Sahara desert dust storms carry harmful bacteria and fungi around the globe

We often dismiss springtime allergies as reactions to local pollen. Yet, something else might cause our sniffles and sneezes: a massive dust storms that originate thousands of miles away in Africa’s Sahara region.

These gargantuan dust plumes travel the globe every summer, carrying a cocktail of pollutants and potential pathogens across continents.

Dr. Shankar Chellam, a Texas A&M University professor is leading the charge to understand the biological hitchhikers within dust storms.

He and his team are working to determine what microbes, specifically bacteria and fungi, migrate with the dust and explore their potential impact on human health.

Hidden passengers in Sahara dust

“We all get allergies and potentially other more severe health effects when we breathe in dust, and it’s not fully known as to what causes those allergies,” said Dr. Chellam.

“Some people may think it is just the sand or clay minerals in the dust. Others think it is the metals or organics in the dust, and then some think it’s the bacteria and fungi.”

The Saharan dust cloud carries vast amounts of sand particles that transport bacteria and fungi.

Dr. Chellam’s research uniquely addresses how Saharan dust storms introduce these microbes into North America.

What the dust storm from Sahara tells us

Dr. Chellam and his team analyzed samples from a Saharan dust event that reached Houston in 2018. They measured metals, bacteria, and fungi to investigate any connections.

Fascinatingly, their findings revealed strong links between the biodiversity of the microbes and specific elements, especially calcium.

While these elements occur naturally in the Sahara, they also exist in our local environments. Pinpointing the exact origin of the dust and its cargo remains a challenge that scientists continue to tackle.

Our air – Not as empty as we think

Perhaps the most startling discovery is that even seemingly lifeless clouds of dust brim with biological activity.

“A key takeaway from this study is that a lot of biodiversity is not scientifically described. It doesn’t have a name, it can’t be cultured, and because it can’t be cultured, it’s difficult to study,” explained Dr. Daniel Spalink, assistant professor at Texas A&M.

The team’s high-tech DNA analysis allowed them to create an inventory of bacteria and fungi, even if the microbes themselves weren’t active.

Surprisingly, they found traces of several pathogens known to cause disease in humans, as listed by the World Health Organization (WHO).

“It doesn’t tell us if they are going to be able to infect us and make us sick,” Spalink cautions, “But at least the DNA of several pathogenic bacteria and fungi were identified in the African dust.”

Impact of climate change on Sahara dust

Climate change is altering weather patterns globally. This transformation affects dust storm behavior, leading to variations in their frequency and intensity.

In 2020, the United States experienced the most massive Saharan dust storm ever recorded, which experts named “Godzilla.”

This event highlighted the potential for increasing occurrences of such dust invasions. “The whole dynamics of the Saharan dust coming to Houston is primarily driven by atmospheric processes,” said Dr. Sourav Das, a former student of Dr. Chellam.

Global connection of Sahara dust

Sahara dust storm travels far beyond the borders of North America, affecting global environmental systems in profound ways.

This dust, originating from the vast Sahara Desert, embarks on transcontinental journeys that influence climate, ocean biology, and ecosystems far removed from its source.

The Saharan dust plays a critical role in climate regulation. As it travels across oceans and continents, it reflects sunlight back into space, cooling the Earth’s surface.

This natural phenomenon acts as a counterbalance to the warming effects of greenhouse gases, showcasing how desert dust can influence global temperatures.

However, the dust also carries microorganisms and nutrients, such as phosphorus, that fertilize remote ecosystems, from the Amazon rainforest to the Caribbean Sea, demonstrating nature’s complex nutrient cycles.

Benefits to oceans

Ocean biology benefits from the nutrient-rich dust as well. When Saharan dust settles on ocean waters, it delivers essential minerals that stimulate the growth of phytoplankton.

These microscopic plants form the foundation of the oceanic food chain, supporting a diverse array of marine life.

The influx of nutrients from the Sahara can thus boost marine productivity, affecting fish populations and the global fishing industry.

Disadvantages

The impact of Saharan dust is not universally beneficial. In ecosystems unaccustomed to the influx of foreign particles and nutrients, the dust can disrupt local environments.

For example, excessive dust deposition can smother coral reefs, blocking sunlight and hindering photosynthesis. This can stress coral ecosystems, leading to bleaching events and loss of biodiversity.

Moreover, the health implications of Saharan dust extend across continents. The dust carries not only nutrients but also pollutants and pathogens that can affect air quality and public health.

Communities in the path of these dust plumes may experience increased respiratory issues, allergies, and diseases, highlighting the need for global health monitoring and preparedness.

Study insights

It’s crucial to gather data across multiple dust events, spanning many years, to get a clearer picture of these airborne microbial communities and how they might transform over time.

While a lot remains unknown, research like this shines a spotlight on the hidden travelers swirling in the air we breathe — travelers who might be affecting our health in surprising ways.

The next time you catch a glimpse of a dust storm rolling in, remember the globe-trotting microbes it carries!

The findings of the study are published in Environmental Science & Technology.

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