Relating taxonomy-based traits of macroinvertebrates with river sediment quality based on basic and zero-inflated Poisson models
To date, approaches in environmental risk assessment (ERA) are based on taxonomy-based descriptions of ecosystems. Due to the widespread occurrence of numerous types of chemicals in the environment and ensuing environmental risks, there is a need to get insight in the relationship between the response of the ecosystem to pollution and the characteristics (traits) of the organisms. The main hypothesis of the present research is that the trait composition of macroinvertebrate communities changes in a consistent manner along general environmental disturbance gradients. In this study, the relationship between maximal body length of macroinvertebrates and environmental variables (e.g. Cu concentration) reflecting river sediment quality in Flanders (Belgium) was analysed. It was found that the abundance at almost all body lengths decreased with a decreasing quality of the river sediment, which could be associated with a decrease in abundance of macroinvertebrate taxa. It was also observed that the number of different body lengths decreased with increasing pollution, which can be linked to a decrease in diversity of the macroinvertebrate community. At low levels of general environmental pollution especially small taxa (< 20 mm) experienced negative effects, but with increasing pollution also the abundance of larger taxa (> 60 mm) decreased. The trend observed for general environmental pollution was further analysed for specific types of metal contamination. Basic and zero-inflated Poisson models showed that with increasing copper pollution, the abundance of larger taxa quickly decreased and only relatively small taxa remained abundant. However, the observed trend was not generally applicable for all contaminants. The results of this research indicate that by using only individual metal concentrations it is not possible to explain the shifts in size distribution of macroinvertebrates. Including other environmental characteristics and other traits could enhance the understanding of how the macroinvertebrate community composition responds to environmental disturbances.
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