This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An international team of scientists has recreated a 1,000-year timeline documenting ecological changes and human impact on the area surrounding Crawford Lake, the famed location of the proposed Anthropocene. By analyzing sedimentary ancient DNA (sedaDNA) samples preserved in lake-bottom sediment, scientists were able to reconstruct a diverse, high-resolution data set of the entire ecosystem surrounding the lake—including plants, animals, bacteria and fungi—and map changes over the centuries.
The findings are published in the journal Molecular Ecology. "Our analysis of these sedimentary biomolecules shows us how the whole ecosystem changed over time—from the period before local agriculture, through periods of Indigenous farming by Longhouse Peoples, followed by site abandonment and local ecological succession, and then into the Euro-Canadian period with renewed impacts from logging, lumbering, milling, farming, and eventually global markers in the upper layers from industrialization," said Tyler Murchie, co-first author of the study. Crawford Lake is a meromictic lake, meaning the water column does not mix with the lakebed.
Its unique properties cause sediment in the upper layers to settle on the lake floor, where it is preserved in alternating layers of calcite and organic laminae (sediment layers that are rich in organic material). "Like the rings of a tree, each layer of sediment can be dated to a specific year, offering an exceptionally preserved record of environmental changes over time," said Matthew Emery, co-first author of the study and assistant professor of anthropology at Binghamton University. The lake gained global prominence within the scientific community as researchers debated the merits of the Anthropocene, a proposed geological epoch marked by humanity's lasting impacts on the environment.
Because Crawford Lake's sediment contains a well-preserved record of human impact—including fossil fuel remnants, plastics, artificial fertilizers, acid rain and even plutonium—it was a favorite among geologists supporting the new epoch. Though ultimately rejected, debate about the validity of the Anthropocene continues. Since Crawford Lake has been the subject of decades of scientific scrutiny, it offered scientists using sedaDNA an unparalleled opportunity to validate their work and reveal new insights.
"Some of what we found confirmed what decades of research at Crawford Lake had already shown, but the sedaDNA also revealed things no one had seen before," Murchie said. "For example, cattle DNA appears in sediments dating to the early 1800s, giving us new evidence of cattle in the surrounding landscape that wasn't visible in the traditional paleoecological record. In addition, we were able to simultaneously track the shifting mosaic of algae, bacteria, plants, animals and insects—all through the fragments of environmental DNA they left behind over the last 1,000 years." Murchie, along with co-senior author Hendrik Poinar, professor of anthropology at McMaster University, has worked extensively to sequence ancient DNA found in sedimentary rock and other sources.
To separate useful DNA from background noise, scientists use genetic baits made of RNA that bind to the DNA of a specific species, if it is present in the sample. The RNA also binds to magnetic beads, allowing researchers to reel in their target DNA using a magnet. Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly.
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