Aulacoseira Islandica Research Articles

Spring phytoplankton of Lake Onego as a trophic resource for deep-water benthos

In the past few years the relict deep-water crustacean Monoporeia affinis (Lindström, 1855) has become less abundant in Lake Onego, Europe’s second largest lake. Further studies are needed, therefore, to better understand the formation of spring phytoplankton as food for deep-water benthos. The aim of the present project was to study the temperature-dependent vertical distribution of phytoplankton in Petrozavodsk Bay of Lake Onego in the spring season. In May 2019, the total abundance, biomass and species composition of phytoplankton were assessed. The transparency and temperature of Onego water were also measured. The median values of phytoplankton’s total abundance and biomass at various growth stages were 1.15–1.67 M cells/l and 1.96–3.12 mg/l, respectively. The above indices were consistent with the long-term maximum growth of phytoplankton in Petrozavodsk Bay in spring and were not markedly different (p<0.05) from those for spring phytoplankton in 1989-2015, indicating the permanent trophic status of Petrozavodsk Bay in the spring season over the past 30 years. A significant difference (p>0.05) in the vertical distribution of phytoplankton, dominated by Aulacoseira islandica (O. Müll.) Sim diatoms, was found between the stations in May 2019. The reproduction of the relict deep-water crustacean M. affinis, taking place simultaneously with the intensive vegetation and the settling of its major food resource, A. islandica, on the bottom, suggests the formation of favourable feeding conditions for deep-water benthos in Petrozavodsk Bay of Lake Onego.

Arctic warming drives striking twenty-first century ecosystem shifts in Great Slave Lake (Subarctic Canada), North America's deepest lake.

Great Slave Lake (GSL), one of the world's largest and deepest lakes, has undergone an aquatic ecosystem transformation in response to twenty-first-century accelerated Arctic warming that is unparalleled in at least the past two centuries. Algal remains from four high-resolution palaeolimnological records retrieved from the West Basin provide baseline limnological data that we compared with historical phycological surveys undertaken on GSL between the 1940s and 1990s. We document the rapid restructuring of algal community composition ca 2000 CE that is consistent with recent increases in regional air temperature and declines in ice cover and wind speed, that collectively altered habitats for aquatic biota. This new limnological regime initiated the first observation of scaled chrysophytes and favoured the rapid proliferation of small planktonic cyclotelloid diatoms which replaced the long-established dominance of large filamentous Aulacoseira islandica in West Basin sedimentary records. Such abrupt transformations in the primary producers of this socioecologically valuable 'northern Great Lake' may have widespread implications for the entire food web with unknown consequences for aquatic ecosystem functioning and fisheries, which First Nations, Métis and other northern communities depend upon, pointing to the need for new studies.

Diatom Assemblages in the Sediment Traps in Lake Onega

The paper presents the first study of the composition and structure of the diatom assemblages from sediment traps installed in different parts of Lake Onega. 171 species and intraspecific diatom taxa were observed belonging to 59 genera. The predominance of planktonic diatoms is favored by large depths of the lake and a small area of the littoral zone. Aulacoseira islandica and A. subarctica, the most abundant species in spring phytoplankton in Lake Onega dominate in the sediment-traps diatom assemblages. In the sites subject to anthropogenic eutrophication, Aulacoseira ambigua is numerous as well. In a number of sites Lindavia radiosa and Pantocsekiella tripartita are among the subdominating species, while P. schumannii, Stephanodiscus neoastraea and Stephanodiscus sp. are less common. Higher proportions of periphytic Tabellaria fenestrata were recorded in the sites with the largest areas colonized by macrophytes. In all sampling sites, neutrophilous oligo-mesotrophic and oligo-hypereutrophic taxa prevail in the diatom assemblages. The predominance of two or three species in the diatom assemblage results in low values of the floristic diversity index. More diverse diatom assemblages were found in rathers isolated bays. Concentrations of diatom valves and chrysophyte cysts in sediment traps material were also calculated.

Long-term dynamics of dominant diatom species abundance of spring phytoplankton in three basins of the pelagic zone of Lake Baikal in 1964-1984 and 2007-2016

Abstract. Analysis of long-term observations of dominant diatom species of spring phytoplankton of Lake Baikal Synedra acus subsp. radians, Aulacoseira baicalensis, Aulacoseira islandica, Stephanodiscus meyeri and Nitzschia graciliformis was demonstrated. It is shown, how the abundance of these species varied in Southern, Central and Northern Baikal in 2007-2016 compared to other observation periods in 1964-1968 and 1969-1984. It is found out that, species ratio changed in 2007-2016. The abundance of S. acus subsp. radians increased in Southern and Central Baikal, while for other species - A. baicalensis, A. islandica, N. graciliformis and S. meyeri, it significantly decreased. In Northern Baikal, the ratio of species in 2007-2016 was comparable to 1969-1984. Despite the change in the ratio of species over the past decade, the contribution of these five dominant species to the total abundance of spring phytoplankton of Lake Baikal has comparable values in all studied periods.

Changes in valve morphogenesis of Aulacoseira islandica by γ-tubulin inhibitor gatastatin

Diatom valve morphogenesis occurs under the control of microtubules. It is known that γ-tubulin is an important component of the microtubule center, which controls the polymerization of microtubules and provides their nucleation in the cell. In this work, using Aulacoseira islandica as an example, α-tubulin was visualized during valve formation after cytokinesis and during interphase. It was shown that inhibition of γ-tubulin in A. islandica cells causes the formation of valves with an abnormal structure and an increased number of death cells in culture at gatastatin concentrations of 3 and 10 μM, with a threefold decrease in the number of dividing cells. The small number of valves formed under the influence of gatastatin suggests that γ-tubulin activity is required both for the nucleation of microtubules in the cell and for the onset of valve morphogenesis. The results obtained clarify the role of the microtubule center in the morphogenesis of diatom valves.

Characteristic of phytoplankton and water quality assessment in the Amur River at Khabarovsk in the ice-free period of 2018–2019

Species composition and taxonomic structure of phytoplankton communities in the main channel of the Amur at Khabarovsk (Russia) were monitored from spring to autumn of 2018–2019. In total, 187 species, varieties and forms of algae and cyanobacteria were found belonged to 8 phyla (Cyanobacteria, Bacillariophyta, Charophyta, Chlorophyta, Heterokontophyta, Rhodophyta, Euglenozoa, and Miozoa) and 75 genera. Diatoms formed the basis of the algal flora (94.7 % of the total species number). Mass vegetations of the diatoms and charophytes were observed with dominance of Asterionella formosa, Aulacoseira islandica, A. ambigua, A. granulata var. granulata, A. granulata var. angustissima, Ulnaria ulna, Diatoma tenue, Nitzschia acicularis, Stephanodiscus sp., Tabellaria flocculosa, Hannaea arcus var. rectus, Melosira varians, Fragilaria capucina var. vaucheriae, F. crotonensis, and Mougeotia sp. ster. Total number and biomass of plankton algae and cyanobacteria varied in the ranges of 1.74–5724.39 million cells/L and 2.5–2648.5 mg/L in spring-summer and 0.07–0.62 million cells/L and 0.2–1.4 mg/L in autumn. The water quality was evaluated by Pantle-Buck method modified by Sládeček as the betamezosaprobic III class (slightly polluted).

Anomalies in the valve morphogenesis of the centric diatom alga Aulacoseira islandica caused by microtubule inhibitors.

ABSTRACTOf all unicellular organisms possessing a cell wall, diatoms are the most adept at micro- and nanoscale embellishment of their frustules. Elements of their cell walls are formed inside the cell under cytoskeletal control. In this work, we used laser scanning microscopy and electron microscopy to describe the major stages of cell wall formation in the centric diatom algae Aulacoseira islandica and to study the effect of various microtubule inhibitors on the morphogenesis of frustule elements. Our results show that colchicine inhibits karyokinesis and cytokinesis in A. islandica colonies. In contrast, valve morphogenesis is changed, rather than inhibited altogether. In normal cells, this process starts simultaneously in both daughter cells, beginning with the formation of two adjacent discs that later become valve faces and connecting spines. Under colchicine treatment, however, the cleavage furrow is blocked and a single lateral valve forms on the side of the cylindrical frustule. As a result, a single hollow pipe forms instead of two separate drinking glass-shaped frustules; such pipes can form up to 35% of all forming frustules. Colchicine inhibits the formation of connecting spines, whereas paclitaxel causes spines to form a complex, branching shape. At the same time, inhibitors do not affect the formation of areolae (openings) in the frustule. We discuss the possibility that various processes of the diatom frustule morphogenesis are controlled by two different mechanisms: membrane-related micromorphogenesis and cytoskeleton-mediated macromorphogenesis.

Fatty acid trophic markers in Lake Baikal phytoplankton: A comparison of endemic and cosmopolitan diatom-dominated phytoplankton assemblages

Recent changes in phytoplankton community in Lake Baikal suggest the reduction in bloom of endemic diatoms takes place. How much these changes affect primary production remains unknown. Fatty acids are suitable biomarkers of the phytoplankton food quality. In our work we present the data of the qualitative and quantitative analysis of fatty acids (FA) in net samples of Lake Baikal phytoplankton. According to microscopic analysis of the samples the main phytoplankton groups were diatoms (Bacillarophyceae), golden algae (Chrysophyceae), green algae (Chlorophyceae), and Dinophytes (Dinophyceae). Visual quantification of cells showed that Synedra acus subsp. radians, Aulacoseira islandica, Synedra ulna, and Aulacoseira baicalensis were dominant diatom species. The first three species are cosmopolitan and the last one is endemic. Gas chromatography–mass spectrometry analysis revealed that the fatty acid biomarker values reflect changes in phytoplankton community structure in Lake Baikal. The trophic markers of the phytoplankton dominated by endemic A. baicalensis were higher compared to the phytoplankton dominated by cosmopolitan S. acus subsp. radians. The long-chain essential FA (LCEFA, %DW) and FA-based food quality index (FQI) for endemic assemblage were 1.85 and 0.75, while for the cosmopolitan assemblage −0.70 and 0.28, correspondingly. Our data suggest that reduction in bloom of endemic A. baicalensis may negatively affect the Lake Baikal ecosystem due to probable lower LCEFA production and, consequently, lower total productivity of the lake.

Winter–spring diatom production in Lake Erie is an important driver of summer hypoxia

Abstract Re-eutrophication and harmful algal blooms in Lake Erie have resulted in a renewed call for remedial measures such as reductions of phosphorus loads to the lake's western basin. The action of further nutrient reductions may also reduce the intensity of seasonal central basin hypolimnetic anoxia by reducing algal biomass. However, winter–spring blooms of diatoms have not been fully recognized as a source of algal biomass that might contribute significantly to summer hypoxia. We compared spring and summer phytoplankton abundance in central and western Lake Erie based on monitoring data to show that spring phytoplankton biovolume was 1.5- to 6-fold greater than summer biovolume and that most spring biovolume was composed of filamentous diatoms, primarily Aulacoseira islandica , that is likely supported by an increasing silica load from Lake Huron. The rise of silica export was attributed to the dreissenid mussel invasion and establishment that reduced diatom abundance in Lake Huron and thereby increased silica availability in the receiving water body of Lake Erie. The relationship between phosphorus and winter–spring diatom blooms was unclear, but diatoms probably contributed the majority of the algal biomass that accumulated annually in the hypolimnion of the central basin of Lake Erie. Remedial measures aimed at reducing hypoxia must consider the winter–spring phytoplankton bloom in Lake Erie as an important and reoccurring feature of the lake that delivers a considerable quantity of algal biomass to the profundal zone of the lake.

The spring phytoplankton in the pelagic zone of Lake Baikal during 2007‒2011

An assessment is made of the current status of the phytoplankton in the pelagic zone of Lake Baikal for 2007‒2011, as the continuation of previous long-term research. We investigated the species composition, population, biomass and spatial distribution of the phytoplankton in the pelagic zone of Baikal. Its quantitative indicators for 2007‒2011 have been compared with data of long-term investigations (1964‒1990). It is shown that the species composition of the phytoplankton remained stable at different periods. The values of population and biomass for 2007‒2011 fitted in the range of long-term fluctuations (1964‒1990), with the species assemblage characteristic for that period. As in the case with previous research, the main contribution to the biomass of the spring phytoplankton in the lake was made by the diatoms Aulacoseira baicalensis, Synedra acus subsp. radians, Aulacoseira islandica, and Stephanodiscus meyeri. Their maximum and minimum concentrations were observed in the southern and middle lake depressions, and in Northern Baikal, respectively. The study revealed a correlation of phytoplankton biomass with silicon concentration; no correlation with nitrates, phosphates and temperature was ascertained.

Sub-Ice Microalgal and Bacterial Communities in Freshwater Lake Baikal, Russia.

The sub-ice environment of Lake Baikal represents a special ecotope where strongly increasing microbial biomass causes an "ice-bloom" contributing therefore to the ecosystem functioning and global element turnover under low temperature in the world's largest freshwater lake. In this work, we analyzed bacterial and microalgal communities and their succession in the sub-ice environment in March-April 2010-2012. It was found out that two dinoflagellate species (Gymnodinium baicalense var. minor and Peridinium baicalense Kisselew et Zwetkow) and four diatom species (Aulacoseira islandica, A. baicalensis, Synedra acus subsp. radians, and Synedra ulna) predominated in the microalgal communities. Interestingly, among all microalgae, the diatom A. islandica showed the highest number of physically attached bacterial cells (up to 67 ± 16 bacteria per alga). Bacterial communities analyzed with pyrosequencing of 16S rRNA gene fragments were diverse and represented by 161 genera. Phyla Proteobacteria, Verrucomicrobia, Actinobacteria, Acidobacteria, Bacteroidetes, and Cyanobacteria represented a core community independently on microalgal composition, although the relative abundance of these bacterial phyla strongly varied across sampling sites and time points; unique OTUs from other groups were rare.

Sensitivity and responses of diatoms to climate warming in lakes heavily influenced by humans

Summary Diatom communities have been shown to respond strongly to current climate warming in remote lakes, while evidence remains equivocal for lakes under strong local human pressures. Temporal dynamics of planktonic diatoms in three subalpine lakes (Geneva, Annecy and Bourget) reconstructed from palaeolimnological approaches were used to assess the relative effects of phosphorus concentrations, fisheries management practices and climate warming in structuring communities over the last century. Changes in total phosphorous concentration (TP), air temperature and fish predation pressure could explain the temporal dynamics of most diatom species in the sediment records. TP was found to be not only the main driver of changes in community composition but also an important factor modulating diatom sensitivity and responses to climate warming. The diatom community of Lake Bourget showed the highest vulnerability and direct responses to climate warming, favouring spring species that can resist earlier stratification in mesotrophic lakes (such as Asterionella formosa, Aulacoseira islandica and Stephanodiscus parvus) and summer species that can make the best trade‐off between decreasing nutrient concentrations and increased water column stability (Diatoma tenuis, A. islandica). In Lake Geneva, climate warming also contributed to shaping diatom communities but through an indirect pathway; fisheries management practices and climate warming interacted to reinforce top‐down control, favouring large, colonial inedible species (Stephanodicus binderanus and A. formosa). For Lake Annecy, the most nutrient limited of the three lakes studied, no changes in diatom community structure were directly related to warmer air temperatures over the last 25 years. All three lakes have been subjected to the same climate variability. Yet the magnitude and responses of their diatom communities to climate warming were dissimilar and strongly modulated by differences in lake trophic status and fish management practices.

Aulacoseira calypsi sp. nov. (Coscinodiscophyceae) from an Amazonian lake, northern Brazil

SummaryThis paper describes a new diatom species, Aulacoseira calypsi Tremarin, Torgan & Ludwig, from specimens in plankton samples from Água Preta lake. This Amazonian lake is a shallow mesotrophic environment situated in northern Brazil. The species is characterized by long filaments united by spatulate linking spines, obovate to conic separation spines, a valve surface variably ornamented, straight striae on the mantle, a narrow ringleist, and one row of sessile rimoportulae near the ringleist. Aulacoseira calypsi's morphometric features are compared with the following similar species: Aulacoseira nygaardii (Camburn) Camburn & Charles, Aulacoseira lacustris (Grunow) Krammer, Aulacoseira coroniformis Pearce & Cremer, Aulacoseira occulta Siver & Hamilton, Aulacoseira lancea Siver & Hamilton, Aulacoseira gessneri (Hustedt) Simonsen, and Aulacoseira islandica (Müller) Simonsen. The species shares similarities as to frustule size, striation pattern, and narrowness of ringleist; but differs in the morphology of separation and linking spines, and the number and position of the rimoportulae.

Diatom diversity and ecological variables in the Arctic lakes of the Kostyanoi Nos Cape (Nenetsky Natural Reserve, Russian North)

We identified 185 diatom species in 87 samples collected from 17 Arctic lakes of the Kostyanoi Nos Cape in July 2003. Species richness varies from 9 to 97 per lake with Aulacoseira islandica (O.F. Müller) Simonsen, Fragilariamesolepta Rabenhorst, Psammothidium subatomoides (Hustedt) L. Bukhtiyarova and Round as dominant species. Bioindication attests to preponderance of temperate, moderately oxygenated, low-to-moderate organic-enriched alkaline, and circumneutral low saline water. Oligotrophic to mesotrophic state correlates with the type of sediments and low organic pollution (saprobity index 0.81–1.73 and Classes 2–3 of water quality). The diatom assemblages contain cosmopolitan species accompanied by the large group of 45 boreal species including 28 Arctic–alpine taxa. Canonical correspondence analysis shows conductivity and the type of sediments being the most important variables. Multivariate regression testifies to importance of depth and area of the lake. The community level analysis reveals four groups correlated with species richness, type of sediments, pH, and salinity. Potential species richness is estimated as 800 species square kilometer based on species–area relationships. Since the diatom assemblages of Arctic lakes are sensitive to climate warming and associated changes of salinity and trophic conditions, they are under high risk of extinction, the diversity losses being scarcely compensated by the rise of tolerant species.

Seasonal Si:C ratios in Lake Erie diatoms — Evidence of an active winter diatom community

Recent investigations of Lake Erie in the winter have demonstrated the occurrence of substantial phytoplankton communities largely consisting of the diatom Aulacoseira islandica (O. Müller) Simonsen. To assess the activity of this diatom community, multiple measures of production, both general and diatom-specific, were undertaken. We measured oxygen (O2) evolution as proxy for carbon (C)-fixation and 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl) methoxy)-phenyl)oxazole (PDMPO) incorporation as a measure of silica (Si) deposition. The latter demonstrated conclusively that diatoms were active during winter months and confirmed that diatoms are the primary drivers of winter productivity. The stoichiometric relationship between carbon and silica in the winter Lake Erie phytoplankton assemblage was further compared to the activity of the summer community. Although the winter phytoplankton community was observed to be active, it was less active than the summer community, with lower measured rates of O2 evolution and Si deposition. These findings provide a new and expanded understanding of the biological carbon production in Lake Erie.

Structure and spatial distribution of winter phytoplankton of the Curonian Lagoon (Baltic Sea)

The winter phytoplankton of the Russian part of the hyper-trophic Curonian Lagoon (Baltic Sea) was studied in 2010. Diatoms, cyanobacteria and cryptomonads prevailed in phytoplankton. Diatom Aulacoseira islandica was dominant and especially prevailing in the southern area of the lagoon, i. e. the area influenced by the Deyma River. Cyanobacteria Planktothrix agardhii was also a dominant species. The composition of the complex of dominant species and vertical distribution of phytoplankton differed compared to the results obtained 30 years ago in the same area. The study revealed the increase of the abundance of winter phytoplankton compared to the formerly recorded data.

Bentoso dumblių bendrijos skirtingos vandens kokybės Lietuvos upėse

Straipsnyje pateikti 2004–2006 m. duomenys apie bentoso dumblių bendrijas skirtingos vandens kokybės Lietuvos upėse. Skirtingos vandens kokybės upėse daugiausia dominuoja Cladophora glomerata–Vaucheria sessilis–Fontinalis antipyretica dumblių samanų bendrija. Skirtingos vandens kokybės upių būklę geriau rodo bendrijose vietomis gausiai besivystančios dumblių rūšys. Švarių vandens telkinių – Hildenbrandia rivularis, Audouinella chalybea ir A. hermanii; mažai užterštų – Vaucheria sessilis ir Fontinalis antipyretica; vidutiniškai užterštų Stigeoclonium nanum, S. tenue, Aulacoseira islandica ir Melosira varians. Skirtingos vandens kokybės ir atskirų upių išilginiame pjūvyje bentoso dumblių bendrijų struktūra kito. Tai galėjo lemti substrato heterogeniškumas, vandens tekėjimo greičio, upės gylio, šviesos intensyvumo bei pagrindinių biogenų koncentracijos pokyčiai.

Cool winters versus mild winters: effects on spring plankton in Lake Peipsi

The influence of two winter periods with a different duration of the ice cover on Lake Peipsi (Estonia) on plankton and nutrient content was analysed. The winters of 2005 and 2006 were cold with ice duration of 140 days, whereas the winters of 2007 and 2008 were mild with about 50 and 15 days of ice duration, respectively. Total phosphorus (TP) concentration was lower, while silicon content and the nitrogen-phosphorus ratio (TN : TP) were markedly higher in the springs after the short winters of 2007 and 2008. The high Si concentration and TN : TP ratio persisted throughout the growing season of those years. Unicellular centric diatoms showed a sharp increase in April 2008, while the large filiform diatom Aulacoseira islandica dominated in the cool winters and after ice break-up. The high spring peak of diatoms was followed by their low biomass in summer. In May 2008, total zooplankton biomass, cladoceran biomass, and rotifer biomass were two times and that of copepods three times as high as in the Mays after the long-lasting ice cover. In the Junes after the mild winters the biomasses of total zooplankton and both crustacean groups (Cladocera, Copepoda) were about two times as high as the corresponding indicators for the Junes after the cool winters. The biomass of rotifers, on the contrary, was two times lower in the Junes after the warm winters because the numerous cold stenotherms Polyarthra dolichoptera and Synchaeta verrucosa had totally disappeared from zooplankton. The influence of ice duration on phyto- plankton is most likely indirect, acting through nutrients, and on zooplankton direct, acting through water temperatures. The springs after warm winters related positively to zooplankters' mean weight, zooplankton-phytoplankton biomass ratio, and the timing of the clear water period.

PRESENCE OF ALGAE IN FRESHWATER ICE COVER OF FLUVIAL LAC SAINT-PIERRE (ST. LAWRENCE RIVER, CANADA)(1).

Winter ice cover is a fundamental feature of north temperate aquatic systems and is associated with the least productive months of the year. Here we describe a previously unknown freshwater habitat for algal and microbial communities in the ice cover of the freshwater St. Lawrence River, Quebec, Canada. Sampling performed during winter 2005 revealed the presence of viable algal cells, such as Aulacoseira islandica (O. Müll.) Simonsen (Bacillariophyceae), and microbial assemblage growing in the ice and at the ice-water interface. Vertical channels (1-5 mm wide) containing algae were also observed. Concentrations of chl a ranged between 0.5 and 169 μg · L(-1) of melted ice, with maximal concentrations found in the lower part of the ice cores. These algae have the potential to survive when ice breakup occurs and reproduce rapidly in spring/summer conditions. Freshwater ice algae can thus contribute to in situ primary production, biodiversity, and annual carbon budget in various habitats of riverine communities.

Sporulating diatomic alga Aulacoseira islandica (O. Müller) Simonsen from Lake Khanka and the Amur River (Far East, Russia)

Sporulating diatomic alga Aulacoseira islandica (O. Müller) Simonsen from Lake Khanka and the Amur River (Far East, Russia)