A rusticle is a rust formation resembling an icicle that forms underwater when bacteria oxidize wrought iron and steel. These structures are often seen on famous shipwrecks like the RMS Titanic and the German battleship Bismarck. The term "rusticle," a portmanteau of rust and icicle, was coined by Robert Ballard after his 1986 observations on the Titanic. Research led by Roy Cullimore at the University of Regina uncovered bacteria such as Halomonas titanicae living within rusticles. Rusticles also form on subsea equipment and grow faster in warmer waters, even with minimal dissolved oxygen.
Composition
The rusticle consists of up to 35% iron compounds including iron oxides, iron carbonates, and iron hydroxides. Rusticles are found in a tube shapes of iron oxides which are vertical to one another. Rusticles are found to grow at approximately 1 cm (0.39 in) a year and are most often found in areas of sunken hulls underwater.
The remainder of the structure is a complex community of symbiotic or mutualistic microbes including bacteria Halomonas titanicae and fungi that use the rusting metal as a source of food, causing microbial corrosion and collectively producing the mineral compounds that form the rusticle as waste products.
Rusticles have been found to most often be composed of iron, calcium, chloride, magnesium, silica, sodium, and sulfate while there are other chemical compositions of rusticles but in much smaller quantities.6
Structure
Structurally, rusticles contain channels which allow water to flow through, and they seem to build up in a ring structure similar to the growth rings of a tree. They are very delicate and can easily disintegrate into fine powder on even the slightest touch.
Colours
The outer surface of a rusticle is smooth red in appearance from the iron(III) oxide, while the core is bright orange due to the presence of crystals of goethite. There are several morphologies of the rusticle, some of which are conical, cylindrical, and rusticle on the seafloor.
References
"USS Indianapolis: The Final Chapter". Retrieved February 16, 2024. https://www.pbs.org/show/uss-indianapolis/ ↩
"New species of bacteria found in Titanic 'rusticles'". BBC News. 6 December 2010. Retrieved 1 March 2012. https://www.bbc.co.uk/news/science-environment-11926932 ↩
"Titanic being dissolved by newly ID'd bacteria". CBC News. December 6, 2010. Retrieved April 21, 2022. https://www.cbc.ca/news/science/titanic-being-dissolved-by-newly-id-d-bacteria-1.882011 ↩
"Microbiologically influenced corrosion of Gulf of Mexico mooring chain at 6,000 feet depths". Archived from the original on 2016-10-06. Retrieved 2013-02-14. https://web.archive.org/web/20161006100634/http://www.intermoor.com/information-center-23/technical-articles-26/omae-2012-84067-microbiologically-influenced-corrosion-of-gulf-of-mexico-mooring-chain-at-6-000-feet-depths-317 ↩
"Microbiologically influenced corrosion of Gulf of Mexico mooring chain at 6,000 feet depths". Archived from the original on 2016-10-06. Retrieved 2013-02-14. https://web.archive.org/web/20161006100634/http://www.intermoor.com/information-center-23/technical-articles-26/omae-2012-84067-microbiologically-influenced-corrosion-of-gulf-of-mexico-mooring-chain-at-6-000-feet-depths-317 ↩
Silva-Bedoya, Lina (5 January 2021). "Deep-sea corrosion rusticles from iron-hulled shipwrecks". Wiley. ↩