In launching the report Impacts of Sand and Dust Storms on Oceans: A Scientific Environmental Assessment for Policy Makers, author and lecturer at the University of Oxford, Nick Middleton discusses how the dust cycle affects and interacts other biogeochemical cycles on a global scale.
What exactly are we talking about when we refer to the “dust cycle”?
The dust cycle describes the motion of trillions of tiny particles through the Earth’s system. Sand and dust are generated by strong winds from bare or sparsely vegetated soil. While some of this material falls near the source to the surface, the smaller dust particles are carried further into the wind – sometimes thousands of kilometers – before being deposited.
Every year, an estimated two billion tons of dust are taken up into the atmosphere; and a quarter of these reach the oceans.
Is this movement regular and predictable?
This long-distance flow is very seasonal and can vary considerably from year to year. But most dust comes from deserts and semi-deserts, and a particularly dusty area, known as the dust belt, stretches from the Sahara in the Middle East to the deserts of Central and Northeast Asia.
The planet’s largest resources are in the Sahara. Much Sahara dust is transported southwest by the Harmattan wind that prevails between November and April. This substance has a clear effect on the North Atlantic and the Caribbean Sea, but the Sahara substance also affects the Mediterranean Sea and the Red Sea.
What role do sand and dust storms play in a healthy ecosystem?
Desert dust particles consist of minerals, nutrients and organic and inorganic materials. Dust plays a role in a series of the physical, chemical and biogeological processes of the Earth and varies with the cycles of energy, nitrogen, carbon and water. Everything is needed for Earth System functions.
How does it affect ocean ecosystems?
Dust carries nutrients such as phosphorus and trace metals – including iron, manganese, titanium, aluminum – to ocean ecosystems, elements that are essential for all life forms. In this way, desert dust is the main driver of primary productivity in the ocean, which forms the basis of the marine food web.
Marine primary production also drives the global carbon cycle by exchanging CO2 between ocean and atmosphere, so that desert dust has an impact on our climate system. Dust also provides some of the building blocks for coral reefs: dust particles are taken up in coral skeletons as they grow.
Desert dust also provides the primary source of iron to foreign waters, but the solubility of iron aerosol is poorly understood. Iron is required for the growth of phytoplankton, but the iron must be in a form that can be used by living organisms, which is partly dependent on its solubility. Therefore, our understanding of how the dust cycle interacts with the iron cycle is critical to our understanding of marine productivity, and therefore biodiversity in the oceans.
Every year, about two billion tons of dust are taken up into the atmosphere; and a quarter of these reach the oceans.
What are the negative effects of sand and dust storms?
It is suspected that the fertilizing effect of desert dust affects algae blooms, some of which can be harmful and may contribute to Sargassum seaweed mats. Unusually large flowers of floating Sargassum seaweed have been spotted in parts of the Caribbean Sea and along the Atlantic coastlines of West Africa and Brazil since 2011. These floating seaweed mats are an important habitat for many species in the open ocean, but near the coast it can disrupt shipping, fishing and tourism.
Potential links have also been identified between microorganisms, trace metals and organic pollutants transported in desert dust, and some of the complex changes on coral reefs that have been observed in numerous parts of the world. Disease has undoubtedly been a major factor in the recent decline in coral reefs, and several diseases that affect corals are related to microorganisms transported in desert dust.
A wide variety of microorganisms – including fungi, bacteria and viruses – have been found in desert dust. Most of these pathogens come from dryland soil and are very resistant to dehydration, extreme temperature, high salinity and exposure to ultraviolet radiation. They are therefore usually able to survive in the atmosphere for many days.
Do sand and dust storms play a role in the transport of diseases such as COVID-19?
We still have numerous basic questions to answer regarding these desert-derived bioaerosols. It is thought that many of the microorganisms transported in desert dust can cause disease outbreaks in a wide variety of organisms, both on land and in the sea, but we have little information on specific microbes found in dust storms. which is known to cause diseases in humans and animals. .
How does this report contribute to existing knowledge about sand and dust storms?
Although our understanding of the dust cycle has greatly improved in recent decades, there are large uncertainties and knowledge gaps. Nevertheless, this knowledge has significant implications for a number of objectives for sustainable development – in particular Objective 14 on underwater life and Objective 15 on life on land.
This report marks the beginning of the United Nations Decade of Ocean Science for Sustainable Development (2021-2030) and examines the impact of sand and dust storms on oceans – their ecosystem functions, goods and services – which are potentially vast and wide. which varies. Sand and dust storms therefore guarantee continuous close monitoring and research.
For more information, contact Maarten Kappelle: [email protected]