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The study provides significant insights into the community structure, species diversity and the environmental factors affecting the diversity of MPB in the tropical estuarine habitat of the Cochin estuary. A significant outcome of the present study was the taxonomic identification of 59 species of MPB belonging to 22 genera, which comprised 49 species of diatoms, one species of dinoflagellate, six species of cyanobacteria, two species of euglenophytes and one species of chlorophyte. Major MPB identified in the study were Navicula erifuga, Gyrosigma wansbeckii, Navicula flanatica, Nitzschia sigma, Nitzschia fluminensis, Amphora cymbifera, Nitzschia clausii, Nitzschia lorenziana, Navicula arenaria and Gyrosigma balticum. Principal component analysis indicated that the porewater salinity, sediment temperature, sediment pH, dissolved oxygen (DO), C:N ratio, porewater silicate and sediment chlorophyll a were positively correlated with the diversity of MPB. The intensity of rainfall, OC%, C:S ratio, and TN% were negatively correlated with the diversity of MPB. The study provides a detailed taxonomic inventory of MPB diversity and environmental influences, offering additional insights into tropical estuarine ecology. [ABSTRACT FROM AUTHOR]

Benthic diatoms have been studied in different areas of the Mediterranean Sea, but no data have been available for Israeli coastal waters until the present time. In this work, the composition, ecology, and phytogeography of diatoms of the macrophytes epiphyton are presented for the first time. Altogether, 85 diatom taxa were found among the epiphyton of 25 species of green, brown, and red macroalgae from the Israeli coast between March and May of 2021. These diatoms represent three classes, 17 orders, 26 families, and 41 genera. The taxonomic composition, ecology, and phytogeography of species are discussed. The distribution of diatoms are compared to that of other macrophytes and anthropogenic loads across the shoreline. The dominant species are given. Ecological characteristics and abundance in communities of revealed species are represented and statistically analyzed. The index of saprobity S varies between 1.69–2.71. Sites that stressed aquatic communities are indicated. The influence of the anthropogenic loads on the coastal territories is defined as a major factor that stimulated diatom species richness. Sites with anthropogenic stress for aquatic communities are indicated. Based on the composition of bioindicators, it is concluded that the section of the Israeli coast studied is oligo-mesotrophic compared to the eutrophic Gulf of Tartus. [ABSTRACT FROM AUTHOR]

The positive occupancy-abundance relationship (OAR) is considered a ubiquitous pattern and well explained by species niches. However, OAR can change largely with functional groups. Benthic diatoms in tropical rivers are subject to seasonal hydrological disturbance. Their OAR can be affected by their attachment mode and shows a strong seasonality with precipitation. We investigated benthic diatoms in a river basin in South China during wet and dry seasons. Using hierarchical models, we detected the seasonal effects of niche position and breadth on diatom occupancy, abundance, and OAR for the three attachment groups. Multilevel modeling demonstrated that niche position was the main predictor that substantially explained the variations in diatom occupancy. Compared with niche breadth, niche position had a larger effect on the abundances of strongly and moderately attached diatoms; but it had a smaller effect on that of weakly attached diatoms. Weakly attached diatoms had the lowest OAR slope, and moderately attached diatoms had the highest slope. The OAR slope exhibited marked seasonality and positively correlated with precipitation. Attachment mode is a key functional trait that largely determines the distribution and abundance of diatoms and mediates their OAR. Our study provides insight into diatom-based biological monitoring of tropical streams and rivers. [ABSTRACT FROM AUTHOR]

Diatoms are among the most common epibionts and have been recorded on the surfaces of various living substrates, either plants or animals. However, studies on them are still scarce in view of the many substrata available. In this study, epibiotic diatoms living on Callinectes bellicosus were identified for the first time from a subtropical coastal lagoon in Northwest Mexico. We tested the null hypothesis that the diatom flora living on the carapaces of C. bellicosus would not be similar to that recorded for mangrove sediments, its typical habitat. The epibiotic diatoms were brushed off from the carapaces of two specimens, acid-cleaned, mounted in synthetic resin, and identified based on frustule morphology. This way, 106 taxa from 46 genera were recorded, including 25 singletons, and 6 new records for the Mexican northwest region. The best-represented genera were Nitzschia (10 taxa), Mastogloia (9), Diploneis (8), Navicula (7), Amphora (5), Cocconeis (5), Tryblionella (4), and Gyrosigma (4). Species composition included 93% of local taxa, thus refuting the proposed hypothesis and supporting the alternate one. Although the estimated species richness was lower than that in sediments, it deems the green crab carapace a favorable substrate for the growth of benthic diatoms. [ABSTRACT FROM AUTHOR]

Streams systems draining upland landscapes provide valuable ecosystem services, but they are vulnerable to incision and channelization caused by anthropogenic disturbance. Restoring a degraded stream to its pre‐disturbance condition by reconnecting the channel to its historical floodplain aims to recover lost hydro‐morphological processes and functions. Seeking evidence to indicate whether that aim is met in practice, we examined diatoms and the stream macroinvertebrate trophic structures in three reaches of Whychus Creek, Oregon, United States. Two reaches were reconnected to their pre‐disturbance floodplains in 2012 and 2016. The third, control reach, was not restored and was selected to represent the degraded stream condition prior to restoration. Ordinations showed that benthic diatom species composition shifted from the control reach to the restored reaches. Compared to the control reach, reconnection decreased the percentages of diatoms with nitrogen (N)‐fixing cyanobacterial endosymbionts in the 2012 restored reach and decreased diatoms tolerant to low N conditions in both the restored reaches. δ15N values in both stream macroinvertebrates and tree leaves in the riparian zone were higher in the restored reaches. These findings suggest that floodplain reconnection may modify hydro‐morphological processes and ecosystem functions in ways that enhance organic matter retention and hyporheic exchange, resulting in increased nutrient availability, improved nutrient cycling, and greater primary productivity. More generally, our results suggest that characterizing diatom species composition and trophic interactions using stable isotopes provides the basis for identifying and evaluating the beneficial effects of stream restoration on ecosystem functions and the food‐web. [ABSTRACT FROM AUTHOR]

Introduction: Non-perennial rivers and streams are increasingly present, in part because of climate change, even in the temperate climate. However, how the loss of connectivity and complete drying affect microphytobenthos in general and diatom communities in particular has gone mostly unstudied. Methods: With this paper, we aim to close this gap, identifying diatom biodiversity through manual digital microscopy and rbcL amplicon sequencing, to observe a) which method is better suited to it and b) how the ecotone flowpool-dry affects diatom diversity under duress. Three karstic, non-perennial rivers and streams with a gradient from natural to anthropogenically disturbed were sampled under flooding conditions and after a long and intense drought in 2022. Results: Our results show that digital microscopy shows a higher diversity and species richness than amplicon sequencing. We posit that this might be due to a reduced pool of subaerophile taxa having been sequenced and being part of the reference database. Furthermore, the effect of drying only resulted in a reduction in diversity after this drought, although the biofilm was still alive under these conditions. Discussion: To use amplicon sequencing for non-perennial river diatom diversity monitoring, the reference databases will have to be adapted to such systems, as most rivers may be subjected to drying regularly in the future. [ABSTRACT FROM AUTHOR]

Benthic diatoms have been studied in different areas of the Mediterranean Sea, but no data have been available for Israeli coastal waters until the present time. In this work, the composition, ecology, and phytogeography of diatoms of the macrophytes epiphyton are presented for the first time. Altogether, 85 diatom taxa were found among the epiphyton of 25 species of green, brown, and red macroalgae from the Israeli coast between March and May of 2021. These diatoms represent three classes, 17 orders, 26 families, and 41 genera. The taxonomic composition, ecology, and phytogeography of species are discussed. The distribution of diatoms are compared to that of other macrophytes and anthropogenic loads across the shoreline. The dominant species are given. Ecological characteristics and abundance in communities of revealed species are represented and statistically analyzed. The index of saprobity S varies between 1.69–2.71. Sites that stressed aquatic communities are indicated. The influence of the anthropogenic loads on the coastal territories is defined as a major factor that stimulated diatom species richness. Sites with anthropogenic stress for aquatic communities are indicated. Based on the composition of bioindicators, it is concluded that the section of the Israeli coast studied is oligo-mesotrophic compared to the eutrophic Gulf of Tartus.

The objectives of this review were to synthesize the community structure of phytoplankton and the role of atelomix in the phytoplankton dynamics in Ethiopian highland lakes. Changes in a lake’s physical structure, light dynamics, and availability of nutrients are closely associated with phytoplankton ecology, and phytoplankton assemblages provide insight into phytoplankton responses to these environmental changes. Based on the available information, a total of 173 species of phytoplankton are grouped under seven classes, Chlorophyceae (80 taxa), Bacillariophyceae (55 taxa), Cyanophyceae (24 taxa), Dinophyceae (6 taxa), Eugleonophyceae (6 taxa), Xanthophyceae (1 taxon), and Cryptophyceae (1 taxon) were recorded in five different tropical Ethiopian highland lakes. Chlorophyceae and Bacillariophyceae dominated in terms of species composition. Partial atelomixis, seasonality, and low nutrient concentrations seem to be the main drivers in structuring phytoplankton composition and abundances in Ethiopian highland lakes, characterized by a high diversity of atelomix-dependent benthic diatoms and desmids. Thus, this review will help understand the role of atelomix and nutrient availability in the phytoplankton composition and biomass of tropical highland lakes of Ethiopia.

IntroductionNon-perennial rivers and streams are increasingly present, in part because of climate change, even in the temperate climate. However, how the loss of connectivity and complete drying affect microphytobenthos in general and diatom communities in particular has gone mostly unstudied. MethodsWith this paper, we aim to close this gap, identifying diatom biodiversity through manual digital microscopy and rbcL amplicon sequencing, to observe a) which method is better suited to it and b) how the ecotone flow-pool-dry affects diatom diversity under duress. Three karstic, non-perennial rivers and streams with a gradient from natural to anthropogenically disturbed were sampled under flooding conditions and after a long and intense drought in 2022.ResultsOur results show that digital microscopy shows a higher diversity and species richness than amplicon sequencing. We posit that this might be due to a reduced pool of subaerophile taxa having been sequenced and being part of the reference database. Furthermore, the effect of drying only resulted in a reduction in diversity after this drought, although the biofilm was still alive under these conditions. DiscussionTo use amplicon sequencing for non-perennial river diatom diversity monitoring, the reference databases will have to be adapted to such systems, as most rivers may be subjected to drying regularly in the future.

In polar regions, the microphytobenthos has important ecological functions in shallow-water habitats, such as on top of coastal sediments. This community is dominated by benthic diatoms, which contribute significantly to primary production and biogeochemical cycling while also being an important component of polar food webs. Polar diatoms are able to cope with markedly changing light conditions and prolonged periods of darkness during the polar night in Antarctica. However, the underlying mechanisms are poorly understood. In this study, five strains of Antarctic benthic diatoms were isolated in the field, and the resulting unialgal cultures were identified as four distinct species, of which one is described as a new species, Planothidium wetzelii sp. nov. All four species were thoroughly examined using physiological, cell biological, and biochemical methods over a fully controlled dark period of 3 months. The results showed that the utilization of storage lipids is one of the key mechanisms in Antarctic benthic diatoms to survive the polar night, although different fatty acids were involved in the investigated taxa. In all tested species, the storage lipid content declined significantly, along with an ultrastructurally observable degradation of the chloroplasts. Surprisingly, photosynthetic performance did not change significantly despite chloroplasts decreasing in thylakoid membranes and an increased number of plastoglobules. Thus, a combination of biochemical and cell biological mechanisms allows Antarctic benthic diatoms to survive the polar night. [ABSTRACT FROM AUTHOR]

Diatoms are among the most common epibionts and have been recorded on the surfaces of various living substrates, either plants or animals. However, studies on them are still scarce in view of the many substrata available. In this study, epibiotic diatoms living on Callinectes bellicosus were identified for the first time from a subtropical coastal lagoon in Northwest Mexico. We tested the null hypothesis that the diatom flora living on the carapaces of C. bellicosus would not be similar to that recorded for mangrove sediments, its typical habitat. The epibiotic diatoms were brushed off from the carapaces of two specimens, acid-cleaned, mounted in synthetic resin, and identified based on frustule morphology. This way, 106 taxa from 46 genera were recorded, including 25 singletons, and 6 new records for the Mexican northwest region. The best-represented genera were Nitzschia (10 taxa), Mastogloia (9), Diploneis (8), Navicula (7), Amphora (5), Cocconeis (5), Tryblionella (4), and Gyrosigma (4). Species composition included 93% of local taxa, thus refuting the proposed hypothesis and supporting the alternate one. Although the estimated species richness was lower than that in sediments, it deems the green crab carapace a favorable substrate for the growth of benthic diatoms.

We propose a procedure to update ecological quality indices using species autoecology estimated by gradient analysis when new species are found, or taxonomy is updated. When updating an index, the new values must be comparable to the old ones to avoid recalibration and quality class boundary changes. As gradient length influences the values of the species optima, we propose to avoid adding new species to existing lists and we suggest recalibrating the index with a new calibration dataset and rescaling species optima. This final step reduces index updating-induced quality classification changes. An example is shown using the EPI-L diatom index, a quality index for lakes affected by trophic pressure.

A sulfated polysaccharide from Navicula incerta (SPNi) was extracted, and its physicochemical characteristics, antioxidant activity, and anti-hemolytic property were investigated. The polysaccharide yield was 4.8% (SPNi weight/biomass dry weight). Glucose, galactose, mannose, and xylose were the primary sugars. The sulfate content and Mw values were 0.46% and 45 kDa, respectively. The FT-IR spectrum showed characteristic bands at 3276,1079,1255, and 820 cm−1, related to -OH, C-O-C, S=O, and C-O-S stretching vibration. The 1H-NMR analysis revealed signals of anomeric protons, indicating the presence of CH2-O and CH-O groups. SPNi registered ferric-reducing antioxidant power (up to 1.47 µmol TE/g) and 54% anti-radical activity on ABTS+. This polysaccharide registered 90% hemolysis inhibition achieving integrity of the erythrocyte membrane. The results indicate that SPNi could be a candidate for biotechnology applications where antioxidant activity and hemolysis inhibition are required.

The ecological significance of benthic diatom taxocoenoses in marine ecosystems renders them a suitable reference when making decisions on conservation, as well as ecological and biogeographical issues. This study focuses on floristics of epiphytic diatoms of macroalgae from the central region of the Gulf of California and their biogeographical affinities. Based on current floristics for benthic diatoms of the Mexican NW, it was hypothesized that species richness would be higher for the central gulf (transitional) than for the tropical Revillagigedo Archipelago. Additionally, it was hypothesized that it would be composed mainly of common taxa of the region, with tropical and temperate components. Likewise, it was hypothesized that Mastogloia (tropical) would include less taxa and Lyrella would include more taxa in the transitional central gulf. The diatom flora yielded 333 taxa and 101 genera, and out of which the best represented were Navicula with 29 taxa, Amphora (27), Cocconeis (25), Nitzschia (24), Diploneis (19), Achnanthes (13), Halamphora (14), Fallacia (10), Lyrella (9), and Mastogloia (8), adding up to 53% of the total. The inspected diatom taxocoenosis included mostly taxa commonly distributed in the Mexican NW, albeit with 16 new records. This, plus the high species richness, as well as the proportions of selected taxa depicting this diatom taxocoenosis as being of transitional biogeographical affinity, back the posed hypotheses. [ABSTRACT FROM AUTHOR]

MOSE is a system of mobile gates engineered to temporarily isolate the Venice Lagoon from the Adriatic Sea and to protect the city from flooding during extreme high tides. Within the framework of the Venezia2021 program, we conducted two enclosure experiments in July 2019 (over 48 h) and October 2020 (over 28 h) by means of 18 mesocosms, in order to simulate the structural alterations that microphytobenthos (MPB) assemblages might encounter when the MOSE system is operational. The reduced hydrodynamics inside the mesocosms favored the deposition of organic matter and the sinking of cells from the water column towards the sediment. Consequently, MPB abundances increased over the course of both experiments and significant changes in the taxonomic composition of the community were recorded. Species richness increased in summer while it slightly decreased in autumn, this latter due to the increase in relative abundances of taxa favored by high organic loads and fine grain size. By coupling classical taxonomy with 18S rRNA gene metabarcoding we were able to obtain a comprehensive view of the whole community potential, highlighting the complementarity of these two approaches in ecological studies. Changes in the structure of MPB could affect sediment biostabilization, water turbidity and lagoon primary production. [ABSTRACT FROM AUTHOR]

This study aims to examine the ecological status of the Aksaz wetland based on diatom indices and diatom community. Sampling was done between March 2020 and December 2020. 50 taxa belonging to benthic diatom flora were identified. Navicula Bory and Nitzschia Hassall genera were observed in all samples and constituted 47% of the identified taxa. The index and ecological quality values in the Aksaz wetland indicate that the water body is moderately polluted. [ABSTRACT FROM AUTHOR]

In polar regions, the microphytobenthos has important ecological functions in shallow-water habitats, such as on top of coastal sediments. This community is dominated by benthic diatoms, which contribute significantly to primary production and biogeochemical cycling while also being an important component of polar food webs. Polar diatoms are able to cope with markedly changing light conditions and prolonged periods of darkness during the polar night in Antarctica. However, the underlying mechanisms are poorly understood. In this study, five strains of Antarctic benthic diatoms were isolated in the field, and the resulting unialgal cultures were identified as four distinct species, of which one is described as a new species, Planothidium wetzelii sp. nov. All four species were thoroughly examined using physiological, cell biological, and biochemical methods over a fully controlled dark period of 3 months. The results showed that the utilization of storage lipids is one of the key mechanisms in Antarctic benthic diatoms to survive the polar night, although different fatty acids were involved in the investigated taxa. In all tested species, the storage lipid content declined significantly, along with an ultrastructurally observable degradation of the chloroplasts. Surprisingly, photosynthetic performance did not change significantly despite chloroplasts decreasing in thylakoid membranes and an increased number of plastoglobules. Thus, a combination of biochemical and cell biological mechanisms allows Antarctic benthic diatoms to survive the polar night.

The uncontrolled colonization of benthic organisms on submerged surfaces, also called biofouling, causes severe damage in the shipping and aquaculture industries. Biofouling starts with a benthic biofilm composed of a complex assemblage of microbes, bacteria and benthic diatoms, called microfouling, on which macrofouling invertebrate species settle and grow. Invertebrate larvae may use natural soundscapes to orientate inshore and choose their optimal habitat. Recent studies have demonstrated that ship sounds enhance the larval settlement and growth of several invertebrate species, such as mussels, associated with biofouling. Among invertebrates, effects of sound generated by offshore human activities are still poorly studied. This study aims to assess the effect of pile driving, drilling and vessel sounds on model species associated with micro and macrofouling. First, the biofilm development of Navicula pelliculosa and Amphora coffeaeformis was assessed, then, the larval development of the blue mussel (Mytilus edulis) was evaluated from the D-veliger to the postlarval stage. Mussel larvae and microalgae were exposed 12 h each day in tanks (Larvosonic) adapted to sound experiments under controlled conditions. All anthropogenic sounds induced a thinner N. pelliculosa biofilm coupled with a lower microalgae concentration. The drilling sound had a stronger effect on the biofilm thickness. The drilling sound significantly reduced the pediveliger settlement and the postlarvae clearance rate by 70.4% and tended to diminish settler sizes compared to control sound. Contrary to our expectation, pile driving tended to enhance larval recruitment by 22% (P=0.077) and the boat sound did not stimulate larval settlements or recruitment. Drilling sound generated a stressful acoustic environment for pediveliger settlements and postlarvae seem to maintain their shell valves closed to preserve energy. We identify potential causes and mechanisms involved in these impacts of anthropophony on larval ecology and microfouling dynamics.

Two morphologically similar populations of Didymosphenia were reported from the West Branch of the Farmington River, Connecticut, USA in 2014 and 2016. We described one of them as a new species, D. hullii. The other was observed subsequently in late 2016 and resembled D. geminata, but given the worldwide nuisance characteristic of this species, the identification required confirmation. In this work we used geometric morphometrics analysis to test for quantitative distinctions between the two Connecticut populations, along with two morphologically similar taxa from the literature, D. laticollis and D. pumila. We successfully separated the four entities and confirmed the identity of the second blooming diatom in the Farmington River, Connecticut, as D. geminata, which is the first confirmed report of this species for the state. We conclude that geometric morphometrics, in combination with features viewed with scanning electron microscopy and light microscopy, enhances the ability to distinguish among these morphologically similar species of Didymosphenia. We summarize these findings and pinpoint morphological distinctions that can be used to separate the taxa during routine light microscopy analyses. Geometric morphometrics was used to differentiate four Didymosphenia taxa. Morphological comparisons of D. hullii and D. geminata are shown. Didymosphenia geminata was recently reported in Connecticut, USA. [ABSTRACT FROM AUTHOR]

The present study evaluates the effect of climatic events La Niña and drought on the structure of phytoplankton and hydrological variables in the Amazon estuary. Samples were collected at three sampling stations in the Taperaçu Estuary, on the Brazilian Amazon coast, in 2010 and 2011. During the rainy season of the La Niña (RS-LN) event, salinity reached significantly lower (p < 0.05) than normal values in the upper sector (10.5 ± 5.9), and significant spatial variation (p < 0.05) was recorded in the concentrations of silicate, chlorophyll-a, and phytoflagellates abundance. Significant differences were also found in salinity, turbidity, and the concentrations of dissolved nutrients and chlorophyll-a, as well as the abundance of specific phytoplankton groups, between the dry seasons of the post-drought (DS-PD) and La Niña (DS-LN) periods. During the post-drought dry season (DS-PD), high salinity (37.1 ± 1.3) and reduced precipitation contributed to the development of Psammodictyon panduriforme, a dominant marine species recorded during this period. During periods of higher rainfall (RS-LN and, to a lesser extent, DS-LN), salinity reached its lowest levels, which favored the growth of diatoms such as Cymatosira belgica, Plagiogrammopsis sp., and Skeletonema costatum. The present results indicate that the dynamics of the phytoplankton community of the Taperaçu Estuary is highly influenced by seasonality of rainfall, which is increased (more than 20%) by anomalous climate oscillations and directly affect environmental variables. This pattern would be expected in the dozens of other estuaries that have similar characteristics on the Amazon coast and in other tropical coastal zones around the world. [ABSTRACT FROM AUTHOR]

The present study is based on the identification of benthic diatoms sampled along the Coastal Central Constantine in northeastern of Algeria. Our work aims to address relationships between environmental variables and characterize the spatial and temporal distribution of the diatom flora. Diatoms and samples for physicochemical analysis were collected from 26 sampling sites between May 2017 and August 2018. The number of species accounted for was 109 species in the Safsaf watershed, 117 taxa in the Kebir and 129 species in the watershed of Guebli which was the most diversified catchment. The great majority of diatom taxa were cosmopolitan species. Naviculaceae were the most abundant (47.87%). Our results demonstrated the main environmental variables controlling the diatom distribution in all the watersheds, including conductivity, and pollution gradients highlighted in Canonical Correspondence Analyses (CCA). The results of the Shannon diversity index (H') showed that the species diversity observed in the sampled sites during summer is higher than that observed in spring and winter. During this season, mean Shannon diversity values were around H' = 4.49, 3.98, and 4.17, respectively, while species richness varied between 13 and 34 across the three watersheds. [ABSTRACT FROM AUTHOR]

This study investigated differences in total biomass (ash-free dry weight) of the periphyton and autotrophic biomass (chlorophyll-a content) of benthic diatoms in the absence or presence (No Grazer vs With Grazer) of two invertebrate grazers (Stichopus cf. horrens and Trochus maculatus) under simulated ambient (PRESENT), independent ocean acidification (OA) and warming (OW), and their combination (FUTURE) over an eight-day period. In the absence of a grazer, there were no significant differences in the average of the total and autotrophic biomass among treatments for both experiments. Stichopus significantly reduced the total and autotrophic biomass after 1 day, except under OW. Trochus significantly reduced the total biomass in the OA and OW treatments after 5 days, and the autotrophic biomass in the OA treatment after 1 and 5 days of grazing. In treatments where total and autotrophic biomass were not reduced, nutrients from the fecal matter and metabolic wastes of grazers seemingly stimulated the regeneration of microalgal biomass. The amount of fecal matter produced also affected the rate of microalgal renewal. In addition, due to the unexpected difference in seawater nutrient concentration during the two experiments, comparison of primary production under PRESENT was done to tease out nutrient effects. In PRESENT, autotrophic biomass was higher in Experiment 1 than Experiment 2, which was likely influenced by differences in nutrient concentrations. Results of this study elucidate underlying mechanisms in microalgal interactions with biotic and abiotic factors in tropical systems under changing ocean conditions. • Periphyton was not affected by acidification and warming as nutrients are replete. • Direct effects of acidification and warming on grazers indirectly affected periphyton. • Differences in fecal production of grazers affected rate of periphyton regeneration. • Complex multiple factor interactions are important considerations for future studies. [ABSTRACT FROM AUTHOR]

Diatom cultures can help answer taxonomic, biogeographic and ecological questions on a local and global scale. Unialgal cultures are derived from a single cell and provide abundant material for morphological and molecular analyses. The link between the historic morphological species concept and the molecular data is becoming increasingly important with the use of eDNA metabarcoding. Additionally, cultures provide insights into the life cycle of diatoms and thereby complement taxonomy and species ecology. In this study, we present an approach to extract benthic diatoms from an environmental sample to generate unialgal cultures. We explored diatom diversity in preserved assemblages and by culturing as many different taxa as possible from benthic freshwater samples taken on the same day from the Bow River in Calgary, Canada. With both methods we found a total of 221 different benthic diatom taxa, of which 182 were identified in the preserved diatom assemblages. Interestingly, an additional 39 taxa only appeared in the cultures. In total 129 strains were cultivated representing 71 different taxa. This study includes pictures of living cells demonstrating the additional merits of unialgal cultures, as they provide information on plastid details, auxospores and endosymbionts. Both, the identification of the diatom assemblages and the generation and identification of strains provide the foundation for additional water quality assessment tools, taxonomic insights and molecular references libraries.

This study evaluated the suitability of five diatom species (Amphora sp., Cocconeis sp., Navicula ramosissima, Nitzschia sp., and Tryblionella sp.) as food to abalone Haliotis asinina early juveniles (5-mm shell length). Grazing periodicity, grazing rate, and feeding preference were measured; at the same time, abalone gut content was examined. Grazing incidence appeared to be continuous with significantly higher grazing intensity observed at nighttime from 6 p.m. to 10 p.m. (79%) than at daytime from 10 a.m. to 2 p.m. (40%) (p < 0.05). Grazing rates from 6 p.m. to 10 p.m. were significantly higher on N. ramosissima (1.6 × 105) among diatom species but was not statistically different from Cocconeis sp. (1.1 × 105) (p > 0.05). Broken cells of Amphora sp. (22%) were significantly higher in the gut of H. asinina compared to Cocconeis sp. (2.8%), N. ramosissima, (1.8%), and Tryblionella sp. (0.2%) although the abundance of Nitzschia sp. (6%) was not significantly different from Amphora sp. (p > 0.05). Early juveniles showed significant preference for Cocconeis sp. (18.6%), followed by Nitzschia sp. (16.2%), N. ramosissima (13.9%), and Amphora sp. (13.4%), with the least preference for Tryblionella sp. (7.8%). Survival of H. asinina was similar in 4 diatom species (46–71%) except in Tryblionella sp. (8–12%). These findings suggest that diatom species Cocconeis sp., Nitzschia sp., Amphora sp., and N. ramosissima are the suitable live food for H. asinina early juveniles. Knowledge from this study would contribute to the development of a feeding protocol that would maximize production of H. asinina early juveniles in the hatchery. [ABSTRACT FROM AUTHOR]

A sulfated polysaccharide from Navicula incerta (SPNi) was extracted, and its physicochemical characteristics, antioxidant activity, and anti-hemolytic property were investigated. The polysaccharide yield was 4.8% (SPNi weight/biomass dry weight). Glucose, galactose, mannose, and xylose were the primary sugars. The sulfate content and Mw values were 0.46% and 45 kDa, respectively. The FT-IR spectrum showed characteristic bands at 3276,1079,1255, and 820 cm-1, related to -OH, C-O-C, S=O, and C-O-S stretching vibration. The 1H-NMR analysis revealed signals of anomeric protons, indicating the presence of CH2-O and CH-O groups. SPNi registered ferricreducing antioxidant power (up to 1.47 μmol TE/g) and 54% anti-radical activity on ABTS+. This polysaccharide registered 90% hemolysis inhibition achieving integrity of the erythrocyte membrane. The results indicate that SPNi could be a candidate for biotechnology applications where antioxidant activity and hemolysis inhibition are required. [ABSTRACT FROM AUTHOR]

Living organisms are used in water quality evaluation, thus reflecting the constantly changing physical and chemical characteristics of aquatic ecosystems. Diatoms are among the aquatic organisms used in water quality monitoring of both lentic and lotic ecosystems. The objectives of our present study were to summarize the topics in diatoms for water quality evaluation, and identify the past trends as well as the future directions through the analyses of trends in diatoms bioassessment topics in Africa. We retrieved diatoms distribution data from Web of Science (WoS) database using the following keywords “Diatoms for water quality monitoring in Africa”, and “Diatoms for bioassessment in Africa”. We used VOS viewer software (version 1.16.15) in the construction of knowledge map of application diatoms in monitoring and bioassessment. A total of 481 documents on diatom in water quality monitoring and bioassessment were found. A subsequent thresholding of keywords centered on 15 times occurrence yielded 37 keywords. Diatom indicators were related to diversity, benthic diatoms, communities, community structure, assemblages, land-use, and water quality as clustered by VOS viewer software. Regionally, South Africa is one of the top most developed country in Africa, and this has been attributted to greater infrastructural, human resource, and financial capacity to carry out research that led to substantial collaborations both locally and globally. Institutionally, the connection between University of Cape Town and Bayworld Centre for Research and Education in South Africa was strongest probably due to their better infrastructural capacity in diatoms research. Therefore, the study provided insights that are likely to contribute to the future development of water quality monitoring framework using diatoms in Africa, thereby enhancing global environmental sustainability. [ABSTRACT FROM AUTHOR]

Benthic diatoms are the primary beach vegetation on sandy coasts, acting as the main primary producers in such environments. Changes in their community structure and biomass can have substantial impact on both the entire micro-food web and the nearshore shallow marine ecosystem. This study focused on four typical beaches along the southern coast of China (Fuzhou Changle Beach, Xiamen Huizhan Beach, Xiamen Guanyinshan Beach, and Beihai Silver Beach). Analysis of benthic diatoms and environmental factors revealed that the distribution of benthic diatom communities on the studied beaches is influenced by elevation, salinity changes due to freshwater inputs, sediment composition, and hydrodynamic factors. The most important factor is elevation, which reflects the location of the beach in the tidal zone. On Beihai Silver Beach and the Xiamen beaches, the mid-tidal and low tidal zones are more conducive to growth and reproduction of benthic diatoms, and some diatom species show preference for different tidal zones. On dissipative beaches, benthic diatom abundance peaks in the mid-tidal zone, whereas on low tidal terrace beaches, diatom abundance is generally low in the high tidal zone and relatively high in the low tidal zone. Additionally, low tidal terrace beaches exhibit a "steep increase zone" of diatom abundance at the junction of the steep and gentle slopes, indicating that benthic diatom abundance responds more to this type of beach landform than to that of dissipative beaches., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Benthic diatoms serve as exemplary indicators for the assessment of ecological conditions in freshwater ecosystems. However, an approach to assessing and managing transitional water zones by benthic diatoms is relatively less. This study entailed a detailed analysis and comparison of the seasonal dynamics in species- and guild-based benthic diatom communities and their driving factors in a small-scale transitional water zone of the Yellow River Delta. Our findings revealed substantial seasonal variations in the composition and abundance of dominant species, as well as in the α and β diversity of the species-based community. Temperature emerged as the predominant environmental factor driving significant seasonal variations in the species-based community. However, no significant seasonal changes were observed in the composition and relative abundance of dominant guilds, as well as in the α, β, and functional diversity of the guild-based community. Redundancy analysis and Mantel tests demonstrated the guild-based community exhibited a stronger correlation with environmental factors compared to the species-based community. The guild-based community exhibited resilience to the influence of seasonal temperature fluctuations and exhibited a strong correlation with phosphate concentration variations. Our findings suggest that the guild-based community is a feasible approach to assessing ecological status across various seasons in the transitional water zone of the Yellow River Delta., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Eutrophication is one of the most pervasive stressors impacting streams, often leading to loss of biodiversity or change in natural functions. To protect against these adverse effects, managers can set targets for environmental indicators to limit eutrophication that are likely to maintain high biological integrity. To identify protective management targets, we evaluated the responses of three bioassessment indices (one for benthic macroinvertebrates and two for benthic algae assemblages) to five eutrophication indicators (total nitrogen [TN], total phosphorus [TP], benthic chlorophyll-a [chl-a], benthic ash-free dry mass [AFDM], and percent macroalgal cover [% cover] of the streambed). First, we used a bioassessment data set of 1249 sites in California to create logistic regression models of the likelihood of achieving several biointegrity goals for each index along increasing gradients of each indicator. Then, we evaluated eutrophication thresholds at concentrations corresponding to several relative probabilities (from 50 to 95 %), reflecting a range of policy makers’ potential tolerance for risk of failing to meet biointegrity goals. Finally, we validated the thresholds with relative risk assessment, and identified the lowest validated threshold across the three indices. All eutrophication indicators were significantly associated with increased risks to biointegrity, resulting in a set of validated thresholds for each biointegrity goal. For example, thresholds of 0.24 mg/L TN, 0.05 mg/L TP, 44 mg/m2 benthic chl-a, 2.5 mg/cm2 AFDM, and 26 % cover would achieve index scores above the 10th percentile of reference (a biointegrity goal that has been used in certain regulatory applications) with an 80 % probability. If these thresholds were applied ambient monitoring statewide dataset, TN was the most pervasively exceeded threshold (37 % of sites), particularly within the highly agricultural Central Valley (76 %), although exceedances of TN and AFDM were also common in the urbanized South Coast region (68 % and 72 % of sites, respectively).

Conclusions The results of the diatom study in the coastal zone of the Gulf of Gda'nsk, between Gdynia and Sopot, indicate the presence of a diverse flora belonging to epilithic, epipsammic, epipelic and epiphytic assemblages. The diatom research in the coastal zone of the Gulf of Gda'nsk was used to determine the degree of water organic pollution ([7]; [72]) and to investigate diatom preferences with respect to habitat ([66]). Biodiversity of the benthic diatom flora in the coastal zone of the Gulf of Gda'nsk: a case study of the Gdynia-Sopot transect Graph: Figure 2 The number of diatom taxa (species, subspecies, varieties, forms) versus ecological preferences: *eh-euhalobous, mh-mesohalobous, oh-oligohalobous halophilous, oi-oligohalobous indifferent; **et-eutraphentic, emt-eumesotraphentic, mt-mesotraphentic, mot-meso-oligotraphentic, ot-oligotraphentic, edt-eurydystrophic, ir-irrelevant; ***ps-polysaprobous, ams- -mesosaprobous, abms- - -mesosaprobous, bms- -mesosaprobous, os- oligosaprobous, x-xenosaprobous, ir-irrelevant Diatom taphocoenoses of the shallow coastal zone of the Gulf of Gda'nsk are usually dominated by benthic species. Despite many years of research on diatoms in the coastal zone of the Gulf of Gda'nsk, knowledge about the relationship between the species composition of benthic diatoms and microhabitats requires further investigation. [Extracted from the article]

The shallow coastal water zone of the tide-less southern Baltic Sea is dominated by exposed sandy sediments which are typically inhabited by microphytobenthic communities, but their primary production is poorly studied, and hence four stations between 3.0 and 6.2 m depth were investigated. Sediment cores were carefully taken to keep the natural layering and exposed in a controlled self-constructed incubator. Respiratory oxygen consumption and photosynthetic oxygen production were recorded applying planar oxygen optode sensors. We hypothesized that with increasing water depths the effects of wind- and wave-induced erosion and mixing of the upper sediment layer are dampened and expected higher microphytobenthic biomass and primary production in the incubated cores.Our data partly confirm this hypothesis, as cores sampled at the most exposed stations contained only 50% chlorophyll a m−2 compared to the deeper stations. However, primary production was highly variable, probably due to fluctuating sediment-disturbing conditions before the cores were taken. Due to these physical forces sand grains were highly mobile and rounded, and small epipsamic benthic diatoms dominated, which preferentially occurred in some cracks and crevices as visualized by scanning electron microscopy. The data fill an important gap in reliable production data for sandy sediments of the southern Baltic Sea, and point to the ecological importance and relevant contribution of microphytobenthic communities to the total primary production of this marine ecosystem. Oxygen planar optode sensor spots proved to be a reliable, sensitive and fast detection system for ex situ oxygen exchange measurements in the overlying water of intact sediment cores.

The ecological significance of benthic diatom taxocoenoses in marine ecosystems renders them a suitable reference when making decisions on conservation, as well as ecological and biogeographical issues. This study focuses on floristics of epiphytic diatoms of macroalgae from the central region of the Gulf of California and their biogeographical affinities. Based on current floristics for benthic diatoms of the Mexican NW, it was hypothesized that species richness would be higher for the central gulf (transitional) than for the tropical Revillagigedo Archipelago. Additionally, it was hypothesized that it would be composed mainly of common taxa of the region, with tropical and temperate components. Likewise, it was hypothesized that Mastogloia (tropical) would include less taxa and Lyrella would include more taxa in the transitional central gulf. The diatom flora yielded 333 taxa and 101 genera, and out of which the best represented were Navicula with 29 taxa, Amphora (27), Cocconeis (25), Nitzschia (24), Diploneis (19), Achnanthes (13), Halamphora (14), Fallacia (10), Lyrella (9), and Mastogloia (8), adding up to 53% of the total. The inspected diatom taxocoenosis included mostly taxa commonly distributed in the Mexican NW, albeit with 16 new records. This, plus the high species richness, as well as the proportions of selected taxa depicting this diatom taxocoenosis as being of transitional biogeographical affinity, back the posed hypotheses.

MOSE is a system of mobile gates engineered to temporarily isolate the Venice Lagoon from the Adriatic Sea and to protect the city from flooding during extreme high tides. Within the framework of the Venezia2021 program, we conducted two enclosure experiments in July 2019 (over 48 h) and October 2020 (over 28 h) by means of 18 mesocosms, in order to simulate the structural alterations that microphytobenthos (MPB) assemblages might encounter when the MOSE system is operational. The reduced hydrodynamics inside the mesocosms favored the deposition of organic matter and the sinking of cells from the water column towards the sediment. Consequently, MPB abundances increased over the course of both experiments and significant changes in the taxonomic composition of the community were recorded. Species richness increased in summer while it slightly decreased in autumn, this latter due to the increase in relative abundances of taxa favored by high organic loads and fine grain size. By coupling classical taxonomy with 18S rRNA gene metabarcoding we were able to obtain a comprehensive view of the whole community potential, highlighting the complementarity of these two approaches in ecological studies. Changes in the structure of MPB could affect sediment biostabilization, water turbidity and lagoon primary production.

The present study enhances knowledge of the biodiversity of diatoms in Chuuk, Micronesia following our 2018 study on the seaweed-associated diatoms. We collected planktonic samples of diatoms from five sites of reef flats using a 20 μm mesh net, and two samples of seaweeds with epiphytes by hand from an islet on the barrier reef. In addition, the seaweed-associated diatoms from our 2018 study were analysed using scanning electron microscopy. A total of 109 diatom taxa are documented in the present study. Of these, 70 species were from net samples, and 39 species from the seaweed-associated diatoms. Thirty-one species are newly recorded from Micronesian waters. Most taxa are benthic or tychoplanktonic; euplanktonic diatoms were rare. The occurrence of benthic diatoms from the water column might be related to the Chuuk environmental conditions which include shallow water, strong light intensity and high grazing pressure, to which benthic diatoms seem to be able to better adapt than planktonic diatoms. [ABSTRACT FROM AUTHOR]

River impoundments have transformed river ecosystems globally due to the modification of various abiotic and biotic factors. This study provides rare evidence quantifying how water supply reservoirs alter water temperature regimes and its effects on macroinvertebrate and diatom communities over a 4‐year period. We obtained near‐continuous water temperature measurements upstream and downstream of three reservoirs and analysed thermal variables in association with macroinvertebrate and diatom community indices (including taxonomic richness, proportion of Ephemeroptera, Plecoptera and Trichoptera taxa [%EPT] and diatom ecological guilds). Reservoirs typically decreased downstream thermal variability, with reduced summer temperatures and increased winter temperatures, and a delayed timing of annual temperature extremes. Marked differences in thermal regime modifications between reservoirs were observed, including evidence of inter‐annual variation associated with inter‐basin water transfers downstream of one reservoir. Biomonitoring indices showed associations with thermal indices that differed between site types (regulated versus non‐regulated) and seasons (spring vs. autumn). Various macroinvertebrate and diatom indices capturing community diversity elements and sensitivities to different environmental pressures were associated with higher maximum summer temperatures and lower minimum winter temperatures, suggesting ecological effects of reduced thermal variation downstream of reservoirs. Different ecological responses to thermal indices were observed between seasons, likely due to organism life‐cycle effects and intra‐annual thermal variations. Contrasting macroinvertebrate and diatom communities were observed between regulated and non‐regulated sites, which may be driven by differences in the thermal regime and other abiotic factors at regulated sites, including nutrient, sediment and flow regimes. Long‐term continuous water temperature monitoring of both multiple regulated and non‐regulated river systems is necessary to better understand the environmental and ecological effects of river impoundments. Given the extent to which river impoundment has modified stream temperatures globally, the inclusion of thermal regime data in environmental flow studies alongside hydrological information may guide the implementation of mitigation measures on impounded waterbodies. [ABSTRACT FROM AUTHOR]

The aim of this paper was to present the composition and seasonal dynamics of epilthic diatoms in the Timok River basin. The diatom samples were collected along the Timok River basin in March, May, August and November 2017. Permanent diatom slides were prepared after oxidizing the organic material by the hydrogen peroxide (H 2 O 2). The cleaned diatom materials were mounted on permanent slides using ZRAX glue. A total of 85 taxa were identified in the Timok River Basin. The benthic diatom taxa belong to 31 genera with the highest diversity observed within Navicula Bory (15), Nitzschia Hassall (12) and Gomphonema Ehrenberg (8). Quantitative analysis showed that in all seasons, Achnanthidium minutissimum and Amphora pediculus were dominant taxa. In May, they were joined by the Achnanthidium pyrenaicum, Gomphonema olivaceum and Ulnaria ulna; in August by the Cocconeis placentula, Denticula kuetzingii, Melosira varians, Navicula metareichardtiana, Nitzschia capitellata, N. fonticola and N. palea; in November by the D. kuetzingii, G. olivaceum, G. pumilum, N. metareichardtiana, N. veneta, Nitzschia capitellata and N. palea and in March by A. pyrenaicum, Diatoma moniliformis, G. olivaceum, N. palea and U. ulna. Our research is the floristical and ecological study of benthic diatoms in this basin and can form the groundwork for further research work.

The Taperaçu Estuary is distinct from other Amazonian estuaries due to the absence of significant fluvial discharge and consequent dominance of marine influence. The present study investigated the influence of physical-chemical variables on the composition and dynamics of the local phytoplankton and their spatiotemporal variation, with emphasis on the taxonomic analysis of the diatoms of the order Eupodiscales. During the rainy and dry seasons of 2013 and 2014, three sectors of this estuary were monitored over cycles of 24 hours. The samples were analyzed by light and scanning electron microscopy. Significant temporal and spatial differences were found in salinity, which was high (>32) in all the sectors. Turbidity and Chl- a concentrations were higher during the rainy period due to the increased input of water from the relatively small drainage basin of the estuary, as well as the material washed out of the soil of the adjacent mangroves. The local phytoplankton community was dominated by diatoms, which reached high abundances during the dry season. The local hydrodynamics determined the occurrence of benthic and/or tychoplanktonic species in the water column, including the Eupodiscales Hobaniella longicruris, Odontella aurita , and Zygoceros rhombus , while the high salinity recorded during the dry season favored the presence of Trieres species. The presence of high abundances of the benthic diatom Cymatosira belgica contributed to the observed high Chl- a concentrations and endorse the ecological importance of sediment resuspension processes and the consequent accumulation of phytobenthos cells in the water column in shallow estuarine Amazonian ecosystems. [ABSTRACT FROM AUTHOR]

Diatom cultures can help answer taxonomic, biogeographic and ecological questions on a local and global scale. Unialgal cultures are derived from a single cell and provide abundant material for morphological and molecular analyses. The link between the historic morphological species concept and molecular data is becoming increasingly important with the use of eDNA metabarcoding. Additionally, cultures provide insights into the life cycle of diatoms and thereby complement taxonomy and species ecology. In this study, we present an approach to extract benthic diatoms from an environmental sample to generate unialgal cultures. We explored diatom diversity in preserved assemblages and by culturing as many different taxa as possible from benthic freshwater samples taken on the same day from the Bow River in Calgary, Canada. With both methods we found a total of 221 different benthic diatom taxa, of which 182 were identified in the preserved diatom assemblages. Interestingly, an additional 39 taxa only appeared in the cultures. In total 129 strains were cultivated, representing 71 different taxa. This study includes pictures of living cells demonstrating the additional merits of unialgal cultures, as they provide information on plastid details, auxospores and endosymbionts. Both, the identification of the diatom assemblages and the generation and identification of strains provide the foundation for additional water quality assessment tools, taxonomic insights, and molecular references libraries. [ABSTRACT FROM AUTHOR]

Even though microscopic algae play pivotal role in the healthy functioning of freshwater ecosystems, recent water protection strategies rarely consider them and primarily focus on macroscopic organisms. Here, we studied the effect of protection level and utilization type of lowland standing waters on the composition and diversity of benthic diatom assemblages and on the diatom-based ecological status of waters. We hypothesized that (i) protected waters will sustain more diverse diatom assemblages and better ecological quality than not protected ones. We also hypothesized that (ii) the increase in number of utilization will affect negatively on biodiversity and on ecological quality. Clear taxonomic differences were revealed only in protected and not utilized waters while trait composition in protected waters was independent from the utilization type. Neither biodiversity nor ecological status of waters were influenced by protection level. The increase in number of utilization types, however, significantly decreased functional richness. Although high biodiversity of algae can effectively buffer the negative effects of climate change and anthropogenic impact, recent protection strategies are insufficient to support it.

In recent years diatoms have emerged as a major algal source for the production of bioactive compounds. Marine diatoms grow quickly and can store high amount of lipids. Unfortunately, they are little studied and underexploited resources. The current work deals with an original and rarely investigated source of diatoms: intertidal mudflats. It aims to evaluate the lipid production potential of some strains of benthic diatom species, isolated and hosted in the Nantes Culture Collection (NCC) when cultivated in an airlift photobioreactor. Six strains known for their high biomass and/or lipid productivity: Amphora sp. (NCC169), Entomoneis paludosa (NCC18.2), Nitzschia alexandrina (NCC33), Nitzschia sp. (NCC109), Opephora sp. (NCC366), and Staurosira sp. (NCC182) were cultivated in airlift photobioreactors for the first time. Their lipid class composition, fatty acid, and sterol distribution were studied. Total lipid production varied from 11.4 (Amphora sp.) to 41%DW (Staurosira sp.). Neutral lipid amounts varied from 23 (Amphora sp.) to 76% (Staurosira sp.) of total lipids (%TL). Glycolipids ranged from 18 (Staurosira sp.) to 59%TL (Opephora sp.) and phospholipids accounted for 6 (Staurosira sp.) to 26%TL (Amphora sp.). Some qualitative and quantitative differences were identified in both fatty acid and sterol composition in the different strains analyzed. Staurosira sp. seems to be the most promising species in terms of lipid production and most particularly in triacylglycerol production. Entomoneis paludosa produced phytosterols and eicosapentaenoic acid (EPA), compounds with potential for application in the pharmaceutical sector. Nitzschia alexandrina produced squalene and low levels of saturated fatty acids which could both be interesting in the nutraceutical industry as antioxidants. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) frequently deals with membrane biofouling caused by deposition of algal organic matter (AOM) from algal blooms, hampering the treatment efficiency. In this study, AOMs, which are soluble extracellular polymeric substance (sEPS), bounded EPS (bEPS), and internal organic matter (IOM) from three benthic species (Amphora coffeaeformis, Cylindrotheca fusiformis, and Navicula incerta) were exposed to a temperature range to resemble the MD process. Results showed that EPS had higher polysaccharide fraction than protein with 85.71%, 68.26%, and 71.91% for A. coffeaeformis, N. incerta, and C. fusiformis, respectively. Both the EPS polysaccharide and protein concentration linearly increase with temperature, but the opposite was true for IOM and high‐molecular‐weight (HMW) polysaccharide. At 80°C, 5812.94 μg/g out of 6304.28 μg/g polysaccharide in A. coffeaeformis was of low molecular weight (LMW); hence, these findings suggested that they were the major foulants to clog the narrow pores within virgin hydrophobic membrane, forming a conditioning layer followed by deposition of HMW and hydrophilic polysaccharides onto the macropores to cause irreversible fouling. Cell lysis occurring at higher temperature increases the total protein content about 25% within the EPS matrix, inducing membrane plugging via hydrophobic–hydrophobic interactions. Overall, the AOM composition at different temperatures will likely dictate the fouling severity in MD. Practitioner points: EPS production of three benthic diatoms was the highest at 80°C.EPS from diatoms consists of at least 75.29% of polysaccharides.Small molecular weight carbohydrates (<12 kDa) were potential foulants.Proteins of internal organic matter (>56%) give irreversible attachment towards membranes.A. coffeaeformis was considered as the most fouling diatoms with highest EPS amount of 6304.28 μg/g. [ABSTRACT FROM AUTHOR]

Microphytobenthos (MPB) plays an integral role in contributing to the productivity and sustenance of shallow marine ecosystem. MPB forms an integral component in the trophic structure of mangrove forest and its biogeochemistry. Microphytobenthos from three selected mangrove ecosystems (S1, Kannur; S2, Kochi and S3, Kollam) along the southwest coast of India was studied in detail for 1 year (2018–2019). Spatial and temporal (seasonal) variations in the community structure were addressed along with major environmental factors influencing the pattern of distribution. A total of 148 species of microphytobenthos under 58 genera were identified during the study. Diatoms (Bacillariophyceae) were the most abundant and diverse class of MPB present followed by Cyanophyceae, Dinophyceae and Euglenophyceae. The analysis of physicochemical parameters showed that salinity, temperature, sediment texture and nutrient characteristics were the major factors governing the community structure of MPB. Seasonally, maximum abundance was observed during monsoon and pre-monsoon with lesser diversity and extensive mats of cyanobacteria dominated by Oscillatoria spp. However, post-monsoon season with high nutrient concentration, increased salinity and more of sandy sediment texture supported diverse assemblage of diatoms. Dominant diatoms observed were Amphora spp., Diploneis sp., Navicula spp., Nitzschia spp., Pleurosigma sp. and Gyrosigma sp. Regionally, S3 Kollam was observed to be more diverse with the dominance of diatoms, whereas S2 Kochi observed lesser diversity with cyanobacterial dominance. Increased sediment grain size (sand ~ 68%) favoured diverse diatom assemblage at S3 resulting in an overall high MPB diversity of the area than S1 and S2. [ABSTRACT FROM AUTHOR]

The colonisation patterns of diatom assemblages were studied on artificial substrates in lowland streams with different urban pollution levels. Density, diversity, colonisation rates, ecological guilds and cell size classes of the assemblage at each of two sites were followed for 1 week. In addition, assemblages growing on glass, in natural epipelic biofilm and in water were compared at each site. At both sites, diatom colonisation on glass substrates had already started after 30-min exposure. At the less polluted site, total diatom density was higher, along with the proportion of low-profile and motile species, and there was a higher amount of diatoms in size class 5 (>1500 μm3). At the more polluted site, species from the high-profile guild and size class 3 (300–599 μm3) dominated. Ecological traits (ecological guilds and size class) were not sensitive enough descriptors of early colonisation in nutrient-rich lowland, but the largest cells constituted the first settlers. The results show that the assemblage developed on artificial substrata was a good proxy of the composition in the sediment. Early diatom colonisation in two urban streams, one exposed to a low to moderate anthropogenic effect and the other a heavily polluted stream, was evaluated. Diatom density, diversity, colonisation rates, ecological guilds and cell size classes were studied during the first week of colonisation on sterile glass substrates, and distinct patterns were found for each stream. [ABSTRACT FROM AUTHOR]

Aim: Contemporary dispersal constraints and environmental conditions are broadly recognized as significant drivers of beta diversity patterns. However, beta diversity patterns may also reflect the legacy of past climatic and geological events. In this study, we investigated the relative importance of historical and contemporary factors as drivers of taxonomic, functional and phylogenetic beta diversity in Neotropical stream communities. Location: The Colombian Orinoco basin. Taxon: Diatoms and insects. Methods: We estimated taxonomic, phylogenetic and functional beta diversity using Baselga's (BAS) and Podani's (POD) frameworks. Following both frameworks, we further partitioned every biodiversity facet into turnover and nestedness or richness difference components. Then, we used generalized linear models (GLM) to relate each biodiversity facet with environmental, spatial and historical factors. Results: We found that both historical and contemporary factors affected current patterns of beta diversity. Historical factors and water pH and temperature had the strongest effect on beta diversity patterns, particularly for taxonomic and phylogenetic facets. GLM models performed better for insects than for diatoms in all three facets. Within communities, our analysis also revealed a partial congruence between BAS‐ and POD‐based results. Main conclusions: Due to their past geological history and contemporary environmental gradients, tropical montane streams are natural laboratories for disentangling the joint effects of ecological and biogeographical factors on biodiversity patterns. Our study reveals that present‐day distribution patterns cannot be fully explained without accounting for the effects of past geological and climatic events on mountain landscapes. In the Neotropics, montane geology sets the stage for speciation and landscape formation, with which ecological (e.g., dispersal limitation) and environmental factors interact to generate spatial variation in species turnover. [ABSTRACT FROM AUTHOR]

River phytoplankton has been studied to understand its occurrence and composition since the end of the nineteenth century. Later, pioneers addressed mechanisms that affected river phytoplankton by "origin of plankton", "turbulent mixing", "flow heterogeneity", "paradox of potamoplankton maintenance" and "dead zones" as keywords along the twentieth century. A major shift came with the recognition that characteristic units in phytoplankton compositions could be linked to specific set of environmental conditions, known as the "Phytoplankton Functional Group concept" sensu Reynolds. The FG concept could successfully be applied to river phytoplankton due to its close resemblance to shallow lakes phytoplankton. The FG approach enables one to separate the effects of "natural constraints" and "human impacts" on river phytoplankton and to evaluate the ecological status of rivers. The FG classification has mainly been advocated in the context of how the environment shaped the functional composition of phytoplankton. It may be further developed in the future by a trait-based mechanistic classification of taxa into FGs, and by the exact quantification of FGs on ecosystem functioning. These improvements will help quantify how global warming and human impacts affect river phytoplankton and corresponding alterations in ecosystem functioning. [ABSTRACT FROM AUTHOR]

The global biodiversity loss has raised interest in the different facets of diversity, and the importance of diversity for ecosystem functions has been recognized. However, our knowledge on seasonal and inter-annual variation in the composition and diversity of communities is still poor. Here, we investigated the seasonal and inter-annual changes in taxonomic and functional community composition and diversity of benthic diatoms in a coastal habitat of the northern Baltic Sea, where seasonal and inter-annual variation of climate is pronounced. We found that the taxonomic and functional alpha diversity remained stable at seasonal and inter-annual level despite strong changes in community composition. However, alpha diversity decreased during an exceptionally warm winter possibly due to disturbances induced by the lack of ice. This may suggest that climate warming and consequently limited ice cover will affect the diversity of benthic communities.

The amphipod Gondogeneia antarctica is among the most abundant benthic organisms, and a key food web species along the rapidly warming West Antarctic Peninsula (WAP). However, little is known about its trophic strategy for dealing with the extreme seasonality of Antarctic marine primary production. This study, using trophic markers, for the first time investigated seasonal dietary shifts of G. antarctica in a WAP fjord. We analyzed δ13C and δ15N in G. antarctica and its potential food sources. The isotopic signatures revealed a substantial contribution of red algae to the amphipod diet and also indicated a significant contribution of benthic diatoms. The isotope results were further supported by fatty acid (FA) analysis, which showed high similarities in FA composition (64% spring–summer, 58% fall–winter) between G. antarctica and the red algal species. G. antarctica δ13C showed a small shift seasonally (−18.9 to −21.4‰), suggesting that the main diets do not change much year-round. However, the relatively high δ15N values as for primary consumers indicated additional dietary sources such as animal parts. Interestingly, G. antarctica and its potential food sources were significantly enriched with δ15N during the fall–winter season, presumably through a degradation process, suggesting that G. antarctica consumes a substantial portion of its diets in the form of detritus. Overall, the results revealed that G. antarctica relies primarily on food sources derived from benthic primary producers throughout much of the year. Thus, G. antarctica is unlikely very affected by seasonal Antarctic primary production, and this strategy seems to have allowed them to adapt to shallow Antarctic nearshore waters.

The paper presents the results of the analysis of diatoms from surface sediments (stones, sands) and macroflora (seagrass, macroalgae) collected at 16 sampling sites located along the inner coastal zone of Puck Bay (southern Baltic Sea) along the Hel Peninsula. The main diatom species of epilithon, epipsammon and epiphyton were characterized with respect to their autecological preferences (habitat, salinity, trophic status, saprobity). Three groups of diatoms were distinguished with respect to the type of substrate based on the results of benthic flora analysis: diatoms (i) of one type of substrate, (ii) of two types and (iii) those occurring on all types of substrates. Moreover, the distribution of benthic diatom communities indicates ecological differences in the study area. Marine and brackish-water species were observed in large numbers in the coastal zone of the Outer Puck Bay, whereas freshwater flora occurred with a higher frequency in the coastal zone of the Puck Lagoon. The content of polysaprobionts and of α-mesosaprobionts indicates that the region of the Hel Tip is highly eutrophicated and very polluted. The coast in the vicinity of Kuznica is less polluted, whereas the best environmental conditions are found in the Jurata–Jastarnia region, as evidenced by the frequency of diatoms that are β-mesosaprobionts. [ABSTRACT FROM AUTHOR]