Marine National Park Headquarters

2016 Coral Reef General Survey – Coral Cover Results for Dongsha and Penghu South Four Islands

　　The Marine National Park Headquarters (hereinafter referred to as the Headquarters) has completed the 2016 comprehensive coral reef surveys for Dongsha Atoll National Park and Penghu South Four Islands National Park under its jurisdiction. Compared with previous years’ results, coral growth in both national parks remains generally stable. However, populations of indicator fish species and invertebrates are still relatively low, suggesting continued pressure from fishing activities and environmental factors.

　　The Dongsha Atoll coral reef survey was conducted from May 13 to 15, covering seven monitoring stations both inside and outside the atoll, which spans approximately 50,000 hectares. Coral communities on the outer reef flats displayed distinct assemblage characteristics, with coverage reaching 77–89%. In addition to common hard corals such as Acropora, staghorn corals, and Favia species, the northern outer reef flat was dominated by high-density soft corals, with single-station coverage reaching up to 76%. Due to strong currents outside the reef flat, coral growth forms are mostly encrusting or low, compact colonies capable of resisting wave action, resulting in fewer large cavities for shelter. Consequently, resident fish are primarily butterflyfish, damselfish, and small wrasses. Inside the atoll, currents are calmer; however, the surrounding reef flat restricts water exchange in the lagoon. Summer water temperatures often exceed 30°C, leading to a shift from heat-sensitive branching corals to more stress-tolerant massive or foliose forms. The inner reef topography is complex, often forming large patch reefs hundreds of meters in diameter. Coral cover varies widely from 26% to 56%, and the more three-dimensional reef structures provide shelter for larger fish species such as parrotfish and sweetlips.

　　The Penghu South Four Islands coral reef survey was jointly conducted by the Penghu County Government Agriculture and Fisheries Bureau and the Headquarters on July 27–28, covering the four main islands: Dongji Islet, Xiji Islet, Dongyuping Islet, and Xiyuping Islet. Coral cover ranged from 47% to 78%, mostly meeting the standard for healthy coral reefs (above 50%). The survey also found that the unexplained bleaching and mortality of Montipora foliosa observed since spring 2015 had improved this year. Although partial bleaching of Acropora was observed in May, recovery was noted by July. However, in Dongji Harbor, dense algal growth has been observed between the branches of Acropora corals over the past two years, and continued monitoring is needed to assess long-term impacts. Overall, no large-scale bleaching events were detected in the waters of the Four Islands. Nevertheless, indicator fish and large invertebrates remain relatively scarce. Sea cucumbers, which have been protected by Penghu County in recent years, have shown recovery to standard levels.
The Headquarters noted that both Dongsha Atoll National Park and Penghu South Four Islands National Park possess unique marine ecosystems and face distinct conservation challenges. Although only the latter is currently open to the public, increasing marine recreational activities are gradually exerting pressure on its ecosystems. Visitors are once again urged to develop proper marine awareness before engaging in ocean activities to avoid inadvertently harming marine environments.