Taxonomic and Functional Responses of Species-Poor Riverine Fish Assemblages to the Interplay of Human-Induced Stressors

Nicole Colin,Alberto Maceda-Veiga,Konrad Górski,Evelyn Habit,Aliro Manosalva

doi:10.3390/w14030355

Abstract

The effects of human-induced stressors on riverine fish assemblages are still poorly understood, especially in species-poor assemblages such as those of temperate South American rivers. In this study we evaluated the effects of human-induced stressors on the taxonomic and functional facets of fish assemblages of two central-southern Chilean rivers: the Biobío River (flow regulated by multiple dams) and the Valdivia River (free-flowing). The study design considered reference condition, urban polluted, and urban-industrial polluted sites. To evaluate the effects of stressors on fish assemblages we assessed: (i) components of beta diversity; (ii) spatial and temporal patterns of fish structure using a multivariate approach; and (iii) functional diversity (specialization, originality, dispersion, and entropy) using linear models. We found a strong association between taxonomic and functional fish assemblage facets with a predominance of natural processes in the Valdivia River reflected in marked temporal dynamics. In contrast, the Biobío River showed a clear loss of association with seasonal pattern, and both taxonomic and functional facets appeared to respond significantly to pollution zones. Implementation of stricter environmental policies and integrated river basin management are instrumental for conserving species-poor fish assemblages in Chilean temperate rivers characterized by low functional traits redundancy.

Highlights

A variety of human activities associated with river ecosystems worldwide have generated different stressors that negatively affect these ecosystems and their biota [1,2]
The species registered only in one basin are inside their endemic distribution ranges; in the Biobío River these were Bullockia maldonadoi, Cheirodon galusdae, Percilia irwini and Percichthys melanops, and in the Valdivia River, Diplomystes camposensis, Cheirodon kiliani, Aplochiton taeniatus and Hatcheria macrei
Decomposition of beta diversity based on species presence-absence revealed significant differences in fish assemblages structuring between the Biobío and Valdivia River basins

Summary

Introduction

A variety of human activities associated with river ecosystems worldwide have generated different stressors that negatively affect these ecosystems and their biota [1,2]. These stressors will be superimposed by climate emergency and are expected to cause significant impacts on both short and medium temporal scales. Winter precipitation and associated river discharges are expected to decrease about 40% within three decades in central-southern Chile [3,4] This discharge decrease, in turn, will exacerbate effects of other stressors (e.g., water pollution) by directly increasing concentrations of pollutants [5]. As a consequence, accelerated deterioration of water and its ecological qualities are currently evidenced in multiple river basins across Chile [5]

Methods

Results

Discussion

Conclusion