Taiwan Reef Check 2018 Reveals Reefs Covered by Silts

A huge amount of silt can suffocate corals and ultimately kill coral reefs. Hence, it is necessary to monitor the deposition of marine sediments to ensure that a coral reef can survive in the long-term. To monitor local coral ecosystems in Chaojing (潮境) of Keelung and Fanzaiao (番仔澳) of New Taipei, the Taiwan Environmental Information Association (TEIA) coordinates Reef Check in Taiwan annually. Last year, some sediment deposition were observed at various reefs and this deposition process is still ongoing. Approximately, 5% of reefs in Chaojing are covered by silts. A thin layer of silt was even observed at Fanzaiao, which was 10 meters under the sea surface (FZA 10m).

The health of live corals cover (i.e. both soft and hard corals) range from “Poor” to “Average” across both sites. Specific indicator organisms such as fishes and invertebrates were also recorded.

In July and August 2018, the TEIA worked with its volunteer scuba divers to conduct the Reef Check Taiwan in Chaojing and Fanzaiao. They reported that the total living corals coverage ranged from 21.9% to 35%. The lowest cover was at Fanzaiao 5 meters under the sea surface (FZA 5m), with the highest at Chaojing 10 meters under the sea surface (CJ 10m).

Living corals coverage at FZA 5m and CJ 10m are of average health (i.e. 25%-50%). Of particular interest was that 5% of the reefs at Chaojing were covered by sediments. Also, further observations found that some corals at Chaojing were already covered by silts. While no silts were recorded at FZA 10m, volunteer divers had already observed a thin layer of silts formsing.

The grain size of silt is smaller than sand. Therefore, silt require a longer time to be deposited once they have been disturbed. Suspended stilt thus affects the visibility of seawater, and may also cover the surfaces of coral reefs. The corals are able to activate their self-protective mechanism when the amount of covering silt is small. However, when the amount exceeds their tolerance threshold, the corals will suffocate and die.

In 2009, Taiwan Power Company (TaiPower, 台電) had originally planned to build a coal terminal in Fanzaiao and to retrofit the old coal power plant. This plan was canceled due to protests from local residents, elected representatives, and environmental groups. TaiPower then re-proposed “Alternatives for Shen Ao Retrofit & Expansion Feasibility Study” in 2015. In this plan, TaiPower will build a coal terminal in a CPC Corporation Taiwan owned pier but breakwaters will be built next to Shen'ao Cape (深澳岬). This development could change local ocean surface currents, and dust and bare soils produced by the construction may indirectly affect surrounding ocean ecosystems.

For indicator species for overfishing and aquarium fish collecting, both sites had recorded species such as butterflyfish (Chaetodon spp.), grouper (Serranidae) and moray eel (Muraenidae). The population density of butterflyfish is 1.5 - 3 individuals per 100 m2 with the largest population at FZA 10m; the population density for moray eels ranged from 0 - 0.75 individuals per 100 m2 with the largest population at CJ 10m. It was surprising to have observed groupers at both sites. According to the Coral Check’s manual, only groupers larger than 30 cm will be recorded as large-sized groupers are currently rarely found in natural habitats due to overfishing.

Small amount of sweetlips (Haemulidae) and parrotfish (Scaridae) were similarly recorded.

As for indicator species for overfishing, such as the long-spined black sea urchin (Diadema spp.), sea urchin (Hemicentrotus pulcherrimus), and lobsters were observed at both sites. Sea urchin and lobster are not easily detected because their high economic values. Additionally, banded coral shrimp (Stenopus hispidus) was spotted at CJ 10m.

Based on the 2018 Reef Check Taiwan, the most effective outcome is achieved when an area is both conserved and a strict ban is enforced. Fanzaiao was declared as a part of Rueifang (瑞芳) conservation area by the New Taipei City Government in 2014. Hence fishing and collecting of coral reef species were regulated accordingly. Chaojing was declared as "Wanghaixiang’s Chao-Jing Bay Resource Conservation Area" (望海巷潮境海灣資源保育區) by the Keelung City Government in 2016. Therefore, no fishing activity was allowed beside the harvesting of edible seaweed.

The original article can be found here.