Ikaite Columns Research Articles

Metagenomic exploration of cold-active enzymes for detergent applications: Characterization of a novel, cold-active and alkali-stable GH8 endoglucanase from ikaite columns in SW Greenland.

Microbial communities from extreme environments are largely understudied, but are essential as producers of metabolites, including enzymes, for industrial processes. As cultivation of most microorganisms remains a challenge, culture-independent approaches for enzyme discovery in the form of metagenomics to analyse the genetic potential of a community are rapidly becoming the way forward. This study focused on analysing a metagenome from the cold and alkaline ikaite columns in Greenland, identifying 282 open reading frames (ORFs) that encoded putative carbohydrate-modifying enzymes with potential applications in, for example detergents and other processes where activity at low temperature and high pH is desired. Seventeen selected ORFs, representing eight enzyme families were synthesized and expressed in two host organisms, Escherichia coli and Aliivibrio wodanis. Aliivibrio wodanis demonstrated expression of a more diverse range of enzyme classes compared to E. coli, emphasizing the importance of alternative expression systems for enzymes from extremophilic microorganisms. To demonstrate the validity of the screening strategy, we chose a recombinantly expressed cellulolytic enzyme from the metagenome for further characterization. The enzyme, Cel240, exhibited close to 40% of its relative activity at low temperatures (4°C) and demonstrated endoglucanase characteristics, with a preference for cellulose substrates. Despite low sequence similarity with known enzymes, computational analysis and structural modelling confirmed its cellulase-family affiliation. Cel240 displayed activity at low temperatures and good stability at 25°C, activity at alkaline pH and increased activity in the presence of CaCl2, making it a promising candidate for detergent and washing industry applications.

Investigating eukaryotic and prokaryotic diversity and functional potential in the cold and alkaline ikaite columns in Greenland.

The ikaite columns in the Ikka Fjord, SW Greenland, represent a permanently cold and alkaline environment known to contain a rich bacterial diversity. 16S and 18S rRNA gene amplicon and metagenomic sequencing was used to investigate the microbial diversity in the columns and for the first time, the eukaryotic and archaeal diversity in ikaite columns were analyzed. The results showed a rich prokaryotic diversity that varied across columns as well as within each column. Seven different archaeal phyla were documented in multiple locations inside the columns. The columns also contained a rich eukaryotic diversity with 27 phyla representing microalgae, protists, fungi, and small animals. Based on metagenomic sequencing, 25 high-quality MAGs were assembled and analyzed for the presence of genes involved in cycling of nitrogen, sulfur, and phosphorous as well as genes encoding carbohydrate-active enzymes (CAZymes), showing a potentially very bioactive microbial community.

Complete genome sequence of "Bacillaceae sp. strain IKA-2": a cold-active, amylase-producing bacterium from ikaite columns in SW Greenland.

Bacillaceae sp. strain IKA-2 is a bacterium isolated from the permanently cold and alkaline ikaite columns in the Ikka Fjord in SW Greenland (61°12'05″N; 48°00'50″W). The bacterium grows well at 10°C in a substrate buffered to pH 10. It has a genome size of 4,424,890 bp and a guanine-cytosine (GC) content of 36.2%. The genome harbors genes involved in hydrolysis of long carbohydrates and in protection against cold shock.

Secondary alteration of the Grønnedal-Ika igneous complex and the genesis of ikaite, CaCO3·6H2O, SW Greenland

The mineral ikaite (CaCO3·6H2O) precipitates from a mixture of spring water and seawater as tufa columns which grow at a rate of up to 50 cm per year reaching heights of up to 18 m in Ikka Fjord, SW Greenland. In the fjord, column formation occurs only at the base of a nepheline syenite‑carbonatite complex that flanks the fjord and an association has therefore been proposed. The spring water that seeps up at the bottom of the fjord is oversaturated in Na+ and HCO3−. In this study, we show that these ions were acquired by alteration reactions in the syenite‑carbonatite complex: Na+ is released during replacement of nepheline by illite and analcime in nepheline-syenite rocks and HCO3– is released by oxidation of siderite to goethite in carbonatite rocks. The chemically charged groundwater mixes with seawater and gives rise to the formation of the tufa columns. We performed a mass balance to show that the mass of the carbonatite in the complex is more than sufficient to provide the CO2 needed to produce the observed mass of tufa columns. We estimated a time frame of ~600 years to produce the necessary CO2 to form the 700 ikaite columns in the fjord.

Phototrophic microbes form endolithic biofilms in ikaite tufa columns (SW Greenland).

Marine tufa-columns, formed by the hydrated carbonate mineral ikaite, present a unique alkaline microbial habitat only found in Ikka Fjord (SW-Greenland). The outermost parts of the ikaite columns exhibit a multitude of physico-chemical gradients, and the porous ikaite is colonized by endolithic phototrophic biofilms serving as a substrate for grazing epifauna, where scraping by sea urchins affects overall column-topography. We present a detailed study of the optical microenvironment, spatial organization, and photosynthetic activity of endolithic phototrophs within the porous ikaite crystal matrix. Cyanobacteria and diatoms formed distinctly coloured zones and were closely associated with ikaite-crystals via excretion of exopolymers. Scalar-irradiance measurements showed strong attenuation of visible light (400-700 nm), where only ∼1% of incident irradiance remained at 20 mm depth. Transmission spectra showed in vivo absorption signatures of diatom and cyanobacterial photopigments, which were confirmed by HPLC-analysis. Variable-chlorophyll-fluorescence-imaging showed active photosynthesis with high-light acclimation in the outer diatom layer, and low-light acclimation in the underlying cyanobacterial part. Phototrophs in ikaite thus thrive in polymer-bound endolithic biofilms in a complex gradient microhabitat experiencing constant slow percolation of highly alkaline phosphate-enriched spring water mixing with cold seawater at the tufa-column-apex. We discuss the potential role of these biofilms in ikaite column formation.

Constructing and Screening a Metagenomic Library of a Cold and Alkaline Extreme Environment.

Natural cold or alkaline environments are common on Earth. A rare combination of these two extremes is found in the permanently cold (less than 6 °C) and alkaline (pH above 10) ikaite columns in the Ikka Fjord in Southern Greenland. Bioprospecting efforts have established the ikaite columns as a source of bacteria and enzymes adapted to these conditions. They have also highlighted the limitations of cultivation-based methods in this extreme environment and metagenomic approaches may provide access to novel extremophilic enzymes from the uncultured majority of bacteria. Here, we describe the construction and screening of a metagenomic library of the prokaryotic community inhabiting the ikaite columns.

In situ Dynamics of O2, pH, Light, and Photosynthesis in Ikaite Tufa Columns (Ikka Fjord, Greenland)-A Unique Microbial Habitat.

The Ikka Fjord (SW Greenland) harbors a unique microbial habitat in the form of several hundred submarine tufa columns composed of ikaite, a special hexahydrate form of calcium carbonate that precipitates when alkaline phosphate- and carbonate-enriched spring water seeping out of the sea floor meets cold seawater. While several unique heterotrophic microbes have been isolated from the tufa columns, the microbial activity, and the boundary conditions for microbial growth in ikaite have remained unexplored. We present the first detailed in situ characterization of the physico-chemical microenvironment and activity of oxygenic phototrophs thriving within the ikaite columns. In situ underwater microsensor measurements of pH, temperature, and irradiance in the porous ikaite crystal matrix, revealed an extreme microenvironment characterized by low temperatures, strong light attenuation, and gradients of pH changing from pH 9 at the outer column surface to above pH 10 over the first 1–2 cm of the ikaite. This outer layer of the freshly deposited ikaite matrix contained densely pigmented yellow and green zones harboring a diverse phototrophic community dominated by diatoms and cyanobacteria, respectively, as shown by amplicon sequencing. In situ O2 measurements, as well as underwater variable chlorophyll fluorescence measurements of photosynthetic activity, demonstrated high levels of oxygenic photosynthesis in this extreme gradient environment with strong irradiance-driven O2 dynamics ranging from anoxia to hyperoxic conditions in the ikaite matrix, albeit the local formation of gas bubbles buffered the day-night dynamics of O2 in the tufa columns. The microbial phototrophs in the ikaite matrix are embedded in exopolymers forming endolithic biofilms that may interact with mineral formation and cementing of ikaite crystals.

Genomic and exoproteomic analyses of cold- and alkaline-adapted bacteria reveal an abundance of secreted subtilisin-like proteases.

Proteases active at low temperature or high pH are used in many commercial applications, including the detergent, food and feed industries, and bacteria specifically adapted to these conditions are a potential source of novel proteases. Environments combining these two extremes are very rare, but offer the promise of proteases ideally suited to work at both high pH and low temperature. In this report, bacteria from two cold and alkaline environments, the ikaite columns in Greenland and alkaline ponds in the McMurdo Dry Valley region, Antarctica, were screened for extracellular protease activity. Two isolates, Arsukibacterium ikkense from Greenland and a related strain, Arsukibacterium sp. MJ3, from Antarctica, were further characterized with respect to protease production. Genome sequencing identified a range of potential extracellular proteases including a number of putative secreted subtilisins. An extensive liquid chromatography-tandem mass spectrometry analysis of proteins secreted by A. ikkense identified six subtilisin-like proteases as abundant components of the exoproteome in addition to other peptidases potentially involved in complete degradation of extracellular protein. Screening of Arsukibacterium genome libraries in Escherichia coli identified two orthologous secreted subtilisins active at pH 10 and 20 °C, which were also present in the A. ikkense exoproteome. Recombinant production of both proteases confirmed the observed activity.

Microbial diversity in a permanently cold and alkaline environment in Greenland.

The submarine ikaite columns located in the Ikka Fjord in Southern Greenland represent a unique, permanently cold (less than 6°C) and alkaline (above pH 10) environment and are home to a microbial community adapted to these extreme conditions. The bacterial and archaeal community inhabiting the ikaite columns and surrounding fjord was characterised by high-throughput pyrosequencing of 16S rRNA genes. Analysis of the ikaite community structure revealed the presence of a diverse bacterial community, both in the column interior and at the surface, and very few archaea. A clear difference in overall taxonomic composition was observed between column interior and surface. Whereas the surface, and in particular newly formed ikaite material, was primarily dominated by Cyanobacteria and phototrophic Proteobacteria, the column interior was dominated by Proteobacteria and putative anaerobic representatives of the Firmicutes and Bacteroidetes. The results suggest a stratification of the ikaite columns similar to that of classical soda lakes, with a light-exposed surface inhabited by primary producers and an anoxic subsurface. This was further supported by identification of major taxonomic groups with close relatives in soda lake environments, including members of the genera Rhodobaca, Dethiobacter, Thioalkalivibrio and Tindallia, as well as very abundant groups related to uncharacterised environmental sequences originally isolated from Mono Lake in California.

Polyextremophiles: life under multiple forms of stress

PART 1: OPENING CHAPTERS Introduction J. Seckbach et al. Foreword R.W. Castenholz Preface K. Horikoshi List of Authors and Their Addresses PART 2: GENERAL ASPECTS Polyextremophiles and the Constraints for Terrestrial Habitability M.C. Capece et al. Life on the Edge and Astrobiology: Who Is Who in the Polyextremophiles World J. Seckbach The Dynamic Genomes of Acidophiles F. J. Lopez de Saro et al. PART 3: HALOPHILES Two Centuries of Microbiological Research in the Wadi Natrun, Egypt: A Model System for the Study of the Ecology, Physiology, and Taxonomy of Haloalkaliphilic Microorganisms A. Oren Adaptation in Haloalkaliphiles and Natronophilic Bacteria H.L. Banciu and D.Y. Sorokin A Random Biogeochemical Walk into Three Soda Lakes of the Western USA: With an Introduction to a Few of their Microbial Denizens R.S. Oremland Halophilic, Acidophilic, and Haloacidophilic Prokaryotes H. Minegishi Life in Magnesium- and Calcium-Rich Hypersaline Environments: Salt Stress by Chaotropic Ions A. Oren Survival Strategies of Halophilic Oligotrophic and Desiccation Resistant Prokaryotes H. Stan-Lotter and S. Fendrihan Radiation Resistance in Extremophiles: Fending Off Multiple Attacks K.M. Webb and J. DiRuggiero PART 4: THERMOPHILES Thermoalkaliphilic Microbes V. Kumar and T. Satyanarayana Acido- and Thermophilic Microorganisms, Their Features and Identification of Novel Enzymes or Pathways Y. Kawarabayasi Microbial Diversity in Acidic High Temperature Steam Vents R.L. Weiss Bizzoco and S.T. Kelley PART 5: PSYCHROPHILES Left Out in the Cold: Life in Cryoenvironments J. Goordial et al. Microbial Diversity and Enzymes in Ikaite Columns A Cold and Alkaline Environment in Greenland J.K. Vester et al. Microbial Communities Thriving in Various Ice Ecosystems B. Sattler and B. Post Snow Algae. Adaptation Strategies to Survive on Snow and Ice T. Leya Adaptation of Antarctic Freshwater Green Algae to the Extreme Environments H. Hu PART 6: PRESSURE Deep Sub-Surface Oil Reservoirs as Poly-Extreme Habitats for Microbial Life. A Current Review A. Wentzel et al. Expanding Limits for Life to a New Dimension: Microbial Growth at Hypergravity S. Deguchi and K. Horikoshi PART 7: OXYGEN RELATIONSHIPS Microbial Eukaryotes in Marine Oxygen Minimum Zones W.D. Orsi and V.P. Edgcomb Deep Hypersaline Anoxic Basins as Model Systems for Environmental Selection of Microbial Plankton A. Stock et al. Microbial Eukaryotes in Hypersaline Anoxic Deep Sea Basins V.P. Edgcomb and W.D. Orsi Life at High Salt and Low Oxygen: How Do the Halobacteriaceae Cope with Low Oxygen Concentrations in their Environment? A. Oren PART 8: SELECTED ORGANISMS Niches and Adaptations of Polyextremotolerant Black Fungi M. Grube et al. Polyextremophilic Photoautotrophic Eukaryotic Algae W. Reisser Extremophilic Magnetotactic Bacteria C.T. Lefevre and D. A. Bazylinski Multicellular Extremophiles - The Case of the Tardigrades D. Schulze-Makuch and J. Seckbach PART 9: FINAL COMMENTS Polyextremophiles - Summary and Conclusions J. Chela Flores Erratum Organism Index Subject Index Author Index

Discovery of novel enzymes with industrial potential from a cold and alkaline environment by a combination of functional metagenomics and culturing.

BackgroundThe use of cold-active enzymes has many advantages, including reduced energy consumption and easy inactivation. The ikaite columns of SW Greenland are permanently cold (4-6°C) and alkaline (above pH 10), and the microorganisms living there and their enzymes are adapted to these conditions. Since only a small fraction of the total microbial diversity can be cultured in the laboratory, a combined approach involving functional screening of a strain collection and a metagenomic library was undertaken for discovery of novel enzymes from the ikaite columns.ResultsA strain collection with 322 cultured isolates was screened for enzymatic activities identifying a large number of enzyme producers, with a high re-discovery rate to previously characterized strains. A functional expression library established in Escherichia coli identified a number of novel cold-active enzymes. Both α-amylases and β-galactosidases were characterized in more detail with respect to temperature and pH profiles and one of the β-galactosidases, BGalI17E2, was able to hydrolyze lactose at 5°C. A metagenome sequence of the expression library indicated that the majority of enzymatic activities were not detected by functional expression. Phylogenetic analysis showed that different bacterial communities were targeted with the culture dependent and independent approaches and revealed the bias of multiple displacement amplification (MDA) of DNA isolated from complex microbial communities.ConclusionsMany cold- and/or alkaline-active enzymes of industrial relevance were identified in the culture based approach and the majority of the enzyme-producing isolates were closely related to previously characterized strains. The function-based metagenomic approach, on the other hand, identified several enzymes (β-galactosidases, α-amylases and a phosphatase) with low homology to known sequences that were easily expressed in the production host E. coli. The β-galactosidase BGalI17E2 was able to hydrolyze lactose at low temperature, suggesting a possibly use in the dairy industry for this enzyme. The two different approaches complemented each other by targeting different microbial communities, highlighting the usefulness of combining methods for bioprospecting. Finally, we document here that ikaite columns constitute an important source of cold- and/or alkaline-active enzymes with industrial application potential.

Draft Genome Sequence of the Psychrophilic and Alkaliphilic Rhodonellum psychrophilum Strain GCM71 T

Rhodonellum psychrophilum GCM71T, isolated from the cold and alkaline submarine ikaite columns in the Ikka Fjord in Greenland, displays optimal growth at 5 to 10°C and pH 10. Here, we report the draft genome sequence of this strain, which may provide insight into the mechanisms of adaptation to these extreme conditions.

Improving diversity in cultures of bacteria from an extreme environment

The ikaite columns in the Ikka Fjord in Greenland represent one of the few permanently cold and alkaline environments on Earth, and the interior of the columns is home to a bacterial community adapted to these extreme conditions. The community is characterized by low cell numbers imbedded in a calcium carbonate matrix, making extraction of bacterial cells and DNA a challenge and limiting molecular and genomic studies of this environment. To utilize this genetic resource, cultivation at high pH and low temperature was studied as a method for obtaining biomass and DNA from the fraction of this community that would not otherwise be amenable to genetic analyses. The diversity and community dynamics in mixed cultures of bacteria from ikaite columns was investigated using denaturing gradient gel electrophoresis and pyrosequencing of 16S rDNA. Both medium composition and incubation time influenced the diversity of the culture and many hitherto uncharacterized genera could be brought into culture by extended incubation time. Extended incubation time also gave rise to a more diverse community with a significant number of rare species not detected in the initial community.

Greenland's new legislation on commercial and research-related use of biological resources: implications for the International Polar Year and later

ABSTRACTNew possibilities for economic development have been identified by the Greenland Home Rule Government in recent years. One of these is the potential for development of biotechnology based on Greenland's biodiversity. To ensure that Greenland shares in benefits derived from the exploitation of these resources the Home Rule Parliament recently enacted legislation on commercial and research-related use of biological resources that is premised on rights recognised by the 1992 Convention on Biological Diversity. This legislation represents the first law in an Arctic jurisdiction specifically to create a mechanism for access and benefit sharing in relation to Arctic genetic resources. The main area of research and commercial interest so far relates to potential developments in biotechnology from the microbial diversity of ikaite tufa columns located in the Ikka Fjord in southwest Greenland. The legislation seeks to provide a mechanism for regulating access to such biological resources and a means for Greenland to share in the potential benefits that may come from scientific research on them and subsequent commercialisation. Much research in Greenland now falls within the scope of this legislation. The purpose of this article is to explain the provisions of the legislation to the polar research community as well as to review its implications for research in the International Polar Year and later. The legislation imposes many new obligations on researchers in Greenland including obligations to obtain survey licences, obligations on reporting and the regulation of publication of scientific research. Commercially focussed research is also tightly regulated with a particular emphasis on patent rights. However, many aspects of the legislation are uncertain and it is unclear how much of the legislation will be implemented in practice.

Rhodonellum psychrophilum gen. nov., sp. nov., a novel psychrophilic and alkaliphilic bacterium of the phylum Bacteroidetes isolated from Greenland

A novel alkaliphilic and psychrophilic bacterium was isolated from the cold and alkaline ikaite tufa columns of the Ikka Fjord in south-west Greenland. According to 16S rRNA gene sequence analysis, strain GCM71(T) belonged to the family 'Flexibacteraceae' in the phylum Bacteroidetes. Strain GCM71(T), together with five related isolates from ikaite columns, formed a separate cluster with 86-93 % gene sequence similarity to their closest relative, Belliella baltica. The G+C content of the DNA from strain GCM71(T) was 43.1 mol%, whereas that of B. baltica was reported to be 35 mol%. DNA-DNA hybridization between strain GCM71(T) and B. baltica was 9.5 %. The strain was red pigmented, Gram-negative, strictly aerobic with non-motile, rod-shaped cells. The optimal growth conditions for strain GCM71(T) were pH 9.2-10.0, 5 degrees C and 0.6 % NaCl. The fatty acid profile of the novel strain was dominated by branched and unsaturated fatty acids (90-97 %), with a high abundance of iso-C(17 : 1)omega9c (17.5 %), iso-C(17 : 0) 3-OH (17.5 %) and summed feature 3, comprising iso-C(15 : 0) 2-OH and/or C(16 : 1)omega7c (12.6 %). Phylogenetic, chemotaxonomic and physiological characteristics showed that the novel strain could not be affiliated to any known genus. A new genus, Rhodonellum gen. nov., is proposed to accommodate the novel strain. Strain GCM71(T) (=DSM 17998(T)=LMG 23454(T)) is proposed as the type strain of the type species, Rhodonellum psychrophilum sp. nov.

Arsukibacterium ikkense gen. nov., sp. nov, a novel alkaliphilic, enzyme-producing γ-Proteobacterium isolated from a cold and alkaline environment in Greenland

A novel aerobic, Gram-negative, non-pigmented bacterium, GCM72 T, was isolated from the alkaline, low-saline ikaite columns in the Ikka Fjord, SW Greenland. Strain GCM72 T is a motile, non-pigmented, amylase- and protease-producing, oxidase-positive, and catalase-negative bacterium, showing optimal growth at pH 9.2–10.0, at 15 °C, and at 3% (w/v) NaCl. Major fatty acids were C 12:0 3-OH (12.2±0.1%), C 16:00 (18.0±0.1%), C 18:1 ω7 c (10.7±0.5%), and summed feature 3 comprising C 16:1 ω7 c and/or iso-C 15:0 2-OH (36.3±0.7%). Phylogenetic analysis based on 16S rRNA gene sequences showed that isolate GCM72 T was most closely related to Rheinheimera baltica and Alishewanella fetalis of the γ-Proteobacteria with a 93% sequence similarity to both. The G+C content of DNA isolated from GCM72 T was 49.9 mol% and DNA–DNA hybridization between GCM72 T and R. baltica was 9.5%. Fatty acid analysis and G+C content supports a relationship primarily to R. baltica, but several different features, such as a negative catalase-response and optimal growth at low temperature and high pH, together with the large phylogenetic distance and low DNA similarity to its closest relatives, lead us to propose a new genus, Arsukibacterium, gen. nov., with the new species Arsukibacterium ikkense sp. nov. (type strain is GCM72 T).

Bacterial diversity in permanently cold and alkaline ikaite columns from Greenland

Bacterial diversity in alkaline (pH 10.4) and permanently cold (4 degrees C) ikaite tufa columns from the Ikka Fjord, SW Greenland, was investigated using growth characterization of cultured bacterial isolates with Terminal-restriction fragment length polymorphism (T-RFLP) and sequence analysis of bacterial 16S rRNA gene fragments. More than 200 bacterial isolates were characterized with respect to pH and temperature tolerance, and it was shown that the majority were cold-active alkaliphiles. T-RFLP analysis revealed distinct bacterial communities in different fractions of three ikaite columns, and, along with sequence analysis, it showed the presence of rich and diverse bacterial communities. Rarefaction analysis showed that the 109 sequenced clones in the 16S rRNA gene library represented between 25 and 65% of the predicted species richness in the three ikaite columns investigated. Phylogenetic analysis of the 16S rRNA gene sequences revealed many sequences with similarity to alkaliphilic or psychrophilic bacteria, and showed that 33% of the cloned sequences and 33% of the cultured bacteria showed less than 97% sequence identity to known sequences in databases, and may therefore represent yet unknown species.

Microbial diversity in ikaite tufa columns: an alkaline, cold ecological niche in Greenland.

Ikaite tufa columns from the Ikka Fjord in south-western Greenland constitute a natural, stable environment at low temperature and with a pH ranging from neutral at the exterior to very alkaline (pH 10.4) at the interior of the column. Phylogenetic analysis of culturable organisms revealed ten different isolates representing three of the major bacterial divisions. Nine of the isolates showed 94-99% similarity to known sequences, whereas one isolate displayed a low degree of similarity (less than 90%) to a Cyclobacterium species. Seven of the isolates were shown to be cold active alkaliphiles, whereas three isolates showed optimal growth at neutral pH. Phylogenetic analysis of DNA isolated directly from the ikaite material demonstrated the presence of a microbial flora more diverse than the culturable isolates. Whereas approximately half of the phylotypes showed 90-99% similarity to known meso- or thermophilic alkaliphiles, the rest of the sequences displayed less than 90% similarity when compared to known 16S rRNA gene sequences in databases. Thus, in the present paper, we demonstrate that ikaite columns that host a specialized macroscopic flora and fauna also contain a unique, cold active, alkaliphilic microflora.

Marine Rotifera from Ikka Fjord, SW Greenland. With the description of a new species from the rare mineral ikaite

The rotifers from Ikka Fjord, SW Greenland are described. The descriptions are based on light microscopy, scanning electron microscopy of whole mounted animals and of isolated trophi. A new marine rotifer, Notholca 
 ikaitophila n. sp., was discovered inside the ikaite columns and from ikaite sand during this meiofauna investigation. The presence of movable lateral spines suggests a close relationship to the Notholca striata group. A full description of the new species is given. Beside the new species, eight other rotifer species, including four planktonic species, were found. Six of these are new to Greenland.
 Beside the rotifer descriptions, notes are given on macro- and meiofauna in the fjord. An ecological note regarding the unique habitat for the meiofauna inside the ikaite columns is given for the first time. The interstitial meiofauna inside the ikaite columns is totally different from the eumarine meiofauna found on the surface of the ikaite columns.

A new species of Chroomonas (Cryptophyceae) living inside the submarine ikaite columns in the Ikkafjord, Southwest Greenland, with remarks on its ultrastructure and ecology

A species ofChroomonasthat forms blue‐green patches in the ikaite columns in the Ikkafjord, SW‐Greenland near Iviituut, has been investigated by means of electron microscopy. It has a conspicuous eyespot, two distinct adjacent refractile bodies and a large pyrenoid. The flagellar branch of the gullet is provided with a ligula. A comparison with previously investigated species shows that this combination of characters is unique, and accordingly theChroomonasis described as a new species,C. ikaitensis. Further details of its ultrastructure and of its ecology are discussed.