Freshwater ecology in Amazon-Cerrado forest transition: biodiversity, food webs and land use changes

By Nubia Marques and Kathijo Jankowski.

Marques and Jankowski participated in WHRC’s streams field campaign at Tanguro Ranch this August. Marques is a post-doctoral researcher through an IPAM Long-Term Ecological Research grant from the Brazilian Science Foundation and is being advised by WHRC scientists Linda Deegan, Paulo Brando, and Marcia Macedo. Jankowski is a USGS research scientist and long-term collaborator with WHRC.

How biodiverse are the streams of Amazon River Basin? How will aquatic food webs be modified by land use change? How important are riparian forests for preserving biodiversity? These questions continue to puzzle ecologists in Brazil and beyond, especially as the Amazon Basin is rapidly developed for intensive agriculture. This summer, we accepted the challenge to help find some answers.

Nubia Marques

We ventured deep into the Amazon Basin to the Tanguro Ranch in Mato Grosso, Brazil, an overnight’s bus ride and half day’s drive from the nearest big city. Tanguro, a large soybean and corn farm, is a perfect living laboratory for examining the effects of land use change on streams and WHRC scientists have been working there for more than a decade. Tanguro lies in a landscape of forest fragments surrounded by soybean and corn fields on the edge of the Amazon-Cerrado forest transition, and sits front and center along Brazil’s “Arc of Deforestation”. Here we’ve found streams with intact riparian forest, cropped streams with riparian forests, and cropped streams with no riparian forest, which provide a simple experimental design to help answer our questions. Our group of ten people, including researchers and students from IPAM (Amazon Environmental Research Institute), UFPA (Federal University of Pará), UnB (University of Brasilia), IFMT (Federal Institute of Mato Grosso) and USGS (Upper Midwest Environmental Sciences Center), set out to measure almost everything one could measure in a stream: aquatic macroinvertebrates, fishes, and samples to characterize food web connectivity using stable isotopes analysis and many, many variables (200+) to characterize the habitat heterogeneity of streams and their surrounding riparian zones.

Karinna Matozinhos

The routine was intense; we spent nine days in the field to sample nine streams. We woke up everyday at 6am and were in the field from 7:30am to at least 4pm. We divided the team and spent each morning sampling macroinvertebrates, adult dragon flies, food sources for stable isotope based food web analysis and measuring stream habitat characteristics (stream size, shape, flow, etc). Then, in the afternoons, it was time to sample fishes. Fish sampling took almost everyone’s help. We divided the stream into 10 sections, and had three people – armed and ready with dip nets – get in the stream in each section. We sampled fishes for 12 minutes in each 15 meters to standardize our effort. We repeated this ten times in each stream, in a total of 150 meters per stream. After a full day’s work, we then spent the evenings and nights cleaning and preparing for the next day’s adventure.

We managed to find a treasure trove of species that we are still counting and identifying. We plan to characterize the taxonomic, dietary, and morphological diversity of the macroinvertebrates and fishes that we found and will examine how they are linked to changes in stream habitats that occur with watershed land use change.

Tiago Kisaka

We are far from done, however. The macroinvertebrate and fish samples are currently in Pará with a group of Amazonian biodiversity experts, the stable isotope samples are on their way to the mass spectrometer in Brasília, and many hours of lab and data analysis lie ahead of us. In addition, the Amazon is a mega diverse biome and host to a large part of the Earth’s freshwater biodiversity, which makes our challenge even bigger. We have confidence that our diverse team of professors, graduate students, postdocs and field technicians with extensive knowledge of various subjects (from fish to bugs to functional diversity!) will provide new and valuable information to help manage and preserve biodiversity in the riparian forests and streams of the Amazon Basin.