Invasive ecosystem engineers and biotic indices: Giving a wrong impression of water quality improvement?

Anastasija Zaiko,Darius Daunys

doi:10.1016/j.ecolind.2014.12.023

Abstract

Benthic component of an ecosystem is considered in ecological status assessment of the key European Directives. Most of the metrics proposed for the benthic quality assessment are biodiversity based. Their robustness and applicability are widely discussed in many recent studies. However an impact of invasive alien species on biotic indices and environmental quality assessments has been largely overlooked by researchers so far. In the current study we assessed Benthic Quality Index (BQI) in a coastal ecosystem, highly affected by the invasive zebra mussel Dreissena polymorpha. Zebra mussel is able of modifying benthic habitats and enhancing local biodiversity. In the analyzed ecosystem it affected benthic species richness, abundance and community structure. As a result the calculated BQI values were significantly higher in the presence of zebra mussel with evident outliers in samples with particularly high zebra mussel abundances. Therefore we found that BQI determined in our study was artificially elevated providing false signal of the ecological status improvement. Based on the results presented, we suggested data correction framework that has been tested on the current dataset and proved to be effective minimizing zebra mussel impact on BQI assessment. Our experience could be applied for other coastal ecosystems invaded by the zebra mussel or any other aquatic invasive species with resembling biological traits and bioinvasion impacts.

Highlights

The demand for the universal biotic indicators aimed at ecological status assessment has increased with the development of the key EU Directives, focused on reduction of anthropogenic pressures, improvement of aquatic environment and preventing biodiversity loss (Borja et al 2010, Borja et al 2013, Tett et al 2013)
We test the effect of an invasive alien species on ecological quality assessment We calculate Benthic Quality Index for the coastal lagoon affected by zebra mussel Zebra mussel may modify benthic habitats enhancing local biodiversity This might bias BQI by showing false improvement of ecological status We suggest a framework how the this bias could be minimized
There is a number of biotic metrics proposed for the benthic ecological quality assessment, including Infaunal Trophic Index (ITI) (Maurer et al 1998); Benthic Index of Biotic Integrity (B-IBI) (Kerans and Karr 1994); AztiMarine Biotic Index (AMBI) (Borja et al 2000); Benthic Quality Index (BQI) (Rosenberg et al 2004); Benthic Opportunistic Polychaetes and Amphipods Index (BOPA) (Dauvin and Ruellet 2007); Infaunal Quality Index (IQI) (Kennedy et al 2011)

Summary

Introduction

The demand for the universal biotic indicators aimed at ecological status assessment has increased with the development of the key EU Directives, focused on reduction of anthropogenic pressures, improvement of aquatic environment and preventing biodiversity loss (Borja et al 2010, Borja et al 2013, Tett et al 2013). Zebra mussel is known as a powerful ecosystem engineer capable of modifying physical, morphological, biological and biogeochemical properties of the bottom habitats (Stewart et al 1998, Karatayev et al 2002, Minchin et al 2002, Zaiko et al 2009, Zaiko et al 2010) As it was previously reported, zebra mussels are generally associated with increased benthic macrofauna abundance, species richness and decreased community evenness (Ricciardi et al 1997, Zaiko et al 2009, Atalah et al 2010). It has been shown recently that some eutrophication-related metrics (e.g. nutrient levels, chlorophyll concentrations, water clarity) might be affected and lose their explanatory value in ecosystems invaded by zebra mussel (Atalah et al 2010; Zaiko et al 2014).in this study we test its effect on a benthic quality assessment and suggest a framework how the IAS-related bias could be minimized

Methods

Results

Discussion

Conclusion