Can dead coral benefit new reef?

[ietermagog]

There's a warehouse in town that has literally tonnes of dead coral sitting for about 10 years. Originally intended for export, (who wants that stuff on their mantlepiece?) the company is long gone.
We manage a small, privately arranged marine reserve off the beach which is showing amazing reappearance of fishlife. I was wondering if it would be beneficial to place this coral there as a base for more to grow on. Would the components of the old coral give anything to new coral, or would it be the same as putting down any artificial structure?
Thanks for advice, from Mozambique
Fim do Mundo Safaris: Bay Diving beach resort in Nacala, Northern Mozambique

 

[andrewharvey]

Dear ietermagog

We did some experiments with dead coral as a reef rehabilitation tool in Madagascar. The aragonite that comprises the coral skeleton is an ideal substrate for coral larvae to settle on, providing a combination of appropriate features (porosity, texture, pH etc). Particularly if this dead coral has been out of the water, it will not have the algal biofilm that covers insitu dead coral and prevents polyp settlement.

There are some things to bear in mind though:

- If you are going to go down this route, select your time of deployment carefully. Aim for a week or so before coral spawing (around December full moon?) so that the the structure has some time to precondition but is not inundated by algal cover.

- This technique is only really useful to stabilise rubble fields, providing some 3d stable structure for polyps to settle and develop on. If your reef doesn't have much in the way of rubble, this may not be appropriate.

- Obviously if there are reasons for the lack of coral in the area you want to rehabilitate, they will still apply and could hamper success.

On a side note, this technique can also be used to generate complex habitat to develop your fish communities (best with branching rather than massive forms).

I hope this has given you some food for thought. Keep in touch if you have any other questions, or would like to know more about how to approach this.

 

[ietermagog]

Thank you. The reserve is in conjunction with the local Fishermen's Association, basically a no-fishing zone. Long term netting from shore had destroyed a lot of the coral in the shallows, having been overturned and dragged about, as well as local freedivers breaking it off to weight down their basket traps. In just 18 months there has been an incredible change in the fish life. Because all the bottom dwellers and small fish that live in the seagrass etc are not being pulled in, these have increased in number, as well as the number of baitfish, and as a result shoals of barracuda, flathead mullet, batfish and golden and bluefin kingfish have moved in. (and are available outside the reserve to the line fishermen)
The bottom composition - distance from high tide on shore to a depth of 30m is about 120m. Sandy shore, seagrass to 7m, sandy bottom with bommies of coral from 1 cubic metre to biggest of around 6 cubic metres. 4km away there is a 1km stretch of coral, 3m-30m depth, with 90% coral cover. Massive expanses of healthy, varied hard and soft - not netted from shore.
1/ Is it possible/viable/ethical to take small pieces of these corals and fix it to artificial structures such as the dead coral?
2/Can you direct me to more info on all of this (internet)
3/ This reef is accessible all day every day all year, straight off the beach. It is perfect for research/educational purposes. Do you know of any organisations or individuals wanting to do research of this type?
Like I said, the reserve is a private initiative. With proper scientific evidence of the benefits, we should have more clout with the govt when we want to make it official as well as more of these micro reserves throughout the region and country.
All info and advice welcomed.

 

[andrewharvey]

Hi ietermagog,

It is certainly possible to take sections of coral from elsewhere and transplant, it could even be viable. This is one of the main mechanisms of reproduction in the fast growing pioneer corals like Acroporids, via storm damage etc. Its success depends on whether the reciving area is failing to recruit. If this is the case, then you may see some success. If however the lack of corals is due to other factors which still persist, then the transplanted corals will likely suffer the same fate as the originals.

As your reserve has only been protected for 18months, I would suggest that you are still seeing a legacy from fishing pressures. With a healthy reef only a few k's away, I would anticpate that this provides quite a healthy source for new recruits. It would be worth assessing the suitability of your degraded site for natural coral settlement before going down this road.

For further info you could try googleing coral transplantation, reef ball, reef rehabilitation.

Or visit sciencedirect.com and search for coral transplantation for some technical accounts.

I would suggest seeking technical advice before starting this, coral transplants can be very tempermental and even the people doing this professionally have variable success. Plus you could end up communicating the wrong message to local communities if you are seen doing this.

I would be happy to chat with you further about developing a good programme to collect the evidence needed to support your dialogue with policy makers. I may even be able to refer you to some interested parties. Why don't you pm me and we can discuss the details off list.