Lodgers on manganese nodules: Sponges promote a high diversity
Sponges, which like to settle on the metallic nodules, also provide a
home for many other animals

Date:
June 10, 2021
Source:
Max Planck Institute for Marine Microbiology
Summary:
Deep down in the ocean, valuable raw materials are stored, such
as nodules of manganese. These resources could help meeting our
increasing demand for rare metals. In addition to the nodules,
there is another treasure down there: A complex ecosystem we
barely understand.

Researchers have discovered that sponges settling on the nodules
provide a home for many other animals. Without nodules, diversity
in these deep- sea regions would be significantly lower.



FULL STORY ========================================================================== Polymetallic nodules and crusts cover many thousands of square kilometres
of the world's deep-sea floor. They contain valuable metals and rare earth elements and are therefore of great economic interest. To date, there
is no market-ready technology for deep-seabed mining. But it is already
clear that interventions in the seabed have a massive and lasting impact
on the areas affected. This is also confirmed by a study now published by
Tanja Stratmann from the Max Planck Institute for Marine Microbiology in Bremen, Germany, and researchers from the Senckenberg am Meer Institute
in Wilhelmshaven, Germany, and the Dutch research institute NIOZ.


==========================================================================
In their study, Stratmann and her colleagues used data from a variety
of existing surveys as well as deep seafloor imagery from two regions of
the Pacific Ocean that are rich in manganese nodules. Using these data,
they created a model of interactions in these regions.

"We discovered that stalked sponges are often attached to the polymetallic nodules," Stratmann explained. The sponges use the hard nodules amid the
muddy deep-sea environment as the only available hard substrate. With
their stalks, they anchor themselves to the nodule while their main body protrudes into the water to filter tiny particles from it. Moreover,
the sponges themselves provide a habitat for other animals, such as small worms, crabs and clams. "Our models predict the following: If the nodules
are removed, the sponges will also disappear, and with them the associated fauna," Stratmann added. "This reduces the number of animal species and
links in the food web. Without the nodules, the food web in the deep sea becomes simpler and less divers." Stratmann and her colleagues examined
two nodule-rich regions in the Pacific Ocean, the Clarion-Clipperton Zone
and the Peru Basin. In both regions, a modelled removal of the nodules massively disturbed the ecosystem. This primarily resulted from so-called non-trophic interactions between different animals -- those that do not
revolve around "eat or be eaten." These include interactions between the sponges and the animals that live on them, as well as between the sponge inhabitants themselves. In the Clarion-Clipperton Zone in particular,
more than half of the deep-sea inhabitants depend on the nodules in
one way or another. Removal of the nodules and thus the sponges, as
would be the case through deep-sea mining, would trigger a cascade of
negative effects on the ecosystem. Rapid recovery is unlikely because
the nodules take millions of years to grow to substantial size, and the deep-sea ecosystem regenerates very slowly.

========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_Marine_Microbiology. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Tanja Stratmann, Karline Soetaert, Daniel Kersken, Dick van Oevelen.

Polymetallic nodules are essential for food-web integrity
of a prospective deep-seabed mining area in Pacific
abyssal plains. Scientific Reports, 2021; 11 (1) DOI:
10.1038/s41598-021-91703-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/06/210610091113.htm

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