Disruption to Tiny Life Can Lead to Big Changes in Warmer Climate

TUSCALOOSA, Ala – New research from The University of Alabama supports the growing consensus that, while some animals will find it difficult to adjust to predicted warmer temperatures, a more widespread effect of a changing climate is disruption in how ecosystems function.

In a project led by UA researchers, the gut health of a tadpole was disturbed by warming effects on an ecological community, stunting the tadpole’s growth and fitness. The project shows a warming climate can kick off a domino effect of disruptions that reach the tiniest lifeforms in an ecosystem that, in turn, produce big changes to animal life and the food chain, according to results published recently in Nature Climate Change.

“Our work demonstrates how global-scale climate change can impact even the smallest levels of biological organization, including the symbiotic bacteria living within the digestive tract of a tiny frog species,” said Dr. Sasha Greenspan, a research associate in biological sciences who led the study.

The changes occurred in the tadpole’s microbiome, the community of microbes living on and in an animal that play roles in digestion and immune response. The warming to the tadpoles’ surrounding ecosystem induced in the experiment prevented the microbes from performing key functions needed for the host tadpole to thrive.

“Predicted climate warming will compromise the gut microbial community, and thus the health of vertebrates, by shifting the way vertebrates interact with other organisms in the environment,” said Dr. Gui Becker, assistant professor of biological sciences.

The project built upon research from Becker’s lab group, which includes Greenspan, that studied how tadpole microbiomes were influenced by other animals in the environment in the aquatic ecosystems of the Brazilian rain forest. They found that healthy communities of bacteria and insects, known to be essential for their role in decomposition and other ecosystem functions, also increased so-called good bacteria in the environment such as those that help ward off pathogens in host animals.

The latest research project examined how a warmer climate influenced this food web and the health of vertebrate microbiomes.

The team used bromeliad plants as small ecosystems for the tadpole, which could host the tadpole in a small pool of water in its spiraled leaves. In a small tropical forest in São Paulo, Brazil, the team raised 60 bromeliads, allowing them to be naturally colonized by invertebrates and microorganisms for three months. Some plants were warmed up to 6 degrees above the surrounding temperature through a custom-built heating system to mimic predicted climate change.

The plants and the warming system were then brought into a lab in Brazil. Tadpoles that naturally grow in the bromeliads were collected and added to the center of each plant. They were monitored, and their biological life were inventoried.

The dataset produced showed that warming effects on ecological community networks – including environmental bacteria, worms, mosquito larvae and other aquatic invertebrates – compromised tadpole gut flora, leading to reduced growth, a proxy for fitness. Certain species in the environment grew and reproduced, while others didn’t, and these environmental changes disrupted assembly of healthy microbes in the tadpoles’ digestive system.

“Our findings widen our perspective on microbiome health under global change, supporting growing evidence that changing species interactions may be stronger drivers of climate-linked species extinctions and biodiversity declines than limited host thermal tolerance,” Greenspan said.

Along with Greenspan and Becker, the project included collaborators from São Paulo State University’s Department of Biodiversity and Aquaculture Center as well as the University of Campinas’ Department of Animal Biology and Institute of Biology.

The research was supported by UA, the São Paulo Research Foundation, Brazil’s National Council for Scientific and Technological Development and the Royal Society.