ASSESSMENT OF FRESHWATER MUSSELS AS A PALEOENVIRONMENTAL INDICATOR

Freshwater mussels should be an effective environmental indicator for the paleoenvironment. Anthropogenic sources of waste, including agricultural and sewage effluent, have a profound impact on water chemistry. These practices release ammonium, nitrate, and nitrite into the groundwater, thereby altering natural levels of dissolved inorganic nitrogen (DIN). The increase of anthropogenic, nitrogen rich waste is reflected in the effected watershed chemistry as well as, in theory, the residents of these watersheds.

It has been shown that some species of mussel precipitate shell organic matrix in equilibrium with ambient water, and consequently record anthropogenic influences as variations in the stable isotope ratio, δ¹⁵N, of the soft tissue and shell organic matrix (Watanabe et al., 2009). In addition, bivalves exhibit annual growth cessation lines induced by water temperature that can act as a timeline to archive anthropogenic influence through time.

To date, research has focused almost entirely on saltwater mussels as records of anthropogenic influence on the paleoenvironment. It is intuitive that freshwater mussels should also be useful as indicators of changes in water chemistry, but such a study has not yet been conducted. Through preliminary research, I have found that the freshwater mussel, Lampsilis cardium produces a δ¹⁵N signal that may be consistent with ambient water chemistry. Research by Goewert et al. (2007) documents that Lampsilis cardium precipitates annual growth cessation lines similar to saltwater mussels, and my research will soon show whether or not this mussel is an effective proxy for the paleoclimate. Said conclusion will be valuable to future freshwater research and for interpreting anthropogenic affects on the paleoenvironment.

Goewert, Ann, D. Surge, S.J. Carpenter, J. Downing (2007), Oxygen and carbon isotope ratios of Lampsilis cardium (Unionidae) from two streams in agricultural watersheds of Iowa, USA, Palaeogeography, Palaeoclimatology, Palaeoecology, 252, 637-648.

Watanbe, Satoshi, M. Kodana, M. Fukuda (2009), Nitrogen stable isotope ratios in the manila clam, Ruditapes Philippinarum, reflects eutrophication levels in tidal flats, Marine Pollution Bulletin, 58, 1447-1453.