Baseline reef health surveys at Bangka Island (North Sulawesi, Indonesia) reveal new threats

Abstract

Worldwide coral reef decline appears to be accompanied by an increase in the spread of hard coral diseases. However, whether this is the result of increased direct and indirect human disturbances and/or an increase in natural stresses remains poorly understood. The provision of baseline surveys for monitoring coral health status lays the foundations to assess the effects of any such anthropogenic and/or natural effects on reefs. Therefore, the objectives of this present study were to provide a coral health baseline in a poorly studied area, and to investigate possible correlations between coral health and the level of anthropogenic and natural disturbances. During the survey period, we recorded 20 different types of coral diseases and other compromised health statuses. The most abundant were cases of coral bleaching, followed by skeletal deformations caused by pyrgomatid barnacles, damage caused by fish bites, general pigmentation response and galls caused by cryptochirid crabs. Instances of colonies affected by skeletal eroding bands, and sedimentation damage increased in correlation to the level of bio-chemical disturbance and/or proximity to villages. Moreover, galls caused by cryptochirid crabs appeared more abundant at sites affected by blast fishing and close to a newly opened metal mine. Interestingly, in the investigated area the percentage of corals showing signs of ‘common’ diseases such as black band disease, brown band disease, white syndrome and skeletal eroding band disease were relatively low. Nevertheless, the relatively high occurrence of less common signs of compromised coral-related reef health, including the aggressive overgrowth by sponges, deserves further investigation. Although diseases appear relatively low at the current time, this area may be at the tipping point and an increase in activities such as mining may irredeemably compromise reef health.

Large‐scale coral reef rehabilitation after blast fishing in Indonesia

“…Furthermore, despite the disturbances, the estimates of live coral cover on spiders and on the reef substratum in the rehabilitation area are higher than reported for locales within the Spermonde Archipelago and elsewhere in the Coral Triangle, including MPAs (Crabbe & Smith ; Selig & Bruno ; Polónia et al ; Ponti et al ; Teichberg et al ). The estimates are also higher than coral cover reported for islands in the central Pacific Ocean (including uninhabited ones; Smith et al ) and elsewhere throughout the tropics (Graham & Nash ).…”

First Study on Marine Heterobranchia (Gastropoda, Mollusca) in Bangka Archipelago, North Sulawesi, Indonesia

“…According to the planktonic community index based on recent planktonic studies, the marine environment of BA is considered to be in a good condition [52]. However, Ponti et al [19] consider the health of the corals in the area as critical, despite the low impact of disease, and refer to the general problems in BA of increased human activities, including mining, which irredeemably compromises reef health [19]. Snorkeling in front of the destroyed area at the mining site did not result in any records of nudibranchs, due to the recent stone blocks dumped in front of the site, where only a few corals and sponges were observed to colonize them.…”

“…The islands are home to some villages and a few resorts, of which the oldest one was built in 1987. Bangka, the largest island of this archipelago (approximately 48 km 2 ), has a resident population of nearly 2500 inhabitants and only six resorts [19]. Therefore, this island is less affected by tourists than the more famous Bunaken National Park (BNP), Lembeh Strait, or other Indonesian islands, such as Bali.…”

Studies on seagrasses of North Sulawesi, Indonesia and adjacent waters: A critical review

“…This type of study should be conducted in areas affected or may be affected in the near future. Recently, Ponti et al (2016) provided a baseline survey data on the coral reef health Bangka Island in North Sulawesi, which has been subjected to mining controversies.…”