GCRA
OVERVIEW
FAQ
NEWS
ARTICLES
PHOTOS
REEF ISSUES
RESTORATION
PAPERS
LINKS
|
|
|
|
Installation of a Pilot
Mineral Accretion Coral Nursery
Thomas J. Goreau, Ph.D.
DRAFT SUMMARY A mineral accretion coral and oyster nursery was installed on the seaward edge of the fringing reef of southwestern Kimbe Bay, New Britain, Papua New Guinea, in a cooperative project by the Global Coral Reef Alliance, Walindi Plantation, the Papua New Guinea Dive Association, Mahonia na Dari, and local communities. The pilot nursery project has three parts with a total area of 16.56 square metres, is powered by solar panels, and is intended to help restore coral, shellfish, and finfish diversity on reefs damaged by at least 7 different stress factors. This simple, low-cost pilot project is suitable for replication and enhancement on a larger scale for community-based reef management, and to protect Indo-Pacific coral diversity from the expected impacts of global warming. The project, process, and steps needed for its maintenance and monitoring are described, along with recommendations for future applications. INTRODUCTION: STRESSES TO FRINGING REEFS IN KIMBE BAY Rapid assessment of fringing reefs in Southwestern Kimbe Bay revealed that they were directly impacted by at least seven different stress factors, and potentially by several more, which have resulted in a visible decline from their historic diversity and productivity. Those factors which had caused obvious reduction in coral diversity and abundance, in rough order of importance, included bleaching, diseases, sediments, algae overgrowth, crown of thorns, tranpling, and use of Derris root and other fish poisons. In more detail: 1) Bleaching. Several episodes of coral bleaching have taken place in Kimbe Bay in the last two decades, most of them in the last few years. Coral mortality has been worst in the branching corals, especially Acropora staghorn coral species, and the plate corals, with large fields of Turbinaria lettuce corals wiped out on nearby bank reefs. Recent overall coral mortality is estimated to be in the range of around 10-20%, and is higher on the bank reefs than the fringing reefs. The cause of these bleaching events is the unusually high sea surface temperatures of recent years, as shown in satellite-derived sea surface temperature records of Kimbe Bay, studied since 1982 by T. Goreau. Turbid areas are well known to be less damaged in high temperature bleaching events, as they are subjected to less additional light stress. This explains the higher mortality apparent on nearby bank reefs, compared to inshore fringing reefs. Increased temperatures due to global warming are likely to increase mortality from bleaching in future years. 2) Coral diseases. The Porites heads, which make up around 90% of the live corals on the fringing coral reef, are being attacked by several coral diseases. A significant proportion of all the coral heads are slowly dying from Porites line diseases, which typically kill back coral tissue at around a few centimetres per month. A new, previously unknown, coral disease was observed to be attacking the lower surfaces of Porites in epidemic proportions, causing large patches of very recently dead coral to be white over areas about 10-20 cm across. These were not due to crown of thorns, as they do not eat Porites unless all their favourite coral foods are gone, which is not the case here. Samples of coral tissue infected with both of these diseases were taken by James Cervino and are now under microbial culture to identify any unusual bacteria and fungi associated with these diseases. 3) Sedimentation. The fringing reefs are clearly stressed by river transported sediments from soil erosion. There is a strong turbidity gradient from inshore fringing reefs that are very muddy with a layer of sediment covering dead corals. These stresses are markedly lower on the land-facing side of the nearby offshore bank reefs, only 50-100 metres away, and almost absent on the seaward side of the banks. The degree of sediment stress is likely to be increasing in Kimbe Bay due to clearcutting of forest for Palm oil plantations on the lower hill slopes. 4) Algae overgrowth. Dead corals are overgrown with algae. There is a strong onshore-offshore gradient in algae species composition. The fringing reefs are dominated by green filamentous algae turfs, indicating high nutrient levels. The shoreward side of the bank reefs is dominated by calcareous branching algae, such as Halimeda, and other algae species typical of low to moderate nutrients. The seaward sides of bank reefs are dominated by encrusting calcareous red algae, typical of low nutrient conditions. In all three habitats algae abundance and diversity decreases from the surface to deeper on the reef. These patterns indicate that the major source of nutrients is in land-derived freshwater sources. The role of nutrients in controlling the algae species and abundance is also indicated by the strong onshore-offshore gradient in algae-eating fish species, such as surgeonfish, and in algae-eating sea urchins. These are present in epidemic levels on fringing reefs, but clearly unable to control the algae there, while they are very rare in bank and seamount reefs. Sources of land-based nutrients should be increasing for at least three several reasons. First, land clearance for agriculture causes greater erosion of soils and loss of nutrients from soil and vegetation. Second, fertilizers applied to young oil palms are likely to be leached, especially if the area is recently cleared and plant cover is relatively low. Third, increased population of coastal areas caused by population growth and immigration from inland areas to the coast for employment in oil palm plantations results in greater flows into the sea via rivers and groundwaters of nutrients derived from the decomposition of human sewage and that derived from livestock. 5) Crown of thorns. A plague swarm of crown of thorns was found on fringing reefs, but they were very rare on offshore reefs. One large swarm of crown of thorns was discovered on the Walindi fringing reefs, and over 60 were removed by Dale the next day. Several survivors were found afterwards, and these need to periodically hunted down and removed, since they often hide in under coral and in crevices in the daytime. Large numbers of branching corals were observed to have been recently killed by crown of thorns. 6) Trampling. Reef walking by people collecting fish and shellfish results in killing all but a few species of massive corals. There were few corals alive on any surface that could be stepped on. However the large amounts of mud on the reef flat are also partly to blame for this pattern. 7) Derris root. Derris and other plant poisons have been widely used in the past. These are normally introduced into crevices into which fish have been chased. While derris root kills corals, according local knowledge and experiments conducted by James Cervino, it was not possible to identify the cause of old coral mortality, as these were covered with sediment and algae turf. There were few signs of recent damage that could be attributed to fish poisons, and most recently dead corals were found in exposed situations, where they were clearly due to bleaching, diseases, or crown of thorns. Additional factors which could be acting to reduce coral reef viability at lower levels than those previously mentioned include physical damage from storm and tidal waves, hydrocarbons, and pesticides. In more detail: A) Storms and tsunamis. Kimbe Bay is unusually protected from the seasonal prevailing winds, and is outside of the major typhoon zone, so there is little sign of wave damage. Because New Britain is highly geologically active, volcanic eruptions and earthquakes are able to set off submarine landslides, and trigger tidal waves (tsunamis) such as those that have devastated areas of New Guinea to the west of New Britain in recent years. Such events are unpredictable, but appear to be sufficiently rare that they have not left a visible trace at the site. B) Hydrocarbons. Boat traffic inevitably produces hydrocarbon slicks from leaking oil and petrol. Due to the low levels of boat traffic at this site, no hydrocarbon slicks were noted. But episodic accidental fuel leaks are likely wherever motorized boats are used. While no good studies are known of the chronic effects of low level hydrocarbon pollution, even in highly polluted areas, it is likely that hydrocarbons, by being taken up in coral tissue, could act to disrupt coral reproduction. C) Pesticides and herbicides. Agricultural chemicals are widely used in most commercial agriculture, and their impacts on the marine environment are largely unstudied. Although only relatively low levels are likely to be used in the oil palm plantations, their possible impacts cannot be discounted. Many herbicides and pesticides can enter the marine environment in dissolved form or attached to soil particles, and may remain active in the marine environment with unexpected consequences. Many herbicides also act against marine algae, and many insecticides are also active against shrimps and lobster. For example in the week before this project was started, intensive spraying of insecticides in the northeastern United States, intended to attack mosquitoes transmitting an exotic and deadly disease (West Nile Virus) appears to have destroyed the Long Island lobster industry. Fourth generation lobster fishermen reported that almost all the lobsters died the day after heavy spraying of inland areas near the coast with the widely used and allegedly "harmless" insecticide Malathion. The cumulative effect of these stresses has been greatest on the branching and plate corals, and has been least on the most stress resistant species. As a result, the coral reef is completely dominated by heads of the most stress resistant massive Porites species, which make up around 90% of the corals on the fringing reefs, but only a very small proportion on the offshore reefs. Fish populations are small, few, and dominated by algae eating species. Overall diversity has clearly been greatly reduced in comparison with nearby bank reefs and the coral diversity of the fringing reefs has only recently declined, as seen by the large number of dead corals of species whose living members are now relatively rare. Despite the multiple factors simultaneously damaging corals, the decline in coral reef health in these fringing reefs is far less than would be expected from the intensity of the stresses acting upon the reefs, because of recruitment of coral larvae and fish from the diverse and healthy reefs on the offshore banks and seamounts. However even these are being strongly impacted by both bleaching and diseases, along with potentially increased utilization, so continued replenishment of inshore reefs is likely to decline with time even if the offshore reefs are strictly protected from all forms of destructive utilization. The most obvious impact on harvestable species is the great decrease in fish density, variety, and size, and domination by algae-eating fish, especially surgeonfish, along with very high densities of algae-eating sea-urchins, which were not seen on any of the offshore reefs. It is clear that these reefs are suffering from the simultaneous impact of over harvesting and ecosystem deterioration, and that steps are urgently needed to restore fringing reef health, diversity, and productivity if local populations are to have adequate and easily accessible marine food resources in the future. THE MINERAL ACCRETION PROCESS IN REEF RESTORATION The Mineral Accretion method uses low voltage electrical currents to grow solid rock structures in the sea and to greatly speed up the growth of marine organisms with limestone skeletons and shells, such as corals and oysters, to record rates (Hilbertz & Goreau, US Patent, 1996). This method is unique because if acts directly at the surface of the growing limestone crystals to speed up deposition of calcium carbonate naturally dissolved in sea water, and can be used to create structures of any size or shape. The power requirements are low and ideally suited to sustainable energy sources such as solar panels. Corals in contact with the mineral accretion grow at rates many times faster than normal, depending on the amount of electricity generated (which varies with the angle of the sun above the horizon and the degree of cloud cover), the size and spacing of the meshes, and the types of corals present. Because corals benefiting from mineral accretion grow much faster and are healthier, the mineral accretion process can be used to restore damaged reef ecosystems even in areas of poor water quality, and these corals show much higher ability to survive bleaching (Goreau, Hilbertz, & Hakeem, 2000). Therefore efforts are underway by the Global Coral Reef Alliance to set up large-scale coral nurseries to propagate corals as a front line effort to counteract the effects of global warming. At the moment mineral accretion coral nurseries are operating in the Maldives, Thailand, Indonesia, and Mexico with extremely impressive results. This pilot project reflects the first use of this new approach towards reef restoration in Papua New Guinea. The purposes of this project are to restore coral growth and diversity on damaged reefs, provide habitat for reef fish, and to accelerate the growth rates of oysters, as a potential tool in local coral reef management, and to create refuges for coral species which are potentially threatened by global climate change. DESCRIPTION OF PROJECT The coral and oyster nursery pilot project consists of three pieces of plain (ungalvanized) steel construction mat, each about 2.3 by 2.4 metres in dimension, for a total area of about 16.56 square metres. The construction mats were placed on top of large rounded Porites coral heads, spanning the crevices between them. These mats are made up of 6 millimetre diameter steel rods, with a 20 centimetre square spacing. They are placed adjacent to each other on top of the seaward edge of the reef flat, about 60-70 metres away from the dock pump shed, and are connected via cables to four solar panels mounted on top of the shed roof. The solar panels, donated by the Global Coral Reef Alliance, were previously part of the world's largest solar power plant, which was decommissioned by a large American oil company and sold for scrap. The solar panels are wired in parallel to provide an output in full sunlight of over 100 watts, at a potential of around 6 volts with 16 amperes current. This electrical current is very low, and is entirely safe to humans and marine life. Each mat is separately connected to the negative terminal of the solar panels and is accompanied by a much smaller piece of special inert alloy mesh connected to the positive terminal, and located in a vertical crevice about 0.5 to 1 metre beneath the construction mat. Electrical currents generated by the solar panels flow through sea water between the construction mats and the smaller meshes located beneath them. Due to their electrolytic activity, the red rust on the construction mat will quickly turn from red to black and grey as the rust is converted back into metallic iron. Within a few days white limestone crystals will begin to grow on top of them. As this rock grows thicker, it will solidly cement the mats to the reef structure beneath them. Corals beneath the mats will be able to grow upwards at an accelerated rate, filling the spaces between the growing mineral accretion and often overgrowing it where in direct contact. As the mineral accretion gets thicker it will become stronger, eventually filling the spaces between the mesh with solid coral and limestone, creating sheltered hiding spaces for fish. A special focus of this pilot project will be to increase the growth rates of local species of oysters that are commonly eaten by local villagers. NEXT STEPS The construction and installation of this project had to be done in an extreme rush because the solar panels were unfortunately lost by the airline in transit across the United States, and were not finally delivered to Walindi until two days before I had to leave. While the solar panel installation was done very carefully, the actual water deployment of the cables, construction mat, and meshes had to be done on the very last evening, in conditions of failing light and very high turbidity. There were insufficient time, light, and personnel in the water to do more than the minimum deployment on top of the reef flat, and there was no opportunity to fully attach and secure the mats and meshes, or to transplant corals and oysters onto them. These steps will have to be done as soon as possible by the personnel of Walindi Dive Shop, and detailed directions were given to Lucas, Dale, Michael, and Shane. The near term steps needed include: 1) Silicone sealing the taped electrical connections between the solar panels and the cables, located beneath the shed roof overhang. This should wait until it is clear that the rust on the mats has disappeared, and they have become coated with a white mineral accretion layer. In case the wrong cables were connected accidentally, the mats will continue to rust at an accelerated rate, and mineral accretion will appear on the meshes instead. If this happens the taped connections will need to be undone, the leads to the cables switched, re-connected, and sealed.
2) The cables should be carefully inspected to make sure they are placed on the bottom in a position in which they can not be easily chafed on corals and rocks, or pulled away from the mats by wave action. Rocks should be placed on top of the cables where they enter the water, from the low tide mark to maximum wave height, to protect them from wave damage.
3) If the cable attachment to the mats are loose, a pair of pliers should be used to scrape off any mineral accretion (or rust if they were too loose for electrical current to flow) to expose a good clean metal surface, and the cable copper wire wrapped around it and crimped down with the pliers.
4) Rocks need to be placed on top of the mats to hold them securely down to the bottom, so that they do not flex and can become securely self-cemented as quickly as possible. These rocks should be large enough not to fall through the mat holes, that are larger than 20 centimeters minimum diameter. At least 8 rocks on each mat should provide enough weight, but more can be used if needed. The best choice for this would be rounded rocks from the intertidal zone that have young oyster spat settlement on them.
5) Corals need to be transplanted onto the mesh. Coral should be obtained from similar habitats in nearby reef areas. In order to avoid damage to healthy corals, naturally broken fragments which are readily found in the area, and which will probably die from rolling around in waves, should be used. As long as these are alive, they do not need to be large. The goal should be to rescue already broken corals that would not otherwise survive, not to damage healthy intact corals. The widest range of species and shapes of corals should be used, but the most important corals are the branching ones, which have become rare on the reef due to the effects of bleaching and crown of thorns. By growing more branching and leafy corals, the maximum shelter will be created for fish and invertebrates. The transplanted corals should be firmly attached to the mineral accretion by using pliers to break off a small area of mineral accretion cover, exposing bare shiny metal, to which binding wire should be wrapped and crimped, with the other end wrapping the coral tight to hold it firmly against the mineral accretion so that it can not wobble. This will minimize the time until the coral is firmly cemented into mineral accretion, and maximize their survival and rapid growth. Coral should not be placed so high up that they are exposed to air at low tide: it would be best to attach them to the undersides of the mats.
MONITORING AND MAINTENANCE The simplest way to check that the process is working is to look for fine bubbles rising from the mineral accretion. These can be hard to see under turbid conditions or if the sun is behind the observer, and they are most obvious when they are lit from behind by the sun. If these bubbles are not rising, then one of the wires is broken. These should be carefully checked. Wire breakage is rarely a problem, usually only after a heavy storm.
If a wire leading to the mineral accretion nursery mat structure is broken this can be repaired underwater by exposing bare wire on the cable, breaking off a small piece of mineral accretion to expose the bare metal of a piece of the mat, and crimping the wire around the mat's metal rod with a pliers.
If a wire leading to the mesh is broken, then the mesh and the whole cable needs to be brought to land and replaced. A new cable will probably be needed if it is corroded, but the mesh can be reused. If the mesh wire has been broken for a while, sediment, algae, and detritus may adhere to it, and the area to be connected should be dried and lightly sandpapered, but if it is still clean this is not needed. A new watertight connection must be made between the mesh and the cable. Directions to do this have been explained to Shane. If the wire needs to be replaced and Shane is not available, please contact me directly for instructions.
Routine monitoring is rarely needed except after heavy storms that may have damaged the cables. The position of the meshes should be checked from time to time, and if needed placed in a secure crevice about 0.5 to 1 meter from the mesh. The mesh can be moved around, as the mineral accretion grows fastest near it. By moving meshes under the slower growing portions of mineral accretion on the mat, the growth rates can be made more even. A rock should be placed on the mesh to stabilize it against possible damage from wave surge.
Coral and oyster health on the structures should be visually checked. Corals on mineral accretion nurseries are unusually brightly colored, and the polyps are fully expanded more often than normal corals. The growth rate of the corals and the oysters should be documented periodically by digital video images. Once every three months should be fine, but it would be a good idea to do so around once a month in the first three months. These images should be sent to T. Goreau. Control colonies of similar species of corals in nearby reefs should be photographed from time to time as a comparison, as should oysters growing on rocks in the channel.
Any crown of thorns found in the area should be carefully removed and buried on land. Coral-eating Drupella snails should also be removed.
RECOMMENDATIONS FOR FUTURE PROJECTS Mineral accretion reef restoration will only be viable as a management tool if reef harvesters in local communities can see clear visible improvement in terms of the size and diversity of corals and fish, and rapid increases in the growth of harvestable oysters. Therefore it is important that local village leaders and fishermen get to see the results first hand, and periodic visits should be paid by village leaders, in cooperation with Walindi Dive Shop and Mahonia na Dari. Because of the importance of getting good growth measurements on the oysters, these should not be harvested and made temporarily tambu on grounds of experimental necessity. Once good growth rate measurements have been obtained, some of them can be collected and eaten in order to see how they taste in comparison with slower growing oysters in natural mangrove settings. If local communities are convinced of the benefits of this method in terms of both reef restoration and oyster cultivation, the Global Coral Reef Alliance is prepared to work with local NGOs and community organizations to expand this small pilot scale project on a larger scale if funding can be found. The present pilot project is the simplest and cheapest alternative, but mineral accretion projects can be specifically designed for increasing coral growth or settlement, to provide habitat for fish, and shellfish, or for mariculture of oysters.
Reefs worldwide are threatened by increased mortality from bleaching caused by global warming. Major efforts are needed to preserve Indo-Pacific coral species and to adapt them to the expected future impacts of global climate change. This is best done by propagating as many species as possible on mineral accretion and selecting strains that are especially tolerant of higher temperatures. The very high coral species diversity and the high degree of coral reef destruction in Indonesia and Philippines from dynamite, cyanide, pollution, and bleaching, makes Papua New Guinea one of the best locations in the world for such projects. Due to its unusually sheltered location and the fact that so far damage from bleaching is minor and physical destruction is minimal, Kimbe Bay could be the site of a major coral reef nursery project. Funding for a large-scale project should be sought for a collaborative program between the Global Coral Reef Alliance and local environmental organizations.
ACKNOWLEDGEMENTS The solar panels and special mesh materials were donated by the Global Coral Reef Alliance. The construction mat, cables, wood, and hardware for mounting the solar panels were donated by Walindi Plantation. Special thanks go to Max Benjamin. This project would not have been possible without his encouragement, kind hospitality, and the deep knowledge of long term changes in Kimbe Bay reefs that he shared with us. Thanks also go to the staff of Walindi Plantation Resort and Dive Center for easing our path in a thousand ways, especially Shane, Dale, Lucas, the entire dive staff, and the workers constructing the new dock who helped with the solar panel installation. We thank Shannon Seeto and Paul Lokani of Mahonia na Dari for encouraging this project and related coral reef health monitoring efforts by James Cervino and Katherine Winiarski. Special thanks also go to the leaders of the local villages on the Walindi Committee, especially Leo Batari, for sharing their questions, concerns, and knowledge about the reefs and patterns of their use by local people.
|
|