A predictive index based on environmental filters for the bioassessment of river basins without reference areas in Atlantic Forest biome, Brazil

Natália Freitas De Souza,Daniel Forsin Buss,Darcílio Fernandes Baptista

doi:10.1590/1676-0611-bn-2018-0601

Natália Freitas De Souza, Daniel Forsin Buss + Show 1 more

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https://doi.org/10.1590/1676-0611-bn-2018-0601

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Abstract

Abstract: Biological assessments that use the reference condition approach are based on the concept of comparing a site's observed biology to sites where disturbance is minimal or absent. However, in many regions of the world, such areas are scarce or nonexistent. In this study, an alternative approach proposed by Chessman and Royal for bioassessment without reference areas based on environmental filters was tested in Brazil. This approach assumes that key environmental features act in the selection of potential colonists, from a regional pool of taxa, based on the ecological traits (tolerances) possessed by each taxon. We developed the approach by: 1) determining the regional pool, based on a large Atlantic Forest biome database; 2) selecting environmental filters (elevation, original vegetation and soil type); and 3) including information on the tolerance and preferences of aquatic insects to these filters. With this information we were able to determine the expected taxon under natural conditions and compare with observed taxon, developing a predictive index (Observed/Expected). Although the model was intended to predict the fauna in regions without reference sites, we included reference areas to test the model responsiveness, precision and sensitivity. Our results indicated that the index was able to discriminate impairment classes (F=56.9; p<0,001), it has high precision due to low standard deviation across reference sites values (SD=0.098) and high sensitivity due the correlation with environmental variables that are sensitive to human alteration (r=0.74, p<0.01). Also, it was strongly correlated with multimetric indices developed for multiple watersheds in the state, showing agreement between the methods in relation to ecological quality classification. Even though the predictive index had performed well in our study, we make some considerations that may help to improve its sensitivity of similar methods that are being tested using the environmental filters approach.

Highlights

Biological assessments are generally based on measurements of attributes of biological assemblages, which are often characterized and expressed as indices
The geomorphology of the state is composed of coastal plains separated by hills and two mountain chains that run parallel to the ocean (Serra do Mar, ranging from elevations 0-2,000 m.a.s.l and Serra da Mantiqueira, ranging from 800-2,500 m.a.s.l)
Physical and chemical parameters suggest a gradient of impairment related to organic origin and to non-point source pollution and/or related to environmental degradation

Summary

Introduction

Biological assessments are generally based on measurements of attributes of biological assemblages, which are often characterized and expressed as indices. In many regions of the world due to a long history of anthropogenic alteration of the aquatic ecosystems, those conditions are scarce or absent In such cases, where “minimally disturbed” or “historical condition” sites (sensu Stoddard et al 2006) are missing, some protocols relax the reference criteria and use “best attainable” or “least disturbed” sites as reference (Stoddard et al 2006). The misuse of this practice can generate a series of problems (Chessman 2006, Labay et al 2015, Elias et al 2015). This practice should be applied with great prudence, otherwise can influence indices by incorporating increasing degradation into the modelling

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