was found to differ significantly amongst seasons. The chl-a concentration along the estuarine-riverine continuum increased from spring to a high in summer (river mean = 7.9 mg m−3 and estuary mean = 3.3 mg m−3) before decreasing to a low in winter. Kruskal–Wallis ANOVA showed significant differences among chl-a concentration with seasons and sites. Redundancy analysis identified five factors – salinity, water depth, aerial cover, nitrates and ammonia – that were significant (p < 0.05) in affecting phytoplankton variation. The relatively small study indicates the need for further monitoring to gain a better understanding of Kowie system phytoplankton. [ABSTRACT FROM AUTHOR]

Conventional microbial fuel cells (MFCs) consist of biological anodes and abiotic cathodes separated by a proton-exchange membrane. The abiotic cathode usually catalyses the reduction of oxygen to produce water by means of expensive catalysts such as platinum.1The cathodic reaction is often limiting in MFCs and researchers are now focusing on efficient, low-cost catalysts to improve oxygen reduction at the cathode. This paper describes a photosynthetic biocathode in a sediment-type MFC constructed without a proton-exchange membrane. The carbon and stainless steel cathode did not contain any catalyst, but was covered in a biofilm composed of a complex community including microalgae and cyanobacteria. Although electroactive species were detected in the cathode biofilm, no biocatalysis of oxygen reduction was observed. Enhancement of the current output was mostly due to the production of pure oxygen near the cathode surface by the photosynthetic biofilm. Photosynthesis could produce dissolved oxygen levels approximately four times higher than oxygen levels obtained by aeration. The MFC was able to generate a maximum power density of 11 mW/m2(projected anode area) over six months without feeding. [ABSTRACT FROM AUTHOR]

The microphytobenthos colonizing the intertidal flats forms an important component of the Wadden Sea. Ten sampling points along a 1-km transect were studied in a fringe area of the Solthörn tidal flat, southern North Sea, in order to determine seasonal differences in the microphytobenthos. An accompanying paper deals with the major component of the flora, the diatoms; here we, focus on the minor taxonomic groups. From May 2008 to May 2009 surface sediments were collected during low tide. Variation of environmental factors as well as microphytobenthic density (abundance and chlorophyll a) were monitored. The area investigated was a mixed-sediment mudflat, with a gradient from coarse to fine. Highest biomass was obtained in summer 2008 with 215.9 ± 12.6 mg chlorophyll a m–2. In late autumn the chlorophyll a concentration decreased continuously at all investigated stations. Lowest values were detected in December 2008. Species abundances varied considerably both along the transect and seasonally, depending on species-specific requirements as well as hydrodynamic conditions (tidal currents). Higher densities of benthic pro- and eukaryotic microalgae were observed in sites characterized by fine sediments. Apart from the diatoms, the most abundant microphytobenthic group was the cyanophytes. Coccoid cyanophytes, mainly Merismopedia sp., were most abundant during summer, with cell numbers up to 5.72 × 106 cells cm−2, while diatoms dominated in winter, spring and autumn. Filamentous cyanophytes, particularly Microcoleus chthonoplastes, were most abundant during autumn, while coccoid chlorophytes (spring: Chlorococcum submarinum, Crucigenia tetrapedia, Tetraselmis suecica), euglenophytes (summer: Euglena obtusa), dinophytes (autumn: Amphidinium operculatum, A. herdmanii) and cryptophytes (autumn: Hillea marina, Hemiselmis virescens) contributed to the microphytobenthos during warmer seasons. The statistical analysis confirmed that the composition of the microphytobenthos was related to sediment features and to characteristics of particular seasons. [ABSTRACT FROM PUBLISHER]

Williams and Kociolek (2007: Eur. J. Phycol., 42: 313-319) have presented an opinion paper in which they review some principles of classification and criticize the most recent classification of the diatoms by Medlin & Kaczmarska (2004: Phycologia, 43: 245-270). In their critique of paraphyletic groups, they failed to consider one paraphyletic relationship that is most frequently revealed by molecular data, which in part justifies the recognition of paraphyletic taxa among certain diatom genera. In their criticism of the most recent classification system of the diatoms, they have misinterpreted and misrepresented much of the molecular data that they have used as evidence against this classification system and thus have made incorrect comparisons among published phylogenies of the diatoms. [ABSTRACT FROM AUTHOR]

The formation of many arctic wetlands is associated with the occurrence of polygon- patterned permafrost. Existing scenarios to describe and explain surface landforms in arctic wetlands (low-center and high-center polygons and polygon ponds) invoke competing hypotheses: a cyclic succession (the thaw-lake hypothesis) or a linear succession (terrestrialization). Both hypotheses infer the predictable development of polygon-patterned wetlands over millennia. However, very few studies have applied paleoecological techniques to reconstruct long-term succession in tundra wetlands and thereby test the validity of existing hypotheses. This paper uses the paleoecological record of diatoms to investigate long-term development of individual polygons in a High Arctic wetland. Two landform processes were examined: (1) the millennial-scale development of a polygon-pond, and (2) the transition from low-center to erosive high-center polygons. Diatom assemblages were quantified from habitats associated with contrasting landforms in the present-day landscape, and used as an analog to reconstruct past transitions between polygon types. On the basis of this evidence, the paleoecological record does not support either of the existing models describing the predictable succession of polygon landforms in an arctic wetland. Our results indicate a need for greater paleoecological understanding, in combination with in situ observations in present-day geomorphology, in order to identify patterns of polygon wetland development and elucidate the long-term drivers of these landform transitions. [ABSTRACT FROM AUTHOR]

The paper reports studies on benthic microbial dome-shaped mats found in hypersaline desert pools in Wadi Muqshin, southern Oman, and details the hydrogeological conditions of the pools, including water quality and recharge features. The upper 1 cm layers of these microbial mats are dominated by cyanobacteria, a phototrophic purple sulphur bacterium and diatoms. The dominant cyanobacterium is Microcoleus chthonoplastes and the purple layer below the upper layer is dominated by the photosynthetic sulphur bacterium Chromatium okenii. It is unusual to find standing water containing microbial domes in such a hyper-arid, inland site which borders the Rub' Al Khali (Empty Quarter). The flooding regime here depends largely on 'fossil' groundwater (Zone C, L.UER aquifer) mostly derived from the Pleistocene. Attempts to carry out desert agriculture with abstraction of this 'fossil' groundwater might cause the extinction of the Muqshin pools. [ABSTRACT FROM AUTHOR]

This paper examines attachment point theory in detail by testing the fouling attachment of several fouling groups to a microtextured matrix. Static bioassays were conducted on polycarbonate plates with nine equal regions, comprising eight scales of microtexture (4-512 µm) and one untextured region. The microtextures examined were continuous sinusoidal ridges and troughs of defined height and width. Attachment over the microtextured plates was examined for the diatom Amphora sp., the green alga Ulva rigida, the red alga Centroceras clavulatum, the serpulid tube worm Hydroides elegans and the bryozoan Bugula neritina. It was found that the size of the microtexture in relation to the size of the settling propagules/larvae was important in the selection of attachment sites. Attachment was generally lower when the microtexture wavelength was slightly smaller than the width of the settling propagules/larvae and increased when the wavelength was wider than their width. The effect of attachment points was weak for small motile microfoulers (Amphora sp. and U. rigida) (7 µm), strong for large macrofouling larvae (H. elegans and B. neritina) (129-321 µm) and non-existent for the non-motile algal spores (C. clavulatum) (37 µm). This study reinforces the potential of using attachment points to develop surfaces with increased fouling resistance or, alternatively, surfaces which promote the attachment of selected target sizes of motile propagules or larvae. [ABSTRACT FROM AUTHOR]

Adhesion of raphid diatoms to natural surfaces, which is mediated by the secretion of extracellular polymeric substances (EPS), is an important strategy for growth and survival and contributes to the economically important process of biofouling. An understanding of adhesion processes requires that the genes involved in the EPS biosynthetic pathways and their regulation be characterized. Phaeodactylum tricornutum provides a model system in which to do this but the quantitative adhesion characteristics of the various morphotypes and isolates of this species are currently unknown. The present paper reports on the use of a calibrated fully turbulent flow cell to characterize the whole cell adhesion properties of morphotypes and strains of this species. It has been shown that only the oval cell morphotype adheres to a surface. There are strain/isolate differences in adhesion strength: some strains including strain Pt 1.8.6, the genome of which has been sequenced, show adhesion strengths comparable to other raphid diatoms. In common with some other raphid diatom species, adhesion strength of oval cells of some isolates of P. tricornutum was greater on a hydrophobic surface (Silastic T2 silicone elastomer), than on hydrophilic acid-washed glass. These studies provide a baseline for future molecular genetic and gene expression studies. [ABSTRACT FROM AUTHOR]

The diatom subclass Eunotiophycidae has recently expanded in composition. While it still includes a single order, the Eunotiales, and two families, the Eunotiaceae and Peroniaceae, the former includes four genera, Eunotia , Actinella , Semiorbis and Desmogonium , while the Peroniaceae includes only one, the genus Peronia . After discovery of the predominantly Southern Hemisphere genus Eunophora , a freshwater taxon superficially resembling species of Amphora , other species of diatoms with similarly confusing morphology have come into sharper focus. The recently described genus Amphorotia , based on Eunotia clevei , may be sister taxon (its most closest relative) to Eunophora . This paper presents evidence for including a Miocene, marine, fossil species, Eunotia reedii , with the more or less tropical species, Amphora reichardtiana , in the same genus. Relationships among the Eunotiaceae are further clarified. [ABSTRACT FROM AUTHOR]

This paper explores diatom attachment to a range of laser etched polyimide surfaces to directly test ‘attachment point theory’. Static bioassays were conducted on microtextured polyimide surfaces using four diatom species, Fallacia carpentariae, Nitzschia cf. paleacea , Amphora sp. and Navicula jeffreyi with cell sizes ranging from 1 – 14 µm. The microtextured polyimides were modelled from natural fouling resistant bivalve surfaces and had wavelengths above, below and at the same scale as the diatom cell sizes. Diatoms attached in significantly higher numbers to treatments where the numbers of attachment points was highest. The lowest diatom attachment occurred where cells were slightly larger than the microtexture wavelength, resulting in only two theoretical points of attachment. The results support attachment point theory and highlight the need to address larval/cell size in relation to the number of attachment points on a surface. Further studies examining a range of microtexture scales are needed to apply attachment point theory to a suite of fouling organisms and to develop structured surfaces to control the attachment and development of fouling communities. [ABSTRACT FROM AUTHOR]

Discostella stelligera and allied similar taxa are mainly identified by the presence of marginal fultoportulae located at the end of the striae, and not on the interstriae, as occurs in the genus Cyclotella , from which they have recently been removed. In this paper, valve morphology and ultrastructure of D. stelligera , D. glomerata , D. pseudostelligera and D. woltereckii collected from different environments within the Río Limay basin are described and illustrated. Morphological characters that allow the delimitation of taxa within the group are discussed and the ultrastructure of D. stelligera var. elliptica comb. nov. is shown for the first time. Two organisms that possess distinct morphological characters, and might be considered new species, are described. [ABSTRACT FROM AUTHOR]

The concept of quasiresonance was introduced in connection with inelastic collisions between one atom and a vibro-rotationally excited diatomic molecule. In its original form, the collisions induce quasiresonant transfer of energy between the internal degrees of freedom of the diatom: there is a surprisingly accurate low order rational value for the ratio of the changes in the vibrational and rotational classical actions, provided the vibrational and rotational frequencies of the diatom are approximately related by low order rational values, and the collision was longer than the rotational period of the molecule. In this paper, we show that quasiresonance can be extended to many other processes and systems, and that it may be understood in terms of the adiabatic invariance theory and the method of averaging. [ABSTRACT FROM AUTHOR]

Fouling species produce adhesive polymers during the settlement, adhesion and colonization of new surfaces in the marine environment. The present paper tests the hypothesis that enzymes of the appropriate specificity may prevent biofouling by hydrolysing these adhesive polymers. Seventeen commercially available enzyme preparations designed originally for bulk use in a range of end-use applications were tested for their effects on the settlement and/or adhesion of three major fouling species, viz. the green alga Ulva linza , the diatom Navicula perminuta and the barnacle Balanus amphitrite . The serine-proteases were found to have the broadest antifouling potential reducing the adhesion strength of spores and sporelings of U. linza , cells of N. perminuta and inhibiting settlement of cypris larvae of B. amphitrite . Mode-of-action studies on the serine-protease, Alcalase, indicated that this enzyme reduced adhesion of U. linza in a concentration-dependent manner, that spores of the species could recover their adhesive strength if the enzyme was removed and that the adhesive of U. linza and juvenile cement of B. amphitrite became progressively less sensitive to hydrolysis as they cured. [ABSTRACT FROM AUTHOR]

Living diatoms are commonly found within Antarctic Porifera, and generally interpreted as additional food source, or as mutualists or parasites of sponge tissues. However, no data are available about temporal variations of the abundance of diatoms inside sponges especially during the winter period. In this paper we analysed the amount of diatom frustules and chlorophaeopigment concentration in six species of Antarctic sponges (Dendrilla antarctica, Homaxinella flagelliformis, Kirkpatrickia variolosa, Suberites montiniger, Haliclona dancoi, Haliclona penicillata) sampled weekly from November 2001 ­ before the ice melting ­ to February 2002. Frustule concentration in the sponge tissues was very low at the beginning of November in all the sponge species, and increased between 9 and 22 January, to reach maximum values between 29 January and 7 February. Diatom abundances were significantly higher in H. dancoi tissues, comparing to the other sponge species, reaching values up to 1217±178 cells &ast;106 g-1 dw at the end of January. Chlorophaeopigments, very low at the beginning of November, increased between 5 and 19 December, before the peak of diatoms. Maximum chlphaeo values (650.5±5.9 μg g-1 dw) were observed in D. antarctica. The planktonic Fragilariopsis curta was the most common diatom species recorded inside sponges. These data clearly indicate that diatom concentration inside the sponge tissues is related to the summer phytoplankton bloom. The shift between the pigment and frustule peaks strongly suggests that diatoms are used as a food source by sponges and that their frustules are accumulated inside the sponge body. The lack of frustules at the beginning of summer indicates that diatom frustules are expelled or dissolved during the cold season. [ABSTRACT FROM AUTHOR]

In this paper. we employ a diabatic model Hamiltonian based on the DIM (diatomics-in-molecules) and DIIS (diatomics-in-ionic-systems) methods to describe the valence and ion-pair states of the iodine molecule, with the objective of characterizing the influence of Ar and Kr rare gas matrices on the ion-pair states. In particular, we combined this model Hamiltonian with classical simulations to calculate the shifts of the ion-pair state emission spectra due to solvation environment. The computed main emission peaks in Ar and Kr solids appear at 378 and 417 nm, in excellent agreement with the experimental emission peaks of 380 and 418 nm recently observed by Chergui et al. with the identical transition assignments. Our study also shows that these calculated bands correspond to redshifts from the gas phase of 2600 and 5100 cm-1, compared with shifts of 2900 and 4700 cm-1, respectively, observed in experiments, and the equilibrium bond lengths of the D'(2g) state in Ar and Kr extend to 3.70 and 3.75 A compared to the gas-phase value of 3.594 A. consistent with experimental implications. Emission bands originating from the δ(2g) state are also computed, as well as the counterparts of these hands in the visible region and the results are shown to be in reasonable agreement with experiments. We present a detailed study of the ion-pair state symmetry breaking which mixes the symmetrical gas-phase states resulting in charge localization, and the establishment of permanent molecular dipole moments in these solvated ion-pair state molecules due to local distortion of the polarizable matrix. Finally we use our calculations to explore model defect solvation sites in solid Ar which have been proposed as the source of various ambiguous emission bands in experimental spectra. [ABSTRACT FROM AUTHOR]

In this paper we investigate the temperature sensitivity of the photosynthetic process of the benthic diatom Cylindrotheca closterium grown in light-limited turbidostat cultures at two different growth rates. Photosynthesis was measured as the rate of oxygen evolution and as the photosystem II (PSII) electron transport rate (ETR). The photosynthetic efficiency ( α ), as measured by both methods, was rather insensitive to temperature, and decreased significantly only at the extreme temperatures used (5 and 35°C). The maximum PSII quantum efficiency ( F v / F m ) showed a small but significant trend of reduction with increasing temperature. However, the maximum rate of photosynthesis ( P B max and ETR max ) was extremely temperature sensitive. The effect of temperature on the relationship between P B and ETR was limited to the most extreme temperatures investigated; deviations from linearity were most extreme at 5°C and different conversion factors were observed at 5 and 35°C. A short-term change in temperature (10 - 30°C), as might be experienced during emersion on a European tidal flat, will not significantly affect the relationship between P B and ETR. However, care should be taken when using a single conversion factor between P B and ETR at the extremes of the temperature range. We have also shown that algal absorption measurements are important for correct calculation of ETR. The facts that different species seem to have different conversion factors and that changing environmental conditions will affect the absorption capacity and growth rate of the microphytobenthos (MPB) community suggest that it is wise to perform further calibrations of the relationship in the field before use in primary production modelling. Variable fluorescence measurements are quick and non-invasive and, with knowledge of the absorption properties of the MPB community, allow the quantification of photosynthetic parameters across large areas. Hence they are... [ABSTRACT FROM AUTHOR]

The first completed, circular mitochondrial genome and the first draft, linear chloroplastic genome of the blue diatom Haslea ostrearia (Simonsen 1974, Naviculaceae, Bacillariophyceae) were assembled from Illumina and PacBio sequencing. The mitochondrial genome was composed of 38,696 bases and contained 64 genes, including 31 protein-coding genes (CDS), 2 ribosomal RNA (rRNA) genes and 23 transfer RNA (tRNA) genes. For the chloroplast, the genome was composed of 130,200 bases with 169 genes (131 CDS, 6 rRNA genes, 31 tRNA genes, and 1 transfer messenger RNA gene). Phylogenetic trees, using the maximum-likehood method and partial genes currently available for Haslea ostrearia and other diatom species, suggested the proximity of all the Haslea ostrearia strains/isolates and the possibility of using these genomes as future references. [ABSTRACT FROM AUTHOR]