Monitoring river and stream health is essential for protecting freshwater ecosystems, but collecting and processing biological samples is often expensive and time-consuming. A new study published in Water Biology and Security using data collected across 160 stream sites in Brazil's Cerrado biome suggests that scientists may be able to reduce sampling effort substantially preserving the ability to detect ecological degradation.
Based on the U.S. Environmental Protection Agency's stream assessment protocols, the researchers sampled physical habitat, fish communities, and benthic macroinvertebrates across four Brazilian watersheds. They then tested whether reducing the number of sampled transects from 11 to 6 would still allow reliable classification of streams as least-disturbed, moderately disturbed, or severely disturbed.
The results showed that key habitat indicators such as human disturbance and fine sediment levels remained stable regardless of sampling intensity. Important biological indices based on macroinvertebrates — including ASPT and multimetric indices (MMI) — also continued to distinguish disturbed from preserved streams even with fewer transects.
"Reducing sampling effort had surprisingly limited effects on the ecological indicators most commonly used in rapid stream assessments," says corresponding author Ricardo Solar. "That means agencies and researchers may be able to monitor more streams with the same resources."
Taxonomic richness for both fish and macroinvertebrates did decline as sampling effort decreased, especially for fish assemblages. However, the overall ability to identify disturbance gradients remained largely intact for macroinvertebrate-based assessments.
"Our streamlined approach also produced major practical benefits," says Solar. "Average field time per site dropped from about six hours to three hours, while macroinvertebrate processing time decreased from roughly 15 days to 10 days per site."
The researchers report that field expenditures declined from 5.1% of total project costs in 2010 to 1.6% in 2023 under the reduced-effort approach.
"These savings are especially important for tropical countries where funding for long-term biomonitoring is limited," says co-author Marcos Callisto. "More efficient protocols can help expand monitoring coverage and deliver faster information for conservation and water management."
The authors caution that reduced sampling is most appropriate for rapid ecological assessments and may not be suitable for complete species inventories or studies focused on rare or specialist organisms.
###
Contact the author: Ricardo Solar, Departamento de Genética, Ecologia e Evolução, Universidade Federal de Minas Gerais, Av. Pres. Antônio Carlos, 6627 – Pampulha, Belo Horizonte, MG, 31270-901, Brazil. rrsolar@gmail.com
The publisher KeAi was established by Elsevier and China Science Publishing & Media Ltd to unfold quality research globally. In 2013, our focus shifted to open access publishing. We now proudly publish more than 200 world-class, open access, English language journals, spanning all scientific disciplines. Many of these are titles we publish in partnership with prestigious societies and academic institutions, such as the National Natural Science Foundation of China (NSFC).
Water Biology and Security
Experimental study
Animals
Increasing the cost-effectiveness of neotropical stream assessments based on physical habitat, fish, and macroinvertebrates
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Profs. Robert M. Hughes, Marcos Callisto, and Paulo S. Pompeu are members of the editorial board for Water Biology and Security and were not involved in the editorial review or the decision to publish this article.