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Coral reef restoration by electrolysis

Explore coral occurrences in Swedish waters, the urgency of restoration, and the innovative electrolysis method for rejuvenating coral reefs. Dive into the threats faced by these reefs and understand the critical prerequisites for coral growth. Uncover the success of electrodeposition in seawater for restorative purposes, pioneered by Wolf Hilbertz. Discover the crucial role of calcium carbonate deposition and its impact on coral growth rates. Through this lecture, gain insights into the importance of preserving and restoring coral habitats to ensure marine biodiversity and sustainability.

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Coral reef restoration by electrolysis

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  1. Coral reef restoration by electrolysis From a lecture held February 18, 2008 by Susanna Strömberg for a course in Marine Conservation Biology, at Sven Lovén Centre for Marine Sciences, Tjärnö University of Göteborg Sweden Photo: T. Lundälv

  2. Coral reef restoration by electrolysis • Coral occurrences in swedish waters • Why restoration is needed • The method – history and how it works Photo: T. Lundälv

  3. Global distribution Map from UNEP-WCMC Map: Roshani Sitaula, Bremen University

  4. Deep-water corals in swedish waters NORWAY S. Søster Fjellknausene Saekken Djupekrakk Tisler Strömstad • only one remaining coral reef in swedish waters • 5-6 known former reef sites • trawling is the main reson for extinction • The Saekken reef is protected against trawling since 2001 TMBL Living Extinct TMBL: Tjärnö Marine Biological Laboratory

  5. Prerequisites for corals • temp. 4°-13°C • salinity 32-38,8‰ • depth 39 m - 3 383 m • enhanced bottom currents • growth rate 4–25(19-34 on oil rigs)mm/year Multibeam map and photo: T. Lundälv • THREATS • trawling • oil and gas exploitation • acidification

  6. The Saekken reef is sensitive to disturbances • Small colonies • easily over-turned • Illegal trawling • tracks from trawling gear and disturbed colonies reported in 2004 • Low genetic variation • high clonality (70%) • reproduction mainly by fragmentation • Isolated from other reefs Photos: T. Lundälv

  7. Increased diversity close to corals Lopheliapertusa UV photos: T. Lundälv Panel photos: S. Strömberg

  8. Coral reefs important habitats • invertebrate abundances much higher close to corals • species richness higher • major taxa;Protozoa, Bryozoa, Cnidaria and Annelida (Polychaeta) S2 & S3 has been close to corals Results from a settling experiment at the Saekken reef site (2001-2007), unpublished data. (Susanna Strömberg)

  9. Electrodeposition in seawater- for restoration purposes Wolf • The method was developed by architect Wolf Hilbertz in the mid 70ies • Dr Thomas Goreau invited Wolf to Jamaica in the mid 80ies and tested the method for the purpose of restoring tropical reefs • Since then the method has been used in Indonesia, Maldives, Mexico, Panama, Papua New Guinea, Saya de Malha, Seychelles, Thailand and Palau Tom Photos fromwww.biorock.net

  10. Photo: W. Hilbertz, 2001 Photo: W. Hilbertz, 2002

  11. Pemuteran Bay, Bali, Indonesia Mach, 2006 Photo: Wolf Hilbertz

  12. Observed effects on tropical corals • 3-5 times faster growth rates • copes with stress better • more active polyps • enhanced settling of coral larva Photo: J. Cervino, Bali 2004

  13. magnesium hydroxide calcium carbonate Cathode - Photo: Wolf Hilbertz

  14. Mineral deposition through electrolysis 2H2O + 2e- H2 + 2OH- 2H2O  4H+ + O2 + 4e- (2Cl- Cl2 + 2e-) Ca 2+ + CO32- OH- + HCO3- + Ca2+ CaCO3 + H2O 2OH- + Mg2+ Mg(OH)2 0,1-30 ampere 0-12 voltage Deposition of minerals on the cathode e- Anode + (coated titanium) lowered pH, oxidation Cathode – (iron or steel) alkaline (~0,1 pH units) reduction

  15. 1,5 years of mineral deposition(2-2,5 cm) Photo from www.biorock.net

  16. Aragonite –coral skeleton & elektrodeposition Orthorombic structure CaCO3 Calcite – lime stone Tetragonal structure Illustrations from Wikipedia

  17. Ca2+ + 2HCO3-  H2O + CaCO3 + CO2 • The coral polyp excretes a calcium carbonate skeleton in the form of aragonite • Enzymatic transformation of carbon dioxide to carbonate ions that reacts with calcium cations and form calcium carbonate • Produces an alcaline environment within the calicoblastic cells to drive the production of calcium carbonate Illustration from Wikipedia

  18. Ca2+ + 2HCO3-  H2O + CaCO3 + CO2 • The coral polyp excretes a calcium carbonate skeleton in the form of aragonite • Enzymatic transformation of carbon dioxide to carbonate ions that reacts with calcium cations and form calcium carbonate • Produces an alcaline environment within the calicoblastic cells to drive the production of calcium carbonate Illustration from Wikipedia

  19. Ca2+ + 2HCO3-  H2O + CaCO3 + CO2 • The coral polyp excretes a calcium carbonate skeleton in the form of aragonite • Enzymatic transformation of carbon dioxide to carbonate ions that reacts with calcium cations and form calcium carbonate • Produces an alcaline environment within the calicoblastic cells to drive the production of calcium carbonate Illustration from Wikipedia

  20. increased atmospheric CO2 decreases [CO32-] due to increased[H+] CO2 higher temp – lower solubility lower temp – increased solubility H2O + CO2 H2CO3 HCO3- + H+ CO32- + H+ calcification dissolution [H+]/[OH-] Ca2+ + 2HCO3- H2O + CaCO3 + CO2 increased pH decreased pH saturation horizon for aragonite saturation horizon forcalcite

  21. Conclusions • Deep-water coral reefs are important habitats • Shallow reefs are damaged by trawling • Deeper reefs are threatened by ocean acidification There is a need for restoration efforts Eunice norvegica (Polychaeta) Alcyonium cf norvegicum (Octocorallia) Photos: S. Strömberg

  22. Thank you for your attention! Eunice norvegica Photo: S. Strömberg

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