Lōʻihi Seamount – Part 2: Gourmets of Heavy Metal

Note: Apart from few general sources, all information and citations in this article are gleaned from interviews with, or articles about the work of, marine ecologist David Emerson of the Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine; Craig Moyer, Professor at the Biology Department of Western Washington University; Brian T. Glazer, Ph.D., Associate Professor at the Department of Oceanography University of Hawaii Manoa (UH); and Clara Chan, Assistant Professor of Geological Sciences at the University of Delaware.

LIFE ON THE UNDERWATER SLOPES OF LO’IHI

Expeditions to the volcano have often been joint ventures of scientists from various fields of research, including biologists and microbiologists, which is no surprise given that life on an active undersea volcano cannot be researched in many places of the world; rarely any such location is so relatively easy to access as Lōʻihi Seamount.

First, here are some of the deep sea dwellers on the slopes of Lōʻihi (most of the images were captured by deep-sea vehicles of the Schmidt- and the Woods Hole Oceanographic Institutions). Unlike in other thermally active sea ground habitats, where the living things seem to enjoy the cosy temperatures and the food diversity, there are not very many species found around Lōʻihi. If that has to to with the volcano erupting very often or emitting certain poisonous substances that diminish life, has yet to be found out.

Slatjaw Cuthroat (Synaphobranchus kaupi)

The Slatjaw Cutthroat Eel (Synaphobranchus kaupi) generally occurs as deep as 4800 m. It is probably most common between 800 and 2000 m. This fish has been observed swimming along the bottom by scientists in a submersible. Apparently, this fish can swim backwards, as well as forwards, and can hover head up or down, like a stick in the water!

A goosefish (Sladenia remiger).  Image NOAA

This cute guy, a goosefish, sits on a rock in a submarine canyon, cunningly using its modified dorsal fin to lure unsuspecting small fishes to its mouth. It is common on the summit of Loihi.

Another rare sighting at Lō’ihi, the Rattail, or Grenadier, which is abundant elsewhere though.

Two different types of shrimp, the left one might be the endemic Opaepele loihi

 

 

 

 

 

 

Near the summit of Lō’ihi, small shrimp can be seen. I am not entirely sure if one of these are the Bresiliid shrimp (Opaepele loihi) that are endemic to Lō’ihi Seamount and appear to feed on the microbial mats. It has been said that those have no longer been found after the 1996 eruption, yet these photos are from a 2013(?) exploration.

Anglerfish and Eal

Would you look at him! If eyes could kill! A rare sighting, two fish in one shot! A large anglerfish and a small, sleek eel-like fish.

 

 

I could not but include this mum and her kids (below): Female amphipod with recently hatched young.

Image: Schmidt Ocean Institute.

 

All those were no strangers to the biologists, yet a very special surprise was waiting in the deep for oceanographers and microbiologists:
THE IRON-EATERS OF LO’IHI

Since their discovery in 1987, hydrothermal vent fields at the summit of the volcanic Lōʻihi Seamount, near the island of Hawaii, have been the focus of intense research. But only recently did scientists discover that something unusual and important was also happening at the base of this seamount, 5,000 meters down.

A novel hydrothermal field had been discovered at the base of Lōʻihi Seamount at 5000m bsl. Geochemical analyses demonstrate that “FeMO Deep” derives from a distal, ultra-diffuse hydrothermal source. The area “FeMO Deep” is characterized as a regional seafloor seepage of gelatinous iron- and silica-rich deposits, pooling between and over basalt pillows, in places over a meter thick. The system is capped by mm to cm thick hydrothermally derived iron-oxyhydroxide- and manganese-oxide-layered crusts.

Aboard ship, scientists process samples of Zetaproteobacteria from Loihi’s flanks.
Credit: David Emerson, Bigelow Laboratory

There, previously unknown bacterial communities that feed on iron may be playing unappreciated roles in balancing ocean chemistry. Fe-oxidizing bacteria (FeOB) are the dominant bacteria in Lōʻihi’s iron-rich microbial mats, turning Loihi’s underwater slopes an unusual, and characteristic, orange-red. They’re rarely found in other deep-sea or marine habitats, suggesting that they might be restricted to niches where iron is abundant. For decades it had been recognized that FeOB are associated with hydrothermal venting of Fe(II)-rich fluids associated with seamounts in the world’s oceans. So far, the evidence of their existence was based almost entirely on the mineralogical remains of the microbes, but the living matter had never been cultivated, catalogued or otherwise studied up to 2007. It turns out that those critters live on Fe2+ as the sole energy source and CO2 as the only available carbon source – in scientific terms: obligate, lithotrophic FeOB named Mariprofundus ferrooxydans PV-1 of the class Zetaproteobacteria. Or in less accurate terms, they produce the mats as they munch iron and excrete a rusty waste product; they use a little carbon from CO2 to build their cells; and the energy for all that hard work they derive from the oxidation process.

One study suggested that these biogenic “deposits represent a modern analog for one class of geological iron deposits known as “umbers” (for example, Troodos ophiolites, Cyprus) because of striking similarities in size, setting and internal structures”. So, learning more about them could offer insights on the origin of previously unexplained geological features on Earth. Morphological structures similar to those produced by Zetaproteobacteria can still be identified hundreds of millions (and possibly billions) of years back in the geological record, making them of paleontological, and potentially of exobiological, interest. As knowledge of extant populations grows, it is possible this will also help to inform us of environmental changes in past Earth history.

Troodos Ophiolite sheeted dikes and pillow basalts on Cyprus, Jan. 2007. (Photo: Patrick H. Donohue)
Inset: Microbial mats encrusted with iron oxide on the flank of Loihi Seamount, Hawaii. (Photo: NOAA)

“Ophiolites are oceanic crustal sequences that have been obducted and raised above sea level. To paint with a broad brush, the sequence (from bottom) is one of ultramafic rock, gabbro intrusions, sheeted dykes, pillow lavas, and sometimes topped by pelagic sediment. The Troodos Ophiolite on Cyprus is a fantastic example because it was sort of smeared over the island and at least a little bit of everything can be found at/near the surface. Here we see the sheeted dykes and pillow basalts at a grand scale!” (PH Donohue, Ph.D, on his blog poikiloblastic )

In June 2014 Brian Glazer, an oceanographer at the University of Hawaii Manoa (UH) prepared for an expedition to Lōʻihi, whose base still remains largely unexplored. He and his team from UH, as well as an international group of scientists, were going to survey the seamount’s deeper reaches using Woods Hole Oceanographic’s Sentry autonomous underwater vehicle (AUV).

Glazer and his colleagues first found the iron-oxidizing bacterial formations at the base of Lōʻihi by accident. They were looking for some bare rocks to compare against samples they had been collecting at the summit. But then, in between a few basalt boulders they found huge microbial mats – given away by telltale signs of orange layers, or flocs, between volcanic rock formations.

Left: The telltale signs of orange flocculent material at the base of the Loihi Seamount. Right: The ponded bacterial material revealed after the surface layer removed. Credit: Woods Hole Oceanographic/Brian Glazer

THE RUSTY CITY

Lōʻihi Seamount and its “rust villages”: structures built by iron-oxidizing microbes. Credit: Clara Chan, University of Delaware – Click to enlarge

Scanning-electron microscopy micrographs of mat and crust material from Ula Nui. Scale bar for (a)=10 μm. (a) Overview of Fe-
oxyhydroxide morphologies, including twisted stalk-like structures, spherical structures, long straight stick structures and branching
filaments.

 

 

 

 

 

 

“We don’t usually think of bacteria as villages,” one of the scientist says, “For the Zetaproteobacteria that live at Lōʻihi, that might be a good analogy, though. What they do with rust is remarkable.” These undersea designers fashion “skyscrapers,” spires and highways of iron oxide filaments woven together. Zetaproteobacteria are the ultimate in sustainable architects, they recycle rusty minerals into building blocks. They can produce huge amounts of iron oxides connected by sheaths; 100 cells might crank out as much as three feet of sheath in one day. These complex structures regulate water and nutrient flow in the “villages”.

Iron is the fourth most abundant element in Earth’s crust (other sources say fifth), and is essential for life – as we know, iron is the oxygen-carrying component of hemoglobin in your blood. Only, you can’t eat iron, you need to take it in a processed form with your food. Not so Zetaproteobacteria, they are able to derive energy out of iron oxidation, that is, they sustain themselves by turning pure iron into rust. Which in turn is great for the entire marine environment in that the iron oxides the bacteria produce are widely dispersed in the ocean, where they’re an iron source for plankton and other marine life …and for you too, if you eat fish!

Recent discoveries have expanded their range, to deep within the ocean crust, iron deposits in salt marshes, and to the corrosion on steel. In freshwater, their kin are found in roadside ditches, slow-moving streams, wetlands, and on the roots of submerged plants. One indicator of their presence is a metallic sheen on the water, which is sometimes mistaken for an oil slick.

~~~~~

Today, the research for those iron-oxidizing energy-storing bacteria is in full swing. They have been found in many places of the world, preferredly along the mid-ocean ridges but also along the continental shelfs. Scientific research has yet to find out how exactly the metabolism of the bacteria works, what different populations and strains of them may exist, and how they interact with and change their marine environment. The theories, hypotheses and speculations about their future usefulness are running high – as the one about possibilities of creating renewable energy – so, lets wait and drink tea, until our tea water can be heated with electricity made by the Lōʻihi ironeaters – which hopefully will happen somewhat earlier than our stroll along the beach of Lōʻihi Island!

Enjoy! – GRANYIA

SOURCES

– NOAA Oceanexplorer
– A Novel Lineage of Proteobacteria Involved in Formation of Marine Fe-Oxidizing…
– zetahunters – searching for microbes that rust the crust
– Iron-oxidizing bacteria found along Mid-Atlantic Ridge
– Rust villages of the deep: In Pele’s shadow, iron oxide, or rust, comes to life
– Dr. Craig Moyer’s Research Homepage
– Zeta-Proteobacteria dominate the colonization and formation of microbial mats… (pdf)
– Ultra-diffuse hydrothermal venting supports Fe-oxidizing bacteria and massive umber deposition at 5000m off Hawaii (pdf)
– Schmidt Ocean Institute, Ironeaters
– Hidden in plain sight: discovery of sheath-forming, iron-oxidizing Zetaproteobacteria at Loihi Seamount, Hawaii, USA
– Slatjaw Cutthroat Eel, Synaphobranchus kaupi

Also see:  Lōʻihi Seamount, Part 1. Hānau Ka Moku – An Island is Born

You can find more interesting stuff on Hawaiian volcanoes in agimarc’s article on Kauai and on Maui Nui as well as Bobbi’s trilogy on Oahu in VC:
https://volcanocafe.wordpress.com/2014/10/20/a-short-geologic-history-of-kauai-hawaii/
https://volcanocafe.wordpress.com/2014/06/20/the-volcanic-landmarks-of-oahu-hawaii-part-1-diamond-head/

 

 

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