The accumulation of cadmium, copper and nickel in freshwater mussels (Margaritifera margaritifera), algae (Cladophora sp.), and sediment from Elk Creek, Oregon

Graduation date: 1982Concern about heavy metal pollution has increased during the\ud past decade in which studies have shown that heavy metals are accumulating\ud in the environment and that these metals, in excess, are\ud toxic to organisms, including man. Because of this concern, scientists\ud have suggested the use of indigenous organisms as monitors of\ud environmental pollution levels. However, many factors, in addition\ud to pollution, have recently been shown to affect metal levels in\ud organisms and knowledge of how these factors operate is necessary\ud before biota can be used efficiently as monitors.\ud This study examined how metal levels in three components of a\ud relatively unpolluted freshwater ecosystem varied seasonally. Mussels,\ud algae and sediment were collected during a ten-month period from Elk\ud Creek in the Oregon Coastal Mountain Range. The samples, consisting\ud of whole soft parts of mussels, whole algae and total sediments, were\ud prepared by acid digestion and then analyzed for copper, cadmium and\ud nickel using flame atomic absorption. The results of a Kruskal-Wallis\ud statistical test indicated that metal levels in mussels and sediment\ud varied significantly over the study period. The highest levels\ud occurred in July after which there was an abrupt decrease to approximately\ud one-half the July levels in August and September. The metal\ud levels remained low throughout the winter and spring. In mussels, the\ud order of metal levels was Cu > Ni > Cd. However, in sediment and\ud algae, the order was Ni > Cu >> Cd. The concentrations of Cu and Ni\ud in mussels were similar to those in sediments while Cd concentrations\ud in mussels were ten times greater than in sediment.\ud The high metal levels in July followed by relatively constant\ud levels thereafter may indicate that the variations seen in this study\ud were due to an isolated, temporary point source such as a recent\ud clear-cut and will not be seen in future years. If the observed\ud variation was indicative of true seasonal variation, then growth,\ud reproductive condition or changes in run-off may have been responsible.\ud Measurements of metal levels in M. margaritifera and sediments\ud have potential value in an environmental monitoring program. Cladophora\ud can not he recommended as an indicator organism because of\ud sampling and analytical difficulties. The possibility of seasonal\ud variation should be considered when using any of these components\ud as indicators. Samples from different areas should be taken in the\ud same season or during the same run-off conditions, relative to season,\ud before any inferences as to relative contamination levels can be made