Biology:Rhodolith

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Short description: Calcareous marine nodules composed of crustose red algae
Characteristic mauve coloured rhodolith

Rhodoliths (from Greek for red rocks) are colorful, unattached calcareous nodules, composed of crustose, benthic marine red algae that resemble coral. Rhodolith beds create biogenic habitat for diverse benthic communities. The rhodolithic growth habit has been attained by a number of unrelated coralline red algae,[1] organisms that deposit calcium carbonate within their cell walls to form hard structures or nodules that resemble beds of coral.

Rhodoliths do not attach themselves to the rocky seabed. Rather, they roll like tumbleweeds along the seafloor until they become too large in size to be mobilised by the prevailing wave and current regime. They may then become incorporated into a semi-continuous algal mat or form an algal build-up.[2][3] While corals are animals that are both autotrophic (photosynthesize via their symbionts) or heterotrophic (feeding on plankton), rhodoliths produce energy solely through photosynthesis (i.e. they can only grow and survive in the photic zone of the ocean).

Scientists believe rhodoliths have been present in the world's oceans since at least the Eocene epoch, some 55 million years ago.[4]

Overview

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.[5][6]

Habitat

Benthic communities found in rhodolith beds
Example of the seaweed and zoobenthic communities found in rhodolith beds on the Brazilian coast. This picture highlights the presence of gastropods, echinoderms and a turf algae assemblage.[5]
Vertical and latitudinal changes observed in the size and density of rhodoliths on the floor of the continental shelf off Espírito Santo in Brazil [5]

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,[7] the Mediterranean [8] as off New Zealand[9] and eastern Australia.[10] 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.[4] 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.[11][12][13][14] Rhodoliths come in many shapes, including laminar, branching and columnar growth forms.[15] 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.[1]

  • Rhodoliths on the northern shore of Fuerteventura

  • A fossilised rhodolith from the Messinian of southern Spain

Geological significance

Rhodoliths are a common feature of modern and ancient carbonate shelves worldwide.[16] Rhodolith communities contribute significantly to the global calcium carbonate budget, and fossil rhodoliths are commonly used to obtain paleoecologic and paleoclimatic information.[17][18][19] Under the right circumstances, rhodoliths can be the main carbonate sediment producers,[20][21] often forming rudstone or floatstone beds consisting of rhodoliths and their fragments in grainy matrix.

Climate change and the rhodolith holobiont

A view of rhodolith beds impacted by the warmer and more acidified oceans predicted by the IPPC.[22][5]

Rhodoliths are significant photosynthesizers, calcifiers, and ecosystem engineers, which raises an issue about how they might respond to ocean acidification.[23]

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.[24] Organisms like rhodoliths accrete carbonate as part of their physical structure, since precipitating CaCO3 would be less efficient.[25][26] Ocean acidification presents a threat by potentially affecting their growth and reproduction.[27][28] Coralline algae are particularly sensitive to ocean acidification because they precipitate high magnesium-calcite carbonate skeletons, the most soluble form of CaCO3.[29][30][23]

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.[31] Elevated CO2 levels might impair biomineralization due to decreased seawater carbonate (CO2−3) availability as pH falls, but photosynthesis could be promoted as the availability of bicarbonate (HCO−3) increases.[32] 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.[33][23]

Climate change and the rhodolith holobiont
Expected parabolic relationship between climate change stressors and rhodolith holobiont 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.[23]

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.[34][23]

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.[23]

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.[23]

See also

References

  1. ↑ 1.0 1.1 Steneck, R. S. (1986). "The Ecology of Coralline Algal Crusts: Convergent Patterns and Adaptative Strategies". Annual Review of Ecology and Systematics 17: 273–303. doi:10.1146/annurev.es.17.110186.001421. 
  2. ↑ Basso, Daniela; Nalin, Ronald; Massari, Francesco (2007-05-01). "Genesis and composition of the Pleistocene Coralligène de plateau of the Cutro Terrace (Calabria, southern Italy)" (in en). Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 244 (2): 173–182. doi:10.1127/0077-7749/2007/0244-0173. http://openurl.ingenta.com/content/xref?genre=article&issn=0077-7749&volume=244&issue=2&spage=173. 
  3. ↑ Aguirre, Julio; Braga, Juan Carlos; Bassi, Davide (2017). "Rhodoliths and Rhodolith Beds in the Rock Record" (in en). Rhodolith/Maërl Beds: A Global Perspective. Coastal Research Library. 15. Springer. pp. 105–138. doi:10.1007/978-3-319-29315-8_5. ISBN 978-3-319-29315-8. https://link.springer.com/book/10.1007/978-3-319-29315-8. 
  4. ↑ 4.0 4.1 Science Daily, September 23, 2004
  5. ↑ 5.0 5.1 5.2 5.3 Horta, Paulo Antunes; Riul, Pablo; Amado Filho, Gilberto M.; Gurgel, Carlos Frederico D.; Berchez, Flávio; Nunes, José Marcos de Castro; Scherner, Fernando; Pereira, Sonia et al. (2016). "Rhodoliths in Brazil: Current knowledge and potential impacts of climate change". Brazilian Journal of Oceanography 64: 117–136. doi:10.1590/S1679-875920160870064sp2. . 50px Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License
  6. ↑ Bosellini, Alfonso; Ginsburg, Robert N. (1971). "Form and Internal Structure of Recent Algal Nodules (Rhodolites) from Bermuda". The Journal of Geology 79 (6): 669–682. doi:10.1086/627697. Bibcode: 1971JG.....79..669B. 
  7. ↑ Steller, D. L.; Riosmena‐Rodríguez, R.; Foster, M. S.; Roberts, C. A. (2003). "Rhodolith bed diversity in the Gulf of California: the importance of rhodolith structure and consequences of disturbance" (in en). Aquatic Conservation: Marine and Freshwater Ecosystems 13 (S1): S5–S20. doi:10.1002/aqc.564. ISSN 1099-0755. https://onlinelibrary.wiley.com/doi/abs/10.1002/aqc.564. 
  8. ↑ Basso, Daniela; Babbini, Lorenza; Ramos-Esplá, Angel Alfonso; Salomidi, Maria (2017), Riosmena-Rodríguez, Rafael; Nelson, Wendy; Aguirre, Julio, eds., "Mediterranean Rhodolith Beds", Rhodolith/Maërl Beds: A Global Perspective, Coastal Research Library (Cham: Springer International Publishing) 15: pp. 281–298, doi:10.1007/978-3-319-29315-8_11, ISBN 978-3-319-29313-4, http://link.springer.com/10.1007/978-3-319-29315-8_11, retrieved 2021-01-01 
  9. ↑ Nelson, W. A. (2012). Rhodolith beds in northern New Zealand: characterisation of associated biodiversity and vulnerability to environmental stressors. Wellington, NZ: Ministry for Primary Industries. ISBN 978-0-478-40077-9. OCLC 812180715. 
  10. ↑ 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
  11. ↑ Basso, D.; Babbini, L.; Kaleb, S.; Bracchi, V.A.; Falace, A. (2016). "Monitoring deep Mediterranean rhodolith beds" (in en). Aquatic Conservation: Marine and Freshwater Ecosystems 26 (3): 549–561. doi:10.1002/aqc.2586. ISSN 1052-7613. 
  12. ↑ Barbera, C.; Bordehore, C.; Borg, J.A.; Glémarec, M.; Grall, J.; Hall-Spencer, J. M.; de la Huz, Ch.; Lanfranco, E. et al. (2003). "Conservation and management of northeast Atlantic and Mediterranean maerl beds" (in en). Aquatic Conservation: Marine and Freshwater Ecosystems 13 (S1): S65–S76. doi:10.1002/aqc.569. ISSN 1052-7613. https://www.um.edu.mt/library/oar//handle/123456789/5229. 
  13. ↑ Horta, P.A.; Riul, P.; Amado Filho, G-M.; Gurgel, C.F.D.; Berchez, F.; Nunes, J.M. de Castro; Scherner, F.; Pereira, S. et al. (2016). "Rhodoliths in Brazil: Current knowledge and potential impacts of climate change". Brazilian Journal of Oceanography 64 (SPE2): 117–136. doi:10.1590/S1679-875920160870064sp2. ISSN 1679-8759. 
  14. ↑ Bassi, D.; Braga, J.C.; Owada, M.; Aguirre, J.; Lipps, J.H.; Takayanagi, H.; Iryu, Y. (2020). "Boring bivalve traces in modern reef and deeper water macroid and rhodolith beds" (in en). Progress in Earth and Planetary Science 7 (1): 41. doi:10.1186/s40645-020-00356-w. ISSN 2197-4284. Bibcode: 2020PEPS....7...41B. 
  15. ↑ Bosence, D. W. (1983). "Description and Classification of Rhodoliths (Rhodoids, Rhodolites)". Coated Grains. Berlin: Springer. pp. 217–224. doi:10.1007/978-3-642-68869-0_19. ISBN 9783642688690. https://books.google.com/books?id=-oXuCAAAQBAJ&q=%22Description+and+classification+of+rhodoliths+%28rhodoids%2C+rhodolites%29%22&pg=PA223. 
  16. ↑ Pomar, L.; Baceta, J.I.; Hallock, P.; Mateu-Vicens, G.; Basso, D. (2017). "Reef building and carbonate production modes in the west-central Tethys during the Cenozoic" (in en). Marine and Petroleum Geology 83: 261–304. doi:10.1016/j.marpetgeo.2017.03.015. Bibcode: 2017MarPG..83..261P. https://linkinghub.elsevier.com/retrieve/pii/S0264817217301010. 
  17. ↑ Basso, D. (1998). "Deep rhodolith distribution in the Pontian Islands, Italy: a model for the paleoecology of a temperate sea" (in en). Palaeogeography, Palaeoclimatology, Palaeoecology 137 (1): 173–187. doi:10.1016/S0031-0182(97)00099-0. ISSN 0031-0182. Bibcode: 1998PPP...137..173B. http://www.sciencedirect.com/science/article/pii/S0031018297000990. 
  18. ↑ Halfar, J.; Zack, T.; Kronz, A.; Zachos, J.C. (2000). "Growth and high-resolution paleoenvironmental signals of rhodoliths (coralline red algae): A new biogenic archive" (in en). Journal of Geophysical Research: Oceans 105 (C9): 22107–22116. doi:10.1029/1999JC000128. Bibcode: 2000JGR...10522107H. 
  19. ↑ Ragazzola, F.; Caragnano, A.; Basso, D.; Schmidt, D.N.; Fietzke, J. (2020). "Establishing temperate crustose early Holocene coralline algae as archives for palaeoenvironmental reconstructions of the shallow water habitats of the Mediterranean Sea" (in en). Palaeontology 63 (1): 155–170. doi:10.1111/pala.12447. ISSN 1475-4983. Bibcode: 2020Palgy..63..155R. 
  20. ↑ Basso, D. (2012). "Carbonate production by calcareous red algae and global change" (in en). Geodiversitas 34 (1): 13–33. doi:10.5252/g2012n1a2. ISSN 1280-9659. http://www.bioone.org/doi/abs/10.5252/g2012n1a2. 
  21. ↑ Schubert, N.; Salazar, V. W.; Rich, W. A.; Vivanco Bercovich, M.; Almeida Saá, A. C.; Fadigas, S. D.; Silva, J.; Horta, P. A. (2019-08-01). "Rhodolith primary and carbonate production in a changing ocean: The interplay of warming and nutrients" (in en). Science of the Total Environment 676: 455–468. doi:10.1016/j.scitotenv.2019.04.280. ISSN 0048-9697. PMID 31048175. Bibcode: 2019ScTEn.676..455S. http://www.sciencedirect.com/science/article/pii/S0048969719318157. 
  22. ↑ IPPC (2014) Climate change 2014 impacts, adaptation, and vulnerability, Part B. ISBN:978-1-107-05816-3
  23. ↑ 23.0 23.1 23.2 23.3 23.4 23.5 23.6 Cavalcanti, Giselle S.; Shukla, Priya; Morris, Megan; Ribeiro, Bárbara; Foley, Mariah; Doane, Michael P.; Thompson, Cristiane C.; Edwards, Matthew S. et al. (2018). "Rhodoliths holobionts in a changing ocean: Host-microbes interactions mediate coralline algae resilience under ocean acidification". BMC Genomics 19 (1): 701. doi:10.1186/s12864-018-5064-4. PMID 30249182. . 50px Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License
  24. ↑ Millero, Frank J.; Graham, Taylor B.; Huang, Fen; Bustos-Serrano, Héctor; Pierrot, Denis (2006). "Dissociation constants of carbonic acid in seawater as a function of salinity and temperature". Marine Chemistry 100 (1–2): 80–94. doi:10.1016/j.marchem.2005.12.001. Bibcode: 2006MarCh.100...80M. 
  25. ↑ Orr, James C.; Fabry, Victoria J.; Aumont, Olivier; Bopp, Laurent; Doney, Scott C.; Feely, Richard A.; Gnanadesikan, Anand; Gruber, Nicolas et al. (2005). "Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms". Nature 437 (7059): 681–686. doi:10.1038/nature04095. PMID 16193043. Bibcode: 2005Natur.437..681O. https://epic.awi.de/id/eprint/13479/1/Orr2005a.pdf. 
  26. ↑ Hoegh-Guldberg, O.; Mumby, P. J.; Hooten, A. J.; Steneck, R. S.; Greenfield, P.; Gomez, E.; Harvell, C. D.; Sale, P. F. et al. (2007). "Coral Reefs Under Rapid Climate Change and Ocean Acidification". Science 318 (5857): 1737–1742. doi:10.1126/science.1152509. PMID 18079392. Bibcode: 2007Sci...318.1737H. 
  27. ↑ Kroeker, Kristy J.; Kordas, Rebecca L.; Crim, Ryan; Hendriks, Iris E.; Ramajo, Laura; Singh, Gerald S.; Duarte, Carlos M.; Gattuso, Jean‐Pierre (2013). "Impacts of ocean acidification on marine organisms: Quantifying sensitivities and interaction with warming". Global Change Biology 19 (6): 1884–1896. doi:10.1111/gcb.12179. PMID 23505245. Bibcode: 2013GCBio..19.1884K. 
  28. ↑ Riebesell, Ulf; Gattuso, Jean-Pierre (2015). "Lessons learned from ocean acidification research". Nature Climate Change 5 (1): 12–14. doi:10.1038/nclimate2456. Bibcode: 2015NatCC...5...12R. 
  29. ↑ 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
  30. ↑ Martin, Sophie; Gattuso, Jean-Pierre (2009). "Response of Mediterranean coralline algae to ocean acidification and elevated temperature". Global Change Biology 15 (8): 2089–2100. doi:10.1111/j.1365-2486.2009.01874.x. Bibcode: 2009GCBio..15.2089M. 
  31. ↑ McCoy, Sophie J.; Kamenos, Nicholas A. (2015). "Coralline algae (Rhodophyta) in a changing world: Integrating ecological, physiological, and geochemical responses to global change". Journal of Phycology 51 (1): 6–24. doi:10.1111/jpy.12262. PMID 26986255. 
  32. ↑ Johnson, Maggie Dorothy; Price, Nichole N.; Smith, Jennifer E. (2014). "Contrasting effects of ocean acidification on tropical fleshy and calcareous algae". PeerJ 2: e411. doi:10.7717/peerj.411. PMID 24918033. 
  33. ↑ Ries, J. B.; Cohen, A. L.; McCorkle, D. C. (2009). "Marine calcifiers exhibit mixed responses to CO2-induced ocean acidification". Geology 37 (12): 1131–1134. doi:10.1130/G30210A.1. Bibcode: 2009Geo....37.1131R. 
  34. ↑ Weiss, Anna; Martindale, Rowan C. (2017). "Crustose coralline algae increased framework and diversity on ancient coral reefs". PLOS ONE 12 (8): e0181637. doi:10.1371/journal.pone.0181637. PMID 28783733. Bibcode: 2017PLoSO..1281637W. 

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