Longitudinal trends in macroinvertebrate functional feeding groups in a high-altitude tropical stream (A case study of Gura River)

Abstract

Functional feeding groups (FFGs) classification of aquatic macroinvertebrates is an important tool that enhance the knowledge of trophic dynamics in tropical streams by assigning the benthic community into trophic guilds.

The current study aimed at determining the longitudinal trends in macroinvertebrate functional feeding groups in Gura River. Macroinvertebrates were collected between November and December 2018 in seven sites along the Gura River from an altitude of 2977 to 1547 m a.s.l. At the same time, selected physical chemical variable were measured in situ at every site. Dissolved oxygen concentration (mgL-1), water temperature (oC), electrical conductivity (µScm-1), pH and turbidity (NTU) had a significant difference among the sites (p <0.05). Most of the nitrates and phosphate nutrients had a significant difference among sampled sites (p <0.05) except NO2-N as demonstrated by analysis of variance (one-way ANOVA, F (6,14) = 2, p=0.085).

A total of 4016 macroinvertebrates specimen were collected belonging to 9 orders and 28 families and assigned into 5 respective FFGs. Overall, Scrapers, dominated by Heptageniidae (Afronurus) had the high relative proportion of FFGs in all the sites with a proportion of 42%. Shredders and Predators were the least represented functional feeding groups with proportions of 6% and 3% respectively. This study is crucial in the Gura River because FFGs can be used as an indicator of aquatic ecosystems change in case there is alteration of ecosystem function due to environmental variables.