Growth Rates of Intertidal Molluscs as Indicators of Effects of Unexpected Incidents of Pollution

Abstract

Shells of living molluscs contain a record of previous growth rate if the time interval between check marks is known. The check marks in Mytilus edulis and Littorina littorea are probably annual marks. Growth rates of Mytilus in 1969, the year of significant elemental phosphorus pollution at Long Harbour, Newfoundland, were no different from those in preceding or succeeding years. No Littorina alive in 1969 occurred at Long Harbour, but they were abundant at other locations. This sort of analysis, used with caution because effects of pollutants may be confounded with effects of other variables, provides a method of examining nonlethal effects of unexpected polluting events.