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Judi Lynn

(160,211 posts)
Fri Jul 19, 2019, 01:53 AM Jul 2019

Algae-killing viruses spur nutrient recycling in oceans

July 18, 2019

Scientists have confirmed that viruses can kill marine algae called diatoms and that diatom die-offs near the ocean surface may provide nutrients and organic matter for recycling by other algae, according to a Rutgers-led study.

The study in the journal Nature Microbiology also revealed that environmental conditions can accelerate diatom mortality from viral infection, which is important for understanding how diatoms influence carbon cycling and respond to changes in the oceans, including warming waters from climate change. Diatoms, which are single-celled algae that generate about 20 percent of the Earth's oxygen, help store carbon dioxide, a key greenhouse gas, in the oceans.

"To our knowledge, this is the first time different stages of infection have been diagnosed in natural diatom populations and suggests that diatom populations may be terminated by viruses," said senior author Kim Thamatrakoln, associate research professor in the Department of Marine and Coastal Sciences at Rutgers University-New Brunswick. "Our study showed that when silicon levels in the ocean are low, diatoms can be more rapidly infected and killed by viruses and are then more likely to release their nutrients and other matter in the surface ocean instead of sinking."

Since the Victorian era, diatoms have been known as the "glass houses of the sea" because of their beautiful cell walls made of silicon dioxide, or glass. Silicon is essential for diatom growth, but since glass is heavy, diatoms can sink to the deep ocean when they die. That makes all of their nutrients, carbon and organic matter unavailable for surface recycling by other algae that need sunlight only available in the upper ocean.

More:
https://www.brightsurf.com/news/article/071819488051/algae-killing-viruses-spur-nutrient-recycling-in-oceans.html

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Tiny organisms with a massive impact
07.02.2017 | News

By: Peter Rüegg

Although diatoms are incredibly small, they have a significant impact on the dispersal of nutrients and trace elements in global marine waters. This is the conclusion of a study recently published in the scientific journal “Nature Geoscience ”.



Diatoms from the Southern Ocean, captured by a scanning electron microscope. (photo: Julien Crespin, SEM facility of the Weizmann Institute)


Diatoms are a very common group of algae found not only in freshwater streams, rivers and lakes, but also in marine waters. These unicellular organisms are particularly prevalent in the waters of the Southern Ocean around Antarctica. Given an adequate supply of nutrients and light, diatoms can multiply with such explosive force that they create an algal “bloom”.

During their rapid growth cycle, diatoms absorb huge amounts of trace elements and nutrients from the surface water layer, especially silicon to form their shells, and zinc, which plays a vital physiological role in their development. The heavy depletion of nutrients caused by the algal bloom is most prominent in the uppermost water layer and affects the chemistry of many of the world’s major oceans – a phenomenon described by a team of researchers led by Derek Vance, Professor of Geochemistry and Petrology at ETH Zurich, in an article published recently in the academic journal “Nature Geoscience”.

Diatoms consume nutrients
Researchers can monitor the mass reproduction of these organisms by examining the depth profiles of zinc and silicon concentration in the seawater of different oceans: the profiles are identical for both elements, with a significant depletion in the top kilometre of the water column. The conclusion of the study is that that this is caused by the the biological activity of the diatoms in the surface layer around Antarctica, followed by the transport of the resultant nutrient-depleted water masses to other parts of the ocean in currents.

Depleted of nutrients, the uppermost layer of the water flows in the direction of the Equator. As it reaches a latitude of around 45-50 degrees, it sinks below a warmer surface layer. This middle water layer extends well into the northern oceans and does not mix completely with other layers, and therefore remains starved of nutrients.

More:
https://ethz.ch/content/main/en/news-und-veranstaltungen/eth-news/news/2017/02/diatomeen-dominieren-naehrstoffverteilung.html

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