Thesis Abstracts 2003

Arsenic Speciation in a Marine Foodchain: A Comparison of a Top Foodchain Predator with its Terrestrial Counterpart

By: Mace, Jessica V. MSc. (Environmental Science)

Supervisor: Dr. Kenneth Reimer and Dr. Iris Koch

Abstract

Arsenic exists throughout the environment combining with other elements to form inorganic and organic compounds. The biological transformation of arsenic is not well understood. The focus of this study was to examine arsenic transfer throughout a marine foodchain. Additionally, arsenic compounds in the top foodchain predator of this foodchain (a marine bird species) were compared to another marine bird species and to five terrestrial bird species.

Two study sites were chosen representing marine and terrestrial environments. The marine foodchain selected for this study was from Saglek Bay, Labrador and consisted of benthic invertebrates, benthic-feeding fish, and fish-eating birds. Yellowknife, Northwest Territories has naturally and anthropogenically elevated levels of arsenic and provided an excellent sampling site for terrestrial birds.

Total arsenic concentrations in animal tissues were determined by inductively coupled plasma – optical emission spectrometry (ICP-OES), and neutron activation analysis (NAA). Total arsenic in extracts were obtained from inductively coupled plasma – mass spectrometry (ICP-MS) analysis while arsenic forms were identified by high performance liquid chromatography – hydride generation – atomic absorption spectrometry (HPLC-HG-AAS) and HPLC-ICP-MS.

Arsenic biomagnification did not occur in the Saglek marine foodchain because arsenic concentrations were significantly lower in higher foodchain organisms than in lower foodchain organisms. Arsenic species composition was more diverse in lower foodchain organisms whereas only arsenobetaine was found in the top foodchain predator, suggesting that arsenic was transformed to an end product of arsenobetaine within the foodchain. Arsenosugars were thought to be a precursor for arsenobetaine formation because they were detected in lower foodchain organisms (clams, sea cucumbers, and sea urchins) and not in higher foodchain organisms (sculpin and black guillemots).

Arsenic concentrations were substantially greater in the terrestrial bird species from Yellowknife compared to those previously reported in the literature. In particular American tree sparrow contained 45 ppm total arsenic in liver tissue. The elevated levels of arsenic in soils from the Yellowknife area were thought to be responsible for the high levels of arsenic detected in these birds.

The primary arsenic species detected in two (gray jays and spruce grouse) of the five terrestrial bird species was arsenobetaine. Arsenobetaine is not normally formed or retained by terrestrial animals. The birds in this study were thought to be highly adapted because they were able to form and/or retain this relatively non-toxic arsenic compound. This adaptation is likely a consequence of the elevated concentrations of arsenic in the Yellowknife area. While these two bird species metabolized and/or retained arsenic similarly to marine birds (containing solely or primarily arsenobetaine) the remaining three bird species (American tree sparrows, dark-eyed juncos, and yellow-rumped warblers) had comparable arsenic compounds to those previously found in terrestrial organisms (arsenate (As(V)) and dimethylarsinic acid (DMA)).

This study provides the first arsenic speciation results for three marine organisms (green sea urchins, sandlance, and sculpin), two marine bird species (black guillemots and great black-backed gulls), and five terrestrial bird species (gray jays, American tree sparrows, dark-eyed juncos, yellow-rumped warblers, and spruce grouses). Arsenic characterization in the marine foodchain provided insight into the mechanisms of biological arsenic transformation.