Compositional shifts in macroinvertebrate communities over 30 years of urbanization

WILLIAMS-SUBIZA, EMILIO A.; BRAND, CECILIA; MISERENDINO, MARÍA LAURA

ECOLOGICAL ENGINEERING

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2022 vol. 183

0925-8574

Urban development has putgreat pressures on lotic environments, as human needs have often beenprioritized over ecosystem health. Typical interventions found in urban watercoursesinclude channelization and straightening, clearance of riparian vegetation, andthe discharge of wastewaters, among others. Such environmental changes oftenhave major effects on aquatic biodiversity. The main goal of this study was toinvestigate how freshwater macroinvertebrate assemblages responded to nearlythree decades of population growth and infrastructure development in the citiesof Esquel and Trevelin (Patagonia, Argentina). Data from two field surveys wasused to make comparisons; the first one was conducted in 1990-91, and thesecond one, in 2017-18. We found significant differences between surveys inseveral water quality variables, highlighted by an increase in conductivity anda decrease in oxygen availability. Sites affected by channelization presentedlower diversity and abundance of mayflies (Ephemeroptera) and stoneflies(Plecoptera), likely due to alteration of the physical habitat and riparianvegetation. Similarly, sites located downstream of wastewater treatment dischargesexhibited impoverished communities dominated by stressor-resistant taxa (e.g., Chironomidae).Statistical analyses showed that temporal dissimilarities between samplingsites were best explained by taxa losses, and that these changes were driven byan increase in water conductivity and a decrease in dissolved oxygen. Ourfindings show a pattern of ecological degradation that is all too common inurban streams. In addition, pressure on lotic ecosystems is only expected toincrease due to changes in thermal and precipitation regimes, and increases inhuman demand for freshwater. Therefore, we provide a series of measures thatcould contribute to improve stream health and mitigate commonurbanization-driven impacts.