Date of Award

5-2006

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Ivan J. Fernandez

Second Committee Member

Stephen A. Norton

Third Committee Member

Constance S. Stubbs

Abstract

Bioaccumulation of trace metals in plant foliage and branch tips presents a health risk to wildlife, and potentially to humans. In Maine, U.S., a health advisory is in effect for the consumption of moose livers and kidneys due to high cadmium (Cd) concentrations. The Passamaquoddy Tribe of Maine was concerned about health risks from Cd to tribal members. The initial goal of this study was to quantify the concentrations of Cd in common moose browse vegetation and corresponding forest soils on Passamaquoddy tribal land in eastern Maine. In addition to Cd, we took this opportunity to document plant and soil concentrations of aluminum (Al), calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), nickel (Ni), phosphorus (P), lead (Pb), and zinc (Zn). We collected foliage and branch tips of four major terrestrial moose browse species from hardwood and softwood stands (Abies balsamea, Populus grandidentata, Betula papyrgera, and Acer rubrum), soils (O horizons), and two species of aquatic vegetation (Nuphar advena and Potamogeton spp.). Samples were analyzed for Al, Cd, Cu, Fe, Mn, P, Pb, Ni, and Zn by high resolution ICP-MS and for Ca, K, and Mg on ICPOES. The terrestrial vegetation species mean plant tissue concentrations ranged from 0.1-1.97 mg kg-1 for Cd, 0.65-7.08 mg kg-1 for Ni, 0.29-2.02 mg kg-1 for Pb, and 42-43 1 mg kg-1 for Zn. Our data support suggestions in the literature that aspen and birch species bioaccumulate Cd and Zn, because these plant species had relatively high Cd and Zn concentrations compared to the other species we studied. We observed mean soil concentrations of 0.50 and 1.00 mg kg-1 for Cd, 4.27 and 4.11 mg kg-1 for Ni, 54.83 and 21.36 mg kg-1 for Pb, and 55 and 167 mg kg-1 for Zn in softwood and hardwood soils respectively. Cadmium and Zn concentrations were significantly higher in hardwood compared to softwood soils, Pb concentrations were significantly higher in softwood than hardwood soils, and Ni concentrations were not significantly different between forest types. Softwood soils had significantly lower soil pH than hardwoods, and significantly higher organic matter as estimated by loss on ignition (LOI). There were no significant correlations between soil and foliar trace metal concentrations by species. When we considered all twelve elements together, we found they could be organized into three groups (A, B, and C) based on the patterns of concentration differences in vegetation among ecosystem types. Group A elements included the nutrients Ca, K, Mg, and P and showed a pattern of significantly higher concentrations in hardwood and aquatic vegetation compared to softwoods. Group B elements included four metals, Cd, Cu, Mn, and Zn, and exhibited a pattern of higher concentrations in hardwoods compared to softwoods and aquatic vegetation. Group C elements did not fit the patterns of Group A or B and included the remaining four elements Al, Fe, Ni and Pb. Aluminum, Pb and Ni had significantly higher concentrations in the softwood species compared to hardwoods. Iron concentrations were significantly higher in aquatic vegetation compared to both hardwood and softwood species. We compared branch tip versus foliage element concentrations for the three hardwood species. Most elements, including Mn, Fe, Mg, Zn, K, and P, had significantly higher concentrations in foliage than branch tips. Lead concentrations were significantly higher in branch tips than foliage which may be due to the rougher surface area of branch tips resulting in a greater capture of atmospheric Pb. Our results provide baseline vegetation and soil element concentration data from a remote non-point source impacted region in Maine. Based on these findings, it appears that hardwood species may be more significant sources of Cd to moose compared to softwood or aquatic species in Maine. Further research is needed to better understand the contributions of individual plant species as sources of Cd in moose diets. Research to develop whole ecosystem mass balances and cycling rates for Cd and other elements will be necessary to determine rates of accumulation and risk.

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