For the first time, scientists claim to have found evidence that microscopic organisms in the ocean influence global climate through ecological interactions and responses.

An international team has found that the interactions of microscopic organisms around a particular organic material alter the chemical properties of the ocean and also influence global climate by affecting cloud formation in the atmosphere.

In the ‘Science’ journal, team member Justin Seymour of University of Technology Sydney has described how a relative of the smelly chemical that sea birds and seals use to locate prey -- dimethylsulfide (DMS) -- may serve a similar purpose at the microbial scale, helping marine microorganisms find food and cycle chemicals that are important to climate.

“We found that ecological interactions and behavioural responses taking place within volumes of a fraction of a drop of seawater can ultimately influence important ocean chemical cycling processes,” Seymour said.

Using microfluidic technology, the scientists, led by Prof Roman Stocker of Massachusetts Institute of Technology recorded microbes swimming toward dimethylsulfoniopropionate (DMSP) as the chemical was released into tiny channel occupied by the microbes.

The fact that the microbes actively moved toward the DMSP indicates that the tiny organisms play a role in ocean sulphur and carbon cycles, which exert a powerful influence on Earth’s climate.

How fast the microorganisms consume DMSP is important as DMS is involved in formation of clouds in the atmosphere.

This in turn affects the heat balance of the atmosphere.

The research is the first to make a visual record of microbial behaviour in the presence of DMSP.

“It’s important to be able to directly look at an environment in order to understand its ecology. We can now visualize the behaviour of marine microorganisms much like ecologists have done with macro-organisms for a long time,” Stocker said.

To do this, the team recreated a microcosm of the ocean environment using a microfluidic device about the size of a flash drive with minuscule channels engraved in a clear rubbery material.

The scientists injected DMSP into the channel in a way that mimics the bursting of an algal cell after viral infection -- a common event in the ocean -- then, using a camera attached to a microscope, they recorded whether and how microbes swam towards the chemical.

The scientists found that some marine microbes, including bacteria, are attracted to DMSP because they feed on it, whereas others are drawn to the chemical as it signals the presence of prey.

“By simulating the microscale patches of the chemical cue and directly monitoring the swimming responses of the predators towards these patches, we get a much more accurate perception of these important ecological interactions than can be obtained from traditional approaches,” they said.