Marine fungi are species of fungus that live in marine or Estuary environments. They are not a taxonomic group, but share a common habitat. Obligate marine fungi grow exclusively in the marine habitat while wholly or sporadically submerged in sea water. Facultative marine fungi normally occupy terrestrial or freshwater habitats, but are capable of living or even Spore in a marine habitat. About 2,149 species of marine fungi have been described, within eleven phyla and 856 genera, although only about 64 species have been fully genetically sequenced.[Jones, EB Gareth et al. Marine Fungi. Originally published May 17, 2019. Last updated February 27, 2025. Accessed April 2, 2025.] Many species of marine fungi are known only from and it is likely a large number of species have yet to be discovered.[ In fact, it is thought that less than 1% of all marine fungal species have been described, due to difficulty in targeting marine fungal DNA and difficulties that arise in attempting to grow cultures of marine fungi.][
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Different marine habitats support very different fungal communities. Fungi can be found in niches ranging from ocean depths and coastal waters to and estuaries with low salinity levels.[ Species of Higher Marine Fungi University of Mississippi. Retrieved 2012-02-05.]
There has been some debate as to what exactly a marine fungus should be defined as. A definition used previously was "individuals with a long-term presence and metabolic activities in a marine habitat."[Mitchison-Field, Lorna; et al. (June 2, 2019). "Unconventional cell division cycles from marine-derived yeasts". Current Biology.] is from Ka-Lai et al. 2016: "any fungus that is recovered repeatedly from marine habitats because: 1) it is able to grow and/or sporulate (on substrata) in marine environments; 2) it forms symbiotic relationships with other marine organisms; or 3) it is shown to adapt and evolve at the genetic level or be metabolically active in marine environments."
Overview
Terrestrial fungi play critical roles in nutrient cycling and food webs and can shape macroorganism communities as parasites and mutualists. Although estimates for the number of fungal species on the planet range from 1.5 to over 5 million, likely fewer than 10% of fungi have been identified so far. To date, a relatively small percentage of described species are associated with marine environments, with ~1,100 species retrieved exclusively from the marine environment. Nevertheless, fungi have been found in nearly every marine habitat explored, from the surface of the ocean to kilometers below ocean sediments. Fungi are hypothesized to contribute to phytoplankton population cycles and the biological carbon pump and are active in the chemistry of . Many fungi have been identified as or of marine animals (e.g., corals and sponges), plants, and algae. Despite their varied roles, remarkably little is known about the diversity of this major branch of eukaryotic life in marine ecosystems or their ecological functions.[Amend, A., Burgaud, G., Cunliffe, M., Edgcomb, V.P., Ettinger, C.L., Gutiérrez, M.H., Heitman, J., Hom, E.F., Ianiri, G., Jones, A.C. and Kagami, M. (2019) "Fungi in the marine environment: Open questions and unsolved problems". MBio, 10(2): e01189-18. . Modified text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.]
Fungi represent a large and diverse group of microorganisms in microbiological communities in the marine environment and have an important role in nutrient cycling.[Tisthammer, K.H.; Cobian, G.M.; Amend, A.S. Global biogeography of marine fungi is shaped by the environment. Fungal Ecol. 2016, 19, 39–46.] They are divided into two major groups; obligate marine fungi and marine fungi.[Raghukumar, S. The marine environment and the role of fungi. In Fungi in Coastal and Oceanic Marine Ecosystems: Marine Fungi; Springer International Publishing: Cham, Switzerland, 2017; pp. 17–38.] Obligate marine fungi are adapted to reproduce in the aquatic environment, while facultative marine fungi can grow in aquatic as well as terrestrial environments.[Patyshakuliyeva, A., Falkoski, D.L., Wiebenga, A., Timmermans, K. and De Vries, R.P. (2020) "Macroalgae derived fungi have high abilities to degrade algal polymers". Microorganisms, 8(1): 52. . Modified text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.]
Marine fungal species occur as , , or and colonize a wide range of substrates, such as , , , and .[Jones, E.B.G.; Suetrong, S.; Sakayaroj, J.; Bahkali, A.H.; Abdel-Wahab, M.A.; Boekhout, T.; Pang, K.-L. Classification of marine Ascomycota, Basidiomycota, Blastocladiomycota and Chytridiomycota. Fungal Divers. 2015, 73, 1–72.][Debbab, A.; Aly, A.H.; Proksch, P. Mangrove derived fungal endophytes–a chemical and biological perception. Fungal Divers. 2013, 61, 1–27.]
Factors that influence whether or not marine fungi are present in any particular location include the water temperature, its salinity, the water movement, the presence of suitable substrates for colonization, the presence of propagules in the water, interspecific competition, pollution and the oxygen content of the water.[
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Some marine fungi which have ventured into the sea from terrestrial habitats include species that burrow into sand grains, living in the pores. Others live inside stony corals, and may become pathogenic if the coral is stressed by rising sea temperatures.
In 2011 the phylogeny of marine fungi was elucidated by analysis of their small subunit ribosomal DNA sequences. Thirty six new marine lineages were found, the majority of which were Chytridiomycota but also some filamentous and multicellular fungi. The majority of the species found were Ascomycota and Basidiomycota yeasts.
The secondary metabolites produced by marine fungi have high potential for use in Biotechnology, medical and industrial applications.[ Marine Fungi Retrieved 2012-02-06.]
Evolution
In contrast to plants and animals, the early fossil record of the fungi is meager. Since fungi do not biomineralise, they do not readily enter the fossil record. Fungal fossils are difficult to distinguish from those of other microbes, and are most easily identified when they resemble Extant taxon fungi.
The earliest fossils possessing features typical of fungi date to the Paleoproterozoic era, some (annum). These multicellular benthic organisms had filamentous structures capable of anastomosis, in which hyphal branches recombine.
For much of the Paleozoic Era (542–251 Ma), the fungi appear to have been aquatic and consisted of organisms similar to the extant in having flagellum-bearing spores.
The evolutionary adaptation from an aquatic to a terrestrial lifestyle necessitated a diversification of ecological strategies for obtaining nutrients, including parasitism, saprobism, and the development of mutualistic relationships such as mycorrhiza and lichenization.[Taylor and Taylor, pp. 84–94 and 106–107.] Recent (2009) studies suggest that the ancestral ecological state of the Ascomycota was saprobism, and that independent events have occurred multiple times.
The growth of fungi as hyphae on or in solid substrates or as single cells in aquatic environments is adapted for the efficient extraction of nutrients, because these growth forms have high surface area to volume ratios.[ Hyphae are specifically adapted for growth on solid surfaces, and to invade substrates and tissues.][ They can exert large penetrative mechanical forces; for example, many , including Magnaporthe grisea, form a structure called an appressorium that evolved to puncture plant tissues.][ The pressure generated by the appressorium, directed against the plant epidermis, can exceed .][ The filamentous fungus Paecilomyces lilacinus uses a similar structure to penetrate the eggs of .][
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Fungi were considered to be part of the Plant until the mid-20th century. By the middle of the 20th century, fungi were considered a distinct kingdom, and the newly recognized kingdom Fungus becoming the third major kingdom of multicellular with kingdom and kingdom , the distinguishing feature between these kingdoms being the way they obtain nutrition.
Marine plants
Mangroves
The greatest number of known species of marine fungi are from .[ In one study, blocks of mangrove wood and pieces of driftwood of Avicennia alba, Bruguiera cylindrica and Rhizophora apiculata were examined to identify the lignicolous (wood-decaying) fungi they hosted. Also tested were Nypa fruticans, a mangrove palm and Acanthus ilicifolius, a plant often associated with mangroves. Each material was found to have its own characteristic fungi, the greatest diversity being among those growing on the mangrove palm. It was surmised that this was because the salinity was lower in the estuaries and creeks where Nypa grew, and so it required a lesser degree of adaptation for the fungi to flourish there. Some of these species were closely related to fungi on terrestrial palms. Other studies have shown that driftwood hosts more species of fungus than do exposed test blocks of wood of a similar kind. The mangrove leaf litter also supported a large fungal community which was different from that on the wood and living material. However, few of these were multicellular, higher marine fungi.][
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Other plants
The sea snail Littoraria irrorata damages plants of Spartina in the coastal sea marshes where it lives, which enables spores of intertidal ascomycetous fungi to colonise the plant. The snail eats the fungal growth in preference to the grass itself. This mutualism between the snail and the fungus is considered to be the first example of husbandry among invertebrate animals outside the class Insecta.
Eelgrass, Zostera marina, is sometimes affected by seagrass wasting disease. The primary cause of this seems to be pathogenic strains of the protist Labyrinthula, but it is thought that fungal also contribute and may predispose the eelgrass to disease.[ Disease Analysis in San Juan Archipelago Friday Harbor Laboratories Seagrass Lab. Retrieved 2012-02-06.]
Wood
Many marine fungi are very specific as to which species of floating and submerged wood they colonise. A range of species of fungi colonise beech, while oak supports a different community. When a fungal propagule lands on a suitable piece of wood, it will grow if no other fungi are present. If the wood is already colonised by another fungal species, growth will depend on whether that fungus produces antifungal chemicals and whether the new arrival can resist them. The chemical properties of colonizing fungi also affect the animal communities that graze on them: in one study, when hyphae from five different species of marine fungi were fed to , one species supported less than half the number of nematodes per mg of hyphae than did the others.
Detection of fungi in wood may involve incubation at a suitable temperature in a suitable water medium for a period of six months to upward of eighteen months.[
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Lichens
are mutualistic associations between Fungus, usually an ascomycete with a basidiomycete,[ Many more occur in the splash zone, where they occupy different vertical zones depending on how tolerant they are to submersion.][ Freshwater and marine lichen-forming fungi Retrieved 2012-02-06.] Lichen-like fossils have been found in the Doushantuo Formation in China dating back about 600 million years ago.[
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Fungi from Verrucariales also form marine lichens with the brown algae Petroderma maculiforme,
Lichen-like fossils consisting of coccoid cells (cyanobacteria?) and thin filaments (mucoromycotinan Glomeromycota?) are permineralized in marine phosphorite of the Doushantuo Formation in southern China. These fossils are thought to be 551 to 635 million years old or Ediacaran.
Not to be confused with lichens are Mycophycobiosis, similar to lichens in being a symbiosis of an algae and a fungus. In mycophycobiosis the algae forms the external, multicellular structure housing the fungus. The reproduction of both partners is always disjoint.
Algae and phytoplankton
Marine fungi associated with algae are largely unexplored, despite their ecological role and potential industrial applications. For example, it has been shown that fungi associated with algae produce many bioactive secondary metabolites.[Overy, D.P.; Bayman, P.; Kerr, R.G.; Bills, G.F. An assessment of natural product discovery from marine (sensu stricto) and marine-derived fungi. Mycology 2014, 5, 145–167.][Flewelling, A.J.; Currie, J.; Gray, C.A.; Johnson, J.A. Endophytes from marine macroalgae: Promising sources of novel natural products. Curr. Sci. 2015, 109, 88–111.][Miao, F.; Zuo, J.; Liu, X.; Ji, N. Algicidal activities of secondary metabolites of marine macroalgal-derived endophytic fungi. J. Oceanol. Limnol. 2019, 37, 112–121.] Algae derived fungi can be associated with a variety of algae, including brown algae (e.g., Agarum clathratum, Fucus sp., Laminaria sp., Sargassum sp.), green algae (e.g., Ulva sp., Enteromorpha sp., Flabellia sp.), or red algae (e.g. Chondrus sp., Dilsea sp., Ceramium sp.) algae.[Gnavi, G.; Garzoli, L.; Poli, A.; Prigione, V.; Burgaud, G.; Varese, G.C. The culturable mycobiota of Flabellia petiolata: First survey of marine fungi associated to a Mediterranean green alga. PLoS ONE 2017, 12, e0175941.][Kohlmeyer, J.; Volkmann-Kohlmeyer, B. Illustrated key to the filamentous higher marine fungi. Bot. Mar. 1991, 34, 1–61.][Stanley, S.J. Observations on the seasonal occurrence of marine endophytic and parasitic fungi. Can. J. Bot. 1992, 70, 2089–2096.][Zuccaro, A.; Schoch, C.L.; Spatafora, J.W.; Kohlmeyer, J.; Draeger, S.; Mitchell, J.I. Detection and identification of fungi intimately associated with the brown seaweed Fucus serratus. Appl. Environ. Microbiol. 2008, 74, 931–941.][Lee, S.; Park, M.S.; Lee, H.; Kim, J.J.; Eimes, J.A.; Lim, Y.W. Fungal diversity and enzyme activity associated with the macroalgae, Agarum clathratum. Mycobiology 2019, 47, 50–58.]
Almost one-third of all known marine fungal species are associated with algae.[Balabanova, L.; Slepchenko, L.; Son, O.; Tekutyeva, L. Biotechnology potential of marine fungi degrading plant and algae polymeric substrates. Front. Microbiol. 2018, 9, 15–27.] The most commonly described fungi associated with algae belong to the Ascomycota and are represented by a wide diversity of genera such as Acremonium, Alternaria, Aspergillus, Cladosporium, Phoma, Penicillium, Trichoderma, Emericellopsis, Retrosium, Spathulospora, Pontogenia and Sigmoidea.[Stanley, S.J. Observations on the seasonal occurrence of marine endophytic and parasitic fungi. Can. J. Bot. 1992, 70, 2089–2096. Google CrossRef][Zuccaro, A.; Summerbell, R.C.; Gams, W.; Schroers, H.-J.; Mitchell, J.I. A new Acremonium species associated with Fucus spp., and its affinity with a phylogenetically distinct marine Emericellopsis clade. Stud. Mycol. 2004, 50, 283–297.][Kohlmeyer, J.; Kohlmeyer, E. Marine Mycology: The Higher Fungi; Elsevier: Amsterdam, the Netherlands, 2013.][Wainwright, B.J.; Bauman, A.G.; Zahn, G.L.; Todd, P.A.; Huang, D. Characterization of fungal biodiversity and communities associated with the reef macroalga Sargassum ilicifolium reveals fungal community differentiation according to geographic locality and algal structure. Mar. Biodivers. 2019, 49, 2601–2608.]
Rhyzophydium littoreum is a marine chytrid, a primitive fungus that infects green algae in estuaries. It obtains nutrients from the host alga and produces swimming that must survive in open water, a low nutrient environment, until a new host is encountered.[ Another fungus, Ascochyta salicorniae, found growing on seaweed is being investigated for its action against malaria,]
Invertebrates
The American lobster (Homarus americanus), like many other marine , incubates its eggs beneath its tail segments. Here they are exposed to water-borne micro-organisms including fungi during their long period of development. The lobster has a Symbiosis relationship with a gram-negative bacterium that has anti-fungal properties. This bacterium grows over the eggs and protects them from infection by the pathogenic fungus-like oomycete Lagenidium callinectes. The metabolite produced by the bacterium is tyrosol, a 4-hydroxyphenethyl alcohol, an Antibacterial substance also produced by some terrestrial fungi. Similarly, a shrimp found in estuaries, Palaemon macrodactylis, has a symbiotic bacterium that produces 2,3-indolenedione, a substance that is also toxic to the oomycete Lagenidium callinectes.
Vertebrates
, and are susceptible to fungal diseases but these have been little researched in the field. Mortalities from fungal disease have been reported in captive ; it is thought that stress due to captive conditions may have been predisposing. Transmission among animals in the open sea may naturally limit the spread of fungal diseases. Infectious fungi known from orcas include Aspergillus fumigatus, Candida albicans and Saksenaea vasiformis. Fungal infections in other include Coccidioides immitis, Cryptococcus neoformans, Lacazia loboi, Rhizopus sp., Aspergillus flavus, Blastomyces dermatitidis, Cladophialophora bantiana, Histoplasma capsulatum, Mucor sp., Sporothrix schenckii and Trichophyton sp.
farmed in cages in marine environments may be affected by a number of different fungal infections. Exophiala salmonis causes an infection in which growth of hyphae in the kidneys causes swelling of the abdomen. A cellular response by the fish aims to isolate the fungus by walling it off. Fish are also susceptible to fungus-like oomycetes including Branchiomyces which affects the gills of various fishes, and Saprolegnia which attacks damaged tissue.[ Fungal infections of farmed salmon and trout Retrieved 2012-02-06.]
Marine sediment
Ascomycota, Basidiomycota, and Chytridiomycota have been observed in ranging in depth from 0 to 1740 meters beneath the ocean floor. One study analyzed subsurface samples of marine sediment between these depths and isolated all observable fungi. Isolates showed that most subsurface fungal diversity was found between depths of 0 to 25 meters below the sea floor with Fusarium oxysporum and Rhodotorula mucilaginosa being the most prominent. Overall, the ascomycota are the dominant subsurface phylum.
Contrary to previous beliefs, deep subsurface marine fungi actively grow and germinate, with some studies showing increased growth rates under high hydrostatic pressures. Though the methods by which marine fungi are able to survive the extreme conditions of the seafloor and below is largely unknown, Saccharomyces cerevisiae shines some light onto adaptations that make it possible. This fungus strengthens its outer membrane in order to endure higher hydrostatic pressures.
Several sediment-dwelling marine fungi are involved in biogeochemical processes. Fusarium oxysporum and Fusarium solani are denitrifiers both in marine and terrestrial environments.
Sediment-bound marine fungi played a major role in breaking down oil spilled from the Deepwater Horizons disaster in 2010. Aspergillus, Penicillium, and Fusarium species, among others, can degrade high-molecular-weight hydrocarbons as well as assist hydrocarbon-degrading bacteria.
Arctic marine fungi
Marine fungi have been observed as far north as the Arctic Ocean. Chytridiomycota, the dominant parasitic fungal organism in Arctic waters, take advantage of phytoplankton blooms in brine channels caused by warming temperatures and increased light penetration through the ice. These fungi parasitize diatoms, thereby controlling algal blooms and recycling carbon back into the microbial food web. Arctic blooms also provide conducive environments for other parasitic fungi. Light levels and seasonal factors, such as temperature and salinity, also control chytrid activity independently of phytoplankton populations. During periods of low temperatures and phytoplankton levels, Aureobasidium and Cladosporium populations overtake those of chytrids within the brine channels.
Food webs and the mycoloop
Modified text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
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Human uses
Biomass processors
Medical
Marine fungi produce antiviral and antibacterial compounds as metabolites with upwards of 1,000 having realized and potential uses as anticancer, anti-diabetic, and anti-inflammatory drugs.
The antiviral properties of marine fungi were realized in 1988 after their compounds were used to successfully treat the H1N1 flu virus. In addition to H1N1, antiviral compounds isolated from marine fungi have been shown to have virucidal effects on HIV, herpes simplex 1 and 2, Porcine Reproductive and Respiratory Syndrome Virus, and Respiratory Syncytial Virus. Most of these antiviral metabolites were isolated from species of Aspergillus, Penicillium, Cladosporium, Stachybotrys, and Neosartorya. These metabolites inhibit the virus's ability to replicate, thereby slowing infections.
Mangrove-associated fungi have prominent antibacterial effects on several common pathogenic human bacteria including, Staphylococcus aureus and Pseudomonas aeruginosa. High competition between organisms within mangrove niches lead to increases in antibacterial substances produced by these fungi as defensive agents.
Various deep-sea marine fungi species have recently been shown to produce anti-cancer metabolites. One study uncovered 199 novel cytotoxic compounds with anticancer potential. In addition to cytotoxic metabolites, these compounds have structures capable of disrupting cancer-activated via DNA binding. Others inhibit the topoisomerase enzyme from continuing to aid in the repair and replication of cancer cells.
See also
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Aspergillus sydowii
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Fungal loop hypothesis
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Lichina
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Psathyrella aquatica
Further reading
