This thesis investigates the relationships between mercury (Hg) and stable isotope of
carbon (δ13C) in marine pelagic zooplankton (Calanus spp., Themisto spp. and Euchaeta
spp.) with water mass characteristics in the North Water Polynya (NOW) and in the
Mackenzie shelf – Amundsen Gulf area. Two ship based sampling field expeditions were
carried out in late summer of 2005 and 2006 in both regions on board the CCGS
Amundsen.
In the North Water (NOW) polynya, higher levels of water Hg, depleted δ18O, lower
salinity and lower nitrate levels were measured at sampling locations near the Prince of Wales glacier (POW) on the eastern coast of Ellesmere Island in the Smith Sound area. These results suggest that the glacier may be a source of Hg to this region which, in turn, is responsible for the correspondingly high concentrations of THg and MMHg measured in Calanus spp. and Euchaeta spp. at the same locations. The Mackenzie shelf – Amundsen Gulf region was characterized by fresher surface water
properties (low salinity and depleted δ18O) in the western part and was strongly linked to the influence of the Mackenzie River. Higher THg concentrations in zooplankton were
associated with larger fractions of both meteoric water and sea-ice melt. These findings suggest that in the western Arctic, inorganic Hg uptake in zooplankton via-absorption near surface water was highly driven by freshwater inputs into the system.
Based on the analysis of three main genus Calanus spp. (mostly adult females Calanus
hyperboreus), Euchaeta spp. and Themisto spp. (mostly adult Themisto libellula), THg and MMHg concentrations were the highest in the carnivorous copepod Euchaeta spp. in the
North Water polynya followed by the omnivorous hyperiid amphipod Themisto spp. The herbivorous copepod Calanus spp. had both the lowest THg and MMHg concentrations in the Eastern and the Western Arctic. In addition, the Western Arctic is the area in which each zooplankton genus had the most depleted carbon and the most enriched nitrogen. The highest concentrations of THg in Calanus spp., Euchaeta spp. and Themisto spp. were measured in the Western Arctic as well as the highest MMHg in Calanus spp. and
Themisto spp. The highest %MMHg was calculated in the Archipelago for Themisto spp., in the Eastern Arctic for Euchaeta spp. and in the Western Arctic for Calanus spp. The relationships observed between THg, MMHg, %MMHg and δ13C in all three major
zooplankton taxa and water mass properties were in agreement with what have been
previously described in the literature. Our findings suggested that both Hg and δ13C can be used as tracers to help understand zooplankton vertical distribution, feeding ecology and ultimately to predict climate changes impact at lower trophic level in the pelagic food web. The implications for marine mammals foraging in these regions are also discussed.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:MWU.1993/3068 |
| Date | 11 September 2008 |
| Creators | Pomerleau, Corinne |
| Contributors | Stern, Gary (Environment and Geography), Ferguson, Steven (Environment and Geography) Wang, Feiyue (Chemistry) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_US |
| Detected Language | English |
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