What killed Frame Lake? A precautionary tale for urban planners

Frame Lake, located within the city of Yellowknife, Northwest Territories, Canada, has been identified as requiring significant remediation due to its steadily declining water quality and inability to support fish by the 1970s. Former gold mining operations and urbanization around the lake have been suspected as probable causes for the decline in water quality. While these land-use activities are well documented, little information is available regarding their impact on the lake itself. For this reason, Arcellinida, a group of shelled protozoans known to be reliable bioindicators of land-use change, were used to develop a hydroecological history of the lake. The purpose of this study was to use Arcellinida to: (1) document the contamination history of the lake, particularly related to arsenic (As) associated with aerial deposition from mine roaster stacks; (2) track the progress of water quality deterioration in Frame Lake related to mining, urbanization and other activities; and (3) identify any evidence of natural remediation within the lake. Arcellinida assemblages were assessed at 1-cm intervals through the upper 30 cm of a freeze core obtained from Frame Lake. The assemblages were statistically compared to geochemical and loss-on-ignition results from the core to document the contamination and degradation of conditions in the lake. The chronology of limnological changes recorded in the lake sediments were derived from 210Pb, 14C dating and known stratigraphic events. The progress of urbanization near the lake was tracked using aerial photography. Using Spearman correlations, the five most significant environmental variables impacting Arcellinida distribution were identified as minerogenics, organics, As, iron and mercury (p < 0.05; n = 30). Based on CONISS and ANOSIM analysis, three Arcellinida assemblages are identified. These include the Baseline Limnological Conditions Assemblage (BLCA), ranging from 17–30 cm and deposited in the early Holocene >7,000 years before present; the As Contamination Assemblage (ACA), ranging from 7–16 cm, deposited after ∼1962 when sedimentation began in the lake again following a long hiatus that spanned to the early Holocene; and the Eutrophication Assemblage (EA), ranging from 1–6 cm, comprised of sediments deposited after 1990 following the cessation of As and other metal contaminations. The EA developed in response to nutrient-rich waters entering the lake derived from the urbanization of the lake catchment and a reduction in lake circulation associated with the development at the lake outlet of a major road, later replaced by a causeway with rarely open sluiceways. The eutrophic condition currently charactering the lake—as evidenced by a population explosion of eutrophication indicator taxa Cucurbitella tricuspis—likely led to a massive increase in macrophyte growth and winter fish-kills. This ecological shift ultimately led to a system dominated by Hirudinea (leeches) and cessation of the lake as a recreational area

The Phanerozoic diversification of silica-cycling testate amoebae and its possible links to changes in terrestrial ecosystems

The terrestrial cycling of Si is thought to have a large influence on the terrestrial and marine primary production, as well as the coupled biogeochemical cycles of Si and C. Biomineralization of silica is widespread among terrestrial eukaryotes such as plants, soil diatoms, freshwater sponges, silicifying flagellates and testate amoebae. Two major groups of testate (shelled) amoebae, arcellinids and euglyphids, produce their own silica particles to construct shells. The two are unrelated phylogenetically and acquired biomineralizing capabilities independently. Hyalosphenids, a group within arcellinids, are predators of euglyphids.We demonstrate that hyalosphenids can construct shells using silica scales mineralized by the euglyphids. Parsimony analyses of the current hyalosphenid phylogeny indicate that the ability to “steal” euglyphid scales is most likely ancestral in hyalosphenids, implying that euglyphids should be older than hyalosphenids. However, exactly when euglyphids arose is uncertain. Current fossil record contains unambiguous euglyphid fossils that are as old as 50 million years, but older fossils are scarce and difficult to interpret. Poor taxon sampling of euglyphids has also prevented the development of molecular clocks. Here, we present a novel molecular clock reconstruction for arcellinids and consider the uncertainties due to various previously used calibration points. The new molecular clock puts the origin of hyalosphenids in the early Carboniferous (~370 mya). Notably, this estimate coincides with the widespread colonization of land by Si-accumulating plants, suggesting possible links between the evolution of Arcellinid testate amoebae and the expansion of terrestrial habitats rich in organic matter and bioavailable Si

Az intraspecifikus polimorfizmus és prokarióta szimbionták vizsgálata klonálisan szaporodó amöboid egysejtű szervezeteknél = Intraspecific polymorphism and prokaryotic symbionts in clonal amoeboid organisms

A szabadonélő házas amőbák közé tartozó Arcella (Amoebozoa, Arcellinida) genus különböző fajaiból vegyes és klóntenyészetek létrehozását követően molekuláris filogenetikai vizsgálatokkal elhelyeztem a genust az Amoebozoa törzsfán a Tubulina csoporton belül. Más egysejtű csoportok genusaitól eltérően a 18S rRNS gén az eltérő morfológiájú faj csoportok vonatkozásában nem mutatott számottevő különbséget. A Magyarországon előforuló 17 Arcella faj közül hétnek, köztük az igen ritka Arcella formosa-nak a parciális 18S rRNS génjét sikerült megszekvenáltatni. Házas amőbából első ízben történt endobionta baktériumok kitenyésztése és 16S rRNS génen alapuló karakterizálása. Elsősorban a szimbiózisokban is legjellemzőbb Alpha-, továbbá a Betaproteobacteria dominált. Több, más élőlényekben szimbionta ill. endobionta szervezet mellett néhány humán patogén is mutatkozott. Azonos klóntenyészetből ismételt vizsgálatoknál több taxon (pl. a Rhizobium gallicum) is előkerült. A több diazotróf tulajdonságú baktérium jelenléte felveti egy esetleges mutualisztikus kapcsolat lehetőségét a tápanyagszegény közegben perzisztáló amőbák és endobiontáik között. A FISH vizsgálatok tanúsága szerint a baktériumok a citopazma teljes terjedelmében jelen vannak. Az endobionták és a táplálékszervezetek elhelyezkedése közti különbséget TEM felvételek igazolják. Az endobionta baktériumok átadása a vertikális úton felül az olykor több Arcella egyed közti időleges plazmahidakon át, horizontálisan is történhet. | Different species of the free living testate amoeba genus Arcella (Amoebozoa, Arcellinida) were subjected to molecular phylogenetic study and the genus was placed among the Tubulina on the amoebozoan phylogenetic tree. Contrary to some other protozoan groups, the 18S SSU rRNA gene sequence did not show marked differences among the different morphological groups of Arcella. Seven out of the 17 species recorded in Hungary so far yielded partial sequences, including the very rare Arcella formosa. For the first time in testate amoeba research endobiont bacteria were cultured and characterised by 16S SSU rRNA gene sequences. Dominating groups were Alphaproteobacteria ? most typical in symbiotic relationships ? and Betaproteobacteria. Besides more bacteria of symbiotic or endobiotic nature some human pathogenes have occurred. Repeated investigation of the same clonal culture resulted the repeated appearance of some taxa (e.g. Rhizobium gallicum). The presence of more diazotrophic bacteria suggests the possibility of a putative mutualistic relationship between the hosts persisting under poor nutrient supply and the endobionts. According to FISH surveys the bacteria are present over the whole cytoplasm. TEM micrographs demonstrate the different appearance of a food vacuole containing bacteria and an endobiont. In addition to vertical transfer, an interchange of bacteria may happen in horizontal way through cytoplasmic threads during plasmogamy, occasionally involving more specimens

Testate amoebae as a proxy for reconstructing Holocene water table dynamics in southern Patagonian peat bogs

Funded by Natural Environment Research Council. Grant Numbers: NE/I022809/1, NE/I022981/1, NE/I022833/1, NE/I023104/1 Ricardo Muza and the Wildlife Conservation Society Karukinka Park Acknowledgements This work was supported by the Natural Environment Research Council (grant numbers NE/I022809/1, NE/I022981/1, NE/I022833/1 and NE/I023104/1). We thank Ricardo Muza and the Wildlife Conservation Society (WCS) Karukinka Park rangers for facilitating access to Karukinka Park. We also thank François De Vleeschouwer, Gaël Le Roux, Heleen Vanneste, Sébastien Bertrand, Zakaria Ghazoui and Jean-Yves De Vleeschouwer for fieldwork assistance. Nelson Bahamonde (INIA, Punta Arenas, Chile) and Ernesto Teneb (UMag, Punta Arenas, Chile) provided logistical support for the fieldwork in Chile. Dr Andrea Coronato (CADIC, Ushuaia) kindly provided logistical support for the research in Argentina. Thanks to Jenny Johnston for cartography, David Jolley for assistance in microscopic photography and Audrey Innes for laboratory assistance. We highly appreciate reviews by Matt Amesbury and an anonymous reviewer. R.P. is supported by an Impact Fellowship from the University of Stirling.Peer reviewedPublisher PD

A contribution to the phylogeny of agglutinating Arcellinida (Amoebozoa) based on SSU rRNA gene sequences

Arcellinid testate amoebae include a wide variety of amoeboid organisms whose test (shell) varies in shape, composition and size. A decade ago, we initiated molecular phylogenetic analyses based on SSU rRNA gene sequences and a taxonomic revision of Arcellinida. However, many lineages within Arcellinida still lack molecular data, and the phylogeny of this group is largely incomplete. In this study, we obtained SSU rRNA gene sequences from seven taxa, of which six have agglutinated shell (Difflugia oblonga, D. labiosa, D. gramen, Mediolus corona, Netzelia wailesi, and N. tuberculata), and one has an entirely proteinaceous shell (Arcella intermedia). All species but Difflugia oblonga branched within the recently erected suborder Sphaerothecina, confirming the synapomorphic value of an oviform or discoid shell. Thus, we propose that species with an oviform or discoid shell currently classified within genus Difflugia must be transferred to other genera, thus continuing the process of taxonomic revision of genus Difflugia, the largest Arcellinida genus. We therefore transferred the current and the previously sequenced oviform Difflugia spp. to Netzelia spp., based on the shared globular/oviform shell shape and their monophyly. Another species, D. labiosa, formed an independent lineage that branched as a sister clade to Arcella spp.; based on the shell morphology and their phylogenetic position, we considered D. labiosa as incertae sedis