NWT RESEARCH DATABASE

Regions: Gwich'in Settlement Area

Tags: contaminants, mercury, environmental impact, bioaccumulation, vegetation, caribou

Objective(s): Lichens, cotton grass and willows will be collected in the NWT to be used in a study of caribou diet in comparison with quantitative fatty acid signature (QFASA) and mercury analyses. Fieldwork is being conducted in correlation with a caribou serum and adipose tissue sampling project.

Project Description: Lichens, cotton grass and willows will be collected in the NWT to be used in a study of caribou diet in comparison with quantitative fatty acid signature (QFASA) and mercury analyses. Fieldwork is being conducted in correlation with a caribou serum and adipose tissue sampling project. Mercury (Hg) is a global environmental contaminant that derives mostly from burning fossil fuels. The Porcupine Caribou Herd may be at risk of Hg contamination due to the proximity of their calving grounds to Prudhoe Bay, a major oil and gas complex just west of their calving grounds in Alaska. It is not known whether proximate drilling for oil and gas may increase the exposure of the herd to Hg through their diet, however, female Porcupine caribou have been shown to have higher concentrations of Hg than males in the Yukon territories. (Gamberg M., pp 9-10, 2006) In the spring, pregnant females break off from the rest of the herd for calving and arrive at the calving grounds earlier than bulls and non-pregnant females, where they graze heavily on lichens and cotton grass to prepare for parturition and lactation. It is therefore hypothesized that the exposure of caribou to mercury is higher near the north slope of Alaska during the spring season than when they are wintering in the Yukon. A key question that needs to be answered is whether there is any difference in the diet of the caribou in the two habitats. Quantitative Fatty Acid Signature Analysis (QFASA) in serum samples has been found to be an accurate reflection of recent diet in marine mammals. It is of particular importance to ascertain if and/or how QFASA can be used as an indicator of diet in terrestrial herbivorous ungulates such as caribou. Vegetation sampling: This is a multiyear project; vegetation sampling will be carried out in the fall and spring. Sampling species: because this project rests on the basis of identification of dietary vegetation by QFASA, it is important to sample as broad a range of the caribou diet as possible. Hence, some ten species of lichen have been identified for sampling, along with species of cotton grass and willows. These lichen species have been selected because they are eaten by caribou and are distributed within the range of the Porcupine Caribou Herd (Alaska, NWT and YT) [Brodo et al]. It is understood that the distribution of lichen varies from area to area, and different species are more important in the caribou diet depending on the area and time of the year. Cotton grass and willow: cotton grass (Eriophorum) are highly important to pregnant and lactating caribou for their nutritive qualities [Mauer, in Banerjee, 2003], and are strong competitors amongst other vegetation and sedges in infertile soils in the tundra environment [Stoltz and Greger]. Cotton grass species are particularly important for this study as they are highly valuable to caribou for nutrition, and may be strong indicators in areas with heightened mercury levels. Willow and cotton grass species will be collected in both sampling seasons. Vegetation sampling sites: the collection sites are within the range of the porcupine herd in Yukon and in the NWT. Vegetation from the Porcupine range will be collected by car or truck along the Dempster Highway. Samples will be collected in Dawson, YT, on different sites off the Dempster Highway (Tombstone Mountains, Engineers Creek, Eagle Plains, Rock River, Richardson Mountains), and in Old Crow, Yukon for a total of seven sites. Samples will be taken in duplicate at all sites. However, very small amounts of the sampled vegetation (several grams) are needed for analysis, such that sampling should have a minimal effect on individual plants and the environment on the whole. Analysis: All analysis will take place in the Chan laboritories at the University of Northern British Columbia (UNBC). The researchers will work with the Aurora Research Institute to translate the result into relevant information for communities before dissemination. Fieldwork in the NWT (vegetation sampling) will be conducted from August 17 to September 15, 2007 on different sites off the Dempster Highway on the Richardson Mountains, from 20 km south west of Fort McPherson to the border with the Yukon Territory.