Nicole Spann
Email: ns430@cam.ac.uk
Tel: +44 (0)1223 336617
Research Interests
Despite the recent improvement in wastewater treatment heavy metal contamination still poses a threat to human and environmental safety. Marine mussels and to a much lesser extent freshwater mussels have been used as sentinel organisms to assess heavy metal concentrations in aquatic ecosystems. Because of their considerable filtering capacity mussels ingest high loads of contaminants and store them in their soft tissues and shells.
In my PhD project I will focus on how different mussel taxa depending on their habitat and feeding habit (filter or pedal feeding) take up heavy metals from the surrounding media (sediment and water). This will help to identify why different authors report widely varying correlations of mussel tissue metal concentrations with environmental metal loadings and will enhance the value of mussels as biomonitors. For this aim I collected mussels of different species (Figure 1) in three different rivers and I am measuring the heavy metal content in their tissues (using ICP-AES at the Department of Geography, University of Cambridge).
I am also looking at new ways to utilise freshwater mussels as biomonitors:
While metals reside in soft tissues of mussels for weeks or months, their shells can retain metals permanently. Furthermore many freshwater mussels in temperate climates display distinct annual growth rings (Figure 2). These attributes allow to measure metal concentrations in consecutive rings and get a pollution history of the site where the mussel lived. I used laser ablation ICP-MS (at the Department of Earth Sciences, University of Cambridge) to measure metal concentrations in different growth rings of the painter's mussel, Unio pictorum, and the Chinese pond mussel, Anodonta woodiana, and I want to correlate this data with past water and sediment concentrations.
The current development of metabolomics enables environmental contamination to be assessed from an animal's metabolic profile (e.g. the contents of lipids, sugars and amino acids) and therefore its physiological / health status. Combining this technique with tissue heavy metal analysis will provide new directions for biomonitoring studies using mussels. By exposing Asian clams, Corbicula fluminea, to cadmium and zinc in the lab I want to find out how the metabolic profile of freshwater mussels changes when they are exposed to pollutants (in collaboration with the Department of Biochemistry, University of Cambridge).
During my sampling events, I also encountered many deformed Asian clams (Corbicula fluminea) in the Rivers Thames, Yare and Waveney. For the River Yare, these shell deformations (Figure 3), consisting of a thickening of the shell, especially at the margin, had already been described by Stephan Müller in his PhD thesis (Müller 2003, PhD Thesis, University of Cambridge). We have been able to show that the deformed shell parts consisted of the rare calcium carbonate polymorph vaterite and that the shell microstructure in these parts was different to the usual crossed-lamellar one (Spann, Harper and Aldridge 2010). We have not been able yet to investigate the causes for this abnormal shell formation and I am extremely interested to hear from other places where similar shell deformations in Asian clams or other mollusc species have been found.
My project is funded by a BBSRC studentship and by grants from the Cambridge European Trust, the Balfour Fund and the Malacological Society of London.
Selected publications
Spann, N., Harper, E.M. & Aldridge D.C. (2010) The unusual mineral vaterite in shells of the freshwater bivalve Corbicula fluminea from the UK. Naturwissenschaften, 97, 743-751. doi:10.1007/s00114-010-0692-9
Goedkoop W., Spann N. & Åkerblom N. (2010) Sublethal and sex-specific cypermethrin effects in toxicity tests with the midge Chironomus riparius Meigen. Ecotoxicology, 19, 1201-1208. doi:10.1007/s10646-010-0505-0
