Microalgal Communities Research Articles

Assessment of water samples with complex compositions using microalgal bioassay based on the community level physiological profiling (CLPP)

The ability to effectively characterize the response of microalgal communities to changes in water quality is limited. Earlier, a microalgal bioassay was developed based on community level physiological profiling (CLPP). The efficacy of this assay was evaluated using three wetland water samples, a surface water sample, and two wastewater samples (i.e. primary and secondary), all collected from southwestern Ontario, Canada. In addition, the assay was applied to untreated and activated carbon treated oil sand process water (OSPW). YT (Yeast Identification Test Panel) and Biolog plates were successfully utilized for defined microalgal community under both heterotrophic and mixotrophic growth conditions to characterize the changes in the defined microalgal community due to the changes in water type. It was found that, although the degrees of changes in the algal community varied, all tested water samples were distinguished under both growth regimes using principal component analysis (PCA). The variations in the algal community were caused by the differences of the water samples. The response of the assay due to changes in the algal community caused by different waters was found to be very sensitive and could be used to differentiate different water bodies. It further can be used to monitor temporal changes of water quality of the same water body.

Algal richness in BSCs in forests under different management intensity with some implications for P cycling

Abstract. Biological soil crusts (BSCs) are highly important communities in drylands and disturbed areas worldwide, where the higher vegetation is sparse, with a diverse microalgal community as the key component. They perform important ecological functions, such as stabilization of soil and nutrient enrichment. In temperate regions BSCs are also common, but generally less studied. Changes in land use and land use intensity strongly influence biodiversity per se and ecosystem processes, as can be seen particularly in densely populated regions like Europe. However, systematic studies on the effect of land use gradients, i.e., forest management intensity, on BSCs have been missing up to now. To close this knowledge gap and enhance the understanding of management effects on BSCs from pine and beech forests under different management regimes, key primary producers of these communities (eukaryotic microalgae and cyanobacteria) were studied. Phototrophic microorganisms were identified morphologically and categorized as either coccal taxa, which typically occur in high diversity, or filamentous taxa, which have the potential to initiate BSC formation. In total, 51 algal species were recorded, most of them from the phylum Chlorophyta, followed by Streptophyta and Stramenopiles, and only 1 cyanobacterial taxon. The most abundant crust-initiating filamentous algae were three species of Klebsormidium (Streptophyta), a ubiquitous genus regularly occurring in BSCs because of its broad ecophysiological tolerance. Increasing management intensity in the forests resulted in a higher number of algal species; especially the number of coccal taxa increased. Furthermore, the proportion of inorganic phosphorus showed tendencies towards a negative correlation with the number of algal species. Thus, management of forests has an impact on the diversity of phototrophic organisms in BSCs, which might in turn affect their biogeochemical P cycling.

Rapid analysis of photoautotroph microbial communities in soils by flow cytometric barcoding and fingerprinting

The investigations of soil microbiota and soil interactions are more and more significant from several points of view, including climate studies, environmental or human health. As a rapid cultivation-independent technique to study the alterations in soil photoautotroph microbial community structures flow cytometry was tested in soil-water suspensions prepared from the fresh soil of different crop cultures. Flow cytometric data were analyzed with barcoding and fingerprinting approaches to study the soil algal (<30 µm) community structure based on chlorophyll-a and phycoerythrin autofluorescence. Both statistical approaches revealed larger differences between crop cultures than within, indicating that both methods have potential in studying the dynamic changes of soil microalgal community structures.

Development of marine multi-algae cultures for biodiesel production

The concept of community ecology has become a central issue for sustainable biofuel production. However the development of appropriate multi-algae cultures for the industry remains challenging. Natural marine algae blooms collected from coastal areas of Cyprus were induced to form multi-algae cultures, and five (5) of those were developed and tested. Algae growth characteristics, biomass, and lipid productivity were assessed, and the dominant microalga was isolated in all cultures. Growth characteristics, lipid productivity, and FAME composition varied considerably among the different multi-algae cultures as well as their corresponding dominant species. Our results suggest that competitiveness and species complementarity could be crucial factors for biomass and lipid productivity. In material collected from the marina in Larnaca of Cyprus, the induced BL1_LCA bloom was the most promising culture, dominated by Nannochloropsis sp. and accompanied by cyanobacteria assemblages, exhibiting the highest biomass and lipid productivity compared to the other developed blooms. Biomass and lipid productivity of an axenic monoculture of Nannochloropsis sp. were 2.1 and 2.2 times lower compared to those measured in BL1_LCA. The growth parameters of BL1_LCA and its corresponding dominant species were further tested under culture media of different seawater and wastewater ratios. An increase of wastewater ratio in the culture media resulted in a significant reduction of lipid, FAME concentration as well as biomass productivity both in BL1_LCA and its dominant isolate. Overall, our findings suggest that the complex interactions within microalgae community might be crucial for biodiesel production; moreover, the general assumption that wastewater can be applied as an alternative nutrient source should be used cautiously since species-specific responses seem to take place.

Phytoplankton diversity in three lakes of South Ural, Russia

Kostryukova AM, Krupnova TG, Mashkova IV, Gavrilkina SV, Nikita O. Egorov NO. 2018. Phytoplankton diversity in three lakes of South Ural, Russia. Biodiversitas 19: 1459-1467. Preservation of water ecosystems in their natural state is of great significance. Phytoplankton is one of the biotic indicators of the lake trophic status and ecological state. This study deals with phytoplankton diversity of three lakes of South Ural, Russia. The studied lakes represented different trophic states: Lake Savelkul was oligo-mesotrophic, Lake Ilmenskoe was mesotrophic and Lake Argayash was eutrophic. The species composition of common phytoplankton was recorded in June-July months during 2015 and 2016. The Cyanophyta (blue-green algae) species were dominant in Lake Ilmenskoe(42-64%) and Lake Argayash(55-70%). The Bacillariophyta (diatom algae) species were dominant in the Lake Savelkul(40-66 %). The most common diversity indices namely the Shannon Index, Simpson Index and Margalef Index were determined and the data was also analysed using graphs. The graphs were constructed by the similarity calculating method on the basis of the Sorensen-Czekanowski coefficient. Diversity indices confirm the higher species richness of the microalgal community of Lake Ilmenskoe, classified as mesotrophic. It was shown that the lakes have sufficiently high biodiversity and high ecosystem resilience. Further, statistical analysis (CCA) revealed that orthophosphate-phosphorus, nitrite-nitrogen and pH were the most significant environmental factors influencing phytoplankton community of the lakes studied.

Microalgal Community in Fecal Pellets of the Freshwater Pearl Mussel Margaritifera laevis (Bivalvia: Margaritiferidae) in a Drainage Ditch Connected to the Hida River, Gifu Prefecture, Central Honshu, Japan

Microalgal Community in Fecal Pellets of the Freshwater Pearl Mussel Margaritifera laevis (Bivalvia: Margaritiferidae) in a Drainage Ditch Connected to the Hida River, Gifu Prefecture, Central Honshu, Japan

Biofilm monitoring as a tool to assess the efficiency of artificial reefs as substrates: Toward 3D printed reefs

Habitat destruction is one of the main causes of the decline of biodiversity and of fishery resources in the marine environment. An artificial reef (AR) could be a tool for protecting or restoring these habitats and their declining biodiversity, and also help to enhance sustainable fisheries. The goal is to design non-polluting structures that best mimic the complexity of natural habitats in order to improve their service to the community. To date, the assessment of reef performance has been mostly focused on fish assemblages and species of ecological and/or socio-economic interest, and has disregarded the biofilm communities that determine the first level of an AR’s trophic network. In this work, we used biofilm formation to compare the quality of substrates used as building parts for an AR, in order to optimize an eco-friendly material that will be used to design a new generation of ARs produced by giant 3D printers. The structure of the photosynthetic communities has been identified using pigment biomarkers and their production of exudates has been analysed. These polymeric substances were quantified in terms of total sugar and protein concentrations. They were further analysed in terms of amino acid content. We found no significant differences between the micro-algae communities developed on the different substrates. These photosynthetic communities were mainly composed of diatoms, prasinophytes, haptophytes, and dinoflagellates. However, we showed that the material for ARs is crucial for biofilm development, especially with regard to its secretions of sugar. The choice of an appropriate substrate for AR construction is thus of particular importance since biofilm secretions determine the organic substrate on which sessile macro-organisms will settle.

Hitchhiking in the East Australian Current: rafting as a dispersal mechanism for harmful epibenthic dinoflagellates

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 596:49-60 (2018) - DOI: https://doi.org/10.3354/meps12579 Hitchhiking in the East Australian Current: rafting as a dispersal mechanism for harmful epibenthic dinoflagellates Michaela E. Larsson1,*, Olivier F. Laczka1, Iain M. Suthers2, Penelope A. Ajani1, Martina A. Doblin1 1Climate Change Cluster, University of Technology Sydney, PO Box 123 Broadway, Sydney, NSW 2007, Australia 2Fisheries and Marine Environmental Research Facility, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia *Corresponding author: michaela.e.larsson@student.uts.edu.au ABSTRACT: Due to their small size, planktonic marine microorganisms have large dispersal capacity in the global ocean. However, it is not known how epibenthic microalgae disperse across long distances because they are generally associated with a substrate. In this study, we examined a long-term data series (~50 yr) of microalgal composition from a coastal station in southeast Australia for the presence of epibenthic dinoflagellates in the plankton. In addition, we collected drifting macrophytes (i.e. macroalgae and seagrass) and plastic debris from the East Australian Current, identified the associated microalgal assemblage, assessed their viability, and used phylogenetic analyses to taxonomically identify cryptic harmful epibenthic dinoflagellate species. We found no occurrences of epibenthic dinoflagellates from the genera Gambierdiscus, Fukuyoa, Ostreopsis, and Coolia at the long-term coastal station, concluding that entrainment of cells in ocean currents is an unlikely mechanism for transport of these taxa. The epibenthic microalgal communities associated with macrophyte rafts and plastic debris were primarily comprised of diatom taxa. However, intact cells of potentially harmful epibenthic dinoflagellates from the genera Coolia, Amphidinium, and Prorocentrum were also observed, and their viability was confirmed by division of isolated cells and establishment into clonal cultures. Phylogenetic analyses confirmed the presence of C. palmyrensis on a drifting Sargassum sp. raft, the first report of this potentially harmful epibenthic species in temperate Australian waters. This study shows that epibenthic dinoflagellates can attach to, and remain viable, when associated with macrophyte fragments that drift in the open ocean, therefore revealing rafting as a potential vector for dispersal of these organisms. KEY WORDS: Coolia · Drifting algae · East Australian Current · EAC · Epibenthic · Macrophyte · Rafting · Seagrass Full text in pdf format Supplementary material PreviousNextCite this article as: Larsson ME, Laczka OF, Suthers IM, Ajani PA, Doblin MA (2018) Hitchhiking in the East Australian Current: rafting as a dispersal mechanism for harmful epibenthic dinoflagellates. Mar Ecol Prog Ser 596:49-60. https://doi.org/10.3354/meps12579 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 596. Online publication date: May 28, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Functional divergence in nitrogen uptake rates explains diversity–productivity relationship in microalgal communities

AbstractThe relationship between biodiversity and productivity has emerged as a central theme in ecology. Mechanistic explanations for this relationship suggest that the role organisms play in the ecosystem (i.e., niches or functional traits) is a better predictor of ecosystem stability and productivity than taxonomic richness. Here, we tested the capacity of functional diversity in nitrogen uptake in experimental microalgal communities to predict the complementarity effect (CE) and selection effect (SE) of biodiversity on productivity. We grew five algal species as monocultures and as polycultures in pairwise combinations in homogeneous (ammonium, nitrate, or urea alone) and heterogeneous nitrogen (mixed nitrogen) environments to determine whether complementarity between species may be enhanced in heterogeneous environments. We show that the positive diversity effects on productivity in heterogeneous environments resulted from complementarity effects with no positive contribution by species‐specific SEs. Positive biodiversity effects in homogeneous environments, when present (nitrate and urea treatments but not ammonium), were driven both by CE and SE. Our results suggest that functional diversity increases species complementarity and productivity mainly in heterogeneous resource environments. These results provide evidence that the positive effect of functional diversity on community productivity depends on the diversity of resources present in the environment.

Environmental quality assessment using microalgae structures adjacent fish faming at Setoko Island, Batam City, Kepulaun Riau Province

Along with the increasing challenges that come with the demand for national and international fisheries’ products and the potential emergence of various environmental concerns, various efforts have been made to increase production capacity through extensification and intensification programs. This study aimed to assess the environmental quality and the level of disturbance in the floating net cage aquaculture area based on the microalgae community structure. The research was conducted from August to October 2017 at the water ecosystem used for aquaculture at Setoko Island, Batam City, Kepulauan Riau Province. Purposive random sampling was used by determining 3 sampling stations with three replicates. Data was analyzed using saprobic, Shanon-Wiener (H’) diversity, abundance and domination indices. The result showed that 13 genus microalgae (bawal fish fish farming), 9 genus (fish farming kakap) and 11 genus of microalgae (kerapu fish farming ) consisting of Chlorophyta, Chyanophyta Chrysophyta and Dinophyta were recorded. The value of H’ index at the farming area ranged from 0.73 to 1.5. Microalgae abundance was dominated by Phacus sp, Coscinodiscus sp, Climacosphenia sp and Spirogyra sp. Based on the saprobic index, the farm area has an index value of 1.92, thus it can be refferred to as the oligo/β-meso-saprobic phase, indicating light disturbance by organic enrichment.

Climate conditions, and changes, affect microalgae communities… should we worry?

Microalgae play a pivotal role in the regulation of Earth's climate and its cycles, but are also affected by climate change, mainly by changes in temperature, light, ocean acidification, water stratification, and precipitation-induced nutrient inputs. The changes and impacts on microalgae communities are difficult to study, predict, and manage, but there is no doubt that there will be changes. These changes will have impacts beyond microalgae communities, and many of them will be negative. Some actions are currently ongoing for the mitigation of some of the negative impacts, such as harmful algal blooms and water quality, but global efforts for reducing CO2 emissions, temperature rises, and ocean acidification are paramount for reducing the impact of climate change on microalgae communities, and eventually, on human well-being. Integr Environ Assess Manag 2018;14:181-184. © 2018 SETAC.

Microalgal community structure and primary production in Arctic and Antarctic sea ice: A synthesis

Sea ice is one the largest biomes on earth, yet it is poorly described by biogeochemical and climate models. In this paper, published and unpublished data on sympagic (ice-associated) algal biodiversity and productivity have been compiled from more than 300 sea-ice cores and organized into a systematic framework. Significant patterns in microalgal community structure emerged from this framework. Autotrophic flagellates characterize surface communities, interior communities consist of mixed microalgal populations and pennate diatoms dominate bottom communities. There is overlap between landfast and pack-ice communities, which supports the hypothesis that sympagic microalgae originate from the pelagic environment. Distribution in the Arctic is sometimes quite different compared to the Antarctic. This difference may be related to the time of sampling or lack of dedicated studies. Seasonality has a significant impact on species distribution, with a potentially greater role for flagellates and centric diatoms in early spring. The role of sea-ice algae in seeding pelagic blooms remains uncertain. Photosynthesis in sea ice is mainly controlled by environmental factors on a small scale and therefore cannot be linked to specific ice types. Overall, sea-ice communities show a high capacity for photoacclimation but low maximum productivity compared to pelagic phytoplankton. Low carbon assimilation rates probably result from adaptation to extreme conditions of reduced light and temperature in winter. We hypothesize that in the near future, bottom communities will develop earlier in the season and develop more biomass over a shorter period of time as light penetration increases due to the thinning of sea ice. The Arctic is already witnessing changes. The shift forward in time of the algal bloom can result in a mismatch in trophic relations, but the biogeochemical consequences are still hard to predict. With this paper we provide a number of parameters required to improve the reliability of sea-ice biogeochemical models.

Characterization of microflora composition and antimicrobial activity of algal extracts from italian thermal muds

Aim: Fine granular clay, the so-called “peloids,” allowed to ripen for several months in contact with mineral thermal water and the organic substances derived from metabolic activities, represents the basis of thermal mud therapy. A complex microalgal community (Cyanophyceae, Chlorophyceae and Bacillariophyceae) is responsible for the therapeutic effects of thermal muds. Biological components of peloids produce bioactives, possessing anti-inflammatory, antirheumatic and antioxidant properties; for this reason, such matrix is widely used in thermal spas. The research reports results of a preliminary study aimed to characterize the microflora biodiversity of mature and nonmature thermal mud. Algal components were further extracted in order to test the antimicrobial activity of produced bioactive compounds. Materials and Methods: Microscopic, microbiological and molecular techniques were employed (DNA extraction, polymerase chain reaction and sequencing). For antimicrobial activity of algal extracts, Kirby–Bauer disck method was employed. Results: Results show a significant microfloral diversity in samples and a great number of taxa belonging to widely diffused genera such as Leptolyngbya sp., Nostoc sp., Scenedesmus sp., Navicula sp., and Amphora sp. Microbial communities indicate an absolute prevalence of a nonpathogenic flora, mostly composed of Bacillaceae. Conclusion: The association between the microbial and algal composition and the different maturation stages of thermal clay could represent an essential tool to identify markers of proper ripening. This ensures the best product quality and its beneficial properties. The extension of the study, characterizing the components of mud at different ripening times, consents the standardization of ripening process. Antimicrobial activity assay represents a preliminary step for subsequent analysis for the isolation of single component, employing analytical chemistry techniques, characterizing and identifying bioactive compounds of interest.

Микроводоросли эпизоона культивируемого моллюска Мytilus galloprovincialis Lam. 1819, фитопланктон и гидролого-гидрохимические характеристики акватории мидийно-устричной фермы (Севастополь, Чёрное море)

В местах культивирования моллюсков накапливается большая биомасса органических веществ и метаболитов, поэтому биомониторинг микроводорослей (далее ― МВ) как показателей качества среды в районе марихозяйств является актуальной задачей. Образцы мидий, собранные с коллекторов мидийно-устричной фермы на глубине 6 м в период с февраля 2015 г. по март 2016 г., использовали для изучения МВ, входящих в состав эпизоона моллюсков. Одновременно отбирали пробы воды на горизонтах 0 и 6 м для определения структурных показателей фитопланктона и гидрохимических параметров среды. В воде устанавливали содержание растворённого кислорода, биохимическое потребление кислорода на пятые сутки (БПК5), перманганатную окисляемость в щелочной среде, концентрацию кремния, неорганических и органических форм азота и фосфора согласно общепринятым методам. В эпизооне раковин мидии обнаружено 108 видов и внутривидовых таксонов МВ из 4 отделов: Сyanoprokaryota — 3 вида, Dinophyta и Haptophyta — по 6, Bacillariophyta — 93. Максимальные значения обилия видов (26) и численности МВ эпизоона отмечены в феврале (74,78·103 кл.·см-2, t = 9,7 °С) и апреле 2015 г. (62,0·103 кл.·см-2, t = 10,3 °С), а также в январе 2016 г. (65,1·103 кл.·см-2, t = 9,5 °С), биомассы — в августе (0,272 мг·см-2, t = 25,5 °С). Основной вклад в общую численность МВ вносили диатомовые водоросли Tabularia fasciculata (C. Agardh) D. M. Williams &amp; Round 1986 и Navicula ramosissima (C. Agardh) Cleve 1895, а в биомассу — цианобактерии. В фитопланктоне на горизонтах 0 и 6 м обнаружено 135 видов и внутривидовых таксонов МВ, относящихся к 8 отделам водорослей: Cyanoprokaryota — 2, Bacillariophyta — 47, Dinophyta — 57, Haptophyta — 17, Chlorophyta — 5, Euglenophyta — 2, Cryptophyta — 3 и Chrysophyta — 2. Наибольшее обилие видов диатомовых представлено родом Chaetoceros (18). По численности и биомассе преобладали динофлагеллята Prorocentrum micans Ehrenb. 1833 и гаптофитовая Emiliania huxleyi (Lohmann) W. W. Hay &amp; H. P. Mohler 1967. Максимальная численность (3700·106 кл.·м-3) и биомасса (7560 мг·м-3) фитопланктона отмечены весной и осенью. Всего в фитопланктоне и эпизооне раковин мидии обнаружено 213 таксонов МВ, из них 30 являются общими. Обнаружено 26 потенциально токсичных видов и 24 вида-биоиндикатора, из них 16 являются бетамезосапробионтами — индикаторами умеренного загрязнения вод. Термохалинные характеристики вод в районе марихозяйства не выходят за пределы многолетних наблюдений. На всех горизонтах содержание кислорода находится на уровне 93–125 % насыщения. Окисляемость воды по рыбохозяйственным нормативам не превышает предельно допустимые концентрации. Биогенные вещества имеют высокий уровень концентрации с широким диапазоном колебаний, что свидетельствует об антропогенном воздействии на акваторию. По соотношению концентраций минеральных форм азота к фосфору и кремния к фосфору отмечено лимитирование развития сообщества МВ азотом и кремнием с июля по декабрь. Выявлены сильные корреляционные связи между численностью МВ эпизоона мидии и температурой воды, между численностью МВ эпизоона мидии и содержанием растворённого кислорода, а также между биомассой и неорганическим фосфором, средние ― с минеральным фосфором и органическим азотом. Для фитопланктона установлены средние корреляционные связи между численностью и гидролого-гидрохимическими показателями: в поверхностном слое воды — с нитратами, в придонном ― с температурой, кислородом и органическим азотом. Биомасса фитопланктона имеет среднюю корреляционную связь с концентрацией кремния в воде. Гидролого-гидрохимическая структура морских вод оказывает влияние на видовой состав и количественные характеристики МВ планктона и бентоса, особенно в местах культивирования моллюсков.

Seasonal biodiversity and ecological studies on the epiphytic microalgae communities in polluted and unpolluted aquatic ecosystem at Assiut, Egypt

AbstractA qualitative and quantitative study on epiphytic microalgae was carried out seasonally from November 2015 to August 2016 to follow up their community structures on aquatic macrophytes related to some physico-chemical properties of two polluted and unpolluted water bodies at Assiut, Egypt. A total of 169 species related to 64 genera of epiphytic microalgae were recorded. The most dominant algal group was Bacillariophyceae (43.2%), followed by Chlorophyceae (34.91%), Cyanophyceae (20.71%) and Euglenophyceae (1.18%). The total number of epiphytic algae fluctuated between 11.1 × 104ind.g-1plant dry wt. on Phragmites australis in summer at Nazlet Abdellah (polluted site) and 10.02 × 107ind.g-1plant dry wt. on Myriophyllum spicatum in winter at El-Wasta (unpolluted site). Some epiphytic microalgae were dominant as Pseudanabaena limnetica, Calothrix braunii, Scenedesmus acutus, and Ulnaria ulna. Others were specific on certain macrophytes as Aphanocapsa thermalis and Ulothrix sp., which grow on Phragmites australis, while Synechocystis minuscula attached itself on Myriophyllum spicatum. Analysis of PERMANOVA showed that the most important factors that induced the variation in epiphytic microalgae were the temporal variation and host plant. Water temperature, pH, nitrate, chloride, phosphate and total dissolved salts were the highest abiotic factors correlated with the variation in composition of epiphytic microalgae.

Increasing tetracycline concentrations on the performance and communities of mixed microalgae-bacteria photo-bioreactors

This study investigated the impact of varying concentrations of tetracycline on the performance of mixed microalgae-bacteria photo-bioreactors. Photo-bioreactors were assessed for their ability to remove carbon dioxide (CO2) from the biogas of anaerobic membrane bioreactor (anMBR), and nutrients from the anaerobic effluent. The varying concentrations of tetracycline had no impact on the removal of CO2 from biogas. 29% v/v of CO2 was completely removed to generate >20% v/v of oxygen (O2) in all reactors. Removal of nutrients and biomass was not affected at low concentrations of tetracycline (≤150μg/L), but 20mg/L of tetracycline lowered the biomass generation and removal efficiencies of phosphate. Conversely, high chlorophyll a and b content was observed at 20mg/L of tetracycline. High tetracycline level had no impact on the diversity of 18S rRNA gene-based microalgal communities but adversely affected the 16S rRNA gene-based microbial communities. Specifically, both Proteobacteria and Bacteroidetes phyla decreased in relative abundance but not phylum Chloroplast. Additionally, both nitrogen-fixing (e.g. Flavobacterium, unclassified Burkholderiales and unclassified Rhizobiaceae) and denitrifying groups (e.g. Hydrogenophaga spp.) were significantly reduced in relative abundance at high tetracycline concentration. Phosphate-accumulating microorganisms, Acinetobacter spp. and Pseudomonas spp. were similarly reduced upon exposure to high tetracycline concentration. Unclassified Comamonadaceae, however, increased in relative abundance, which correlated with an increase in the abundance of tetracycline resistance genes associated with efflux pump mechanism. Overall, the findings demonstrate that antibiotic concentrations in municipal wastewaters will not significantly affect the removal of nutrients by the mixed microalgae-bacteria photo-bioreactors. However, utilizing such photo-bioreactors as a polishing step for anMBRs that treat wastewaters with high tetracycline concentration may not be effective as evidenced from the lower nutrient removal and occurrence of antibiotic resistance genes.

Highly structured prokaryote communities exist within the skeleton of coral colonies.

Physiological performance, disease and bleaching prevalence are often patchy within individual coral colonies. These responses are largely influenced by coral-associated microbes, but how the coral microbiome changes over small spatial scales has never been quantified before. We performed a high-resolution quantification of the spatial scale of microbial species turnover (β-diversity) within skeletons of boulder-forming Porites corals. We found very strong prokaryotic species turnover across spatial scales ranging from 4 mm to 2 m within individual colonies, possibly resulting from dispersal limitation and microbial interactions. The microalgal community was more homogeneously distributed, which is likely due to these photosymbionts actively boring through limestone. Our findings highlight unprecedented levels of intra-colony heterogeneity in the skeletal microbiome, which has implications for the experimental design of coral microbiome studies and for our understanding of coral resilience.

Abiotic characteristics and microalgal dynamics in South Africa's largest estuarine lake during a wet to dry transitional phase

The summer of 2012/2013 signified the end of the dry phase in the St Lucia estuarine system that lasted for over a decade. The increased rainfall coupled with the partial re-connection of the Mfolozi River to the estuarine system shifted St Lucia to a new limnetic state. With the increased availability of habitat due to the higher water level, it was expected that microalgal biomass and abundance would rapidly increase through recruitment from refuge areas i.e. South Lake and new introductions. Microalgal and physico-chemical data were collected at three sites within the Mfolozi/Msunduzi River and at 23 sites within the St Lucia estuarine system between June 2014 and February 2015. Results from this study indicated low biomass for both phytoplankton (<5 μg l−1) and microphytobenthos (<60 mg m−2) because of local and external drivers. These included limited nutrient and light availability, variable water residence times, biomass dilution and heterogeneity of the sediment. The high spatio-temporal variability limits the effectiveness of using the microalgal communities to detect change in the estuarine lake. In addition, significant intrasystem differences were observed between the three main lake basins and Narrows, due to the influence of the freshwater input from the Mfolozi River. This study provides insight into the spatio-temporal variability of physico-chemical conditions and microalgal communities during the 2014–2015 limnetic state.

Microalgae community shifts during the biogas upgrading in an alkaline open photobioreactor.

To achieve the functional specialization of a microalgae community through operational tuning of an open photobioreactor used for biogas upgrading under alkaline conditions. An open photobioreactor was inoculated with an indigenous microalgae sample from the Texcoco Soda Lake. A microalgae community was adapted to fix CO2 from synthetic biogas through different culture conditions reaching a maximum of 220mg CO2 l-1 per day. Picochlorum sp. and Scenedesmus sp. were identified as the prominent microalgae genera by molecular fingerprinting (partial sequencing of 16S rRNA and 18S rRNA genes) but only the first was detected by microscopy screening. Changes in the microalgae community profile were monitored by a range-weighted richness index, reaching the lowest value when biogas was upgraded. A robust microalgae community in the open photobioreactor was obtained after different culture conditions. The specialization of microalgae community for CO2 fixation under H2 S presence was driven by biogas upgrading conditions. The alkaline conditions enhance the CO2 absorption from biogas and could optimize specialized microalgae communities in the open photobioreactor. Denaturing gradient gel electrophoresis fingerprinting and richness index comparison are useful methods for the evaluation of microalgae community shifts and photosynthetic activity performance, particularly in systems intended for CO2 removal from biogas where the CO2 assimilation potential can be related to the microbial richness.

Epibiotic communities (microalgae and meiofauna) on the pneumatophores of Avicennia officinalis (L.)

In a mangrove environment, several groups of organisms are symbiotically associated with pneumatophores (aerial roots). But whether these organisms are exclusively found in this habitat (uniqueness) or accidentally settled here from water or sedimentary habitat, is not clearly understood. This hampers our understanding of their functional ecology. Hence the present study aimed to characterise the epibiotic microalga and meiofauna from the pneumatophores of mangrove Avicennia officinalis. To determine the habitat influence, these communities were also compared with those found in water and sedimentary habitat. Four estuarine mangrove sites represented by brackish water (salinity varying from 5 to 12) and located at different spatial scales (5–50 km distance) were chosen to determine whether these communities are consistent or vary with sites. Overall, the microalgal community was found to vary both among the habitats as well as sites. In the pneumatophore habitat, several tychoplanktons such as Coscinodiscus, Thalassionema, Cyclotella, Fragilariopsis, and Biddulphia were observed instead of benthic ones. These diatoms are planktonic genera and might have settled on pneumatophores from the water column. The observed variability in the microalgal composition among the sites is possibly due to predatory interactions or the dominance of particular species of macroalga that govern the diatom community. On the other hand, among the meiofaunal community, diptera, halacarida, tanaidacea, and foraminifera were mainly found in the pneumatophore habitat than in the sediment. Because pneumatophores either provide refugee to meiofauna against predators or are saturated with oxygen that meiofauna can utilize for respiration. Pneumatophores were also found to harbour several rare (abundance <1%) epibionts, the ecological importance of which is discussed in this paper.