Use of Diatoms in River Health Assessment

We review the use of diatoms in monitoring and assessment of river health in the world. First, we summarize the use of diatoms as indicators of nutritional status, acidification, and organic and metal pollution. We then examine some problems that have been associated with diatoms and indices that were used in different regions around the world: 1) incomplete taxonomy; 2) effects of natural geographic differences on diatom distributions (e.g., climate, lithology); 3) effects of natural site differences on diatom distribution and abundance (e.g., substrate, depth, chemistry); 4) differences in sampling, sample processing, and analytical methods; and 5) difficulties in finding minimally disturbed reference sites. Based on these problems, we present the different selections and the research progress of diatoms and indices used in monitoring and assessing river health around the world including the Americas, Europe, Africa, Asia, and Australia. We recommend that future studies and uses of diatoms focus on the following aspects: 1) improve the classification and identification of diatoms; 2) increase the use of diatom predictive indices to monitor and assess water quality; 3) develop global standard methods for sampling diatoms in streams, rivers, and lakes; and 4) apply hind-casting predictive models.