[A-CG41] Coastal Ecosystems -2. Coral reefs, seagrass and macroalgal beds, and mangroves

[ACG41-09] Disease occurrence among various zonation: Status of Coral Reefs at Karimunjawa Island, Indonesia

*Dio Dirgantara¹, Rhesi Kristiana², Kuswadi bin Bunadi³, Takashi Nakamura¹ (1.Faculty of Science, University of The Ryukyus, Nishihara, Okinawa 903-0213, Japan, 2.Marine Education and Research Organisation, Karangasem, Bali 80853, Indonesia, 3.Karimunjawa National Park Office, Semarang, Central Java 50273, Indonesia)

Keywords:Conservation, Disease Prevalence, Genus Diversity, Karimunjawa, Zonation

Coral reef ecosystems are known to have high rates of endemism and being considered as “biodiversity hotspots” (Roberts, 2002). However, coral reefs in the Anthropocene are also being subjected to global as well as local stressors. Local disturbances such as overfishing, habitat destruction, and pollution along with the impacts of climate change such as coral bleaching have been identified as major threats to coral reefs. Coral diseases have been recognized as important drivers to the coral decline worldwide (Weil et al., 2012) where the pathogenic diseases take advantage of the corals that are under other stressors to increase their abundance, becoming more prevalent in degraded environments (Muller et al., 2018). Located within the biodiversity hotspot, coral reefs in Karimunjawa,Indonesia has been surveyed to assess the status since 2000. Although different approaches were utilized to reveal the condition of Karimunjawa reefs, reports on coral disease incidence are scarce. Located in the northern part separate from the mainland Indonesia, Karimunjawa has been utilized for tourism and marine culture activity that may have been dragged down its pristine reef ecosystem. Additionally, there is almost no report available that clarify which of coral genera in Karimunjawa are susceptible to various diseases. To emphasize how far the Karimunjawa reef's current condition altered, disease prevalence; coral genus diversity and coral cover were assessed at 6 sites within three different zones (Tourism, Aquaculture and Protected zones) using two assessment methods (Point Intercept Transect method and Quadrat method with digital image analysis by Coral Point Count with Excel extension). Coral cover (CC) and disease prevalence (DP) results from all site shown strong similar trendline among methods with average PIT results 56.5%±7.89 (CC); 8.23%±3.11(DP) and CPCe results 43.21%±5.91(CC); 9.66%±4.55(DP) respectively. Thus, multivariate and ordination statistics were performed to construct comprehensive analysis on disease prevalence and zonation. Disease prevalence slightly differs from each zone while similar coverage on hard corals has been detected from all site. However, a strong correlation between genus diversity and disease prevalence has been detected in both tourism and aquaculture zones. There are several types of diseases that have not been reported previously from the Karimunjawa were found in these study sites. There are two types of coral killing sponges of Terpios hoshinota and Chalinula nematifera that haven’t been reported previously from the Karimunjawa were found in these study sites. These findings indicated Karimunjawa reefs may have been impacted by human activities. We suggest to continue periodical evaluation in order to keep comprehensive assessment-based on-site zonation as useful tools to guide a better conservation for Karimunjawa reefs in the future.