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5.2. The Ecology of Papuan Coral Reefs

DOUGLAS FENNER

CORAL REEFS are structures in shallow ocean water built at least in part by corals, but often with major contributions from coralline algae and green calcareous algae. Coral reefs are composed of calcium carbonate (CaCO3) produced by living organisms. Reefs range in size from small patches a few meters in diameter to the largest structure on earth built by living organisms, the Great Barrier Reef of Australia, which is about 2,000 km long, covers an area of about 128,000 km2, and contains about 2,500 individual reefs. Coral reefs can also be very thick. At Enewetak Atoll in the Marshall Islands, a hole was drilled through over 1,400 m of coral rock before reaching the underlying volcanic rock. Thus, some reefs are major geological features of planet earth. The coral rock near the bottom of the coral at Enewetak was found to be 65 million years old, indicating that some coral reefs are also very old.

Three of the most widely recognized coral reef shapes are the fringing reef, barrier reef, and atoll. A fringing reef grows along the shore of a landmass, much like a fringe along the edge of a coat. A barrier reef parallels a coastline, with a lagoon between the barrier reef and the shore. These lagoons are relatively shallow (about 10–50 m deep) and usually have a sandy bottom. Barrier reefs are named because if they are continuous and reach the surface, they are a barrier to navigation. An atoll is a ring of coral with no land other than some low sand islands within the ring of coral. The center of the atoll is a lagoon. Other reef shapes include bank or platform reefs where an offshore reef does not reach the surface, and patch reefs, which are small patches of coral in lagoons. There are a wide variety of other shapes and intermediates between categories as well (e.g., Andréfouët 2004; Guilcher 1988; Hopley 1982; Tomascik et al. 1997).

Evolution of Reefs

Charles Darwin proposed a theory of the evolution of coral reefs (Darwin 1842; Tomascik et al. 1997). He proposed that coral reefs begin as fringing reefs, then become barrier reefs, and finally become atolls. Darwin’s theory applied to volcanic islands. He suggested that after an oceanic volcano erupts and builds an island, fringing coral reefs will grow around the shoreline of the volcanic island and that the island will then slowly subside or sink. As the island sinks, the reef will grow upward, and if it can grow upward as fast as the island sinks, eventually the reef will be separated from the island by a lagoon. The reef will then be a barrier reef, and the reef will mark the location of the original shoreline of the island. Eventually the island will sink under water and out of sight under the lagoon sand. The result is an atoll (Figure 5.2.1). Darwin knew that the way to test his theory was to drill into an atoll. He predicted that the drill would reach volcanic rock under the coral. The technology to drill such a deep hole was not available in his time, but eventually atolls such as Enewetak were drilled and volcanic rock was found underneath the coral rock, confirming Darwin’s hypothesis. The full sequence of evolution of coral reefs can be seen in Hawai’i, where the Big Island has an erupting volcano and fringing reefs. Small barrier reefs can be found on older islands such as Oahu and Kaui, and the oldest islands (which are found in the northwestern Hawai’ian Islands) are all atolls (Grigg 1982, 1997; Scott and Rontondon 1983)


Figure 5.2.1. Schematic diagram of the creation of a coral atoll. Charles Darwin proposed that fringing reefs growing on volcanic islands changed over time to produce barrier reefs and ultimately formed coral atolls. See text for details.

Papuan Reefs

Papua Province has many fringing reefs, some barrier reefs, and very few atolls. So, for instance, in the Raja Ampat Islands, reefs are mostly fringing or platform reefs with 36 fringing reefs and nine platform reefs reported in one study (Mc-Kenna, Boli, and Allen 2002). Several maps show coral reefs in the Raja Ampat Islands at the west end of Papua, around the islands in and along the western shore of Cenderawasih Bay, on the south shore roughly across from Cenderawasih Bay, and around the Aru Islands south of the main landmass (UNDP/FAO 1988; Spalding, Ravilious, and Green 2000; Burke, Selig, and Spalding 2002). The south coast of the Vogelkop Peninsula has narrow fringing reefs, with 450 km of coastline suitable for reefs. Tomascik et al. (1997) list nine barrier reefs in Papua, totaling 601 km in length and having an area of 2,366 km2. They also list one atoll in Irian Bay, nine in the Halmahera Sea, and five in the Pacific Ocean.

The extent of coral reefs in Papua may be underestimated due to the assumption that coral reefs cannot live along coasts that have mangroves. The muddy shorelines associated with mangroves are often not suitable habitat for coral reefs, yet in New Guinea there are places where coral reefs grow adjacent to mangroves, and mangroves even grow onto the reef platform (P. Dalzell, per. comm.). Some maps of Papua (e.g., Spalding, Ravilious, and Green 2000) show long stretches of coast containing some of the largest mangrove forests in the world. A long stretch of the north coast is normally depicted as being devoid of coral reefs, but fringing reefs are believed to stretch along much of the coast between Sarmi and the border with Papua New Guinea. Fringing reefs are reported on the northern coast of the Vogelkop Peninsula, as well as east from Jayapura to the Papua New Guinea border, and a fringing reef west of Jayapura for 100 km, possibly for an additional 160 km (Tomascik et al. 1977). The coral reefs of Papua New Guinea are much better studied, and yet about half of its coastline has not been explored for coral reefs (Yamuna and McClanahan 2001). Whitehouse (1973) claimed that on the north coast of Papua New Guinea there are no active coral reefs for 1,250 km, but Kojis, Quinn, and Claereboudt (1985) found fringing reefs with a high coral cover and diversity are common along this coast except near the mouths of rivers. The north coast of Papua probably has similar reefs. The total amount of coral reefs in Papua could be several times that presently known. Reefs in Papua are protected from strong wave action. Reefs at 45 sites in the Raja Ampat Islands off the western end of the Vogelkop Peninsula (described in McKenna, Boli, and Allen 2002) vary from those exposed to the open ocean, to those that are in sheltered bays, to one that was so enclosed it was virtually a saltwater lake (Mayalibit Bay within Waigeo Island). Strong currents were not encountered at most sites. The seas are very calm compared to those at oceanic mid-Pacific reefs or the Great Barrier Reef. The reefs do not feature a reef crest with large crashing waves and high cover of coralline algae, nor extensive reef flats and lagoons. Rather, the bottom usually slopes away directly, starting at the shoreline. This is typical of reefs in the region, as the author has seen in northern Sulawesi (Allen and McKenna 2001), eastern Papua New Guinea (Allen et al. 2003), Malaysia (Harborne et al. 2000), and 11 areas in the Philippines (Fenner, under review c; Werner and Allen 2000). Reefs on the southwest side of Cenderawasih Bay include patch reefs with seaward margins that are sheer drop-offs from the crest to a first ledge at 20–40 m depth. Sub-sea level patch reefs have a variable gradient fore reef. Fringing reefs have a variable gradient in bays and sheltered areas but are steeper elsewhere (UNDP/FAO 1982; UNEP/IUCN 1988).

Coral cover has been used as a measure of coral health. Because damage to reefs reduces coral cover, reefs with higher coral cover have been presumed to be in better condition. Data on coral cover for 13 sites in the Padaido Islands in Cenderawasih Bay are available (Tomascik et al.1997). Most commonly they had cover of 25–50%. In 44 sites in the Raja Ampats, McKenna, Boli, and Allen (2002) found that the average coral cover was 28%. A qualitative scale for coral cover was devised by Gomez et al. (1994), where 75–100% cover was considered excellent, 50–75% good, 25–50% fair, and 0–25% poor. Thus, reefs in these two areas would be considered fair. Indonesia as a whole is reported to have 2.6% of its reefs as excellent, 24.2% good, 31.6% fair, and 41.6% poor condition (Ming et al.1994). Such a scale should be approached with caution, since it implies value judgments that are not based on empirical studies. Coral cover varies substantially depending on habitat and sediment dynamics. No clear generalization can be drawn on the relationship of coral cover to reef health (Maragos 1997). Further, reefs that are among the most pristine known rarely have coral cover in the excellent range, and frequently are in the fair range. Examples include the northwest Hawai’ian Islands (Grigg 1983) and the Great Barrier Reefs (AIMS monitoring, www.aims.gov.au). The scale was originally proposed as a measure of reef health and degradation, yet the natural baseline conditions of reefs are not known. Senior ASEAN scientists assessed eastern Indonesia as having 10% of its reefs degraded 50 years ago and 50% in 1993 (Ming et al. 1994), but figures for Papua were not given. The latest Status of Coral Reefs of the World: 2004 Report (Wilkinson 2004) indicates that the overall reef condition of Indonesia has been improving since 1999, with a shift from reefs with less than 25% cover to reefs with 25–50% cover.

SEA LEVEL CHANGES

The area of eastern Indonesia and New Guinea is a geologically active area, due to the collision of the Indo-Australian, Eurasian, Caroline, Philippine, and Pacific plates. There are many areas of uplift in eastern Indonesia, and many places that have terraces on slopes above the waterline, including along the northwestern coast of Papua (Tomascik et al.1997). On the Huon Peninsula of northeastern Papua New Guinea, continuous uplift of the landmass along with oscillating changes in sea level have produced a stair step series of fossil coral reefs on land. During ice ages, huge amounts of water are withdrawn from the oceans and locked up in giant ice sheets on land in North America, Europe, and Asia, much like in Antartica today. In addition, lower temperatures in the oceans cause the water to contract. These two processes together cause sea levels to drop substantially during ice ages. The last ice age peaked at about 22,500 years ago, causing a drop in sea level of about 120 m. This is well below the lower limits (usually around 30 m) of all presently living coral reefs. Thus all presently living coral reefs were exposed to air at that time and died. The change in sea level happened sufficiently slowly that larvae of sessile organisms such as corals were able to attach farther down and remain alive in the water, and begin building reefs farther down the slopes of islands and continents.

In an area like the Huon Peninsula where land is rising steadily, coral reefs build up along the shore when the water levels rise at about the same rate as the land rises. Then when the sea level drops, the reef is left out of the water and new corals attach farther down. There have been a whole series of ice ages, and so the hillsides on the coast of the Huon Peninsula have a series of benches made of coral reefs up and down their slopes (Figure 5.2.2). A living fringing coral reef is in the water along the shore, and the series of raised reefs on the hillside begins with the youngest at the bottom and progresses to the oldest at the top. There are nine fossil reefs, spanning a period of 95,000 years. A comparison of the species on the living reef and in the fossil reefs shows that the reefs have the same species composition even though they differ in age by up to nearly a hundred thousand years. Complex reef assemblages have been able to reconstitute themselves in the same form time after time over a very long period of time. Differences were actually greater between points along the coast than at the same reef over 95,000 years (Pandolfi 1996). Similar areas of rising land in Papua are likely to have experienced the same series of events, and have similar fossil reefs. In areas where the land is not rising or is even sinking, reefs produced during lower sea level stands are likely to be found underwater. Such reefs produce terraces or ledges, such as the one reported from Cenderawasih Bay.

ZONATION

Coral reefs have several zones. The term zonation refers to situations where the type of organisms present (i.e., species composition) changes along some environmental gradient. Rocky intertidal zones in temperate climates have zonation, with some organisms living only high in the intertidal, others living in the middle intertidal, and still others in the lower intertidal. On coral reefs there are a series of zones encountered as one moves out from shore (Figure 5.2.3). On a barrier reef, the zone closest to shore is the lagoon, which has a sandy bottom and may have seagrasses and algae on the bottom, along with patches of coral. Farther out, a shallow, hard calcareous (composed of calcium carbonate) bottom is called the reef flat and may have scattered corals. The crest is where waves break on the reef, and is usually dominated by crustose coralline algae. This type of algae forms a smooth hard layer over underlying coral rubble or rock, cementing it together and withstanding the force of breaking waves. From the crest, the reef slopes downward in what is called the forereef slope. On the reef slope there may be a series of ridges and gullies running down the slope called spur and groove, tongue and groove, or ridges and sand channels. On some reefs the slope ends in a vertical drop-off that can be called a wall. Walls commonly have overhangs that alternate with steeply sloping sections. Some reefs have caves on reef slopes or walls, and most reefs have small holes in the reef that may extend in a maze through the reef. At the base of a wall, there is usually a slope of sand and debris, but few or no reef-building corals.


Figure 5.2.2. Coral reef benches on the north shore of Huon Peninsula, Papua New Guinea.


Figure 5.2.3. Zones on a barrier reef.


Each of these zones is a distinct habitat. The zones differ in exposure to waves and currents, with lagoons being the most protected from waves and sometimes having restricted circulation. Organisms living in lagoons need to be able to burrow in, or attach to, or live on sand, which is the substrate. The reef flat usually has wave action and strong currents from the waves breaking over the crest, pumping water into the lagoon. Organisms here are also subjected to intense solar radiation on clear days. On the crest, organisms are battered with powerful waves and exposed to intense solar radiation. On the reef slope, wave surge and solar radiation decrease with depth. Coral diversity is usually highest on the reef slope, moderate on the reef crest, and lowest on the reef flat (Karlson, Cornell, and Hughes 2004). On walls, wave surge is usually nonexistent, and solar radiation decreases rapidly with depth. There is enough sunlight on steep slopes on a wall for organisms that need light, like coral and algae, to grow. But overhangs do not have enough light for such organisms, and have a strikingly different community of organisms. Overhangs are usually dominated by sponges, soft corals, and coralline algae (which need light but can grow in lower light levels than most corals). Caves have increasingly lower light levels with distance from their opening. Water circulation decreases with distance into caves and holes, and yet is still sufficient for some types of organisms. Oxygen levels may also decrease with distance inside holes in reefs as organisms use up the oxygen coming in on a limited flow of water. The zonation with decreasing light in caves may parallel over short distances the zonation on the wall or slope below the reef over a larger depth range. Thus an organism (such as a black coral or sclerosponge) that is found in deep water below the reef may also be found in shallower water under overhangs or within caves.

Corals grow most rapidly between depths of about 10 and 30 m. Walls often begin at depths of around 20 m, though in some places they can start in just a few meters (such as several sites in the Philippines) or well below 30 m depth (Discovery Bay, Jamaica). Coral cover is usually highest at depths around 5–20 m, but this does not hold at all locations. Coral cover decreases with depth on most reefs below a depth of around 30 m, though the depth at which this begins is variable. Corals become quite rare most places below about 50 m depth. The deepest corals that require light have been said to be at about 100 m depth, but in Hawai’i living coral has been found as deep as 187 m (Chave and Malahoff 1998). The lower depth of some reefs is determined by habitat, with the reef ending in a sandy slope. Such a sandy slope can be reached at virtually any depth, with some beginning at less than 10 m depth and a few beginning as shallow as 5 m.

Many corals have relatively broad depth ranges, yet some are quite restricted in their depth ranges. I found Acropora aspera to be present only on reef flats less than one meter deep in American Samoa, and Acropora cf. pinguis in Malaysia to be totally restricted to depths of less than two meters. Acropora digitifera is common only in shallow water (about 0–3 m). A. robusta and A. pulchra are rare except in shallow water (about 0–7 m deep). Acropora nana, a species with very thin delicate branches, is restricted to shallow water (about 0–2 m) and is somewhat surprisingly most common in heavy surf zones. The genus Leptoseris is largely restricted to low light level areas such as deep water and overhangs, as are the black corals (Antipatharia). Giant clams, Tridacna sp. and Hippopus sp., are most common in shallow water and densities drop off quickly with depth. Coral communities in lagoons may be dominated by corals that are rare on reef slopes and vice versa.

SEDIMENTATION

Coral reefs are found in warm, shallow, clear tropical saltwater. Corals can only live in saltwater; none are found in freshwater or even brackish water. They are rarely found near the mouths of rivers, and almost never found near large rivers. Most corals thrive best in clear water, and cannot survive in water containing large amounts of sediment or in mud. Most corals require a hard surface to attach to, though there are some corals that do not attach or only attach for a short period in their life cycle. Sediment in the water that settles on a coral can be cleared off by the action of tiny hair-like structures called cilia. The cilia can remove small amounts of sediment but not large amounts. Further, if sediment buildup occurs on the bottom, sediment will begin to cover and smother the coral because the coral is attached and cannot move upward to get above the surface of the sediment. As a result of these processes, coral reefs are not found near the mouths of rivers that release huge volumes of suspended fine sediment into coastal waters. In Papua reefs are found around small islands, and along the western mainland coast. However there are no reefs in the eastern part of the province, where the landmass is large and larger rivers such as the Mamberamo, Pulau, and Digul empty into the ocean. Because the island of New Guinea is a geologically young, very high island in an area of very high rainfall (over 3,000 mm/yr in Papua; Tomascik et al. 1997), runoff of fresh water and sediment is very high. If the temptation to reap large quick profits by cutting the rainforests of Papua is not resisted, the amount of sediment runoff will grow many-fold, and coral reefs will be rapidly killed.

Reef building corals need light to live and grow. Suspended sediment in the water scatters and absorbs light, reducing its availability to coral. Although there are limits to how much sedimentation corals can tolerate, some are able to thrive in areas with moderate levels of sedimentation. A coral reef named Middle Reef about a kilometer offshore of Townsville, Queensland, Australia, survives with high coral cover in water that has a visibility of only about one to two meters. The coral species on this reef are quite different from those found on the nearby outer edge of the Great Barrier Reef, in clear oceanic waters. Further, sediment input to the nearshore waters of Queensland increased dramatically when sheep and cattle were introduced to the area about 100 years ago (McCulloch et al. 2003). This increased sedimentation stresses the surviving corals and renders them less resilient, perhaps to the point of being unable to recover from other types of disturbance.

TEMPERATURE

Coral reefs are restricted to warm waters where the minimum temperature is above about 18 C. The world’s most northern coral reefs are at Kure Atoll in the northwest Hawai’ian Islands, and in Japan, and the most southern are at Lord Howe Island, off southeastern Australia. Some coral communities can be found at even higher latitudes, but they do not accumulate calcium carbonate, and therefore do not form coral reefs. An example is in the Solitary Islands off New South Wales, Australia, where occasionally storms with waves up to ten meters tall sweep most corals off into deep water. Newly settled coral recruits then grow on the non-carbonate rocks, rebuilding the coral community, but their skeletons do not accumulate (Harriott, Smith, and Harrison 1994). Such coral communities can also be found in the tropics near the equator in marginal environments, such as sandy, high sediment, or low circulation areas. In addition, at the extremes of latitude, coral reefs tend to be small, and to have low diversity (Yamano et al. 2001, discussed below). Papua is situated in an area close to the equator, where temperatures are warm year-round (27.5–28.5 C in the Java Sea; Tomascik et al.1997) and nearly ideal for coral reefs.

Most coral reefs are found in warm, clear tropical water. The water is clear because it contains few of the tiny drifting plants and animals, which together are known as plankton. Temperate and polar waters are often opaque with a green or brown color, due to masses of plankton. The tiny drifting plants are called phytoplankton, and they require nutrients such as nitrogen and phosphorous, just as do other plants. In the tropics, the hot sun heats only the surface water but does not penetrate deeper water. Hot water rises above cold water because it expands slightly when heated. The boundary between the warm surface water and colder deep water begins at a depth of about 50 m in Indonesia, and extends down to about 300 m depth (Tomascik et al. 1997). The fact that warm surface waters float on top of the cold deeper water means that these two bodies of water do not mix. Phytoplankton absorb nutrients from the surface water as they perform photosynthesis and grow. The phytoplankton are fed on by zooplankton (tiny drifting animals), which are in turn fed on by larger animals in a food chain or food web. When any of these organisms die, they sink slowly down into the deep cold water and to the bottom, taking nutrients with them. While currents called upwelling bring nutrients from the bottom back up to the surface fueling blooms of plankton in temperate and polar waters, upwelling is rare in tropical waters. The result is low nutrient levels in warm tropical surface waters, low densities of plankton, and hence clear water.

ZOOXANTHELLAE

The low nutrients in warm, clear, shallow tropical waters pose a paradox for coral reefs. Coral reefs have abundant organisms, and high rates of photosynthesis and growth. How can this occur in waters that are low in nutrients? How can this oasis flourish in such a biological desert? A variety of mechanisms probably contribute, but perhaps the most important is the algae living in corals. Corals are animals related to sea anemones and jellyfish. Corals have small polyps that are nearly identical to sea anemones. However, they contain within them the seeds of their success. These are the tiny single-celled algae known as zooxanthellae. The algae are members of a group called dinoflagellates. The algae and the coral animals live in a mutualistic symbiosis (i.e., mutually beneficial coexistence). The waste products of the animal contain the nitrogen and phosphorus that the algae need. The algae perform photosynthesis in the sunlight, and leak much of what they produce into the surrounding animal cells (around 80%). So the algae benefit from the nutrients the coral animal produces, and the coral benefits from the food that the algae produce. In effect, this is a tight recycling arrangement, with nutrients passed from one partner to the other, and then back to the other partner. As a result, the combination of these two partners needs a smaller input of nutrients from the outside, and can survive in nutrient-poor, warm, clear, tropical waters.

Plants on Coral Reefs

On most coral reefs, animals are obvious and appear to be common, while plants are less obvious and appear to be less common. But only plants can produce food through photosynthesis. When animals eat plants, most of the food is used to produce energy to run the animal’s bodily functions, while only a small part is added to the material of the growing animal. As a rule of thumb, only about 10% of what an animal eats is incorporated into its body in growth. As a result, there must be about ten times as much biomass of plants as herbivores that eat them. And there must be about ten times as much herbivore mass as carnivore mass that eats them, and so on up the food chain. Thus there must be about 100 times as much plant biomass as carnivore biomass for carnivores that eat herbivores; 1,000 times as much to support carnivores that eat other carnivores. And yet on coral reefs animals are obvious and appear abundant, while plants are usually less obvious and appear less abundant. How can this be? First, some plants are hidden. Zooxanthellae are found in hard corals, soft corals, giant clams, and a few other animals on coral reefs. They provide a large part of the food production on a coral reef, and yet are not obvious. They actually provide much of the color in corals and giant clams, yet we normally don’t recognize them as plants. Second, the algae which can be seen on coral reefs include some species which are small and hard to see but are highly productive. Large fleshy algae grow slowly and put most of their growth into defenses such as woody cellulose that is hard to digest, calcium, and chemicals that are bad tasting or toxic. Defenses are necessary for a plant to grow large on a coral reef, since there are many hungry mouths of herbivores, such as fish, sea urchins, and snails. Fish alone bite algae about 40,000 to 156,000 times per square meter of reef per day! So herbivory is intense on coral reefs. A second group of algae is the filamentous algae. These algae are made of tiny strings of cells with little or no defense. Their main defense is their ability to grow very rapidly. Herbivores bite most of their growth off daily or hourly, but the base of each filament attached to rock rapidly grows the string back. So filamentous algae are highly productive fast growing algae, but have a very low standing biomass and are hard to see.

Species Diversity

Coral reefs are not only geological structures, but also biological communities. Coral reefs are amazingly diverse and complex ecosystems. They are the most diverse marine ecosystem known (i.e., they are the most species-rich). Sometimes they are said to be the most complex ecosystem on the planet, but they actually have fewer species than tropical rainforests. Rainforests have large numbers of insect species, and insects are by far the most species-rich group of organisms on the planet. There are more insect species known than all other organisms combined, and there are more insects in tropical rainforests than anywhere else on earth. There are very few marine insects, and none known on coral reefs. The total number of species is not known for either coral reefs or rainforests. Around 1.8 million species have been described on earth, with a majority of those being insects. Estimates for the total number of species on earth range from about 3 to 120 million, with about 5–10 million being most likely. About 85% of all species are arthropods, and a majority of those are insects. On coral reefs, one estimate is that 93,000 species may have been described, but the total may be ten times higher (Reaka-Kudla 1995a,b). However, at the level of the largest groups of animals, known as phyla (such as Mollusca, Arthropoda, and Chordata) there are more phyla of multicellular animals (metazoa) in the oceans (about 29 out of 32) than on land (about 13) and in freshwater (about 16) (Rupert and Barnes 1994), and coral reefs probably have more phyla than any other ecosystem (about 26).

Relationships among Organisms

Coral reefs have very large numbers of species living together and interacting in a very complex web of relationships. We have already spoken of the mutualistic relationship between corals and the zooxanthellae they host. There are many other examples of coral reef species that have mutualistic relationships with other species, such as the Anemonefish (Amphiprion) that live among the tentacles of sea anemones; cleaner fish, such as Labroides dimidiatus, and shrimp, such as Periclimenes, that clean parasites off of fish; snapping shrimp (Alpheids) that excavate burrows which they and guardian prawn gobies (Gobiidae), occupy, and the Guard Crabs (Trapezia) that live in the branches of corals (Pocillopora) and defend them.

In another type of symbiosis, commensalism, one organism lives on another and benefits, while the host organism is neither helped nor hurt by the relationship. An example is the shrimp Periclimenes that live on sea anemones, starfish, nudibranchs (sea slugs) and other animals. A third type of symbiosis is parasitism, where one partner benefits at the expense of the other. Many small crustaceans and flatworms live on the skin of fishes, eating mucus and tissue off of the fish. Some crustaceans called isopods live attached on the outsides of fish, sucking tissue and blood. There are so many species of flatworms that are parasitic on snails in at least one stage of their life cycle that it is said that nearly every species of snail is parasitized by a species-specific parasitic flatworm. One parasitic flatworm, Plagioporus, lives in corals, Porites, at one stage in its life, causing the host polyp to expand and turn pink. The larger pink polyp stands out and is often eaten by butterflyfish (Chaetodontidae). This transfers the flatworm to its next host (Aeby 1991).

New relationships like these are being discovered all the time. For example, the snail Dendropoma maxima produces an uncoiled shell in a coral. The snail, called a vermatid because its shell resembles a worm tube, secretes mucus, which it drapes over the coral surface. The snail pulls the mucus in, dragging along with it additional mucus produced by coral, and eats it. The snail is thus parasitic on the coral, and stunts the growth of the surrounding coral (Fenner, under review a). Infectious diseases are similar to parasites, except that the agents that cause the diseases are generally microorganisms such as protozoa, bacteria, and viruses. Coral diseases have increased in number and severity in recent years, both on Caribbean and Indo-Pacific reefs. Diseases were detected at 10 of 45 (22%) sites during a recent survey at the Raja Ampat Islands (McKenna, Boli, and Allen 2002).

Nearly all animals on coral reefs are either predators or herbivores, the exceptions being those hosting endosymbiont algae such as corals. Predation may shape some communities, with apex predators dominating fish communities in pristine coral reefs such as the northwest Hawai’ian Islands. Predators may increase diversity by preying on the most abundant species. Two important predators of corals are the Crown-of-Thorns (COTS) starfish (Acanthaster planci) and snails of the genus Drupella. Crown-of-Thorns starfish came to the attention of scientists and the public in the mid-1960s when there were large outbreaks on the Great Barrier Reef in Australia, and nearly all corals were eaten and killed on some reefs in the midsection of the Great Barrier Reef. Outbreaks were reported on many reefs in the Indo-Pacific, with some of the worst around Okinawa, Japan (Moor 1989). Reports of outbreaks are much less frequent today, and reefs around Okinawa are now largely free of outbreaks. Outbreaks continue to occur on the Great Barrier Reef periodically. The first outbreak of COTS reported in Indonesia occurred in 1995, on the reefs of the Seribu Islands south of Papua (Tomascik et al.1997). In the Raja Ampats, only 3 of 45 (6.7%) sites had any COTS at all (McKenna, Boli, and Allen 2002). A few outbreaks of the snail Drupella have been reported in the Indo-Pacific (Moyer, Emerson, and Ross 1982), but they have not done as much damage as Crown-of-Thorns starfish. In the Raja Ampats study, Drupella were only observed at one site.

The Coral Triangle: The Peak of Diversity

The amazing diversity of species is perhaps the most notable aspect of the coral reefs of Papua Province. Papua is situated within the area that has been called the ‘‘Coral Triangle’’ (e.g., Allen 2002a; Wells 2002). This is the area of the highest diversity coral reefs in the world (Figure 5.2.4). It includes the Philippines, central and eastern Indonesia, and Papua New Guinea. There are more coral species in this area than in anywhere else in the world (Hughes, Bellwood, and Connolly 2002; Stehli and Wells 1971; Veron 1995), and the same is true of fish (Allen 2002a; Hughes, Bellwood, and Connolly 2002; Chapter 4.8), mollusks (Gosliner 2002; Wells 2002), and sponges (van Soest 1997). A recent expedition to the Solomon Islands found that the diversity of corals, fishes, and mollusks there is equally high, indicating that it too is part of the Coral Triangle (Green, Veron, and Allen 2004; Wilkinson 2004). Further, the number of mollusks in the Coral Sea area (Solomons to Great Barrier Reef to Vanuatu) is nearly as high as in the Coral Triangle (Wells 2002). In addition, recent work has found that diversity levels on outer barrier reefs of the northern Great Barrier Reef were marginally below that typical in the Coral Triangle (Fenner, unpublished). Coral diversity on mid-shelf reefs is even higher (Done 1982), so it is likely that the northern Great Barrier Reef has coral diversities within the range of diversities of the Coral Triangle.


Figure 5.2.4. Map of coral species diversity. Coral diversity decreases in all directions from the Coral Triangle (indicated in the darkest shade), which contains 581 coral species.

Source: Reproduced from Veron (2000) with kind permission from the author.

DIVERSITY GRADIENTS

The number of species decreases in all directions from the Coral Triangle (Figure 5.2.4). The diversity gradient to the north and south from the Coral Triangle is called the Latitudinal Diversity Gradient. This is perhaps best illustrated by the gradient in species diversity in southern Japan, with 342 species of coral in the small islands just north of Taiwan, decreasing almost in a straight line to zero species around Tokyo (Figure 5.2.5). A similar diversity gradient extends eastward from the Coral Triangle, with the number of species decreasing to the east in the Pacific until in the eastern Pacific there are a total of only about 33 species over a very large area. This gradient is called the Longitudinal Gradient. Both the Latitudinal and Longitudinal gradients have been documented in several groups of organisms. For instance, Indonesia has 90 species of Crinoids (feather stars), and going north, Palau has 30 and Guam has six. Going east, the Marshall Islands have 14 species and Hawai’i has none. Similarly, there are 536 species of sea slugs (opisthobranchs) known from the north coast of Papua New Guinea, 410 in Guam, 244 in Hawai’i, and 183 in Pacific Panama (Gosliner 1992). The diversity gradient for corals and fish shows a less steep gradient going west from the Coral Triangle in the Indian Ocean. Recent work in the Red Sea by Emre Turak, Lyndon Devantier, and J. E. N. Veron (reflected in the maps in Veron 2000) has doubled the number of species known there from 150 to 300, showing that the Indian Ocean Longitudinal Gradient is not as steep as previously thought.


Figure 5.2.5. Coral diversity in Japan decreases with increasing latitude (n 10, R2 0.96).

Source: Redrawn from Veron (1992).


A recent study (Karlson, Cornell, and Hughes 2004) compared coral species richness on a longitudinal gradient, comparing the number of species in Indonesia, Papua New Guinea, the Solomon Islands, American Samoa, and the Society Islands of French Polynesia. There were three sites in each country, with one of the sites in Indonesia being an island site to the west of the Vogelkop Peninsula of Papua. They separated transects on reef slopes, reef crests, and reef flats, and had an equal number of transects at each location and each reef zone. They found that on reef slopes, there was a high diversity from Sulawesi to the Solomon Islands, with no gradient between these sites. American Samoa and the Society Islands had significantly lower diversity on reef slopes. On reef crests, the diversity was highest in Indonesia, decreasing significantly in Papua New Guinea, decreasing further in the Solomon Islands, and lowest in American Samoa and the Society Islands. Reef flat diversity decreased a lesser amount from Indonesia to the Solomon Islands and on to American Samoa and the Society Islands (Figure 5.2.6). Thus, while the reef slope data indicate that the reefs of Papua New Guinea and the Solomon Islands are as diverse as those in Indonesia, the reef flat data and especially the reef crest data indicate that Indonesia has the highest diversity of all these areas, and that the longitudinal diversity gradient begins between Papua and Papua New Guinea. The authors did not separate the data for Papua from the other two Indonesian sites on Sulawesi. Borel Best et al. (1989) proposed that western Indonesia is outside of the Coral Triangle. Allen (2002b) found a lower diversity of fishes at Weh Island off the western end of Sumatra, which is consistent with this proposal. Thus, the best current data indicates that Papua is in the area of highest coral diversity, but diversity begins to decrease to the east of Papua.


Figure 5.2.6. Coral species richness as a function of longitude in three reef zones. Leftmost points are for Indonesia, followed to the right by Papua New Guinea, the Solomon Islands, American Samoa, and the Society Islands.

Source: Redrawn from Karlson et al. (2004).

Why Is Diversity So High?

The causes of the peak of marine diversity in the Coral Triangle and the latitudinal and longitudinal diversity gradients have been much debated. There have been many proposals. An early idea was that the center of diversity was a center of species formation (e.g., Briggs 1994). A second view is that more rapid extinction in outlying areas reduces the number of species in those areas. During ice ages, for instance, the Coral Triangle area probably experienced a much smaller drop in sea surface temperature than high latitudes and the eastern Pacific, so more coral species survived in the Coral Triangle than in those other areas. Another proposal is that currents in the tropical Pacific flow westward, carrying new species with them and causing the accumulation of species in the Coral Triangle area (Jokiel and Martinelli 1992). The proponents constructed a model that showed just this effect. Yet another proposal is that many islands close together allow any local populations that might go extinct to be rapidly replenished by larvae from nearby islands. The classic theory of island biogeography predicts higher numbers of species when an island is closer to a source of additional species (MacArthur and Wilson 1967). In areas with few islands, a population could go extinct more often on an isolated island before larvae from distant islands could reach it by chance and replenish the local population. Local extinctions have indeed been documented among the corals on the widely separated reefs of the eastern Pacific (Glynn 1977). A model using different densities of islands but random currents produces higher diversities in areas with more islands (Blanco-Martin 2002).

Connell (1978) proposed an ‘‘Intermediate Disturbance Hypothesis’’ to account for high diversity in rainforests and coral reefs. Disturbances of intermediate intensity and frequency open spaces where additional species can settle, whereas without disturbance, superior competitors drive out inferior competitors in a biological succession that ends in lowered diversity. If this theory were used to try to explain diversity gradients, it might suggest that the area of highest diversity is where disturbances are of intermediate intensity and frequency. However, sea surface temperatures in Indonesia and New Guinea are disturbed less by cold events than in areas farther from the equator. Similarly, there are no cyclones near the equator in Indonesia (including Papua) and New Guinea (Figure 5.2.7a,b; Fenner and Riolo, under review). On the other hand, the northern Philippines experiences a moderate to high level of disturbance from cyclones, and yet is part of the Coral Triangle. Cyclones are probably one of the most important natural disturbances on coral reefs (Rogers 1993). Thus, the Intermediate Disturbance Hypothesis is unlikely to explain coral diversity gradients.

In ecosystems with low diversity, each species may be represented by large numbers of individuals. For example, in the tundra of northern Canada and Alaska, there are millions of Snow Geese (Chen hyperboreus) in the summer, and millions of mosquitoes. There is only one large mammal, the Caribou (Rangifer caribou) and it is also present in large numbers. Northern forests are composed of large numbers of individuals of a small number of tree species. By contrast, in the tropics there are large numbers of species, most of which are rare. In a hectare of rainforest in New Guinea, there can be several hundred species of trees, but few individuals of each species. An example from coral reefs is sea slugs (opisthobranchs): in the western Pacific there are many species (over 500), most of which are very rare. In the tropics, functional groups of species, called guilds, usually have many more species than in the temperate or, especially, polar areas. Research on terrestrial systems indicates that the loss of individual species does not have a great impact on a high-diversity ecosystem, because there are many other members of most guilds that can continue to perform that guild’s functions (Grime 1997; Moffat 1996). The loss of a member of a guild in a low-diversity ecosystem may have a much larger impact on the ecosystem, particularly if there is only one member of that guild so that with its loss the guild function is no longer performed. Similarly, Bellwood et al. (2004) have argued that low diversity coral reefs are more vulnerable to the loss of individual species than diverse ecosystems for these reasons. For example, the loss of a single species of sea urchin, Diadema antillarum, in the Caribbean in 1983–1984 (Lessios 1988; Lessios, Robertson, Cubit 1984), led to major phase shifts on some reefs from coral-dominated reefs to algal-dominated hard grounds. The large numbers of a single species in low-diversity ecosystems also makes them more vulnerable to diseases and specialized predators. A dense population of a single species, as was the case with D. antillarum, makes the transmission of disease easier. The die-off of D. antillarum was the largest marine epizootic ever recorded. Similarly, two of the most common coral species in the Caribbean were Acropora palmata and A. cervicornis. Both form large, dense, single-species thickets of genetically identical organisms, or clones. The lack of genetic diversity means that any disease that can kill one individual can kill the whole clone. Both of these species have been decimated in much of the Caribbean by White Band disease (Aronson, Precht, and Macintyre 1998), and were considered for Endangered Species status (Precht, Robbart, and Aronson 2004; Shinn 2004; Wilkinson 2004); they received protected status on 8 June 2006. On diverse coral reefs, most species are rare, so disease transmission is much more difficult, and the likelihood of epizootics is reduced. This probably contributes to the stability of high diversity coral reefs.



Figure 5.2.7. a. Tracks of tropical cyclone and severe storm tracks for the Indo-Pacific region. All storms that were classified above a tropical depression in strength (wind speeds > 30 mph for two or more 6-hour periods) from 1945 to 2003 are included. b. Severe storm density in the Indo-Pacific region. Storm density was computed for each 50 50 km cell by summing the number of tracks found within 200 km of the cell and dividing by the total area sampled in each cell.

Source: Data assembled by Unisys Corporation and Joint Typhoon Warning Center (www.npmoc.navy.mil/jtwc.html) and downloaded from the Pacific Disaster Center website (atlas.pdc.org). Maps by F. Riolo.

Effects of Fishing

Fishing can remove fish that are important for reef health. The removal of herbivorous fish in Jamaica left it vulnerable, so when a disease killed the last herbivore (sea urchins), the reef was overcome with algae (Hughes et al. 1987). Large fish such as sharks, Humphead Wrasse (Cheilinus undulatus), and Bumphead Parrot-fish (Bulbometopon muricatum) are particularly vulnerable. Bumphead Parrotfish have been extirpated from several places in the Indo-Pacific (Bellwood et al. 2003; Dulvy et al. 2003). Humphead Wrasses are under heavy pressure over a large area due to the live food fish trade. Populations are reduced to low levels in areas with higher fishing pressure (Sadovy et al. 2003). Areas of Fiji where fishing pressure is greatest are also the areas where Crown-of-Thorns starfish have outbreaks and eat the tissue off corals, killing the corals (Dulvy et al. 2004). Humphead Wrasses are known to eat toxic invertebrates like the Crown-of-Thorns starfish, so overfishing them may leave reefs vulnerable to Crown-of-Thorns attacks. Although the reefs of Papua are remote and under relatively little pressure from human populations (but see Birkeland 1982), fishing makes sharks and Humphead Wrasse rare, with just two adult Humphead Wrasse seen in 45 sites (Allen 2002b; McKenna et al. 2002).

Few coral reef researchers or managers have seen what truly pristine coral reef fish populations are like, and the amazing dominance of apex predators. Each generation of scientists remembers what coral reefs were like when they first saw them, and tend to think of that as the standard of undisturbed ecosystems. We have lowered our standards in a process called ‘‘shifting baselines.’’ Coral reefs in the Caribbean have declined in three decades from about 50% coral cover to about 10% coral cover (Gardner et al. 2003). Archeological methods have been used to study the effects of pre-Columbian fishing in the Caribbean, and the studies have found that declines began even before the arrival of Europeans (Wing and Wing 2001). Paleontological methods along with archeological and historical methods have shown declines in 14 coral reef systems worldwide since pre-human times (Pandolfi et al. 2003). The 14 reef systems studied had declined between about 28% and 78% of the way from pristine toward ecologically extinct.

Endemism and Extinction

Endemism is commonly used in terrestrial conservation programs as a measure of the need to conserve areas (Allen 2003). It is especially important to avoid the local extinction of endemic species, because their loss represents the loss of an entire species. Endemic species are more vulnerable to extinction partly because any local disturbance can cause global extinction, and also because endemic species usually have small populations. The rates of endemism on coral reefs are quite different in different groups of organisms. Endemism is uncommon in larger organisms, but may be high in some groups of small organisms, and low in the tiniest microscopic organisms. Most groups of larger coral reef organisms have wide dispersal and very few species are endemic. Many coral reef species are broadcast spawners, releasing tiny eggs into the water that are carried with the currents. Currents can carry the eggs considerable distances during the several days to weeks required for them develop to the stage where they are ready to settle. For example, one species of sea urchin, Echinothrix diadema, has been found to be genetically the same species in Hawai’i and the east Pacific, across the largest expanse of open water in the tropics anywhere in the world (Lessios et al.1998). Some coral species have been observed attached to floating objects and thus are probably able to ‘‘raft’’ over vast distances (Jokiel 1990). This is even true of species that brood their young, releasing larvae that quickly attach close to the parent. Reef fish have also been observed rafting by staying near floating debris (Mora 2001). This wide dispersal means that there are few endemic species on most coral reefs, especially in the western Pacific where there are many reefs close together. For instance, currently no endemic coral species are known in the Philippines or Indonesia, where 535 and 581 coral species are currently known, respectively (Fenner, under review c; Turak 2003; Veron 2002), and only one endemic species is known from Papua New Guinea, where 494 coral species are currently known. Levels of endemism in reef fish are also relatively low (Hughes, Bellwood, and Connolly 2002), and the proportion of reef fish that are endemic is lower in the Coral Triangle than in outlying areas (Randall, 1998). Endemism may be overestimated if recently described species are included, because species are often described from small areas and subsequently found in additional areas (Fenner, under review b). So it is likely that Papua has very few endemic large species on its coral reefs.

RAPID ASSESSMENT TECHNIQUE CONFIRMS PAPUA IS IN THE CENTER OF DIVERSITY

Species diversity comparisons among areas are often based on the total number of species that have been found in each area. However, the number of species found in an area is heavily dependent on the amount of time, effort, and area covered searching for species. Additional searching time, effort or area explored almost always leads to additional species being found. Larger areas contain larger numbers of species, which is called the ‘‘species-area effect.’’ The number of species commonly rises as a power function of the area, as it did in a study of coral reef fishes (Chittaro 2002). Although such curves may appear to approach an asymptote on linear scales, on log scales they can be seen not to approach an asymptote. The search for an asymptote has been reported at times to reach areas the size of continents without reaching an asymptote (Williamson et al. 2001). The total number of coral species known from countries in the western Pacific has approximately doubled in the last three decades (Fenner, in review c).

The author has participated in several rapid assessment programs for coral reef areas, such as those sponsored by Conservation International. The goal of such programs is to rapidly assess diversity in an area. It is an attempt to use limited resources in a targeted fashion, to gain information about diversity of an area without spending the enormous resources necessary to get even a near-complete assessment.

In the present study, one scuba dive of approximately 60 minutes was spent by the author at each site in a roving search for coral species. The search began at the bottom of the reef or at about 30 m depth, whichever was less, and progressed upward during the dive, ending in the shallowest area that was accessible to a scuba diver. Comparisons among areas were based on equal numbers of dives.

A strong latitudinal gradient was found in the central Pacific, with diversity falling off from eastern Papua New Guinea to American Samoa and Hawai’i (Figure 5.2.8). The Raja Ampat Islands are in the area of highest diversity. Across Malaysia to Rodrigues in the southwestern Indian Ocean, there is also a latitudinal diversity gradient (Figure 5.2.8), though Rodrigues may be lower in diversity than Malaysia both due to latitude and longitude.

Diversity gradients are well known in the Pacific for corals and other groups of reef organisms. This rapid technique detects diversity gradients in much the same way as more labor intensive techniques. The lack of a gradient in this reef slope data between central Indonesia and New Guinea is consistent with the report that coral diversity on reef slopes is constant across this area (Karlson et al. 2004).


Figure 5.2.8. Longitudinal diversity gradients from rapid ecological assessments. Raja Ampat Islands, Papua, indicated by the open square, is among the areas of highest diversity. Points, in order from east to west, are for Rodrigues, Andaman Islands, Peninsular Malaysia, Sarawak, Sabah, Sulawesi, Raja Ampat Islands, Milne Bay (Papua New Guinea), Fiji, American Samoa, and Hawai’i.


Most coral reef organisms that have been studied have relatively large individuals. Marine invertebrate species with small individuals frequently brood their off-spring instead of broadcast spawning (Reaka-Kudla, 1995a,b). This may be because their small size restricts them to producing relatively small numbers of offspring, and broadcast spawning is a high-risk strategy in which most offspring die. If a small number of offspring are produced, a high-risk strategy increases the likelihood that all offspring will die. This may select for lower-risk reproductive strategies, where more is invested in each offspring by producing larger offspring, which do not disperse as far. This reduced dispersal ability increases the frequency of endemism (Reaka-Kudla, 1995a,b). A good example may be the amphipods, a large group of small-bodied crustaceans that produce relatively large eggs. Some species of amphipods raft on algae or have pelagic hosts such as jellyfish, and thus have wide ranges. But many amphipod species have very small ranges (Thomas 2000). Most species are small, such as insects on land. The view that most marine species have wide ranges is largely based on larger organisms like corals, fish, and echinoderms. Yet most coral reef species are likely to be small (Reaka-Kudla, 1995a,b), and not yet described, let alone have their reproductive mode or biogeographic range studied. Many or most of these species may turn out to be endemics. In addition, some groups of larger organisms that do not have a larval dispersal stage may have high rates of endemism. For example, many or most reef sponges produce negatively buoyant, sticky eggs that do not go far from their parents. An estimated 43% of the sponges recorded from Indonesia are endemic to the region (van Soest 1997). However, studies of Indonesian sponges and sponge biogeography are in early stages. The total number of sponge species is likely to increase considerably and endemism figures to change. Another example is colonial ascidians (sea squirts), which produce tadpole larvae that go only short distances from their parents. As with corals and fish, the actual ranges of these species may be largely determined by their ability to raft, because rafting can spread widely even species with no larval dispersal phase.

A very different view is presented by Fenchel and Findlay (2004). They report that most microbial marine organisms are cosmopolitan, and that the percentage of species found at one temperate marine location that have large ranges decreases with increasing body size. If this should also prove true of coral reefs, then groups of small organisms that are highly endemic, like amphipods, may be unusual. It may be that only groups like amphipods, sponges, and ascidians have high rates of endemism on coral reefs. Or it may be that that the largest organisms and microbes have low endemism, but intermediate size (small) organisms have high rates of endemism.

If there are large numbers of small, undescribed, and unstudied species on coral reefs that are likely to be endemic, it will not be practical to study each species to determine its range. We will not know the ranges of even a fraction of the small species on coral reefs any time in the near future. Long before we can know which species are endemic, coral reefs may be highly degraded, and endemic species lost before they are even discovered. The primary cause of species extinctions is loss of habitat. The best way to save large numbers of small endemic undescribed coral reef species is to protect the habitat itself, without taking the time to discover all the tiny endemic species. Further, the number of small species present at a site is almost certain to be proportional to the number of large species found there. Bellwood and Hughes (2001) found that there is a high correlation between the diversity of organisms in one size group with those of another size group. Thus, the diversity of large species such as corals and fish is likely to be a good indicator for the diversity of small species. Although we know that low diversity coral reefs have a higher proportion of endemic species among large organisms than high diversity reefs, high diversity reefs are likely to have much higher absolute numbers of small endemic species than low diversity reefs. Thus, the conservation of both low and high diversity coral reefs is important. Further, while large species (‘‘charismatic megafauna’’) may capture public support, small endemic species will not (‘‘save the amphipods’’?). Coral reefs, however, are highly charismatic, and have generated significant public support for conservation.

Threats to Papuan Reefs

Coral reefs face threats from a wide variety of human sources. The ‘‘Reefs at Risk’’ program (Burke et al. 2002) identified six principle threats to coral reefs, and evaluated five of those. The five threats they evaluated were coastal development, marine-based pollution, sedimentation and pollution from inland sources, over-fishing, and destructive fishing. The sixth threat was climate change and coral bleaching. Their method was to identify sources of human pressure that produce stress on coral reefs and represent these sources of stress on a map. They developed distance-based rules by which the level of threat declines with distance from the source of the stressor, such as the distance from a river mouth, city, and so on. For Indonesia, destructive fishing (i.e., blast fishing) turned out to be the biggest threat to coral reefs, followed by overfishing, sedimentation, marine-based pollution, and coastal development, in that order. Climate change was not evaluated because of the lack of data and inability to predict strong local variations in this relatively new threat.

The Reefs at Risk program identified the reefs most at risk in eastern Indonesia (Burke et al. 2002). In Papua, reefs in the Raja Ampat area to the northwest of the western end of the Vogelkop Peninsula were shown as being under medium threat, while islands just to the south of that and straight west of the western end of the Vogelkop Peninsula, beginning with the Fam Islands and Batanta Island, were shown as being high or very highly threatened. Biak and Yapen Islands on the north side of Cenderawasih Bay were shown as experiencing medium threat, with reefs at the eastern end of Biak viewed as being under low threat. Reefs along the western side of Cenderawasih Bay were shown as having low threat, while those on the east side of the bay were shown as having high or very high threat. Reefs along the Onin Peninsula and just to the east of that on the south shore of Papua were shown as having medium to low threats. The Aru Islands south of the main landmass of Papua were shown as having high or very high threats. The primary and almost only immediate threat to the coral reefs of Papua was identified as destructive fishing. The two types of destructive fishing that were identified were poison fishing and blast fishing. Poison fishing today uses cyanide to stun and catch fish, and blast fishing utilizes homemade explosives made of fertilizer in bottles.

The Conservation International 2002 Rapid Assessment of reefs in the Raja Ampat Islands found evidence of destructive fishing practices at 13% of the sites visited. Slight fishing pressure was evident at 32 of the 45 sites, and moderate pressure observed at one site. A total of only seven sharks, two Manta Rays (Manta birostris), and only one sea turtle (Hawksbill: Erectmochelys imbricata) were observed by the reef condition team on these 45 sites. Humphead Wrasses were much less common than on less heavily fished sites (Table 5.2.1). Sixteen sites had slight siltation and one site had moderate siltation, with seven of these sites having freshwater input as well. Slight evidence of eutrophication/pollution was observed at eight sites. Nickel mining has been proposed for Gag Island, and there has been some logging of forests. Other stressors such as coral diseases, coral predators, and bleaching were rarely observed (McKenna, Boli, and Allen 2002). In the Raja Am-pats, 90% of the inhabitants lived in coastal areas and depended on marine resources for survival. Humphead Wrasse and groupers (Plectropomus leopardus and P. areolatus) were targeted for the live fish export trade, and cyanide was used to catch them. Shark fins were taken for export, and shark finning was the likely cause for the rarity of sharks. Small sea cucumber and lobster fisheries existed. Illegal fishing methods were used by the poorer communities (Amarmollo and Farid 2002). Although destructive fishing was the main threat to the coral reefs of Papua, we cannot assume that the other threats have not had effects on the coral reefs there. The study by Pandolfi et al. (2003) showed that all 14 coral reefs that they studied around the world showed degradation from human activities, and even the Great Barrier Reef, long thought to be relatively unaffected by human activities, was impacted. Fishing has been allowed on most of the Great Barrier Reef, and even though it is not intense, it has doubled since 1990 and has had an effect. Fish populations in small, strictly protected (i.e., no-take) areas on the Great Barrier Reef are higher than outside those areas. The Raja Ampat Islands to the northwest of the Vogelkop Peninsula have relatively good fish stocks. The average total biomass of fish in 2002 was 209 tons/km2, compared to 124 in Milne Bay Province, Papua New Guinea, 66 in the Togian-Banggai Islands of northern Sulawesi, Indonesia, and 17 in the Calamianes Islands, Philippines (La Tanda 2002). Further, the mean density of groupers was 5.45 per 1,000 m2, compared to 3, 2.7, and 2.9 for each of the other three areas, respectively. The average size of groupers was relatively small (about 25 cm), while at the other three sites they were 20 cm, 20 cm, and 30 cm, respectively. Humphead Wrasses were uncommon (Table 5.2.1), with most individuals under 30 cm length. This species is intensively harvested in this area for export in the live-fish restaurant trade. Further, the reef fish populations are not dominated by apex predators, such as jacks and sharks. The low populations of apex predators in the Raja Ampats indicates that fishing pressure has already made major changes to the structure of fish populations there, while the total biomass indicates that fishing has not yet caused drastic changes to fish populations such as have occurred in many other places in the region.


The long-term future threats to the reefs of Papua are not restricted to destructive fishing and overfishing. If population growth and population transmigration to Papua from western Indonesia continue or intensify, stresses to the coral reefs of Papua will increase with the increasing population and development. Deforestation is currently proceeding rapidly in most other parts of Indonesia, with deliberate forest burning during dry summers causing huge smoke clouds covering large areas where there are intense clearing efforts, such as Kalimantan and Sumatra, with clouds of smoke so large they can be carried to neighboring countries. In the major fires of 1997, smoke from fires in Sumatra provided iron that helped lead to a red tide event that in turn caused the death of coral reefs by asphyxiation. There has been no analogous coral mortality in that area in the last 7,000 years (Abram et al. 2003). Growing world populations and demand for wood and agricultural land can make logging and burning so attractive that it can become common in spite of being illegal. Not long ago, Kalimantan (Indonesian Borneo) was a wild and remote area, but now it is being cleared at an alarming rate. A similar fate could await Papua, followed by massive sediment runoff and reef destruction (McKenna, Boli, and Allen 2002). The low population density and relative underdevelopment of Papua affords time to try to avert coral reef destruction, but complacency could result in much greater threats to reefs in Papua in the future.

Saving the coral reefs of Papua will require the assistance of many people, but luckily Papua’s reefs remain in better condition than many reefs elsewhere in the world. This provides conservationists and managers with a rare opportunity to be proactive in conservation activities. It remains to be seen whether we will be able to take advantage of this opportunity and protect Papua coral reefs for future generations.

Acknowledgments

I thank Conservation International for inviting me to participate in their expedition to Papua, Gerry Allen for inviting me to write this chapter, and Gerry Allen and the editors for helpful suggestions.


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Ecology of Indonesian Papua Part Two

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