Responses of aquatic macroinvertebrates to human pressure in a tropical highland volcanic basin: Birrís River, Irazú Volcano (Costa Rica)

Abstract

Background. Tropical mountain rivers are strategic sources of water for human development while biological communities are indicators of the status of these ecosystems. However, volcanic basins close to large urban areas are affected by increasing human pressures that threaten the future of these ecosystems and their benefits to society. Goals. This paper analyzes the evolution of the responses of the aquatic macroinvertebrate assemblages in the face of increasing pressures in the Birrís River basin, which is essential for providing food and energy for the Greater Metropolitan Area of Costa Rica. The hypothesis that volcanic headwater communities are highly vulnerable to human impacts was tested. Methods. Composition and structure of aquatic macroinvertebrate assemblages were assessed along main river channels over two years. Results. The spatial variability of assemblages was related to organic pollution and the self-purification capacity of the river. Temporal variability was mainly explained by the intra-annual climate variability (seasonality). Macroinvertebrate assemblages were dominated by Chironomidae (Diptera), Simuliidae (Diptera), and Baetidae (Ephemeroptera) throughout the year. High flows during the rainy season (May to December) reduced density while diversity peaked at the end of that season. Ephemeroptera and Trichoptera reached their maximum abundance during the dry season, while Diptera showed maximum richness at the end of the rainy season. Conclusions. Biological communities showed spatial and temporal adaptations to the main environmental stresses, including high levels of organic pollution. However, the high slope of river channels favors the self-purification processes, which offer an opportunity for the recovery of ecological integrity combined with control of the organic discharges. More information is needed on taxonomy and autoecology of aquatic fauna and flora in these fragile volcanic environments that are strategic for the protection of water resources in the tropics.

Ecological indicators for qualitative assessment of Ojarud River: A case study

“…As per their results, the increase in the sewage discharge into the western Gulf, a distinct change in the community structure was raised, and the Ostracoda and oligochaete classes were dominated in the area. Similarly, Marchamalo et al ( 2018 ) investigated the response of benthic invertebrates to human pressure in a volcanic basin at Birrís River. The results showed that the Chironomidae and Simuliidae families (Diptera order) and Baetidae family (Ephemeroptera order) predominated in the region throughout the year.…”

Freshwater insect communities in urban environments around the globe: a review of the state of the field

“…While some authors provided specialized insight through examination of a particular taxonomic order (6.14%), suborder (one study on Amazonian damselflies; Brasil et al, 2017), or family (one study on dytiscid beetles in Finnish ponds, Liao et al, 2020), it was most common for studies to evaluate diversity metrics of the entire macroinvertebrate community (88.59%, Figure 1). Additional focal metrics often aimed to capture the degree of disturbance tolerance by highlighting specific taxa, such as the prevalence of Chironomidae or Oligochaeta (non-biting midge or aquatic worms, e.g., Marchamalo et al, 2018). Acknowledging the range of tolerance values within a single insect order, some studies specified the ratio of Hydropsychidae (a typically tolerant caddisfly family) to the rest of Trichoptera taxa in the benthic community (Rogers et al, 2002;Tszydel et al, 2015).…”