Loki's Castle is a field of five active
hydrothermal vent
Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hot ...
s in the
mid-Atlantic Ocean, located at
73 degrees north on the
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge (a Divergent boundary, divergent or constructive Plate tectonics, plate boundary) located along the floor of the Atlantic Ocean, and part of the List of longest mountain chains on Earth, longest mountai ...
between
Iceland
Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...
and
Svalbard
Svalbard ( , ), previously known as Spitsbergen or Spitzbergen, is a Norway, Norwegian archipelago that lies at the convergence of the Arctic Ocean with the Atlantic Ocean. North of continental Europe, mainland Europe, it lies about midway be ...
at a depth of .
When they were discovered in mid-July 2008, they were the most northerly
black smoker
Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hots ...
vents known to science.
They are of geological interest as they occur in a relatively stable region of the Earth's crust with diminished tectonic forces and consequently fewer hydrothermal vents. They are the site where a biologically distinct class of
archaea
Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
, the
Lokiarchaeota
Promethearchaeota is the sole phylum of the kingdom Promethearchaeati, the kingdom from which the eukaryotes emerged. The phylum has one valid class: Promethearchaeia. The phylum includes all members of the group previously named Deep Sea Arc ...
, were discovered.
Geography
Loki's Castle is located on the
Gakkel Ridge
The Gakkel Ridge (formerly known as the Nansen Cordillera and Arctic Mid-Ocean Ridge) is a mid-oceanic ridge, a divergent tectonic plate boundary between the North American Plate and the Eurasian Plate. It is located in the Eurasian Basin of t ...
(previously the Arctic Mid-Ocean Ridge), where the Mohns and Knipovich ridges converge.
Ocean core complexes are found to the northwest. The field resides approximately deep at the boundary of the
Greenland
Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...
and
Norwegian Sea
The Norwegian Sea (; ; ) is a marginal sea, grouped with either the Atlantic Ocean or the Arctic Ocean, northwest of Norway between the North Sea and the Greenland Sea, adjoining the Barents Sea to the northeast. In the southwest, it is separate ...
.
History
Discovery
The vents were discovered in 2008 by a 25-person multinational scientific expedition of the
University of Bergen
The University of Bergen () is a public university, public research university in Bergen, Norway. As of 2021, the university had over 4,000 employees and 19,000 students. It was established by an act of parliament in 1946 consolidating several sci ...
, Norway. The vents are located more than north of what were previously the northernmost known vents, discovered in 2005. The high-latitude 2005 and 2008 expeditions were both led by geologist Rolf Pedersen of the university's Centre for
Geobiology
Geobiology is a field of scientific research that explores the interactions between the physical Earth and the biosphere. It is a relatively young field, and its borders are fluid. There is considerable overlap with the fields of ecology, evoluti ...
, aboard the research vessel ''G.O. Sars'' (named after the Norwegian marine biologist
Georg Ossian Sars
Prof Georg Ossian Sars HFRSE (20 April 1837 – 9 April 1927) was a Norway, Norwegian marine biology, marine and freshwater biology, freshwater biologist.
Life
Georg Ossian Sars was born on 20 April 1837 in Kinn (former municipality), Kinn, No ...
and launched in May 2003).
[ The vents were located using a remotely controlled underwater vehicle.
The vent field was given the name Loki's Castle as its shape reminded its discoverers of a fantasy castle. The reference is to the ancient Norse god of trickery, ]Loki
Loki is a Æsir, god in Norse mythology. He is the son of Fárbauti (a jötunn) and Laufey (mythology), Laufey (a goddess), and the brother of Helblindi and Býleistr. Loki is married to the goddess Sigyn and they have two sons, Narfi (son of Lo ...
. It was felt to be "an appropriate name for a field that was so difficult to locate".
Recent expeditions
gravity cores were collected from the vent field in 2010.
The field was revisited by the ''G.O. Sars'' in 2018 and 2019 by the United States Geological Survey
The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...
and the University of Bergen to take sediment push cores.
Geology
Loki's Castle is described in literature as a sediment-influenced basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
-hosted hydrothermal field. Due to boron isotopic composition of hydrothermal fluids, it is suggested that vent fluid is recharged (or percholates into the seafloor) in regions densely concentrated with oceanic sediments, rather than unsedimented igneous rock of ridge flanks.
21 types of minerals have been identified at the vent field. When cores were collected in 2018 and 2019, talc
Talc, or talcum, is a clay mineral composed of hydrated magnesium silicate, with the chemical formula . Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent and lubricant ...
was found in samples.
Carbon-14 dating
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...
estimates the oldest hydrothermal material at the field to be over 9,100 years old.
Mounds and chimneys
The vent field is composed of two sulfide mounds, each across, and join into a single composite mound. The size is comparable to that of the TAG field on the Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge (a Divergent boundary, divergent or constructive Plate tectonics, plate boundary) located along the floor of the Atlantic Ocean, and part of the List of longest mountain chains on Earth, longest mountai ...
, one of the largest known hydrothermal fields as of 2010. A member of the 2008 expedition, oceanographer
Oceanography (), also known as oceanology, sea science, ocean science, and marine science, is the scientific study of the ocean, including its physics, chemistry, biology, and geology.
It is an Earth science, which covers a wide range of top ...
Marvin Lilley, has speculated that this may be the largest such deposit ever seen on the sea floor.[
The five active chimneys of Loki's Castle are venting water as hot as and sit on a vast mound of ]sulfide
Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...
minerals that is about in diameter at its base and some across its top.[ The active chimneys are mostly black in colour but are covered with mats of white bacteria that are living on minerals and materials emitted by the vents. The older chimneys are mottled red in colour due to the presence of deposits of oxidised iron.][
Four distinct high-temperature chimneys were sampled between 2008 and 2009: João, Menorah, Camel, and Sleepy. The chimneys are predominantly ]sphalerite
Sphalerite is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimentary exhalative, Carbonate-hoste ...
, pyrite
The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic luster and pale brass-yellow hue ...
, and pyrrhotite
Pyrrhotite (''Pyrrhus of Epirus, pyrrhos'' in Greek language, Greek meaning "flame-coloured"'')'' is an iron sulfide mineral with the formula Fe(1−x)S (x = 0 to 0.125). It is a nonstoichiometric compound, nonstoichiometric variant of FeS, th ...
, and small amounts of chalcopyrite
Chalcopyrite ( ) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a Mohs scale, hardness of 3.5 to 4 ...
. Small barite
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
chimneys (height of <) are located east of the main field, where venting is less pronounced. This section of the system is nicknamed the ''Barite Field''.
Fluid chemistry
Loki's Castle fluids are rich in volatile gases, namely hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
, hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
, and methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...
. The field is also associated with high concentrations of hydrocarbons
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may b ...
, ammonium
Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleu ...
, and alkalinity
Alkalinity (from ) is the capacity of water to resist Freshwater acidification, acidification. It should not be confused with base (chemistry), basicity, which is an absolute measurement on the pH scale. Alkalinity is the strength of a buffer s ...
while being depleted of dissolved iron and manganese. Fluid pH from high-temperature locations are acidic, ranging from 5.5 - 6.1.
Ecology
The bristleworm
Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ma ...
''Nicomache lokii'' (Maldanidae
Maldanidae is a family of more than 200 species of marine polychaetes commonly known as bamboo worms or maldanid worms. They belong to the order Capitellida, in the phylum Annelida. They are most closely related to family Arenicolidae, and toget ...
) is thought to be a key species in the fauna surrounding the hydrothermal vents in the area. This species is one of the more than ten species that were newly discovered here.
''Sclerolinum contortum'' tube worms are located at the field on the largest sulfide mounds. Melitidae
Melitidae is a family (biology), family of Amphipoda, amphipods. It contains around 45 genera, and formerly included a further 40 genera that are now placed in the family Maeridae.
Genera
*''Abludomelita''
*''Allomelita''
*''Alsacomelita''
*'' ...
amphipods are found amongst the tube worms and are common in chimney crevices.
Microbiology
Loki's Castle has dense mats of bacteria on and around vents that use the minerals and compounds expelled by the vents. Common among these are Epsilonproteobacteria and Gammaproteobacteria
''Gammaproteobacteria'' is a class of bacteria in the phylum ''Pseudomonadota'' (synonym ''Proteobacteria''). It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scienti ...
, which oxidize the abundant hydrogen and hydrogen sulfide and form biofilms
A biofilm is a syntrophic community of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymer ...
on active chimney surfaces. Thaumarchaeota have been found at less active chimney sites. '' Sulfurovum'' dominate microbial mats. Samples from 2008 and 2010 contained a diversity of Chlamydiae
The Chlamydiota (synonym Chlamydiae) are a bacterial phylum and class whose members are remarkably diverse, including pathogens of humans and animals, symbionts of ubiquitous protozoa, and marine sediment forms not yet well understood. All of ...
.
Preliminary observations have indicated that the warm area around the vents of Loki's Castle is a marine ecotope
Ecotopes are the smallest ecologically distinct landscape features in a landscape mapping and classification system. As such, they represent relatively homogeneous, spatially explicit landscape functional units that are useful for stratifying lan ...
populated with apparently unique and diverse microorganisms
A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...
, unlike other observed marine hydrothermal vent ecosystems
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
.[ One of these, an archaeal phylum named ]Lokiarchaeota
Promethearchaeota is the sole phylum of the kingdom Promethearchaeati, the kingdom from which the eukaryotes emerged. The phylum has one valid class: Promethearchaeia. The phylum includes all members of the group previously named Deep Sea Arc ...
, was discovered and named after Loki's Castle. Lokiarchaeota is renowned as a potential linkage between prokaryote
A prokaryote (; less commonly spelled procaryote) is a unicellular organism, single-celled organism whose cell (biology), cell lacks a cell nucleus, nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Gree ...
s and eukaryote
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
s in the three-domain system
The three-domain system is a taxonomic classification system that groups all cellular life into three domains, namely Archaea, Bacteria and Eukarya, introduced by Carl Woese, Otto Kandler and Mark Wheelis in 1990. The key difference from ea ...
of life.
Metagenome
Metagenomics is the study of all genetic material from all organisms in a particular environment, providing insights into their composition, diversity, and functional potential. Metagenomics has allowed researchers to profile the microbial co ...
analyses by Bäckström et al. in 2019 showed that there must be a whole series of previously unknown virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...
es that are known as LCVs or Loki's Castle Viruses. These are primarily giant viruses of the Megaviricetes
''Megaviricetes'' is a class of viruses. The class contains giant viruses, all of which are nucleocytoplasmic large DNA viruses that are assigned to the phylum '' Nucleocytoviricota''. Members of the Megaviricetes typically have genomes that are ...
class in the phylum
In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...
Nucleocytoviricota
''Nucleocytoviricota'' is a phylum of viruses. Members of the phylum are also known as the nucleocytoplasmic large DNA viruses (NCLDV), which serves as the basis of the name of the phylum with the suffix - for virus phylum. These viruses are refe ...
(NCLDV) in the area of Loki's Castle. Of the 23 high-quality NCLDV genomic bins:
* 15 are related to pithovirus
''Alphapithovirus'', is a genus of giant virus known from two species, '' Alphapithovirus sibericum'', which infects amoebas, and '' Alphapithovirus massiliense''. It is DNA-based and is a member of the nucleocytoplasmic large DNA viruses clade ...
es,
* 5 are related to Marseille viruses,
* 1 are related to iridovirus
''Iridovirus'' is a genus of viruses in the family ''Iridoviridae''. Arthropods serve as natural hosts. Currently, only two species are placed in this genus. Invertebrate iridescent virus 6 (IIV-6) was recognised as the type species until such ...
es, and
* 2 are related to klosneuvirus
''Klosneuvirus'' (KNV, also KloV) is a new type of giant virus found by the analysis of low-complexity metagenomes from a wastewater treatment plant in Klosterneuburg, Austria. It has a 1.57-Mb genome coding unusually high number of genes typic ...
es
The iridovirus-like gene sequence has been named "LCIVAC01".
See also
*Asgard (archaea)
Promethearchaeati (Synonym (taxonomy), syn. "Asgard") is a Kingdom (biology), kingdom belonging to the Domain (biology), domain Archaea that contain Eukaryote, eukaryotic signature proteins. It appears that the eukaryotes, the Domain (biology), d ...
*Lokiarchaeota
Promethearchaeota is the sole phylum of the kingdom Promethearchaeati, the kingdom from which the eukaryotes emerged. The phylum has one valid class: Promethearchaeia. The phylum includes all members of the group previously named Deep Sea Arc ...
References
{{reflist
External links
*Sandra Hines,
Scientists break record by finding northernmost hydrothermal vent field
', University of Washington Press Release, 24 July 2008.
2008 University of Bergen Expedition Journal for Day 17 (15 July 2008)
describing the moment of discovery.
Photographs of the 2008 University of Bergen Expedition team members
Background information about hydrothermal fields
(provided by the Centre for Geobiology, University of Bergen)
Loki's Castle
InterRidge Vents Database
Hydrothermal vents
Volcanoes of the Atlantic Ocean