According to recent research led by an Oregon State University scientist, dust plays a crucial role in supporting global ocean ecosystems and regulating atmospheric carbon dioxide levels. The study reveals that phytoplankton, the basis of the marine food chain, depend on dust from land-based sources for essential nutrients. Although scientists have known this for some time, accurately estimating the scale of dust’s impact has been a challenge.
The research demonstrates, using modern observational techniques, that the nutrients deposited on the ocean by dust have a significant impact on surface ocean biology on a global scale. The ocean is vital to the carbon cycle, as carbon dioxide from the atmosphere dissolves in surface waters, and phytoplankton turn it into organic matter through photosynthesis.
The newly formed organic matter sinks from the surface ocean to the deep sea, where it is sequestered, in a process known as the biological pump. The research estimates that dust supports 4.5% of the global annual export production, or sink, of carbon, with some regions experiencing an even greater contribution of up to 20% to 40%. This pathway is crucial for removing carbon from the atmosphere and transferring it to the deep ocean, which is a critical control on atmospheric carbon dioxide and a key factor in climate change.
Phytoplankton growth in the ocean is largely dependent on the physical movement of vital nutrients from deep waters to the surface, a process known as upwelling, but atmospheric dust also provides some nutrients. However, previous research on the response of marine ecosystems to atmospheric inputs has been limited to singular large events, such as wildfires, volcanic eruptions, and extreme dust storms. In the new study, scientists led by Toby Westberry and Michael Behrenfeld of Oregon State University used satellite data to examine changes in ocean color following dust inputs worldwide. Changes in ocean color reflect changes in the abundance and health of phytoplankton populations. The scientists at UMBC and NASA used modeling techniques to estimate the transport and deposition of dust to the ocean surface, as it is challenging to measure accurately due to rainstorms. The UMBC team used observations to validate a NASA global model before incorporating its results into the study.
The team of researchers found that the impact of dust on phytoplankton varies depending on the location of the ocean. In low-latitude regions, phytoplankton health improves in response to dust deposition, but not their abundance. On the other hand, in higher-latitude regions, both phytoplankton health and abundance increase in response to dust input. This is because the relationship between phytoplankton and their predators is different in these regions.
The research team plans to continue their study using improved modeling tools and advanced satellite data from NASA’s upcoming PACE satellite mission. As the planet continues to warm, the link between the atmosphere and oceans is expected to change, which makes this research even more important.