Comparing Ecological Effects of two Different Types of Pollution Using Multivariate Techniques

Abstract

Abstract. The effects of pollution by organic wastes were compared with those caused by dumping of coarse metalliferous residues on the benthic faunas in two areas in Greece. The efficiency of several univariate and multivariate methods in describing these effects was evaluated. Both types of pollution caused a decline in the number of species and diversity, except when dumping of solid wastes took place on finer sediments. There, the above parameters increased due to the increased heterogeneity of the sediment. Pollution by organic matter resulted in increased densities of opportunistic species. Conversely, lack of organic matter in the solid wastes did not enhance settlement of opportunists, with the exception of two species which were thought to benefit indirectly from the slag. The effects of organic pollution were described successfully by all mathematical methods used, while diversity and species abundance curves were not very adequate in describing solid waste pollution. Classification was not very helpful in distinguishing between polluted and clean sites, while ordination proved useful in separating polluted and unpolluted stations as well as the two different types of pollution.SummarySeveral univariate and multivariate statistical methods were used to compare the effects of organic pollution on the benthic fauna with those caused by dumping of coarse metalliferous residues. Organic pollution was studied in Saronikos Gulf in the vicinity of the Athens sewer outfall, while the effects of tailings were examined at Larymna in the N. Evoikos Gulf; both sites are in Greece.Organic pollution in Saronikos caused a decline in the number of species and diversity and an increase in the density of opportunistic species such as Capitella capitata, Cirratulus cirratus, Polydora antennata, Prionospio malmgreni, Scolelepis fuliginosa, and Scolelepis girardi. At the dumping site in Larymna the number of species and individuals also decreased with increased level of pollution, except when the coarse wastes were dumped over finer sediments. In the latter case, the above parameters increased due to sediment heterogeneity.The low level of organic carbon in Larymna did not increase the number of opportunistic species. The density of two otherwise rare molluscan species – the bivalves Kellyella miliaris and Leptaxinus ferruginosus– did increase there. It is speculated that these bivalves obtain their nutrition from symbiotic autotrophic bacteria which in turn are favoured by the inorganic compounds found in the tailings.The absence of oppurtunistic species at the dumping site was reflected in the species abundance curves; they proved unsuitable to detect pollution by solid wastes in this oligotrophic area.Similarly, the k‐dominance curves were sensitive only in the organically enriched area of Saronikos.Of the three ordination techniques applied (Principal Component Analysis, Correspondence Analysis, and Multidimensional Scaling), the MDS was better in distinguishing polluted and clean stations as well as the two different types of pollution.