Effects of multiple stressors associated with agriculture on stream macroinvertebrate communities in a tropical catchment.

Aydeé Cornejo,Diana Pérez,Tomás Ríos,Luz Boyero,Alan M Tonin,Ana Raquel Tuñon,Stefani González,Pablo Macchi,Enilda Coronado,Francisco Correa-Araneda,Brenda Checa

doi:10.1371/journal.pone.0220528

Abstract

Tropical forests are declining at unprecedented rates in favour of agriculture, and streams can be severely impacted due to effects of multiple stressors that have rarely been considered together in tropical studies. We studied the effects of multiple stressors associated with agricultural practices (pesticide toxicity, nutrient enrichment and habitat alteration–quantified as TUmax, soluble reactive phosphorus concentration and sedimentation, respectively) on macroinvertebrate communities in a tropical catchment in Panama (13 stream sites sampled in 20 occasions from 2015 to 2017, with 260 samples in total). We examined how macroinvertebrate abundance, taxonomic richness, community composition and biotic indices (SPEAR and BMWP/PAN, which were specifically designed to detect pesticide toxicity and nutrient enrichment, respectively) varied depending on the studied stressors, considering their single and combined effects. Our analyses revealed significant effects of the studied stressors on macroinvertebrate communities, with two particular results that merit further attention: (1) the fact that pesticide toxicity affected BMWP/PAN, but not SPEAR, possibly because the former had been adapted for local fauna; and (2) that most stressors showed antagonistic interactions (i.e., lower combined effects than expected from their individual effects). These results highlight the need for toxicity bioassays with tropical species that allow adaptations of biotic indices, and of observational and manipulative studies exploring the combined effects of multiple stressors on tropical macroinvertebrate communities and ecosystems, in order to predict and manage future anthropogenic impacts on tropical streams.

Highlights

Agriculture is one of the human activities with greatest impact on the Earth’s ecosystems [1]
To our knowledge, the first to assess the joint effect of multiple stressors associated with agriculture on tropical stream macroinvertebrate communities
We demonstrated negative effects of the studied stressors on macroinvertebrate community descriptors and/ or biotic indices

Summary

Introduction

Agriculture is one of the human activities with greatest impact on the Earth’s ecosystems [1]. 40% of the terrestrial surface [2], and it will most likely expand in the few decades as a result of the higher demand of a larger global population [3] This is true for undeveloped countries, many of which are located in tropical regions [4]. Streams are affected by multiple stressors [9,10], all related to agricultural practices, which should be considered together when assessing how agriculture impacts stream communities [11] Such an approach, has rarely been used for the study of streams in the tropics, where information about effects of pesticides is scarce [6] and studies have generally considered the separate effects of nutrient enrichment [12] or altered habitat [13]

Methods

Results

Conclusion