Tiny microalgae may be invisible to the human eye, but they play a huge role in keeping Earth healthy.
They absorb large amounts of carbon dioxide, produce oxygen through photosynthesis and form the foundation of many aquatic food chains.
Now, scientists have discovered that even small increases in temperature can dramatically change how these microscopic organisms behave.
The study, published in The Plant Cell, focused on a green microalga called Chlamydomonas reinhardtii.
This species is widely used by scientists because it is easy to grow in the laboratory and helps researchers understand how many other microalgae respond to environmental changes.
Previous studies mainly examined how algae react to extreme heat or cold.
However, researchers from Friedrich Schiller University Jena and the Leibniz Institute for Natural Product Research and Infection Biology wanted to know what happens during the more moderate temperature changes that are becoming increasingly common as the climate warms.
The team studied temperatures ranging from 18°C to 33°C, which are commonly found in lakes, rivers and soils.
To their surprise, they discovered that even small temperature shifts changed the activity of about one-third of the algae’s protein-coding genes.
These genes control many important functions inside the cell, including photosynthesis, energy production, movement, reproduction and interactions with nearby bacteria. This means that even modest warming can trigger widespread biological changes throughout the entire organism.
The researchers also observed clear physical changes. When the temperature increased from 23°C to 28°C, the algae grew more quickly, producing about 20% more cells than before. At the same time, the tiny hair-like structures called cilia, which the algae use for swimming, became shorter.
The algae also reacted much faster than expected. Within just 15 minutes of a temperature change, they began swimming more slowly and changed direction more often. These behavioral changes happened long before the cells had time to physically remodel themselves.
The algae’s metabolism also shifted. Instead of immediately relying on photosynthesis to produce energy, the cells first used available organic carbon sources. As a result, the start of normal photosynthesis was delayed for several days. Scientists believe this delay could affect how much carbon dioxide the algae remove from the environment and how much oxygen they produce.
The study was made possible through a collaboration between four different research groups, each examining a different part of the algae’s response. Together, they combined information about gene activity, proteins, movement and photosynthesis to create a detailed picture of how the organisms respond to changing temperatures.
The findings are important because microalgae are among the smallest but most essential organisms on Earth. They help regulate the planet’s carbon cycle and support countless aquatic species. If warming temperatures continue to alter how these algae grow, move and carry out photosynthesis, the effects could spread throughout entire ecosystems.
The researchers say the study highlights how climate change can affect living things in ways that are not immediately obvious.
Even small increases in temperature can reshape the biology of organisms that support much of life on Earth. Understanding these tiny but important changes could help scientists better predict how ecosystems will respond as the world’s climate continues to warm.
