Heavy-metal pollution and log-normal distribution of individuals among species in benthic communities

Abstract

The distribution of the number of individuals among species in benthic communities usually fits the log-normal. Organic pollution may lead to increased abundance of some species and a deviation from the log-normal. The hypothesis that heavy-metal pollution does not cause deviation from the log-normal was tested. The study was based on data from benthic-fauna investigations in Norwegian fjords polluted by heavy metals. Correlation between elevated sediment copper and lowered faunal diversity had been found there. The results indicated that the two distribution categories (fit to log-normal; deviation from log-normal) were unrelated to sediment copper and faunal diversity. Although frequently used as a method for detecting organic pollution impact on benthic communities, the test for log-normal distribution will be insufficient or inferior to a diversity index in detecting community changes induced by heavy-metal pollution.