TROPHIC NICHE BREADTH OF DAPHNIA PULEX IN AN ABANDONED AND SUBMERGED MICA MINE

Quebec has the largest number of metal mines in Canada. Before the enactment of a restoration law in 1988, many mines were abandoned after resource depletion without any reclamation obligations. As a result, groundwater flooded mining pits and underground tunnels, creating new artificial aquatic habitats. These hostile environments were subsequently colonized by microorganisms from gallery surfaces and water, along with macroinvertebrates, including zooplankton. Since most mining lakes are only a few decades old, studies on their zooplankton communities remain limited. This study aims to assess how depth-related abiotic factors influence the diversity, community composition, and δ¹³C and δ¹⁵N ratios of Daphnia pulex food resources and to evaluate its trophic niche breadth across depths in an abandoned mine pit lake in Val-des-Monts. Eukaryotic and prokaryotic communities within particulate organic matter (POM) were characterized through rRNA gene sequencing (18S and 16S). To determine D. pulex's trophic niche, isotopic analyses of carbon-13 and nitrogen-15 were conducted on both D. pulex tissues and POM across a depth gradient. Depth-related shifts in microbial community composition and δ¹³C and δ¹⁵N signatures of POM revealed a transition from photosynthetically derived carbon at the surface to microbially processed carbon at greater depths. In response to these environmental gradients, D. pulex exhibited a wider C-isotopic trophic niche breadth in the mixolimnion, likely reflecting greater food resource diversity and availability. Finally, D. pulex did not exhibit diel vertical migration, possibly due to anoxic conditions in the monimolimnion and the absence of fish predation.

Presentation Preference: Poster

Primary Presenter: Lucine Gonnet, Université du Québec à Montréal (gonnetlucine@gmail.com)

Authors:

Lucine Gonnet, Interuniversity Research Group in Limnology, University of Quebec in Montreal  (gonnet.lucine@courrier.uqam.ca)

Alison Derry, Interuniversity Research Group in Limnology, University of Quebec in Montreal  (derry.alison@uqam.ca)

Cassandre Sara Lazar, Interuniversity Research Group in Limnology, University of Quebec in Montreal  (lazar.cassandre@uqam.ca)

Élise Lhoste, Interuniversity Research Group in Limnology, University of Quebec in Montreal  (lhoste.elise@courrier.uqam.ca)

Maikel Rosabal, Interuniversity Research Group in Limnology, University of Quebec in Montreal  (rosabal.maikel@uqam.ca)