So-called foraminifera are found in all the world’s oceans. Now, an international study led by the University of Hamburg has shown that foraminifera are found in all the world’s oceans: The mostly shell-bearing microorganisms absorb phosphate from the water to an unprecedented extent, which pollutes the oceans. The study has been published in the scientific journal "Nature".
Phosphate is one of the main components of many fertilizers. It stimulates the growth of many crops - but not only in the fields, but also in the sea. It gets there via the rivers and can contribute to the tipping of large areas. The fertilizer input in the sea becomes visible, for example, through excessive, sometimes even toxic algae growth, which destroys entire ecosystems.
In 2020, Dr. Nicolaas Glock was the first to discover almost incidentally that foraminifera absorb large amounts of phosphate. The research associate in the Department of Earth System Sciences at Universität Hamburg has now investigated how widespread this property is among unicellular organisms. Together with colleagues from Japan, Canada and the GEOMAR Helmholtz Center in Kiel, he examined foraminifera living on the sea floor. They came from the German Wadden Sea, Peruvian and Japanese coastal waters, the Canadian Bedford Basin and from a depth of 2000 meters from the Mid-Atlantic Ridge.
In the laboratory, the research team shock-froze them, broke them open and scanned them with X-rays. The result: almost all of the species studied had stored phosphate. "And because these single-celled organisms are so widespread and occur in huge quantities, the amount of phosphate they absorb is very, very large overall," says study leader Glock, summarizing the results.
Glock’s team has calculated this precisely for the German Wadden Sea and a single species of foraminifera: Ammonia confertistesta alone stores around five percent of all the phosphate that ends up as fertilizer on the fields in Germany every year. This makes foraminifera an important sink for this substance: without the single-celled organisms, the oceans would be even more heavily polluted with phosphate. Glock’s team has calculated that they delay human phosphate input into the sea by one month for the southern North Sea and Peru. It also suspects that the fact that the Baltic Sea is more over-fertilized than other seas could be due to the fact that significantly fewer foraminifera live there - Baltic Sea water is simply too sweet for them.
Unfortunately, the unicellular organisms cannot break down phosphate," explains the biogeochemist. "They store it as an energy reserve and release it again when needed." Only when the foraminifera die and form new sediments do they permanently remove at least some of the phosphate they have absorbed from the seawater.
Nature publication: Widespread occurrence and relevance of phosphate storage in foraminifera. By Nicolaas Glock, Julien Richirt, Christian Woehle, Christopher Algar, Maria Armstrong, Daniela Eichner, Hanna Firrincieli, Akiko Makabe, Anjaly Govindankutty Menon, Yoshiyuki Ishitani, Thomas Hackl, Raphaël Hubert-Huard, Markus Kienast, Yvonne Milker, André Mutzberg, Sha Ni, Satoshi Okada, Subhadeep Rakshit, Gerhard Schmiedl, Zvi Steiner, Akihiro Tame, Zhouling Zhang and Hidetaka Nomaki. DOI: 10.1038/s41586-024-08431-8
