New research led by the University of East Anglia (UEA) reveals the disruption in the ecological balance of the oceans, caused due to increased acidity in the atmosphere.
The study observed the impact of acidity on nutrient transport to the ocean. The observation shows how nutrient delivery has affected the productivity of the ocean and its ability to absorb CO2 from the atmosphere.
The research titled “Changing atmospheric acidity as a modulator of nutrient deposition and ocean biogeochemistry” has been published in the journal Science Advances. The research was done by an international team of experts, supported by the United Nations Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP).
Human emissions of pollutants have caused significant changes to the acidity of the atmosphere, leading to well-known environmental impacts such as acid rain. Atmospheric acidity affects the quantity and distribution of nutrients (nitrogen, phosphorus, and iron) delivered to the ocean.
Alex Baker, Study Lead Author and Professor, Marine and Atmospheric Chemistry, School of Environmental Sciences, University of East Anglia
“Acids attack the surface of desert dust particles as they are transported through the atmosphere, increasing the proportion of the phosphorus and iron contained in those particles that will dissolve when the dust falls into the ocean,” added Baker.
“Our work suggests that increasing acidity since the Industrial Revolution increased the proportions of phosphorus and iron that are soluble by 14 per cent and 16 per cent respectively. These increases will have had a direct fertilizing effect on marine phytoplankton,” noted Baker.
In the same period, emissions of pollutants have contributed two-fold to the amount of nitrogen added to the oceans through the atmosphere.
Acidity controls the distribution of nitrogen between particles and gases in the atmosphere, so that changes in acidity alter the length of time that nitrogen remains in the atmosphere and hence where in the ocean it will be deposited.
Maria Kanakidou, Professor, University of Crete
Prof. Kanakidou has also contributed to the study using global chemistry transport deposition modeling.
Apart from fertilization, the variations in the amount and geographic distribution of nutrient deposition also impact the ecological balance of the ocean.
“Phytoplankton communities are sensitive to the proportions of nutrients available to them. The changes in nutrient deposition that we have identified will likely have led to ecological shifts as the atmospheric input alters the nutrient balance of surface waters. These changes can promote certain phytoplankton types over others, depending on the organisms’ adaptation to the relative levels of nutrients present in the water,” stated Prof. Kanakidou.
The research team also included Prof. Athanasios Nenes, from the Ecole Polytechnique Fédérale de Lausanne, Switzerland, and the Center for the Study of Air Quality and Climate Change of the Foundation for Research and Technology Hellas in Patras, Greece.
Fine aerosol particles tend to remain strongly acidic, despite considerable reductions in pollutants. Understanding this counter-intuitive behavior and its impact on nutrient supply to the ocean has only become possible thanks to advances in theory and modeling.
Athanasios Nenes, Professor, Ecole Polytechnique Fédérale de Lausanne
“Anthropogenic emissions will continue to change the acidity of the atmosphere into the future. Emissions controls implemented to address acid rain will reduce aerosol acidity in many regions of the world, while continued economic development is likely to see further increases in acidity in other regions,” added Prof. Nenes.
It is unlikely for the system to return to its pre-industrial state as wildfires influence both acidity and nutrient supply, which plays a key role in a warmer climate with a highly uncertain impact.
“Knowledge of the complex interactions between nutrient supply and marine microbial communities is limited. Predictions of the consequences of long-term changes in atmospheric acidity on marine ecosystems will need to be considered alongside other stressors on the system, such as ocean acidification, warming, and deoxygenation,” concluded Prof. Baker.
Baker, A. R., et al. (2021) Changing atmospheric acidity as a modulator of nutrient deposition and ocean biogeochemistry. Science Advances. doi.org/10.1126/sciadv.abd8800.