Reef-based tourism has been developing rapidly in recent decades yet its impacts on reef ecosystems are often overlooked. In Tan-awan, Oslob, Philippines, whale sharks are attracted to the shallow reefs where they are provisioned up to 50 tons y −1 of feed and this phenomenon in turn attracts >300,000 y −1 visitors. Given the intensive provisioning and concentrating tourism activities, we hypothesized that the whale shark tourism-impacted site (IS) will have greater impacts on reef degradation and higher anthropogenic nitrogen pollution level compared to its reference site (RS). Ecological surveys revealed that relative to the RS, the IS had 36% higher relative abundance of Pocillopora and Porites coral over other genera, >2.5-fold lower coral density, and 20% higher macroalgal cover, which we concluded are signs of reef degradation. Also, we conducted stable nitrogen isotope analysis on gorgonian skeletons to trace nitrogen sources at both sites through time. Although an average 1‰ isotope enrichment found in the IS relative to the RS could indicate anthropogenic nitrogen inputs in the IS, this enrichment was consistent over time and existed before the tourism developed. Despite that, we cautioned against the imminent threat of local eutrophication caused by the continued inputs of nitrogen derived from provisioning and tourism activities. In summary, this study provided the first documentation of the impacts of provisioned whale shark tourism on the local reefs in Tan-awan and established an ecological baseline for future comparisons. Such assessments can offer important information on reef health, coastal development, and tourism management.
Bibliographical noteFunding Information:
The authors wish to thank Large Marine Vertebrates Research Institute Philippines (LAMAVE) for the logistical support during our expedition in Tan-awan. We are grateful to be granted an export commodity clearance from the Bureau of Fisheries and Aquatic Resources—Region 7, Department of Agriculture, Republic of the Philippines. We also thank Mr. Ronald Guaren, the municipal mayor of Oslob, Cebu, for permitting the collection of samples for this study. We would like to acknowledge Ms. Holly Wong from the Department of Earth Sciences at the University of Hong Kong for assistance with stable isotope analyses as well as Dr. Nicolas Duprey, Jeffrey Yuen, and Arthur Chung for their support in laboratory work.
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- Coastal development
- Reef degradation
- Retrospective isotope analysis
- Tourism management
- Whale shark tourism