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: Lakes play an important role in capturing and storing carbon, which accumulates in their sediments. But the amounts they can absorb have varied considerably over time.
Jean-François Lapierre, a professor in the Department of Biological Sciences at Université de Montréal, is part of a research team sorting out natural variations from human-influenced changes. Working with Hydro-Québec, the team set out to assess the impact of hydroelectric reservoirs on the carbon cycle compared with natural variations. Partial results have been published in the journal Environmental Research Letters.
"Many studies have focused on the long term or the industrial era, but we wanted to compare the evolution of accumulation rates in lake sediments over the past 11,000 years with trends over the last 150 years," explained Aude Flamand, a member of the research team. To do so, the researchers relied on existing data. "We had neither the time nor the funds to collect new data in the field, but there is a wealth of data already available that we were able to use," Flamand said.
The existing data were incomplete, as they mostly came from studies that weren't focused on carbon accumulation, but they often contained at least two of the three variables—sediment density, percentage carbon content and dating—needed to calculate carbon accumulation. The team therefore developed a predictive model that links sediment density to organic matter content and is specifically adapted to the wide variety of boreal and temperate lake sediments. "The existing models were not suited to boreal lakes, which generally contain very high levels of organic matter," Flamand said.
The disparate data sources presented numerous challenges. For one thing, the dating methods varied—radiocarbon for the oldest samples and lead-210 for the more recent ones. "Two dating methods are rarely used on the same core," Lapierre explained.
"It makes it difficult to compare accumulation rates across centuries and millennia." While there have been significant climatic disruptions at various points during the Holocene, the most pronounced changes in accumulation rates occurred in recent centuries. "It seems that the arrival of the first settlers already disrupted accumulation rates, but starting in 1850, with the beginnings of industrialization, the variations intensified," Lapierre said. In some lakes, sporadic decreases in carbon accumulation rates were found.
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