Recent climate change has been especially pronounced in the High Arctic, however, the responses of aquatic biota, such as diatoms, can be modified by site-specific environmental characteristics. To assess if climate-mediated ice cover changes affect the diatom response to climate, we used paleolimnological techniques to examine shifts in diatom assemblages from ten High Arctic lakes and ponds from Ellesmere Island and nearby Pim Island (Nunavut, Canada). The sites were divided a priori into four groups (“warm”, “cool”, “cold”, and “oasis”) based on local elevation and microclimatic differences that result in differing lengths of the ice-free season, as well as about three decades of personal observations. We characterized the species changes as a shift from Condition 1 (i.e. a generally low diversity, predominantly epipelic and epilithic diatom assemblage) to Condition 2 (i.e. a typically more diverse and ecologically complex assemblage with an increasing proportion of epiphytic species). This shift from Condition 1 to Condition 2 was a consistent pattern recorded across the sites that experienced a change in ice cover with warming. The “warm” sites are amongst the first to lose their ice covers in summer and recorded the earliest and highest magnitude changes. The “cool” sites also exhibited a shift from Condition 1 to Condition 2, but, as predicted, the timing of the response lagged the “warm” sites. Meanwhile some of the “cold” sites, which until recently still retained an ice raft in summer, only exhibited this shift in the upper-most sediments. The warmer “oasis” ponds likely supported aquatic vegetation throughout their records. Consequently, the diatoms of the “oasis” sites were characterized as high-diversity, Condition 2 assemblages throughout the record. Our results support the hypothesis that the length of the ice-free season is the principal driver of diatom assemblage responses to climate in the High Arctic, largely driven by the establishment of new aquatic habitats, resulting in increased diversity and the emergence of novel growth forms and epiphytic species.
Col Broken stick
Col Pond plot of broken stick model results
Col Coniss
Col Pond plot of CONISS model results
Col N2
Col Pond Hill's N2 and chlorophyll a output
Col Pond
Col Pond diatom raw count data and relative abundances including basionyms and modern taxonomic designations
Elison broken stick
Elison Lake plot of broken stick model results
High broken stick
High Lake plot of broken stick model results
Moraine broken stick
Moraine Pond plot of broken stick model results
Paradise Broken stick
Paradise Pond plot of broken stick model results
Plateau Pond 2 broken stick
Plateau Pond 2 plot of broken stick model results
Proteus broken stick
Proteus Lake plot of broken stick model results
SV5 broken stick
SV Pond 5 plot of broken stick model results
SV8 broken stick
SV Pond 8 plot of broken stick model results
West broken stick
West Lake plot of broken stick model results
Elison coniss
Elison Lake plot of CONISS model results
High coniss
High Lake plot of CONISS model results
Moraine Coniss
Moraine Pond plot of CONISS model results
Paradise Coniss
Paradise Pond plot of CONISS model results
Plateau pond 2 coniss
Plateau Pond 2 plot of CONISS model results
Proteus coniss
Proteus Lake plot of CONISS model results
SV5 coniss
SV Pond 5 plot of CONISS model results
SV8 coniss
SV Pond 8 plot of CONISS model results
West coniss
West Lake plot of CONISS model results
Elison N2
Elison Lake Hill's N2 and Chlorophyll a values
High N2
High Lake Hill's N2 and Chlorophyll a values
Moraine N2
Moraine Pond Hill's N2 and Chlorophyll a values
Paradise N2
Paradise Pond Hill's N2 and Chlorophyll a values
PP2 N2
Plateau Pond 2 Hill's N2 and Chlorophyll a values
Proteus N2
Proteus Lake Hill's N2 and Chlorophyll a values
SV5 N2
SV Pond 5 Hill's N2 and Chlorophyll a values
SV8 N2
SV Pond 8 Hill's N2 and Chlorophyll a values
West N2
West Lake Hill's N2 and Chlorophyll a values
Elison Lake
Elison Lake diatom raw count data and relative abundances including basionyms and modern taxonomic designations
High Lake
High Lake diatom raw count data and relative abundances including basionyms and modern taxonomic designations
Moraine Pond
Moraine Pond diatom raw count data and relative abundances including basionyms and modern taxonomic designations
Paradise Pond
Paradise Pond diatom raw count data and relative abundances including basionyms and modern taxonomic designations
Plateau Pond 2
Plateau Pond 2 diatom raw count data and relative abundances including basionyms and modern taxonomic designations
Proteus lake
Proteus Lake diatom raw count data and relative abundances including basionyms and modern taxonomic designations
Sverdrup Pass Ponds
Sverdrup Pond 5 and 8 diatom raw count data and relative abundances including basionyms and modern taxonomic designations
West Lake
West Lake diatom raw count data and relative abundances including basionyms and modern taxonomic designations
Elison_Lake_July_17_2007-July 16 2011 thermistor
Elison Lake thermistor data from July 17 2007 to July 16 2011
Grouping rationale
Additional summary of field notes providing support for grouping rationale.
High Lake activity
High Lake 210Pb activity from gamma-dating
Moraine activity
Moraine Pond 210Pb activity from gamma-dating
Paradise activity
Paradise Pond 210Pb activity from gamma-dating
Plateau Pond2 activity
Plateau Pond 2 210Pb activity from gamma-dating
Proteus activity
Protease Lake 210Pb activity from gamma-dating
SV Pond 5 activity
SV Pond 5 210Pb activity from gamma-dating
SV Pond 8 activity
SV Pond 8 210Pb activity from gamma-dating
Water chem additional parameters all sites
Additional water chemistry parameters for all sites
West activity
West Lake 210Pb activity from gamma-dating
High Lake dates
High Lake 210Pb dates using CRS dating method
Moraine Pond Dates
Moraine Pond 210Pb dates using CRS dating method
Moraine dates
Paradise dates
Paradise Pond 210Pb dates using CRS dating method
Plateau Pond2 dates
Plateau Pond 2 210Pb dates using CRS dating method
Proteus dates
Proteus Lake 210Pb dates using CRS dating method
SV Pond 5 dates
SV Pond 5 210Pb dates using CRS dating method
SV Pond 8 dates
SV Pond 8 210Pb dates using CRS dating method
West Lake dates
West Lake 210Pb dates using CRS dating method
SV Ponds 14C dating
SV Pond 5 and 8 14C dates and types of microfossils dated
Hills N2 script
Hill's N2 R script used to calculate Hill's N2 and rarify species count data (using pre-made packages)