Sea Fan Repair & Restoration

We provided the following information in response to direct requests for information and help on coral reef restoration in the aftermath of the tsunami. The information is based on our experiences with coral reef transplanting and restoration and on the generous input of Dr. Henry Hudson, an expert on coral reef restoration with NPS. We have provided information on two main methods.

Overview

While sea fan restoration can be a difficult proposition, it can be done successfully. It requires attention and patience. The following two methods are suggested. They use cement (or similar adhesive) to attach the sea fans to the substrate. Cement is a good method in most situations but epoxy has also been used. Epoxy requires crevices to get a firmer hold. In trials since the tsunami, marine epoxy has been less effective that marine cement, and cement is therefore recommended. The methods suggested have been used on relatively large fans (i.e. with large "sail" areas).

First, sea fans are easier to attach to a hard substrate e.g. dead coral, rock etc. because these offer a better anchor. Anchoring sea fans to sand is difficult.

Sea fans live in areas of surge and it is important that they are placed in the right habitat. But the surge can make it more difficult to attach them to the rock if you are working underwater.

Immobilize the sea fan in some way to prevent it from swaying back and forth. You might have one or two divers hold the fronds gently in place.

Method 1

This technique applies if the seafan has a holdfast (or a good part of the holdfast still remains) and you have suitable substrate (dead coral, or the right type of rock).

  1. Have one diver gently immobilize the sea fan. Attach the holdfast to the substrate i.e. dead coral or rock using 2-4 hardened masonry nails. You have to drive the nails through the holdfast into the substrate- this will not kill the sea fan. The nails provide a temporary anchor for the seafan, but will not hold it indefinitely. You need to cement the holdfast and fill in around the crevices. Use lime based, Portland cement to fill in around the holdfast. (You can only use masonry nails if the rock is not too friable, otherwise it crumbles. If the rock is too hard it can also be too difficult to drive masonry nails into the substrate) Note, to hammer in nails, we have used large hammers with the handle shortened (by us) so that the hammer falls under its own weight underwater.
  2. Mix the cement in the boat, make it into a ball, and place in a plastic bag (ziplock bags are often ideal). Dive down to the sea fan and cement the holdfast and area around the holdfast. This holds the sea fan in place and allows it to sway naturally in the surge. Quick setting cement is best, and you will have to hold the sea fan in place for a few minutes until the cement is hard enough.

Note—apply the cement to the base, and keep it away from the living tissue as much as possible.

Important safety tip— lime base cement is corrosive on your hands, so be sure that divers use latex or other gloves.

If there is little of the holdfast left, it may be possible to make an artificial circular holdfast from cement or epoxy, which is then anchored to the rock using cement. See method 2 below.

Method 2

This involves brining the sea fan to the surface to create an artificial base or holdfast. It is useful when you have little or no holdfast left, or cannot use masonry nails, and it is too difficult to work underwater. It might be useful if you have to put sea fans into the sand (but this is more difficult and it is still better to attach them to a hard substrate).

  1. Bring the seafan to the surface. Sea fans can tolerate being out of water for a short period of time, but it is best to keep it in the shade and moist, if possible.
  2. Make a quick hardening cement by mixing some molding plaster with the portland lime cement (ratio 4 parts cement to 1 part molding plaster.) NOTE this will set very fast. Attach this to the holdfast, or what remains of the holdfast or "stalk" of the sea fan. - i.e. whatever you have available to work with depending on the condition of the sea fan.
  3. After you have created an artificial holdfast (rock) at the base of the sea fan, you can attach this to a flat substrate e.g. a rock or patio tile. Take the tile with the sea fan attached and cement the tile to the rocky substrate.

(Note, that depending on the bottom type and surge, it MAY be possible to attach the seafan to larger rock that can be laid on a sandy substrate, or the rock can be embedded deep into the sand to provide an anchor, but this will be difficult to do underwater.)

Please note that the sea fan fronds should not be in contact with rods e.g. steel rods or other substances. This causes abrasion which then leads to infection of the sea fan. (In the pictures that you sent me, it seems that the fans are tight against the steel, and so you might want to be careful not to abrade or damage the fronds).

Also it's important not to put too much stress on the "joints" near the holdfast as this can cause breakage.

(Back to Key Efforts.)