Ice-cover is the principal driver of ecological change in High Arctic lakes and ponds

Abstract

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.

Long‐term limnological changes in the Ecuadorian páramo: Comparing the ecological responses to climate warming of shallow waterbodies versus deep lakes

“…Nitzschia species (~10%-15% relative abundance), mainly N. angustatula and N. frustulum, occurring within the last three decades (Figures 3 and 4). Increases in the relative abundance of Nitzschia taxa have been recorded in High Arctic ponds with the onset of warming (Griffiths et al 2017). In the Arctic, the driving factor behind the Nitzschia increases is explained by a greening of the catchment and subsequent increase in nutrient inputs associated with extended growing seasons.…”

Climate drivers of diatom distribution in shallow subarctic lakes

“…The proposed mechanisms are diverse, including changes in thermal regimes particularly pertinent to deeper lakes (Boeff et al, 2016;R€ uhland et al, 2015;Sorvari et al, 2002), diversification of benthic habitats identified as a key mediator of change in the High Arctic (Douglas et al, 1994;Griffiths et al, 2017), and alterations to lake water acid-base balance observed from dilute lakes in alpine and arctic environments (Sommaruga-W€ ograth et al, 1997;Wolfe, 2002).…”

“…Bonilla, Villeneuve, & Vincent, 2005;Daniels, Kling, & Giblin, 2015), a growing number of studies are suggesting that also nutrient forcing affects the productivity and composition of the benthic community (Hogan, McGowan, & Anderson, 2014;Lange, Liess, Piggott, Townsend, & Matthaei, 2011;Lepori & Robin, 2014). Habitat diversification under lengthening growing season is another potential key driver of change in periphytic diatom communities, as illustrated by studies from the High Arctic (Douglas, Smol, & Blake, 1994;Griffiths, Michelutti, Sugar, Douglas, & Smol, 2017). Another characteristic feature of small and shallow lakes is their tight connection with the terrestrial environment.…”

“…In more lush environments, the effect may be more related to compositional shifts in the epiphytes (Griffiths et al, 2017). Epithemia are commonly described as epiphyton, and D. kuetzingii and D. tenuis have shown a preference for moss substrate in arctic lakes (Michelutti et al, 2006).…”

“…The connection between ice cover and diatom community change has been illustrated from diverse aquatic environments (e.g. Boeff et al, 2016;Griffiths et al, 2017;R€ uhland et al, 2015;Sorvari et al, 2002), however, instrumental or observational ice cover data from comparable remote small and shallow lakes in the study region are few (Weck-str€ om et al, 2014). While this prevents attempts to quantitatively assess the link between temperature, ice cover dynamics and diatom community change in the lake, it does not undermine the assumption of the importance of ice regimes.…”