Permafrost thaw lakes and ponds as habitats for abundant rotifer populations

• Published in: Arctic Science
• Main Authors: Paschale N. Bégin, Warwick F. Vincent
• Format: Article in Journal/Newspaper
• Language: English; French
• Published: Canadian Science Publishing 2018
• Subjects: diversity; permafrost; rotifers; thermokarst; zooplankton; Environmental sciences; GE1-350; Environmental engineering; TA170-171; Nunavik; Canada; Arctic; Subarctic; Thermokarst; Rotifer
• Online Access: https://doi.org/10.1139/as-2016-0017; https://doaj.org/article/57f00f6c12474b23ba478a4800f33665

Thermokarst lakes and ponds were sampled across a range of permafrost landscapes in subarctic Québec (Nunavik, Canada) to compare their rotifer and other zooplankton characteristics with a set of rock-basin lakes and ponds in the region. A total of 24 rotifer species were identified, with an average of seven taxa per waterbody. Rotifer abundance was an order of magnitude higher in the thaw ponds than in rock-basin waters. In some thaw ponds, rotifers accounted for >50% of the total zooplankton biomass, but for <10% in all of the rock-basin waters. Neither α- nor β-diversity was significantly different between the two waterbody types. Grazing experiments with microspheres (0.5–6 µm diameter) showed that medium-sized particles (2–3 µm) were preferred to smaller and larger particles; clearance rates were <0.05% of the water column per day, implying that the rotifer populations were unlikely to be bottom-up limited by food availability. Rotifer abundance was negatively correlated with cladoceran densities, suggesting possible interference effects. Chaoborus larvae were also present and may exert a top-down control. Thermokarst ponds are currently favorable environments for rotifers, but the rapid change they have begun to experience brings uncertainty about their ongoing capacity to sustain these prolific communities.