rhodolith

Rhodoliths (including maërl) have been defined as calcareous nodules composed of more than 50% of coralline red algal material and consisting of one to several coralline species growing together.{{Cite journal|doi = 10.1086/627697|title = Form and Internal Structure of Recent Algal Nodules (Rhodolites) from Bermuda|year = 1971|last1 = Bosellini|first1 = Alfonso|last2 = Ginsburg|first2 = Robert N.|journal = The Journal of Geology|volume = 79|issue = 6|pages = 669–682|bibcode = 1971JG.....79..669B|s2cid = 225041671}}

File:Communities found in rhodolith beds.jpg Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License]]]

File:Vertical and latitudinal changes in rhodoliths on the seafloor.jpg in Brazil ]]

Rhodolith beds have been found throughout the world's oceans, including in the Arctic near Greenland, in waters off British Columbia, Canada, the Gulf of California, Mexico,{{Cite journal|last1=Steller|first1=D. L.|last2=Riosmena‐Rodríguez|first2=R.|last3=Foster|first3=M. S.|last4=Roberts|first4=C. A.|date=2003|title=Rhodolith bed diversity in the Gulf of California: the importance of rhodolith structure and consequences of disturbance|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/aqc.564|journal=Aquatic Conservation: Marine and Freshwater Ecosystems|language=en|volume=13|issue=S1|pages=S5–S20|doi=10.1002/aqc.564|issn=1099-0755|url-access=subscription}} the Mediterranean {{Citation|last1=Basso|first1=Daniela|title=Mediterranean Rhodolith Beds|date=2017|url=http://link.springer.com/10.1007/978-3-319-29315-8_11|work=Rhodolith/Maërl Beds: A Global Perspective|volume=15|pages=281–298|editor-last=Riosmena-Rodríguez|editor-first=Rafael|place=Cham|publisher=Springer International Publishing|doi=10.1007/978-3-319-29315-8_11|isbn=978-3-319-29313-4|access-date=2021-01-01|last2=Babbini|first2=Lorenza|last3=Ramos-Esplá|first3=Angel Alfonso|last4=Salomidi|first4=Maria|series=Coastal Research Library |editor2-last=Nelson|editor2-first=Wendy|editor3-last=Aguirre|editor3-first=Julio|url-access=subscription}} as off New Zealand{{Cite book|title=Rhodolith beds in northern New Zealand: characterisation of associated biodiversity and vulnerability to environmental stressors|date=2012|publisher=Ministry for Primary Industries|author=Nelson, W. A. |isbn=978-0-478-40077-9|location=Wellington, NZ|oclc=812180715}} and eastern Australia.Harris, P.T., Tsuji, Y., Marshall, J.F., Davies, P.J., Honda, N., Matsuda, H., 1996. Sand and rhodolith-gravel entrainment on the mid- to outer-shelf under a western boundary current: Fraser Island continental shelf, eastern Australia. Marine Geology 129, 313–330 Globally, rhodoliths fill an important niche in the marine ecosystem, serving as a transition habitat between rocky areas and barren, sandy areas. Rhodoliths provide a stable and three-dimensional habitat onto and into which a wide variety of species can attach, including other algae, commercial species such as clams and scallops, and true corals. Rhodoliths are resilient to a variety of environmental disturbances, but can be severely impacted by harvesting of commercial species. For these reasons, rhodolith beds deserve specific actions for monitoring and conservation.{{Cite journal|last1=Basso|first1=D.|last2=Babbini|first2=L.|last3=Kaleb|first3=S.|last4=Bracchi|first4=V.A.|last5=Falace|first5=A.|date=2016|title=Monitoring deep Mediterranean rhodolith beds|journal=Aquatic Conservation: Marine and Freshwater Ecosystems|language=en|volume=26|issue=3|pages=549–561|doi=10.1002/aqc.2586|issn=1052-7613|doi-access=free|hdl=11368/2849200|hdl-access=free}}{{Cite journal|last1=Barbera|first1=C.|last2=Bordehore|first2=C.|last3=Borg|first3=J.A.|last4=Glémarec|first4=M.|last5=Grall|first5=J.|last6=Hall-Spencer|first6=J. M.|last7=de la Huz|first7=Ch.|last8=Lanfranco|first8=E.|last9=Lastra|first9=M.|last10=Moore|first10=P.G.|last11=Mora|first11=J.|date=2003|title=Conservation and management of northeast Atlantic and Mediterranean maerl beds |journal=Aquatic Conservation: Marine and Freshwater Ecosystems|language=en|volume=13|issue=S1|pages=S65–S76|doi=10.1002/aqc.569|issn=1052-7613|url=https://www.um.edu.mt/library/oar//handle/123456789/5229 }}{{Cite journal|last1=Horta|first1=P.A.|last2=Riul|first2=P.|last3=Amado Filho|first3=G-M.|last4=Gurgel|first4=C.F.D.|last5=Berchez|first5=F.|last6=Nunes|first6=J.M. de Castro|last7=Scherner|first7=F.|last8=Pereira|first8=S.|last9=Lotufo|first9=T.|last10=Peres|first10=L.|last11=Sissini|first11=M.|date=2016|title=Rhodoliths in Brazil: Current knowledge and potential impacts of climate change|journal=Brazilian Journal of Oceanography|volume=64|issue=SPE2|pages=117–136|doi=10.1590/S1679-875920160870064sp2|issn=1679-8759|doi-access=free}}{{Cite journal|last1=Bassi|first1=D.|last2=Braga|first2=J.C.|last3=Owada|first3=M.|last4=Aguirre|first4=J.|last5=Lipps|first5=J.H.|last6=Takayanagi|first6=H.|last7=Iryu|first7=Y.|date=2020|title=Boring bivalve traces in modern reef and deeper water macroid and rhodolith beds|journal=Progress in Earth and Planetary Science|language=en|volume=7|issue=1 |page=41 |doi=10.1186/s40645-020-00356-w|bibcode=2020PEPS....7...41B |issn=2197-4284|doi-access=free|hdl=10481/64249|hdl-access=free}} Rhodoliths come in many shapes, including laminar, branching and columnar growth forms.{{cite book |last=Bosence |first=D. W. |chapter=Description and Classification of Rhodoliths (Rhodoids, Rhodolites) |year=1983 |chapter-url=https://books.google.com/books?id=-oXuCAAAQBAJ&q=%22Description+and+classification+of+rhodoliths+%28rhodoids%2C+rhodolites%29%22&pg=PA223 |title=Coated Grains |pages=217–224 |publisher=Springer |location=Berlin |doi=10.1007/978-3-642-68869-0_19 |isbn=9783642688690}} In shallow water and high-energy environments, rhodoliths are typically mounded, thick or unbranched; branching is also rarer in deeper water, and most profuse in tropical, mid-depth waters.

File:Rhodoliths on the northwestern shore of Fuerteventura.jpg|Rhodoliths on the northern shore of Fuerteventura

File:Messinian rhodolith.JPG|A fossilised rhodolith from the Messinian of southern Spain

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Rhodoliths are a common feature of modern and ancient carbonate shelves worldwide.{{Cite journal|last1=Pomar|first1=L.|last2=Baceta|first2=J.I.|last3=Hallock|first3=P.|last4=Mateu-Vicens|first4=G.|last5=Basso|first5=D.|date=2017|title=Reef building and carbonate production modes in the west-central Tethys during the Cenozoic|url=https://linkinghub.elsevier.com/retrieve/pii/S0264817217301010|journal=Marine and Petroleum Geology|language=en|volume=83|pages=261–304|doi=10.1016/j.marpetgeo.2017.03.015|bibcode=2017MarPG..83..261P |hdl=10281/148633|hdl-access=free}} Rhodolith communities contribute significantly to the global calcium carbonate budget, and fossil rhodoliths are commonly used to obtain paleoecologic and paleoclimatic information.{{Cite journal|last=Basso|first=D.|date=1998|title=Deep rhodolith distribution in the Pontian Islands, Italy: a model for the paleoecology of a temperate sea|url=http://www.sciencedirect.com/science/article/pii/S0031018297000990|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|language=en|volume=137|issue=1|pages=173–187|doi=10.1016/S0031-0182(97)00099-0|bibcode=1998PPP...137..173B|issn=0031-0182|url-access=subscription}}{{Cite journal|last1=Halfar|first1=J.|last2=Zack|first2=T.|last3=Kronz |first3=A.|last4=Zachos|first4=J.C.|date=2000|title=Growth and high-resolution paleoenvironmental signals of rhodoliths (coralline red algae): A new biogenic archive |journal=Journal of Geophysical Research: Oceans|language=en |volume=105 |issue=C9 |pages=22107–22116 |doi=10.1029/1999JC000128|bibcode=2000JGR...10522107H|doi-access=free}}{{Cite journal |last1=Ragazzola |first1=F. |last2=Caragnano |first2=A. |last3=Basso|first3=D. |last4=Schmidt |first4=D.N. |last5=Fietzke |first5=J. |date=2020 |title=Establishing temperate crustose early Holocene coralline algae as archives for palaeoenvironmental reconstructions of the shallow water habitats of the Mediterranean Sea|journal=Palaeontology |language=en |volume=63 |issue=1 |pages=155–170 |doi=10.1111/pala.12447|bibcode=2020Palgy..63..155R |issn=1475-4983 |doi-access=free |hdl=1983/ab309cb5-6b7a-4d3f-b1ef-b4f3cde74579 |hdl-access=free }} Under the right circumstances, rhodoliths can be the main carbonate sediment producers,{{Cite journal|last=Basso|first=D.|date=2012|title=Carbonate production by calcareous red algae and global change|url=http://www.bioone.org/doi/abs/10.5252/g2012n1a2|journal=Geodiversitas|language=en|volume=34|issue=1|pages=13–33|doi=10.5252/g2012n1a2|s2cid=86112464|issn=1280-9659|url-access=subscription}}{{Cite journal|last1=Schubert|first1=N.|last2=Salazar|first2=V. W.|last3=Rich|first3=W. A.|last4=Vivanco Bercovich|first4=M.|last5=Almeida Saá|first5=A. C.|last6=Fadigas|first6=S. D.|last7=Silva|first7=J.|last8=Horta|first8=P. A.|date=2019-08-01|title=Rhodolith primary and carbonate production in a changing ocean: The interplay of warming and nutrients|url=http://www.sciencedirect.com/science/article/pii/S0048969719318157|journal=Science of the Total Environment|language=en|volume=676|pages=455–468|doi=10.1016/j.scitotenv.2019.04.280|pmid=31048175|bibcode=2019ScTEn.676..455S|issn=0048-9697|hdl=10754/632548|s2cid=143435207|hdl-access=free}} often forming rudstone or floatstone beds consisting of rhodoliths and their fragments in grainy matrix.

File:Rhodolith bed physiognomy impacted by warmer and more acidified waters.jpg

Rhodoliths are significant photosynthesizers, calcifiers, and ecosystem engineers, which raises an issue about how they might respond to ocean acidification.

Changes in ocean carbonate chemistry driven by increasing anthropogenic carbon dioxide emissions promotes ocean acidification. Increasing the ocean carbon dioxide uptake results in increases in pCO₂ (the partial pressure of carbon dioxide in the ocean) as well as lower pH levels and a lower carbonate saturation in the seawater. These affect the calcification process.{{Cite journal|doi = 10.1016/j.marchem.2005.12.001|title = Dissociation constants of carbonic acid in seawater as a function of salinity and temperature|year = 2006|last1 = Millero|first1 = Frank J.|last2 = Graham|first2 = Taylor B.|last3 = Huang|first3 = Fen|last4 = Bustos-Serrano|first4 = Héctor|last5 = Pierrot|first5 = Denis|journal = Marine Chemistry|volume = 100|issue = 1–2|pages = 80–94| bibcode=2006MarCh.100...80M }} Organisms like rhodoliths accrete carbonate as part of their physical structure, since precipitating CaCO₃ would be less efficient.{{Cite journal|doi=10.1038/nature04095|title=Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms|year=2005|last1=Orr|first1=James C.|last2=Fabry|first2=Victoria J.|last3=Aumont|first3=Olivier|last4=Bopp|first4=Laurent|last5=Doney|first5=Scott C.|last6=Feely|first6=Richard A.|last7=Gnanadesikan|first7=Anand|last8=Gruber|first8=Nicolas|last9=Ishida|first9=Akio|last10=Joos|first10=Fortunat|last11=Key|first11=Robert M.|last12=Lindsay|first12=Keith|last13=Maier-Reimer|first13=Ernst|last14=Matear|first14=Richard|last15=Monfray|first15=Patrick|last16=Mouchet|first16=Anne|last17=Najjar|first17=Raymond G.|last18=Plattner|first18=Gian-Kasper|last19=Rodgers|first19=Keith B.|last20=Sabine|first20=Christopher L.|last21=Sarmiento|first21=Jorge L.|last22=Schlitzer|first22=Reiner|last23=Slater|first23=Richard D.|last24=Totterdell|first24=Ian J.|last25=Weirig|first25=Marie-France|last26=Yamanaka|first26=Yasuhiro|last27=Yool|first27=Andrew|journal=Nature|volume=437|issue=7059|pages=681–686|pmid=16193043|bibcode=2005Natur.437..681O|s2cid=4306199|url=https://epic.awi.de/id/eprint/13479/1/Orr2005a.pdf}}{{Cite journal|doi = 10.1126/science.1152509|title = Coral Reefs Under Rapid Climate Change and Ocean Acidification|year = 2007|last1 = Hoegh-Guldberg|first1 = O.|last2 = Mumby|first2 = P. J.|last3 = Hooten|first3 = A. J.|last4 = Steneck|first4 = R. S.|last5 = Greenfield|first5 = P.|last6 = Gomez|first6 = E.|last7 = Harvell|first7 = C. D.|last8 = Sale|first8 = P. F.|last9 = Edwards|first9 = A. J.|last10 = Caldeira|first10 = K.|last11 = Knowlton|first11 = N.|last12 = Eakin|first12 = C. M.|last13 = Iglesias-Prieto|first13 = R.|last14 = Muthiga|first14 = N.|last15 = Bradbury|first15 = R. H.|last16 = Dubi|first16 = A.|last17 = Hatziolos|first17 = M. E.|journal = Science|volume = 318|issue = 5857|pages = 1737–1742|pmid = 18079392|bibcode = 2007Sci...318.1737H|s2cid = 12607336|hdl = 1885/28834|hdl-access = free}} Ocean acidification presents a threat by potentially affecting their growth and reproduction.{{Cite journal|doi = 10.1111/gcb.12179|title = Impacts of ocean acidification on marine organisms: Quantifying sensitivities and interaction with warming|year = 2013|last1 = Kroeker|first1 = Kristy J.|last2 = Kordas|first2 = Rebecca L.|last3 = Crim|first3 = Ryan|last4 = Hendriks|first4 = Iris E.|last5 = Ramajo|first5 = Laura|last6 = Singh|first6 = Gerald S.|last7 = Duarte|first7 = Carlos M.|last8 = Gattuso|first8 = Jean‐Pierre|journal = Global Change Biology|volume = 19|issue = 6|pages = 1884–1896|pmid = 23505245|pmc = 3664023|bibcode = 2013GCBio..19.1884K}}{{Cite journal|doi = 10.1038/nclimate2456|title = Lessons learned from ocean acidification research|year = 2015|last1 = Riebesell|first1 = Ulf|last2 = Gattuso|first2 = Jean-Pierre|journal = Nature Climate Change|volume = 5|issue = 1|pages = 12–14|bibcode = 2015NatCC...5...12R}} Coralline algae are particularly sensitive to ocean acidification because they precipitate high magnesium-calcite carbonate skeletons, the most soluble form of CaCO₃.Bischoff, W.D., Bishop, F.C. and Mackenzie, F.T. (1983) "Biogenically produced magnesian calcite; inhomogeneities in chemical and physical properties; comparison with synthetic phases". American Mineralogist, 68(11–12): 1183–1188{{Cite journal|doi = 10.1111/j.1365-2486.2009.01874.x|title = Response of Mediterranean coralline algae to ocean acidification and elevated temperature|year = 2009|last1 = Martin|first1 = Sophie|last2 = Gattuso|first2 = Jean-Pierre|journal = Global Change Biology|volume = 15|issue = 8|pages = 2089–2100|bibcode = 2009GCBio..15.2089M| s2cid=55942151 }}

Calcification rates in coralline algae are thought to be directly related to their photosynthetic rates, but it is not clear how a high-CO₂ environment might affect rhodoliths.{{Cite journal|doi = 10.1111/jpy.12262|title = Coralline algae (Rhodophyta) in a changing world: Integrating ecological, physiological, and geochemical responses to global change|year = 2015|last1 = McCoy|first1 = Sophie J.|last2 = Kamenos|first2 = Nicholas A.|journal = Journal of Phycology|volume = 51|issue = 1|pages = 6–24|pmid = 26986255|pmc = 4964943}} Elevated CO₂ levels might impair biomineralization due to decreased seawater carbonate ({{chem|CO|3|2-}}) availability as pH falls, but photosynthesis could be promoted as the availability of bicarbonate ({{chem|HCO|3|−}}) increases.{{Cite journal|doi = 10.7717/peerj.411|title = Contrasting effects of ocean acidification on tropical fleshy and calcareous algae|year = 2014|last1 = Johnson|first1 = Maggie Dorothy|last2 = Price|first2 = Nichole N.|last3 = Smith|first3 = Jennifer E.|journal = PeerJ|volume = 2|pages = e411|pmid = 24918033|pmc = 4045329 | doi-access=free }} This would result in a parabolic relationship between declining pH and coralline algal fitness, which could explain why varied responses to declining pH and elevated pCO₂ have been recorded to date.{{Cite journal|doi = 10.1130/G30210A.1|title = Marine calcifiers exhibit mixed responses to CO2-induced ocean acidification|year = 2009|last1 = Ries|first1 = J. B.|last2 = Cohen|first2 = A. L.|last3 = McCorkle|first3 = D. C.|journal = Geology|volume = 37|issue = 12|pages = 1131–1134|bibcode = 2009Geo....37.1131R}}

File:Climate change stressors and rhodolith holobiont fitness.webp fitness. Under normal conditions healthy rhodoliths possess stable microbiomes, important to holobiont function. However, beyond the thresholds of algal physiological tolerance, disruption of positive host-microbiome interactions occurs, detrimentally affecting holobiont fitness.{{cite journal |doi=10.1186/s12864-018-5064-4|title=Rhodoliths holobionts in a changing ocean: Host-microbes interactions mediate coralline algae resilience under ocean acidification|year=2018|last1=Cavalcanti|first1=Giselle S.|last2=Shukla|first2=Priya|last3=Morris|first3=Megan|last4=Ribeiro|first4=Bárbara|last5=Foley|first5=Mariah|last6=Doane|first6=Michael P.|last7=Thompson|first7=Cristiane C.|last8=Edwards|first8=Matthew S.|last9=Dinsdale|first9=Elizabeth A.|last10=Thompson|first10=Fabiano L.|journal=BMC Genomics|volume=19|issue=1|page=701|pmid=30249182|pmc=6154897 |doi-access=free }}. 50px Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License]]]

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The widespread distribution of rhodoliths hints at the resilience of this algal group, which have persisted as chief components of benthic marine communities through considerable environment changes over geologic times.{{Cite journal|doi=10.1371/journal.pone.0181637|title=Crustose coralline algae increased framework and diversity on ancient coral reefs|year=2017|last1=Weiss|first1=Anna|last2=Martindale|first2=Rowan C.|journal=PLOS ONE|volume=12|issue=8|pages=e0181637|pmid=28783733|pmc=5544230|bibcode=2017PLoSO..1281637W|doi-access=free}}

In 2018 the first metagenomic analysis of live rhodoliths was published. Whole genome shotgun sequencing was performed on a variety of rhodolith bed constituents. This revealed a stable live rhodolith microbiome thriving under elevated pCO₂ conditions, with positive physiological responses such as increased photosynthetic activity and no calcium carbonate biomass loss over time. However, the seawater column and coralline skeleton biofilms showed significant microbial shifts. These findings reinforce the existence of a close host-microbe functional entity, where the metabolic crosstalk within the rhodolith as a holobiont could be exerting reciprocal influence over the associated microbiome.

While the microbiome associated with live rhodoliths remained stable and resembled a healthy holobiont, the microbial community associated with the water column changed after exposure to elevated pCO₂.

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• Maerl

{{reflist}}

• Riosmena-Rodríguez R, Nelson W and Aguirre J (Eds.) (2016) [https://books.google.com/books?id=9ec4DQAAQBAJ&q=%22Rhodolith%2FMa%C3%ABrl+Beds%3A+A+Global+Perspective%22 Rhodolith/Maërl Beds: A Global Perspective] Springer. {{ISBN|9783319293158}}.

Category:Red algae

Category:Fossil algae

Category:Extant Eocene first appearances