Cham Islands coral reefs

• Category: Marine and Oceanic Biomes.
• Geographic Location: South China Sea.
• Summary: This biodiverse system of coral reefs is an ecologically rich area that has been adversely affected by excessive coral harvesting, aggressive commercial fishing, and exploitation from tourism.

The Cham Islands are a group of eight islands, nine nautical miles (17 kilometers) off the coast of Vietnam in the South China Sea. The islands are Hon Lao, Hon Dai, Hon Mo, Hon Kho Me, Hon Kho Con, Hon La, Hon Tai, and Hon Ong. Sandy beaches and forested hills are the rule here; most of the population is engaged in fishing. The islands, known locally as Cu Lao Cham, are part of Cu Lao Cham Marine Park, a world Biosphere Reserve recognized by the United Nations Educational, Scientific and Cultural Organization (UNESCO), in large part because of its coral reefs and diverse marine life.

The islands were first settled about 3,000 years ago and are the only Vietnamese islands included in the old Silk Road network of international trading. Today, ecotourism is important to the islands' economy; tourists explore the coral reefs either by diving or by riding in glass-bottom boats. The nearest city is Hoi An, on the mainland coast. In 2011, due to its proximity to Cu Lao Cham Marine Park, Hoi An was designated Vietnam's first ecological city, and United Nations funds were released to help fund a project that will include mitigating climate-change-related environmental problems and the redevelopment of the city's infrastructure.

The Cham Islands are somewhat cooler and more humid than the mainland; the humidity remains around 85 percent year-round. Typhoons and other heavy storms are common in September and October. The islands experience tidal activity on a semi-diurnal cycle: two high tides and two low tides a day, on most days of the month, with two periods of flood tide every month. These floods can reach dangerous levels from September to December.

Biodiversity

A total of 947 marine species have been identified in the biome encompassing the waters around the islands. Surrounding the islands are about 410 acres (166 hectares) of coral reef and 1,200 acres (486 hectares) of seaweed beds. The reefs include more than 270 species of coral, along with 84 species of mollusks and four species of tiger shrimp. Six of the coral species are endemic (found nowhere else on Earth) to Vietnam. The biosphere has at least 202 fish species in 85 genera and 36 families.

A major component of the marine ecosystem of the coral reef community is the butterflyfish, of which 29 species have been recorded in the area, the most common of which are Chaetodon lunula, C. octofasciatus, C. auriga, C. melannotus, C. speculm, C. trifascialis, C. trifasciatus, and Heniochus chrysostomus. Butterflyfish feed on coral and are helpful as an indicator species because of their sensitivity to coral degradation.

New species are discovered in the ecosystem on a regular basis. During a sample collection from 1989 to 1994 comprising 813 specimens, 326 fish species were collected from around the coral reefs in 117 genera and 44 families; 69 of them had never been recorded before. In addition to butterflyfish, damselfish (Pomacentridae), wrasses (Labridae), parrotfish (Scaridae), snappers (Lutjanidae), rock cods (Serranidae), and surgeonfish (Acanthuridae) are abundant. The reef-edge grooves are frequented by large species of these fish, as well as Epinephalae, Letherinae, and Cheilinae.

The reef flats and clusters are home to smaller fish, including butterflyfish; surgeonfish; and species of Abudefduf, Thalassoma, Halichoeres, Siganus, and Caesio. Damselfish seem to be the most abundant, with 53 species of 12 genera found among the reefs, all of them fairly small and feeding among the reef flats and clusters. Given the abundance of species, it is likely that there are scores more yet to be discovered.

Environmental Threats

The area continues to be important to the commercial fishing industry, particularly for lobster, grouper, snapper, crab, shrimp, and clam. One of the major threats to the coral reef ecosystem is dynamite fishing, which involves detonating explosives to kill large numbers of fish. This practice causes significant damage to organisms irrelevant to the catch. In the case of butterflyfish, the population density has suffered, with numerical recovery very slow.

Destructive fishing methods are not limited to dynamite fishing. Other such techniques include electric fishing (in which clusters of marine life are electrocuted) and the use of sluice traps, trawling nets, and gill nets. Destructive fishing is still the norm in the islands, as in most of Vietnam. The various methods of catching fish are employed to maximize the catch while mitigating the economic risk of the fishers.

Another victim of exploitation is the local population of sea cucumber. When processed as a dried animal product, sea cucumber is valuable in markets in China, Japan, Hong Kong, Singapore, and Taiwan. The coral trade is also seriously threatened, affected by increased tourism and the popularity of coral exports. Since 2000, the harvesting and cleaning of live corals sold as coral skeletons has advanced. However, no one is managing or maintaining the informal industry, or maintaining statistics.

The condition of the coral reefs is suffering. Only 1.4 percent of the reef areas in all of Vietnam's waters are considered to be in excellent condition; less than 33 percent are in good condition. Approximately half of the coral reefs are in fair condition, and 37 percent are considered to be in poor condition. While Cu Lao Cham's coral reefs are in generally better shape than those located closer to major population centers, the intensity of commercial fishing operations and storms, exacerbated by climate change, are two major threats to the ecosystem. Global warming means that seawater temperature rises, a threat indicator for coral, as it tends to drive off the beneficial symbiotic organisms that help keep coral healthy and prevent bleaching events.

In 1997, Typhoon Linda destroyed a major area of coral-reef habitat in the Con Dao islands, considered the best-protected coral reefs in Vietnam. This weather episode was followed months later by significant bleaching events in the same reefs. A similarly strong storm in the Cu Lao Cham Islands produced long-lasting reef damage.

Conservation Efforts

As part of the Biosphere Reserve, the area is the subject of managed integrated conservation and development efforts, with emphasis on land/seascape diversity, habitats, species, and genetic resources. The Management Board of Cham Island (MBCI) has been working since 2013 to attempt to revive and safeguard the reef.  The MBCI partnered with Nha Trang Institute of Oceanography in 2012 to grow over 7,000 colonies of coral to create a new reef ecosystem in the region. Authorities in the area also banned exploiting corals in any form to try to deter the harvesting and selling of coral.

One of the challenges of the reserve is to conserve biodiversity, species abundance, and the health of the coral reefs without impinging on the economy of the islands, which currently is almost entirely dependent on fisheries. Tourism is believed to be the best remedy for the reefs, helping to convert the islands' economy to one more dependent on visitors seeking to witness the area's biodiversity.

Bibliography

"Atchafalaya River Basin." The Nature Conservancy, 19 July 2024, www.nature.org/en-us/about-us/where-we-work/united-states/louisiana/stories-in-louisiana/the-atchafalaya-river-basin/. Accessed 28 Oct. 2024.

Couvillion, Brady, et al. Land Area Change in Coastal Louisiana From 1932 to 2010. U.S. Geological Survey, 2011.

Kistner, Rocky. "Rescuing the Massive Swamp Our Country Depends on but Has Mostly Forgotten." HuffPost, 30 Apr. 2022, www.huffpost.com/entry/atchafalaya-basin-ticking-time-bomb‗n‗624c4afce4b007d3845b506f. Accessed 28 Oct. 2024.

Louisiana Department of Natural Resources. Atchafalaya Basin FY2012 Annual Plan. LDNR, 2011.

Roberts, Harry. "Delta Switching: Early Responses to the Atchafalaya River Diversion." Journal of Coastal Research, vol. 14, no. 3, 1998, pp. 826-45.