Date of Award
Doctor of Philosophy (PhD)
Dr. M.J. Risk
Marine contamination has been the object of a number of scientific studies, including the use of bivalves as biological monitors: This study investigates the feasibility of using Mytilus edulis shells as environmental recorders for lead contamination.
Samples of suspended particulate matter, surficial sediments and live mussels were collected from three locations: New Brunswick's northshore, in an industrialized region involved with the refining (Belledune Harbour) and stockpiling (Dalhousie Harbour) of lead/zinc ores; tidal flats near an urbanized area (Rimouski, Quebec), and a remote estuary (Negro Harbour, Nova Scotia). Organic and inorganic carbon fractions of the sediments were determined by combustion. Major and trace elements were determined by X-ray fluorescence spectrometry. Sequential extraction techniques were employed to study the partitioning of iron, manganese and lead among various sedimentary phases. Atomic absorption spectrometry was applied for the analyses of these three metals, as well as the lead obtained from the acid digests of the suspended particulate matter, tissue and shell components. A method was developed to separate the outer calcitic and inner aragonitic shell layers. Scanning electron microscopy was used to define the separation boundary between these two shell rayers. The number and thickness of the "annual layers" in the nacreous shell component were determined using acetate peels. The variation of lead contamination occurring during the mussels Iifetime was estimated by subsampling the oldest and most recently deposited nacre in the shells.
The total lead concentrations in the sediments collected from Belledune Harbour, Dalhousie Harbour, Rimouski and Negro Harbour were 941, 108, 21 and 29 μg/g, respectively. Similar amounts of lead were extracted from the sediments except at Negro Harbour where only 13 μg/g lead was extracted. The highest and lowest tissue (shell) lead levels were detected in mussels collected from near Belledune Harbour and Negro Harbour, 456 (49) and 2 (<0.5) μg/g, respectively, whereas mussels sampled from Dalhousie Harbour and Rimouski contained comparable amounts of lead, 9 (0.8) μg/g. The tissue and shell lead concentrations were not influenced by mussel size. The lead levels in the nacreous shell layers were correlated (r:0.966) with those in the tissues, and were best related to the lead obtained from the second fraction of the sequential extraction, lead bound to carbonates. The higher phosphorus concentration at one station in Belledune Harbour, B3 (1.33%), may have suppressed the uptake of lead in the mussels at this site, 150 μg/g tissue Pb and 13 μg/g shell Pb. Significant changes of lead concentrations within the nacreous shells of mussels collected near Belledune Harbour (19 and 45 μg/g), reflected variations of lead levels in sediments.
This study demonstrates that Mytilus edulis-shells, reflect the biological uptake of lead during the lifespan of the organisms, and serve as environmental lead recorders.
Bourgoin, Bernard Patrick, "Mytilus edulis Shells as Environmental Recorders for Lead Contamination" (1987). Open Access Dissertations and Theses. Paper 2137.