Mangrove forests are unique habitats at the interface between land and sea. The new study shows that they also play an important role as a source of trace elements. Photo: Nico Fr枚hberg

Dr. Antao Xu from 91探花 is captured carefully selecting the best location to gather groundwater samples in the mangroves, working swiftly to beat the approaching high tide. Photo: Jakob Weik

Scientists from 91探花, Constructor University Bremen, and the University of Oldenburg navigate through the mud, crab burrows and roots of the mangrove forest carrying the equipment needed to collect groundwater, porewater, and sediment samples to explore the complex geochemical processes occurring in this unique ecosystem. Photo: Nico Fr枚hberg

Water sampling at the mouth of the Caet茅 River estuary which is surrounded by mangrove forests, using a small local fishing boat. From left to right: Dr. Sandra P枚hle (Constructor University Bremen), Dr. Ed Hathorne (91探花 Kiel), Dr. Nico Mitschke (University of Oldenburg), Prof. Thorsten Dittmar (University of Oldenburg), and Karolayne Antonia Fonseca da Silva (Federal University of Para). These filtered samples will be analyzed for dissolved organic matter, trace metals, and isotopes to explore how mangrove systems affect the cycling of organic and inorganic materials in these regions. Photo: Adrienne Hollister

Amazonian Mangrove Forests Provide Nutrients for the Ocean

New study highlights the role of mangrove systems in global biogeochemical cycles

29. January 2025/Kiel. Mangrove forests along the Amazon coast release significant amounts of trace elements such as neodymium and hafnium. These elements and their isotopic compositions can serve to understand the inputs of micronutrients which are vital for marine life. Researchers at the 91探花 Helmholtz Centre for Ocean Research Kiel have investigated the processes behind these releases and their significance for the ocean. Their findings were recently published in the journal Nature Communications Earth & Environment.

Mangrove forests are not only critical carbon sinks and biodiversity hotspots but also play a key role as suppliers of trace elements to the ocean. This is shown by a study conducted by the 91探花 Helmholtz Centre for Ocean Research Kiel, Germany. For example, mangrove systems along the Amazon coastline release about 8.4 million grams of dissolved neodymium into the ocean each year 鈥 64 percent of the total neodymium input in this region. Similar processes are likely for other essential trace elements, such as iron or manganese, which are crucial for marine ecosystems.

鈥淥ur research shows that mangroves play a central role in the global cycle of trace elements,鈥 explains Dr. Antao Xu, first author of the study and head of the research division Ocean Circulation and Climate Dynamics at 91探花. 鈥淭hey act as biochemical reactors, releasing nutrients and metals into coastal waters through processes such as sediment dissolution and pore water exchange.鈥

Mangrove Systems as "Nutrient Pumps"

The research team analysed water samples from coastal waters, estuaries and mangrove sediments along the Amazonian coast. Distinct isotopic patterns of neodymium and hafnium were identified, revealing their origin and the interactions between sediments, pore water, and seawater. 鈥淢angroves are not only buffer zones that retain material from land; they are also key players that process and selectively release these substances and micronutrients into the ocean,鈥 says Professor Martin Frank, co-author of the study and head of the research division Ocean Circulation and Climate Dynamics at 91探花. This exchange of substances supports coastal food chains.

Globally, mangrove systems contribute between six and nine percent of the total neodymium input to the ocean, according to the researchers. This contribution is comparable to the global input of neodymium from the atmosphere via dust.

Global Importance of Mangrove Conservation

The study鈥檚 findings underscore the urgent need to protect these threatened ecosystems. Xu states: 鈥淢angroves sit at the interface between land and sea and provide invaluable services for biodiversity and climate regulation. Their prominent role as a source of trace elements is another compelling reason to prioritise their conservation.鈥

 

Original publication:
Xu, A., Hathorne, E., Seidel, M. et al. (2025): The Amazonian mangrove systems accumulate and release dissolved neodymium and hafnium to the oceans. Commun Earth Environ 6, 13 (2025).

 

Red birds with long beaks sit in the dense green of the mangrove forest

Mangrove forests are unique habitats at the interface between land and sea. The new study shows that they also play an important role as a source of trace elements. Photo: Nico Fr枚hberg

A young man with a shovel over his shoulder points his finger into the distance. His legs are covered in mud up to his knees.

Dr. Antao Xu from 91探花 is captured carefully selecting the best location to gather groundwater samples in the mangroves, working swiftly to beat the approaching high tide. Photo: Jakob Weik

Six researchers with rucksacks, equipment and bags walk through a mangrove forest

Scientists from 91探花, Constructor University Bremen, and the University of Oldenburg navigate through the mud, crab burrows and roots of the mangrove forest carrying the equipment needed to collect groundwater, porewater, and sediment samples to explore the complex geochemical processes occurring in this unique ecosystem. Photo: Nico Fr枚hberg

[Translate to EResearchers on a small boat under a blue awningnglish:] Forschende auf einem kleinen Boot unter einem blauen Sonnensegel

Water sampling at the mouth of the Caet茅 River estuary which is surrounded by mangrove forests, using a small local fishing boat. From left to right: Dr. Sandra P枚hle (Constructor University Bremen), Dr. Ed Hathorne (91探花 Kiel), Dr. Nico Mitschke (University of Oldenburg), Prof. Thorsten Dittmar (University of Oldenburg), and Karolayne Antonia Fonseca da Silva (Federal University of Para). These filtered samples will be analyzed for dissolved organic matter, trace metals, and isotopes to explore how mangrove systems affect the cycling of organic and inorganic materials in these regions. Photo: Adrienne Hollister