Cerf Island, a treasure trove of sprigging coral

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Coral reefs are extremely sensitive to environmental change and those off the coast of Seychelles are no different. By 2016 Seychelles had lost 50% of its coral, with North Island losing a whopping 80% of its coral beds.

Coral loss results from smothering, stress and damage from land reclamation projects, the El Niño events in 1998 and 2016, and the 2004 tsunami. The loss of these reefs has encouraged conservationists to get involved by creating coral nurseries and artificial reefs.

“If corals cannot re-establish over the long term, there will be a shift from a coral-dominated reef to
an algae-dominated reef, which is generally less diverse. This leads to a decrease in local fish populations, which are important for providing food to coastal communities,” warns Dr David Rowat, chairman of the Marine Conservation Society of Seychelles (MCSS).

Coral gardening seychelles

Photo: MCSS

MCSS stepped in to resolve the coral conundrum via the Cerf Island Conservation Programme, setting up coral nurseries to regrow coral fragments and translocate them to coral gardens. Faster-growing, digitate corals are easier to cultivate in coral nurseries, but in order to have a fully functioning reef, a high diversity of corals is required.

Broken coral fragments ranging between 2cm and 5cm are attached to the nurseries, and nurseries are then placed in areas with good light and slight water movement. The areas should have minimum temperature and salinity variations, and should be situated away from land-based pollution. Poor water quality is linked to increased algal growth, which competes with coral.

MCSS is currently managing two iarge-scale nurseries of approximately 1 400 corals each. The aim for the larger nurseries is to produce 5 000 pieces of coral. The smaller nurseries hold 120 corals each and take between 10 and 12 months to grow before translocation.

 

The Cerf Island project has three staff members who collect coral and clean the nurseries twice a week: Nina Andrews, Leo arret and Dr David Rowat also monitor survival rates and progress. Once the coral reaches a certain size it is relocated to coral gardens.

In order to have a fully functioning reef, a high diversity of corals is required.

The first type of coral garden is an igloo-shaped wireframe ideal for a completely dilapidated reef structure. The 10mm steel rods are coated with anti-rust epoxy and sand to make them coral-friendly. “Once a coral
is held secure with cable ties it will begin to self-attach,” says Andrews.

cleaning artificial coral reefs

Photo: MCSS

The rebar method is similar to the igloos, where metal bars are driven into the sediment. Coral can then be translocated among sandy or rubble type substrates. “In April 2018, 110 Acropora colonies were translocated using this method, and have restored 27m2 of the reef,” Barret explains.

Another alternative is to use what is available. “At the moment, we are focusing on using cement to attach our propagated corals to existing dead coral structures, so we are using the topography that previous corals have created,” says Andrews. This type of translocation process only requires coral-friendly cement and an underwater cake-piping bag.

Photo: MCSS

Once every two months MCSS attends to the coral gardens, which are populated with 270 colonies of nine different coral genera. The coral garden is checked for drupella, sea snails that eat staghorn corals.
These snails are found in high densities on man-made reefs. The project is the result of a collaboration with local resorts, guest houses and the Seychelles National Parks Authority.

Seychelles coral reef facts

  •  Branching coral: is more susceptible to breakages; however the fragments can be easily collected and regrown.
  •  Staghorn corals (Acropora): are some of the fastest growing corals.
  •  Pearl bubble coral (Physogyra lichtensteini): is as an EDGE (evolutionary distinct and globally endangered) species of coral found around Cerf’s Island
  • Harlequin filefish and razor fish are dependent on coral reefs
  • Stony corals (Porites), cauliflower coral (Pocillopora), staghorn corals (Acropora), and colonial stony corals (Pavona) are the ideal species for coral nurseries.

Written by: Georgina Lockwood 

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