Nav: Home

Conundrum of missing iron in oxygen minimum zones solved

October 28, 2016

In principle, there is no lack of iron on Earth as the metal is one of the most abundant elements in the Earth's crust. However in the ocean, dissolved iron is very rare, since it reacts rapidly with oxygen forming iron minerals which are poorly soluble and therefore unavailable for organisms. Nevertheless, dissolved iron is an essential nutrient for life. Without iron there would be no plankton growth, no food chain, no photosynthesis and no carbon fixation in the oceans. The sources of this micronutrients is therefore a central question for marine research. In theory, plenty of dissolved iron should be present in low-oxygen areas because there the reaction partner oxygen is missing. However, measurements show that this is not the case even in the large and essentially anoxic oxygen minimum zones of the tropical oceans.

An international research team lead by scientists from GEOMAR Helmholtz Centre for Ocean Re-search Kiel carried out a complex interdisciplinary study in the context of the Collaborative Re-search Project (SFB) 754 "Climate-Biogeochemistry Interactions in the Tropical Ocean" and dis-covered a process which explains the iron removal under anoxic conditions. "The results can also help to understand fundamental processes in the nitrogen and the carbon cycle", explains Dr. Flo-rian Scholz from GEOMAR. He is the first author of the study, which has recently been published in the international journal Earth and Planetary Science Letters.

The conundrum about the relative "iron deficiency" in the tropical oxygen minimum zones was even greater since previous studies had shown that in these regions huge amounts of iron are released in the ocean from anoxic sea floor sediments. "However, only a small part of this iron reaches the surface layers and the open ocean where biological productivity is limited by iron", Florian Scholz explains. Thus, the question was: Which process is removing the iron from the seawater?

In order to solve this question, the team took samples from the seabed, from the boundary layer between the seabed and seawater, as well as from different water layers in the tropical oxygen minimum zone during the Expedition M92 with the German research vessel METEOR in January 2013. These samples were then extensively investigated for chemical, physical and biological parameters.

"Among other tasks microbiologists carried out genetic analyses of the microorganisms living in the water in order to evaluate which metabolic processes are predominant", Scholz explains. In addition, the team studied particle samples from the water column at the synchrotron radiation source at the Karlsruhe Institute of Technology (KIT). With this analysis they were able to determine which iron minerals occur in the different water layers.

These analyses revealed that the iron reacts with nitrate instead of oxygen. This is due to certain microorganisms, which are also responsible for the decomposition of bioavailable nitrogen. "So far, these processes have not been detected in oxygen minimum zones", Florian Scholz explains, "but they are important to understand the overall system. Only when we know when and where certain nutrients are available for plankton growth we can also estimate how much carbon the plankton can bind by photosynthesis and thus remove from the atmosphere".

As head of a new Emmy Noether junior research group funded by the German Science Foundation, Dr. Florian Scholz will continue to study the fluxes of iron and other micronutrients across the seafloor in the coming years. "At present, we are further developing existing, autonomous deep-sea laboratories such that they can also detect very small concentrations of certain trace elements, such as iron. Yet, we do not fully understand the circumstances under which seafloor sediments represent a source or a sink for these essential elements", emphasizes the biogeochemist.
-end-


Helmholtz Centre for Ocean Research Kiel (GEOMAR)

Related Plankton Articles:

Dramatic decrease in cold-water plankton during industrial era
There has been a dramatic decrease in cold-water plankton during the 20th century, in contrast to thousands of years of stability, according to a new UCL-led study.
Study shows six decades of change in plankton communities
New research published in Global Change Biology shows that some species have experienced a 75% population decrease in the past 60 years, while others are more than twice as abundant due to rises in sea surface temperatures.
Tiny, but effective
Barely visible to the naked eye, gelatinous zooplankton is an important part of the marine ecosystem.
There are variations in plankton biodiversity and activity from the equator to the poles
New results from the Tara Oceans expedition, led by a collaboration between the Tara Ocean Foundation and teams from the CNRS, EMBL, CEA, Sorbonne Université and Université Paris Science Lettres between 2009 and 2013 show that the diversity and functions of planktonic species in the global ocean change dramatically according to latitude.
UCI-led study: Plankton are more resilient to nutrient stress than previously thought
Surface ocean phosphate is a key mineral supporting the growth and diversification of phytoplankton, a marine organism the absorbs significant amounts of carbon dioxide from Earth's atmosphere.
Ancient plankton help researchers predict near-future climate
Temperature data inferred from plankton fossils from the Pliocene, an era with CO2 levels similar to today's, allowed a UA-led team to rectify discrepancies between climate models and other proxy temperature measurements.
Dinoflagellate plankton glow so that their predators won't eat them
Some dinoflagellate plankton species are bioluminescent, with a remarkable ability to produce light to make themselves and the water they swim in glow.
Plankton as a climate driver instead of the sun?
Fluctuations in the orbital parameters of the Earth are considered to be the trigger for long-term climatic fluctuations such as ice ages.
How predatory plankton created modern ecosystems after 'Snowball Earth'
After global glaciation, predatory plankton apparently enabled the development of today's ecosystems.
Glacier depth affects plankton blooms off Greenland
The unusual timing of highly-productive summer plankton blooms off Greenland indicates a connection between increasing amounts of meltwater and nutrients in these coastal waters.
More Plankton News and Plankton Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.