Rising temperatures reshape how microbes process carbon from decomposing animal remains in water

As global temperatures continue to rise, scientists are working to understand how warming affects the planet’s carbon cycle. A new study published in Biocontaminant reveals that higher temperatures significantly alter how aquatic microbes process carbon released during the decomposition of animal carcasses, with important implications for water quality and climate change predictions.

When animals die in aquatic environments such as rivers, lakes, and wetlands, their bodies release a surge of organic carbon into the surrounding water. This sudden input, often called a carbon pulse, fuels microbial activity. Until now, little was known about how rising temperatures influence the genes microbes use to break down and recycle this carbon.

To address this gap, researchers conducted a controlled experiment using fish carcasses placed in river water at five different temperatures ranging from 23 to 35 degrees Celsius. Using metagenomic sequencing, the team examined how microbial communities and their carbon cycling genes responded to both decomposition and warming.

“We wanted to understand not just which microbes are present, but what they are capable of doing,” said corresponding author Huan Li. “Functional genes respond very quickly to environmental change, and they offer a powerful lens for predicting how ecosystems behave under climate warming.”

The researchers found that carcass decomposition increased total carbon levels in the water by nearly 87 percent, regardless of temperature. However, temperature strongly shaped how microbes processed that carbon. About half of all detected carbon cycling genes were sensitive to temperature changes, while others remained stable across the temperature range.

As temperatures increased, the diversity of carbon cycling genes declined in water without carcasses, suggesting that warming alone can reduce functional diversity. In contrast, in water containing decomposing carcasses, gene diversity remained relatively stable, likely because abundant nutrients supported a wider range of microbial functions.

“Our results show that nutrient-rich conditions created by decomposition can buffer microbial communities against some of the negative effects of warming,” Li explained. “But this buffering has limits and does not apply to all carbon processing pathways.”

The study revealed a clear microbial preference for easily degradable carbon compounds such as starches and simple carbohydrates. Genes involved in breaking down these labile carbon sources increased with temperature and were strongly linked to rising total carbon levels. In contrast, genes responsible for degrading more resistant materials like cellulose, hemicellulose, and lignin showed little or no relationship with total carbon concentrations.

This pattern suggests that microbes prioritize quick energy gains, especially under warming conditions. Carbon degradation dominated the system, while carbon fixation pathways played a relatively minor role during decomposition. Fermentation-related genes also increased, producing compounds such as acetate and ethanol.

“These findings indicate that warming accelerates the recycling of easy carbon but does not necessarily promote long-term carbon storage,” said Li. “That has important implications for greenhouse gas emissions and aquatic ecosystem health.”

The research also showed that environmental factors such as nutrient concentrations had a stronger influence on carbon cycling genes than microbial species composition itself. This decoupling highlights the importance of focusing on functional genes rather than only microbial identities when predicting ecosystem responses to climate change.

By clarifying how temperature and decomposition interact to regulate microbial carbon pathways, the study provides new insights into how aquatic carbon cycling may shift in a warming world. The authors emphasize that these processes should be considered in models of climate feedbacks, water pollution, and ecosystem management.

“As extreme heat events become more frequent, understanding these microbial mechanisms is essential,” Li said. “They help us anticipate how carbon moves through aquatic systems and how those systems may respond in the future.”

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Journal reference: Wang X, Bi J, Yu Q, Zhang X, Shi Y, et al. 2025. Animal corpse decomposition under elevating temperature: a metabolic bridge from labile to recalcitrant carbon pools. Biocontaminant 1: e016  

https://www.maxapress.com/article/doi/10.48130/biocontam-0025-0012  

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About Biocontaminant:
Biocontaminant is a multidisciplinary platform dedicated to advancing fundamental and applied research on biological contaminants across diverse environments and systems. The journal serves as an innovative, efficient, and professional forum for global researchers to disseminate findings in this rapidly evolving field.

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