Photo: T. Lundälv

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

Coral reef restoration by electrolysis

• Coral occurrences in swedish waters • Why restoration is needed • The method – history and how it works

Global distribution

Map from UNEP-WCMC Map: Roshani Sitaula, Bremen University

Deep-water corals in swedish waters

S. S øster

NORWAY

Fjellknausene Djupekrakk Tisler Saekken

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 Living Extinct TMBL TMBL: Tjärnö Marine Biological Laboratory

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

The Saekken reef is sensitive to disturbances

• Small colonies – easily over-turned • Illegal trawling – tracks from trawling gear and disturbed colonies reported in 2004

Photos: T. Lundälv

• Low genetic variation – high clonality (70%) – reproduction mainly by fragmentation – Isolated from other reefs

Increased diversity close to corals

Lophelia pertusa

UV photos: T. Lundälv Panel photos: S. Strömberg

0% 80% 60% 40% 20% 100%

Coral reefs important habitats

Abundance (N)

• invertebrate abundances much higher close to corals 3500 3000 2500 • species richness higher 2000 • major taxa; Protozoa, Bryozoa, Cnidaria and Annelida (Polychaeta) 1500 1000 500 0 S1 S2 S3 S4 S5 S6

Major Phyla Comparison Species richness (S)

140 120 100 CHORDATA ECHINODERMATA BRACHIOPODA ECTOPROCTA BRYOZOA ENTOPROCTA ARTHROPODA MOLLUSCA ANNELIDA CNIDARIA PORIFERA PROTOZOA 80 60 40 20 0 S1 S2 S3 S4 S5 S6 S2 & S3 has been close to corals Results from a settling experiment at the Saekken reef site (2001 2007), unpublished data. (Susanna Strömberg) S S1 S S2 S S3 S S4 S S5 S S6

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 from

www.biorock.net

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

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

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

Cathode -

magnesium hydroxide calcium carbonate

Photo: Wolf Hilbertz

Mineral deposition through electrolysis

2H 2 O + 2e  H 2 + 2OH Ca 2+ + CO 3 2 OH + HCO 3 + Ca 2+  CaCO 3 + H 2 O 2OH + Mg 2+  Mg(OH) 2 Deposition of minerals on the cathode 2H 2 O  4H + + O 2 + 4e (2Cl  Cl 2 + 2e ) 0,1-30 ampere 0-12 voltage

e Anode +

(coated titanium) lowered pH, oxidation

Cathode –

(iron or steel) alkaline (~0,1 pH units) reduction

1,5 years of mineral deposition

(2-2,5 cm)

Photo from www.biorock.net

Aragonite

– coral skeleton & elektrodeposition Orthorombic structure

Calcite

– lime stone

CaCO 3

Tetragonal structure Illustrations from Wikipedia

Ca

2+

+ 2HCO

3 

H

2

O + CaCO

3

+ CO

2 Illustration from Wikipedia • 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

Ca

2+

+ 2HCO

3 

H

2

O + CaCO

3

+ CO

2 Illustration from Wikipedia • 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

Ca

2+

+ 2HCO

3 

H

2

O + CaCO

3

+ CO

2 Illustration from Wikipedia • 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

CO 2 increased atmospheric CO 2 decreases [CO 3 2 ] due to increased [H + ]

higher temp – lower solubility lower temp – increased solubility

H 2 O + CO 2 H 2 CO 3 HCO 3 + H + CO 3 2 + H +

dissolution Ca 2+ + 2HCO 3 [H+] / [OH ] calcification H 2 O + CaCO 3 + CO 2 decreased pH increased pH saturation horizon for aragonite saturation horizon for calcite

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

Thank you for your attention!

Photo: S. Strömberg Eunice norvegica