Comportamiento cíclico uniaxial

The choice of coral species to be reared in a nursery should be dictated largely by the site(s) you wish to rehabilitate. The species must be ones that can thrive at the site to which they are to be transplanted (see Figure 2.3 in Chapter 2). To reduce the risks of mortality from bleaching events and predation and maintain genetic diversity, you should normally rear a mix of species and genotypes (Chapter 3). Fast growing branching species such as acroporids and pocilloporids may generate a rapid increase in structural complexity (and are thus sometimes called “engineering species”) but tend to be more vulnerable to both bleaching and predators than slower growing massive, submassive and encrusting species such as poritids and faviids. The environment at the nursery should be sufficiently similar to that at the site being rehabilitated (or more benign) so that transplants will be adequately adapted to the conditions when outplanted.

Collection of material

The nursery may be stocked with natural fragments (“corals of opportunity”) or fragments carefully removed from donor colonies. You should ensure that collection does as little collateral damage to healthy reefs as possible.

Corals of opportunity

Corals of opportunity are natural fragments, detached coral colonies, or recruits on unstable substrates (both natural such as coral rubble, and artificial such as ropes and chains) that have little chance of surviving naturally but have a good chance of survival if reared in a nursery, or transplanted directly and securely fixed to the natural reef. Corals fragments resulting from breakage of branching corals are often found lying on the bottom. Massive, submassive, plating and encrusting corals of opportunity may be less common. After storms or destructive human impacts such as ship groundings, corals of opportunity may

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Good Practice Checklist

Minimise collateral damage to healthy reefs by using “corals of opportunity” (naturally detached fragments with a low chance of survival) as transplants where feasible.

Always remove dead, moribund or diseased tissue from corals of opportunity before either transplanting directly or rearing in a nursery.

Base your choice of coral species to rear in a nursery on what you expect will survive well at the site you wish to rehabilitate or a comparable “reference” site (section 2.3).

As a precautionary measure, aim to remove no more than 10% of a donor colony if obtaining fragments by pruning coral colonies in situ.

Build coral nurseries out of robust and durable materials. Poor construction can lead to the death of thousands of corals.

When deciding on the size of mesh rearing trays, take into consideration how you plan to transport the grown colonies from the nursery to the rehabilitation site. Smaller trays (e.g. 30 cm x 50 cm) are easier to handle and transport.

We recommend using sub-surface rather than surface buoys to support floating nurseries to help reduce interference (e.g. theft of buoys, disturbance of corals by curious divers, etc.) and collision damage by passing boats.

“Environmentally friendly” anti-fouling paint applied to mesh of rearing trays and other structural parts of a nursery can reduce maintenance by about a half.

Rearing substrates for coral fragments should: 1) be cheap and easy to obtain, 2) allow coral fragments to be easily managed and maintained in the nursery, and 3) allow grown colonies to be quickly and easily deployed at the rehabilitation site.

“Cleaning” of the nursery – removal of algae and fouling invertebrates,

accumulated sediment, corallivorous organisms, and any diseased corals – must be carried out regularly.

Floating nurseries should be temporarily lowered in the water column when storms or tropical cyclones are forecast.

Use of NOAA sea surface temperature (SST) anomaly charts and inexpensive temperature loggers can allow you to anticipate bleaching events and take measures to try to protect corals being reared in a nursery (e.g. shading, lowering in water column).

be abundant, but it is unclear how abundant or

taxonomically diverse they are on the average reef adjacent to areas in need of restoration. A study of five such areas in the Philippines indicated an average of about 1–7 detached fragments per square metre of reef with average geometric mean diameters ranging from 2.4–5.3 cm. About 10 species were represented in a sample of 620 fragments. This snapshot suggests yields of tens of thousands of corals of opportunity per hectare may not be unusual although a rather limited number of common species appeared to dominate.

Corals of opportunity are easily collected and transported to a land or boat facility where they can be prepared for the nursery. Small fragments (c. 2 cm in size) may just need trimming to remove dead, moribund or diseased tissue; larger fragments (over 4–5 cm) may need to be further fragmented (Box 4.2). After trimming, you should gently wash off any debris from the corals of opportunity and fragment further if required. If corals are attached to artificial substrates (mooring ropes, chains, buoys, etc.), they should be carefully detached from them by cutting at the base of attachment with hammer and chisel. If the size of corals of opportunity is above 4–5 cm diameter, corals can be further fragmented as explained below (Box 4.2). If size is below 4–5 cm they can be easily attached (as described below) to substrates for nursery rearing. When attaching small coral fragments to flat substrates for rearing, be sure to smooth the base of the fragment by trimming with an electrician’s wire cutter or rubbing it with sand or emery paper. This improves the bonding of the coral to the substrate by the glue. If the corals of opportunity are small recruits of branching species on bits of rubble, we suggest they are left on their substrate and this is bonded to plastic substrate until corals reach 2–3 cm in diameter and can be gently detached at the base and reattached on pins or wall plugs as explained below.

Fragmentation of donor colonies

For branching colonies, carefully cut small branches, 2–5 cm long, from the periphery of the donor colonies using an electrician’s wire-cutter or other side-cutting pliers. It is recommended, as a precautionary measure, that you do not prune more than 10% of the donor colony8_{. This}

reduces the chance of negative impacts on the donor colony. Wear clean cotton (or surgical) gloves and be sure to hold part of the coral colony during the cutting since a strong force applied to the edge of a colony might lead to breakage of a bigger portion than required. Where appropriate try to choose parts of a colony that may be prone to harm in the future (e.g. parts too close to a neighbouring colony or likely to covered by sediment or encroaching macroalgae).

For submassive, massive, encrusting and foliose species up to 10% of the colony (precautionary measure) can be collected using a hammer and chisel. We recommend that

Inserting a nursery-reared coral colony (c. 8 cm diameter), grown over one year from a 3 cm fragment, into a pre-drilled hole in coral rock at a restoration site.

you generally take fragments from the edge of colonies to minimise impacts on the donor and facilitate healing. Cuts should be performed diagonally or vertically to the surface of the colony in an effort to minimise the amount of skeleton removed and the amount exposed to attack by boring organisms.

Excision of branches or fragments should be performed underwater with fragments being placed in plastic bags, fine mesh nets, or plastic baskets before being transferred to boat or shore for further processing. You should place each genotype in a separate container to avoid harmful

interactions.

Substrates for culturing corals

A variety of substrates have been used for culturing coral fragments in in-situ nurseries. These range from slabs of local marble (20 cm x 5 cm x 1.5 cm) to which coral fragments were bound with galvanized steel wire9_{, to}

10–12 mm diameter plastic wall-plugs into which small (c. 2 cm long) branch fragments are inserted. Over time (often within a few weeks) the coral fragments self-attach to their substrates, growing tissue over the substrate at points of contact, and thus become securely bound to the substrate. In the first case, after several months in the nursery the reared corals on their slabs were wedged into crevices on the reef with their heavy bases providing temporary stability9_{; in the second case after 9–12 months}

rearing the small coral colonies on their wall-plugs were just inserted into holes drilled into the bare coral rock. Choice of rearing substrate is critical to the cost-effectiveness of transplantation as an intervention.

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Box 4.2

The following protocols can be used to make coral fragments and nubbins (small fragments approx. 0.25–0.5 cm2

in area)10_.

1. The collected coral fragments should be kept wet with clean seawater at all times.

2. For branching species it is recommended that the height of the fragment should be no more than 2–3 times the diameter of the base and should not exceed 3–5 cm. This allows a more stable attachment to rearing substrates and thus lower detachment rates of fragments in the nursery.

3. When fragmenting branching corals of opportunity, you can use branches from all parts of the colony – tip, mid-branch and bases. Additional fragments can be made by cutting the coral pieces using side-cutting pliers, hammer and chisel, or hacksaw.

4. Exposed coral skeleton is susceptible to attack by various organisms. When cutting encrusting/massive species having a thick skeleton with only a thin tissue layer (e.g. Diploastrea

heliopora or massive Porites) it is advisable to reduce the

skeleton thickness to allow faster coverage of the exposed area by new tissue and facilitate attachment to the nursery substrate (a hacksaw is effective in trimming excess skeleton).

5. After cutting, wash tissue and skeleton debris from fragments by shaking them in fresh seawater.

6. One way to protect exposed skeleton is to make sure it is coated with epoxy-glue when attaching it to the nursery- rearing substrate.

7. Attach prepared fragments to a nursery-rearing substrate (see below for details on substrates) either by gluing the base with a drop of cyanoacrylate glue (‘superglue’) to the substrate or by inserting the fragments into plastic wall-plugs or tubing11_.

8. To accelerate attachment of the coral fragment to the substrate, you can sprinkle a thin layer of baking soda (sodium bicarbonate) on the substrate prior to applying a drop of superglue. This can be helpful when attaching larger or problematic fragments.

9. Do the work out of water (i.e. on the deck of a boat or on shore), but make sure that the corals remain moist and in the shade, and use cotton (or surgical) gloves in order to minimize damage to coral tissues.

A faviid fragment that has had exposed skeleton coated with epoxy putty when being attached to a plastic pin for rearing. This helps to protect it from attack by organisms such as boring sponges (S. Shafir).

Ideally the substrate should be 1) cheap, 2) allow easy attachment of fragments for rearing in the nursery, 3) allow easy maintenance (e.g. removal or algae and other fouling organisms) during the rearing phase, and 4) allow easy deployment of reared corals at the site being rehabilitated.

Three cheap plastic substrates have been trialled extensively in recent years with reasonable success (Box 4.3). Firstly plastic pins with a 2 cm diameter head and a 9 cm long pin (waste products of plastic injection moulding), secondly large (10–12 mm diameter) wall-plugs, and thirdly short segments of plastic hose pipe (or any plastic tubing). The latter two substrates are suitable primarily for branching and submassive species (e.g. Acropora, Montipora,

Pocillopora, Stylophora, Heliopora, Hydnophora, Porites rus, P. nigrescens, P. cylindrica). The plastic pins have also been

used with faviids and massive Porites. All these substrates

can be inserted in plastic mesh trays, which facilitates management and maintenance of the fragments during rearing. Also all these substrates can be inserted into appropriate sized holes drilled into the reef being rehabilitated.

The advantage of wall-plugs and hosepipe is that you can just insert the coral fragments into the open end of a wall-plug or one end of a piece of hosepipe without the need for glue to fix the fragment. Further, having part of the skeleton inserted into the substrate reduces detachment. This speeds up the nursery stocking process and reduces its cost. The disadvantage is that it is only suitable for fairly thin fragments from corals with a branching morphology. The flat-headed plastic pins allow a wider range of morphologies to be attached, but require the use of an adhesive to bond these to the pin head.

This can be more time consuming and thus expensive. Also, until self-attachment by growth of coral tissue over the pin head, corals remain more vulnerable to detachment.

Attachment of plating, encrusting and massive fragments directly to plastic mesh with superglue is currently being experimented with and appears promising. Once the fragments have grown in the nursery to a size suitable for outplanting, then the mesh can be cut into patches around each colony and the mesh nailed to the reef using broad headed masonry nails or large galvanised staples.

Segments of PVC pipe have also been tested as substrates for massive and encrusting species. Each piece of pipe has holes drilled at diagonally opposed corners; these allow you to tie the substrate to the mesh trays during rearing using cable ties or plastic coated wire, and can be later used to anchor the substrate to the reef using masonry nails or large staples when outplanting at the rehabilitation site.

Several species of massive corals (Favites, Platygyra, Favia) attached to segments of black PVC pipe with superglue prior to immersion in the nursery. The plastic segments are attached to the mesh of the rearing tray with plastic cable-ties or plastic coasted wire (S. Shafir).

Arrangement and spacing of corals in the nursery

The sessile life-styles and the growth forms of corals can lead to tissue contacts between adjacent colonies. On the one hand, if these contacts are between fragments from the same donor coral colony (isogeneic ramets) there will be fusions between the colonies, and these will later need to be separated. On the other hand, if these contacts are between different genotypes of the same species (allogeneic conspecifics) or different species (xenogeneic) there can be a striking array of interactions, including nematocyst discharge, development of mesenterial filaments and sweeper tentacles, release of chemicals that inhibit growth, or overgrowth. The net result is that for each interaction there may be deleterious outcomes (e.g., partial mortality, slower growth) for one partner in the interaction. Although some research has been done to look at which species are compatible and which are not, it is easier just to space farmed corals in the nursery to avoid tissue contact.

How long to culture corals in the nursery?

Because of the costs of maintaining corals in a nursery, you generally wish to transplant them as soon as they are large enough to have a good chance of survival on the reef targeted for rehabilitation. This size will vary from site to site depending on ambient conditions (e.g. water quality, herbivory levels) and will also vary with species. Slow growing massive and submassive species appear to survive transplantation better than faster growing branching species and may be transplantable at smaller sizes. Based on the few data available, we would recommend outplanting branching species at around 7–10 cm diameter and massive, sub-massive and encrusting species at around 4–5 cm. At such sizes they will have passed through the stage when they are vulnerable to being destroyed by a single bite from a predator, and transplants of a range of species have shown good survival at these sizes.

For branching coral species, 7–10 cm colonies can be

Left: a 9 cm long plastic pin (waste product of injection moulding). Centre left: Coral fragments being mounted on pins with superglue prior to immersion. Centre right: 10 mm wall-plug with a freshly inserted Millepora dichotoma fragment. Right: A fragment of Acropora variabilis being reared on a plastic wall-plug substrate. Note how the basal tissues have grown over the wall-plug. (S. Shafir).

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Box 4.3

1. Plastic pins can be used for branching, massive and encrusting coral species (for massive and encrusting morphotypes we recommend using ad hoc designed pins or plastic surfaces with enough area to allow the coral fragments to spread). Out of water, place the plastic pin vertically in a mesh tray and place a small drop of super glue (we have used Loctite® superglue successfully) on the plastic pin head. Take a coral fragment out of the water with forceps and place it with the exposed skeleton side on a paper towel to absorb excess water. Using forceps, place the fragment’s exposed skeleton onto the drop of cyanoacrylate glue. Gently press the fragment against the plastic for few seconds. After checking that the fragment is properly attached to the substrate, insert the pin into a plastic mesh-tray and submerge in seawater. Coral fragments should not be exposed to air for more than one minute during this procedure.

2. Plastic wall-plugs are suitable primarily for thinner branching corals and are less time-consuming to set up than plastic pins. Since the coral is inserted into the mouth of the wall-plug, it is less prone to become detached, and this method is therefore particularly recommended when corals are handled by inexperienced workers. Wall-plugs come in a range of sizes and many brands are available. Larger sizes (e.g., 10–12 mm drill bit size) are usually used but thin branched Seriatopora or Pocillopora damicornis might be more suited to smaller diameter

wall-plugs. If the branch fits tightly, no glue may be necessary. If in any doubt, add a small drop of cyanoacrylate glue to the inside of the mouth of the wall-plug and then firmly insert a coral branch into a suitable sized wall-plug, check the attachment and then insert the wall-plug in a mesh tray before submerging in seawater.

3. Segments of plastic tubing or hosepipe inserted vertically into mesh trays also make good substrates for rearing fragments of branching coral species. Thinner tubing can be appropriate for narrower branched species and thicker hose-pipe for thicker branched species. You should insert the coral fragments into the tubes so that they fit snugly, only applying a drop of cyanoacrylate glue (or bit of epoxy putty) to the inside of the mouth of the tube if necessary. You should cut the base of the tube or hosepipe obliquely into a tapering point so that it will slot snugly into the mesh trays of the nursery and be held securely in place.

grown from c. 3 cm high fragments within 9–12 months12_.

At such a size the colonies should be suitable for transplantation to rehabilitation sites. For massive,

sub-massive and encrusting species, 4–5 cm colonies can