To assess the affects of permafrost degradation on key components of the aquatic food
web, an in situ manipulative mesocosm experiment was performed in an upland,
unslumped Arctic lake located near Inuvik, Northwest Territories. In total, twelve
replicate mesocosms were established, 3 control and 3 replicates of 3 treatment levels
each dosed with differing amounts of sediments sourced from a nearby thermokarst
slumped lake. Findings from the experiment showed that pelagic autotrophic processes
had the greatest potential to contribute to higher trophic levels regardless of treatment.
Even in the high sediment treatment level, which showed the least pelagic autotrophic
production, pelagic autotrophic production was two orders of magnitude greater than
pelagic heterotrophic production and 5 times greater than benthic autotrophic or
heterotrophic production. Sediment treatment had no significant effect on benthic
primary productivity; however, a 500% increase in benthic heterotrophic production was
observed. This raises the possibility that increased activity in benthic heterotrophic
production is the first step in thermokarst-affected lake ecosystem succession leading to
the proliferation of benthic primary production observed in many slumped lakes in the
western Canadian Arctic. Water column phosphorus concentrations increased with
increasing sediment treatment while pelagic primary production decreased and
zooplankton biomass increased. These results suggest that the initial effect of thermokarst
disturbance is an enrichment of the system and that top-down predation from zooplankton
regulate the abundance of phytoplankton in these systems. If incidences of thermokarst
disturbance continue to increase as predicted by current climate models/scenarios, results from this study suggest that the structure and function of Arctic aquatic ecosystems will
be significantly impacted. This study highlights the need for further research to obtain a
better mechanistic and predictive understanding of the potential effects of thermokarst
disturbance on the geochemistry and ecology of Arctic lakes at relevant spatial and
temporal scales. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3748 |
| Date | 19 December 2011 |
| Creators | Moquin, Paul |
| Contributors | Wrona, Frederick John |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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