Great biomonitoring insights achievable with shorter and cheaper stream surveys

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 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

Funder: 

We are grateful for the continuous support of the Programa Peixe Vivo of Companhia Energética de Minas Gerais (CEMIG) Research and Development across multiple projects, as well as the support of the Agência Nacional de Energia Elétrica (ANEEL) and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). RRCS, MC, DRM, and PSP were awarded National Council for Scientific and Technological Development (CNPq) research productivity grants (308350/2022-7, 304060/2020-8, 311002/2023-4, and 302328/2022-0, respectively). LC received a CAPES Ph.D. scholarship. RMH received a Fulbright-Brazil Distinguished Scholar Grant.

Conflict of interest:

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.

See the article: 

Hughes, R.M., Solar, R., Callisto, M., Pompeu, P.S., Macedo, D.R., Caiafa, L. and Alves, C.B., 2026. Increasing the cost-effectiveness of neotropical stream assessments based on physical habitat, fish, and macroinvertebrates. Water Biology and Security, 100607. DOI 10.1016/j.watbs.2026.100607.