Biotic responses to multiple aquatic and terrestrial gradients in shallow subarctic lakes (Old Crow Flats, Yukon, Canada)

Abstract

Biotic communities in shallow northern lakes are frequently used to assess environmental change; however, complex interactions among multiple factors remain understudied. Here, we present analyses of a comprehensive data set that evaluates the influence input waters, catchment characteristics, limnology, and sediment properties on diatom and chironomid assemblages in surface sediments of~49 shallow mainly thermokarst lakes in Old Crow Flats, Yukon. Multivariate analyses and ANOSIM tests identified that composition of diatom (119 taxa) and chironomid (68 taxa) assemblages differs significantly (p < 0.05) between lakes with snowmelt-versus rainfall-dominated input water. Redundancy analyses revealed strong correlation of limnological, sediment, and catchment variables with input waters. Variation partitioning analyses showed that unique effects of limnological variables account for the largest proportion of variation in diatom and chironomid assemblages (17.2% and 12.6%, respectively). Important independent roles of sediment properties (8.5% and 9.5%) and catchment characteristics (4.9% and 5.1%) were also identified. We suggest that the substantial variation shared among these classes (6.1% and 7.9%) is largely attributable to hydrological processes. Our study demonstrates the utility of multi-factor analysis in northern aquatic research and draws attention to the limitations of one-dimensional comparisons and their interpretations when modelling biotic responses to environmental change.Key words: thermokarst lakes, limnology, variation partitioning analysis, diatoms, chironomids.Résumé : Les communautés biotiques des lacs peu profonds du nord sont fréquemment utilisées pour évaluer le changement environnemental; cependant, les interactions complexes parmi des facteurs multiples demeurent peu étudiées. Ici, nous présentons les analyses d'un ensemble de données complet qui évaluent l'effet des apports d'eau, des caractéristiques de bassins versants, de la limnologie et des propriétés de sédiments sur les assemblages de diatomées et de chironomidés dans les sédiments de surface d'environ 49 lacs principalement thermokartiques peu profonds de la plaine Old Crow au Yukon. Des analyses multivariées et des tests d'ANOSIM ont déterminé que la composition d'assemblages de diatomées (119 taxons) et de chironomidés (68 taxons) diffère significativement (p , 0,05) entre les lacs dont l'apport d'eau provient principalement de la fonte de neige par rapport aux lacs alimentés surtout par les averses. Les analyses de redondance ont révélé

The role of ecological drift in structuring periphytic diatom communities

“…Shallow lakes in the arctic and subarctic provide an opportunity to assess the influence of ecological drift (as opposed to environmental filtering) on periphytic diatom communities. In the Old Crow Flats, previous aquatic community studies determined that spatially variable selection exerts only weak control on diatom communities (Balasubramaniam et al 2017). Our analyses support this conclusion, as we found weak and non-significant concordance between diatom community composition and a comprehensive matrix of hydrologic and water quality parameters, regardless of lake size.…”

“…Periphytic diatoms provide an opportunity to test the influence of drift on a biotic community because of their rapid growth cycles, small size and high abundance relative to larger organisms, and well-established taxonomy. Previous work in the Old Crow Flats (Yukon, Canada), a northern lake-rich landscape, found that water chemistry best explained the diatom community assembly deposited in lake sediment when compared to sediment and catchment properties, but only accounted for 17.18% of the variance in community composition (Balasubramaniam et al 2017). Unexplained variance in the diatom community could potentially be attributed to stochastic processes, namely ecological drift.…”

Identifying the influence of terrestrial–aquatic connectivity on palaeoecological inferences of past climate in Arctic lakes

“…2015; Balasubramaniam et al . 2017). This is observed at Lake PG03, where shifts in assemblages are likely the result of changes in aquatic habitat.…”

“…Although aquatic production in Arctic lakes is known to be principally governed by temperature, the influence of habitat has also been shown to be important (Lotter & Bigler 2000;Medeiros et al 2015;Balasubramaniam et al 2017). This is observed at Lake PG03, where shifts in assemblages are likely the result of changes in aquatic habitat.…”

“…The consequences of increased terrestrially derived inputs to lake systems can cause abrupt and cascading responses from aquatic biota, such as inducing alterations to benthic invertebrates (Moquin et al 2014). The most abundant of Arctic benthos are the Chironomidae (Insecta: Diptera), which are commonly used as bioindicators of environmental change in palaeolimnological records due to known responses to variables such as temperature (Quinlan et al 2005;Walker & Cwynar 2006;Upiter et al 2014), nutrients (Brooks et al 2001;Moquin et al 2014;Medeiros et al 2015), habitat (Marziali et al 2006;Balasubramaniam et al 2017), and dissolved oxygen (Brodersen & Quinlan 2006;Walker 2006). The ubiquitous nature of chironomids, in particular, establishes this family as prominent proxies of palaeo-climate reconstruction.…”