5) Diverse picophytoplankton found inpermafrost thaw lakes that are net heterotrophic
•Small lakes formed by thawing permafrost are typically heterotrophicbecause of high organic inputs•However, 18S rRNA amplicons combined with pigment analysesshow a diverse and active photosynthetic•community
Aquatic protist communities in the midst ofenvironmental change: using 18S rRNA gene surveys toidentify diversity over time and space
Mary Thaler ([email protected]) Sophie Crevecoeur, Nathalie Joli, Deo Onda,Bérangère Péquin, Anna Przytulska-Bartosiewicz, Warwick Vincent, Connie Lovejoy
Introduction•Protist communities are a central component of aquatic ecosystems, and their taxonomic structure issensitive to environmental change•We use 18S rRNA gene surveys to capture such changes at a fine taxonomic scale, taking advantage ofhigh throughput techniques to include many taxa poorly sampled by classical methods•Five projects from Arctic and temperate waters map the eukaryotic diversity through broad-scale changesincluding ice regimes, seasonal wind patterns and permafrost thawing.
Take-home points•18S rRNA gene surveys can uncoverprofound changes in the protistcommunity in response to intrinsic andenvironmental factors•At high latitudes, recent rapidenvironmental change requires urgentstudy before its impact can beunderstood
1.03Peridinium wierzejskiiDinoflagellate
1.00Chlorella sp.Chlorophyte
1.07Lemmermannia punctataChlorophyte
1.22Urosolenia eriensisDiatom
1.31Dinophyceae sp.Dinoflagellate
1.71Cryptomonas tetrapyrenoidosaCryptophyte
3.83CercozoaRhizaria
6.03Uroglena sp.Chrysophyte
8.65Stokesia vernalisCiliate
•The balance ofheterotrophic andautotrophic activity isimportant because itdetermines CO2 flux tothe atmosphere
Nine most common taxa (>1%) in 18S rRNA datafrom thaw lake SAS2A. Known photosyntheticorganisms are highlighted %
2) Unique high-latitude system threatened withextinction•Milne Fiord Epishelf Lake, on the northern coast of Ellesmere Island,consists of 16 m of freshwater floating over seawater behind an icedam•High throughput 18S rRNA gene sequencing shows that, unlike anyother fresh- or salt-water environment studied in the Canadian Arctic,Milne Fiord is dominated by a genus of largegreen microalgae, Carteria•Potential break-up ofan increasinglyunstable ice shelf willeventually lead to theloss of the last epishelflake in the Arctic•Aim is to describe thissystem before itvanishes, and tounderstand associatedbiological processes
•Changes in the diversity of the protistcommunity will have an impact atmultiple scales system scales withecosystem-wide consequences
1) Loss of protist diversity in the northernCanada Basin during an ice minimum year•Summer of 2012 saw unprecedented retreat of sea-ice, passing 80°Nlatitude in the Canada Basin•Overall diversity of 18S rRNA was exceptionally low for all taxa <3µm.
Ice chart showing minimum ice extent inthe Canada Basin in 2012. Red represents>90% ice cover. Dashed line shows iceextent in a “normal” year (2010)
Phylogenetic diversity in Canada Basinsamples (< 3 µm) was significantly lowerin 2012 than in other years.
•Future work is to determine which protist taxa are driving this changeand how this will impact biological processes in the water column
Contact: [email protected] Contact: [email protected]
3) Nine years of monitoring the protistcommunity in Northern Baffin Bay, 2005–2014•Pico-sized (< 2µm) eukaryotes are increasingly dominant in theBeaufort Sea in response to greater stratification and nutrientlimitations
Arctic ecotypes of small greenalgae, such as Micromonas,may change in distribution
•The aim of the present study is todescribe interannual changes at afine taxonomic scale•Monitoring period includes yearsof dramatic sea-ice loss
•It is unknown howthis trend willmanifest in an areaof complexhydrography likeBaffin Bay
Warm Greenlandcurrent
Cold Arcticcurrent
West-east temperature section of Baffin Bay showingfronts between currents
x
Contact: [email protected]
4) High wind events plus top-down control bydinoflagellates modulate picophytoflagellates inthe Magdalen Islands
•Protist community composition was tracked over summer andautumn in a coastal lagoon using high-throughput sequencing ofthe 18S DNA gene•Windy periods appear to be unfavourable for dinoflagellates,releasing the phytoflagellates from predation control
WIND
dinoflagellates
phytoflagellates
Contact: [email protected]
•Taxonomic composition issignificant for localaquaculture, since dinoflagellates are themain food source for farmed mussels
Contact: [email protected]
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