Introduction

Various anthropogenic activities have significantly contributed to the decline in coral reef populations globally (Aeby et al., 2024; Selig and Bruno, 2010). The intensity of these activities is particularly high in coastal areas, where habitat destruction, marine traffic, and fishing are more intense compared to open sea regions (Gattuso et al., 2015). The initiative of Marine Protected Areas (MPAs) has emerged as an effective strategy to address the damage occurring in maritime and coastal environments. Empirical evidence demonstrates the success of MPAs in revitalizing aquatic ecosystems, including the presence of coral reefs (Davis et al., 2019), which raises optimism about their potential to indirectly benefit fish populations. This is achieved through regulations that reduce various threats, including overfishing, which could otherwise lead to coral reef degradation and mortality due to the use of environmentally destructive fishing gear.

Furthermore, MPAs support the sustainable use of marine resources, which in turn can enhance fishery productivity in the long term (Jin et al., 2024; Pike et al., 2024). These protected areas also contribute to the overall improvement of ecosystem health (Costello, 2014; Gill et al., 2023). Despite the substantial benefits offered by the concept of MPAs, it continues to generate diverse viewpoints among researchers. The global debate on MPAs reflects an evolving discourse on their environmental and economic impacts. There are various perspectives on the value of MPAs, compiling narratives about their advantages and disadvantages. The involvement of economics in this knowledge is a crucial step toward advancing our understanding. Economics provides a framework for objectively assessing benefits and costs by translating ecological value into monetary terms. Such an approach will facilitate more informed decision-making by offering policymakers a standard method to weigh trade-offs between different options (Beaumont et al., 2008).

Indonesia, as one of the countries actively engaged in coral reef restoration initiatives in recent years, has emerged as a global leader in this endeavor (Sebastian et al., 2024). Its location at the heart of the Coral Triangle, the global center of coral reef biodiversity, positions it uniquely concerning marine conservation (Razak et al., 2024). This is supported by the fact that over 70% of the world's recognized reef-building species, as documented by ReefBase, can be found in Indonesia (ReefBase, 2010). Thus, Indonesia bears significant responsibility for marine biodiversity. Specifically, the eastern region of Bintan Island, Riau Islands Province, Indonesia, exemplifies the significant implementation of MPAs, as outlined in the Decree of the Indonesian Ministry of Marine Affairs and Fisheries No. 18 of 2022. The conservation area spans 138,561.42 ha with three conservation zones, making Bintan Regency a highly relevant location. Notably, Bintan Regency possesses nearly 9,100 ha of coral reef ecosystems, with about 50% in good condition, showing a live coral cover rate of 58.9% (MMAF, 2012). In 2009, the abundance of hard corals and fish on the northern coast of Bintan Island remained at high levels, averaging over 50% coral cover and over 0.7 fish m^-3 (Chou et al., 2010). Consequently, the decision to establish and manage MPAs on Bintan Island is indeed based on evidence supporting the potential ecological benefits of such actions. This condition must be maintained and enhanced, partly through effective MPAs management, to achieve increased biodiversity, abundance, and biomass of fish species (Gallacher et al., 2016), with the potential to increase fish abundance by 2 to 5 times in conservation areas compared to fishing areas (McClanahan, 1994).

Marine Protected Areas not only provide ecological benefits but also present several impacts that need to be considered. From a financial perspective, the costs of establishing MPAs include various stages: from initiation, encompassing site designation and policy socialization, such as the relocation of fishing activities, to the operational phase, which includes continuous maintenance, monitoring, and evaluation. Global ecological restoration costs are declared to range between USD 100 - 1,000 ha^-1 (Cao et al., 2018). As a result, there is complexity in evaluating how the benefits of MPAs can be directly transferred to the fishing population. Besides the significant costs of ecological restoration within MPAs, the importance of comprehensive economic analysis becomes clear to avoid inefficiencies in MPAs project implementation. Although analyses of ecosystem services provided by MPAs are well documented, challenges arise when estimating economic value using specific ecosystem modeling of designated zones, which often do not reflect the true measurable value.

In the context of MPAs initiatives, only a few studies have explored cost-benefit analysis (Newton et al., 2012). Conventional economic analyses related to MPAs often focus on estimating the ecological benefits for coastal communities, such as fishermen. Meanwhile, ecological researchers report on ecosystem conditions such as coral reef density and fish biomass. There are challenges in estimating the benefits and costs of MPAs, such as designing MPAs that efficiently protect vital ecosystem components while maintaining minimal economic impact on local communities (Dalton, 2004). Recognizing these challenges, our research proposes an approach that integrates the estimation of ecological service values within a comprehensive economic analysis framework. This approach is recommended as a vital tool to support stakeholders in making informed decisions about fisheries resource management within MPAs schemes. Thus, this effort is oriented not only toward ecosystem conservation but also toward the socioeconomic well-being of communities dependent on these resources.

2. Materials and Methods

2.1 Field Observation

Field observations were conducted at three observation sites located within the MPAs of Bintan Island during the period from June to November 2021. Two of these stations are situated within the MPAs boundaries Station 1 on Mapur Island (1° 0' 52.002"N, 104° 50' 42.3702"E) and Station 2 on Larang Island (1° 1' 41.16"N, 104° 48' 56.7966"E), while the third site is located outside the MPAs environment Station 3 on Pangkil Besar Island (0° 56' 37.0644"N, 104° 43' 58.4184"E). The MPAs of Bintan Island covers a total area of 138,561.42 ha, which includes a core zone designated as a no-take zone spanning 2,101.87 ha, a limited use zone with scattered coral reefs covering 132,973.45 ha, and other zones comprising shipping lanes, rehabilitation areas, ports, and marine structures totaling 3,486.1 ha (Figure 1).

Station 1 (Mapur Island) is located in a relatively sheltered area within the MPAs' core zone, with a seabed dominated by rocky and coral rubble substrates. Water currents are moderate, and the surrounding ecosystem includes coastal vegetations, which provides important habitats for both marine and terrestrial species. Station 2 (Larang Island), also within the MPAs' core zone, experiences higher macroalgae presence, particularly Sargassum sp., suggesting moderate nutrient availability. The seabed consists of fringing reef formations interspersed with sand and coral debris, while the area supports a diverse reef fish community. Station 3 (Pangkil Besar Island), located outside the MPAs, is more exposed to ocean currents and waves. This site features fringing reefs with steeper slopes, a rocky coastline, and undisturbed coastal forests. The coastal areas across all three stations are characterized by white sandy and rocky beaches, covered with natural coastal vegetation and scattered coconut trees.

2.2 Environmental Condition

To analyze the environment in the MPAs area, 50 mL seawater was collected from the surface water at three stations. Phytoplankton species were identified and the number of the cells was counted using an invented microscope (Niko cooperation) for a 50 µL aliquot of the water sample. The chlorophyll a (chl.a) concentration was determined for the water sample after sized fractionation with a 5 µm pore size net and without fractionation (total) for 300 mL of seawater sample using the method of SCOR/UNESCO (Strickland et al., 1972). Temperature, and dissolved oxygen (DO) were recorded by multi parameter quality checker. Water salinity analyzed using hand d refractometer. The brightness was analyzed by Secchi disk. The seawater sample also sent to Marine Aquaculture Agency (Balai Budidaya Laut) in Batam City, then they used to analyze the Phosphorus (PO₄), Ammonium (NH₄⁺), Nitrate (NO₃), and Nitrite (NO₂) concentration.

2.3 Coral Reef and Fish

Free visual observations from the seashore to the reef where transects were made at each research station were carried out to get a general picture of the research station. We used the method following Ahmadia et al. (2013) for collecting data on coral reefs and fish each station. For coral reefs, the data will be collected using Point Intercept Transect (PIT) along 50 m with three times repetition.

Underwater photo transects (UPT) was used to collect the coral reef data. The picture is captured along a transect with a frame of 44x58 cm (Giyanto, 2012). The capture started at 1 m until 50 m with a distance space of 1 m. The picture data was analyzed using the coral point count for excel (CPCe) version 4.1 software, where 50 points of every picture were randomly chosen (Kohler et al., 2005). There were eleven benthic categories, namely hard coral (HC), dead coral (DC), dead coral with algae (DCA), soft coral (SC), sponge (SP), fleshy seaweed (FS), other biota (OT), rubble (R), sand (S), silt (SI) and rock (RK). Consequently, for each station with 50 photo frames, there are 2500 points that are analyzed to determine the percentage of cover for each benthic category, which is calculated using the formula (Formula 1). Then detmining coral cover categories based on the Ministry of Environment of Republic of Indonesia No. 4/2001.

where \(W\) is fish biomass (g m^-3), \(a\) is the intercept, and \(L\) is the total length (cm).

2.4 Ecosystem Services Provided by MPAs

To estimate the total economic value (TEV) of the ecosystem services provided by the oyster culture, the direct and indirect use values (MEA, 2005) were applied. For the assessment of the direct use value, the market price-based approaches were applied. The market price method market price method estimates the economic value of ecosystem products or services that are bought and sold in commercial markets (King et al., 2000). This approach is most often used to obtain the value of provisioning services (Brander et al., 2012). To estimate the indirect use value, a cost-based approach was applied. The cost-based approach is based on an estimation of the cost incurred if the ecosystem services need to be recreated through artificial means (Garrod and Willis, 1994). The travel cost method is used to estimate economic use values associated with ecosystems or sites that are used for recreation. The benefit transfer method is used to estimate economic values for ecosystem services by transferring available information from studies already completed in another location and/or context (King et al., 2000). MPAs is a restricted area for fishing activity. Therefore, to estimate the ecosystem service provided by this area. Firstly, we estimated the fish biomass then converted to area cover and multiplied to price of fish from the local market price. For tourism, the data number of visitors cited by local government statistic in 2019 (BPS, 2019). For biodiversity and physical coastal protection, we used benefit transfer method as mentioned in Table 1.

To estimate the feasibility study of the MPAs project, we evaluate the economic analysis using the Cost-benefit Analysis (CBA). The spent cost for maintenance and monitoring of MPAs in term of the coral reef ecosystem has been confirmed by the central government, local government, and Non-Government (NGO) (see Table 3).

3. Results

3.1 Environmental Condition

During the observation period, the temperature ranged between 27°C and 30°C, with salinity around 30 ppt. The lowest brightness levels were recorded at Stations 1 and 2, measuring 2.2 m and 2.3 m respectively. However, Station 2 exhibited a high DO concentration, approximately 6.5 mg L^-1. The concentration of chl.a was higher in June compared to the November period (Table 2). Similarly, nutrient concentrations were higher in June than in November.

Among the various species of phytoplankton identified, there was a significant dominance of Skeletonema costatum and Chaetoceros sp. Observations regarding phytoplankton abundance indicated higher numbers in June compared to November, particularly at Station 3 (Figure 2).

3.2 Coral Reef Condition

The results of the benthic survey conducted in June and November 2021 are displayed in the graph below. The graph indicates that Stations 1, 2, and 3 exhibit different percentages of coral cover. The live coral cover percentages at these stations are 49.31%, 31.2%, and 40% respectively, predominantly consisting of HC. In contrast, the DCA is 37.96%, 40.47%, and 23.20% respectively. On average, the HC value stands at 40%, indicating that the coral cover is categorized as moderate (Figure 3). Other benthic surveys show significantly lower resilience levels, with SC at 5%, FS at 0.1%, and R at 0.1% (Figure 4).

3.3 Fish Biomass

Eight economically important families of reef fish were observed: Casionidae, Ephippidae, Labridae, Lutjanidae, Scaridae, Serranidae, Siganidae, and Chaetodontidae. These families represent three functional groups: corallivores, herbivores, and carnivores. The most dominant reef fish family, with the highest percentage of presence, was Casionidae (69%), followed by Lutjanidae (14%), Chaetodontidae (10%), Siganidae (4%), and both Labridae and Scaridae (3% each). No presence of Ephippidae and Serranidae was recorded (Figure 5).

Based on the biomass of reef fish in the MPAs of Bintan Island, it was found that the eight observed fish families across all monitoring locations in the MPAs of Bintan Island ranged from 286 to 1,343 fish ha^-1. Casionidae had the highest biomass (108.83 kg ha^-1), followed by Lutjanidae (19.98 kg ha^-1), Chaetodontidae (14.88 kg ha^-1), Siganidae (5 kg ha^-1), Labridae (4.92 kg ha^-1), and Scaridae (3.71 kg ha^-1). The remaining two families were not present (Figure 6).

3.4 Ecosystem Services Provided by MPAs on Bintan Island

The coral reef has functioned as a spawning, nursery, and feeding ground for created life in coastal areas. The landscape of coral reef becomes the trigger of tourisms destinations. Ecologically, coral reef ecosystems play a role in coastal protection from heavy waves.

MPAs of Bintan Island has good environmental condition. It is suitable for marine culture in terms of the feasibility study. Based on the carrying capacity of MPAs, 17 thousand fish sea cages were estimated built up in MPAs of Bintan island. To maintain The MPAs of Bintan Island, the government and NGO spent around USD 50,000 in 2021 (Table 3). This budget was divided into several programs such as restoration and monitoring of reef health.

4. Discussion and Conclusions

4.1 Environmental Conditions and Phytoplankton Abundance

Phytoplankton play a crucial role in the marine trophic chain (Guo et al., 2024), making information about phytoplankton indicators important for biodiversity management, including the management of MPAs. This is because phytoplankton indicators are used to interpret the dynamics of predator species, which are often a priority in conservation efforts, either for their economic value (Aura et al., 2021) or their conservation value (Trubovitz et al., 2023). One of the phytoplankton indicators is phytoplankton abundance, which not only reflects biodiversity (Gregory et al., 2024) but also represents the efficiency of trophic energy transfer (Chowdhury et al., 2024), significantly influencing fish population dynamics (Perretti et al., 2017). In this study, we found that S. costatum and Chaetoceros sp. dominated the phytoplankton abundance in the MPAs of Bintan Island. These marine diatom plankton are commonly found in various Indonesian waters, such as in the waters of Bintan, Riau (Syakti et al., 2019), and Tanjung Benoa, Bali (Suteja et al., 2021). According to Figure 2, phytoplankton abundance was higher in June compared to November. This can be evidenced by the high chl.a values at all stations during different sampling periods (Table 2). Phytoplankton contain chl.a, which functions to capture light energy and drive the photosynthesis process, thus contributing to the overall chl.a concentration in the water (Wang et al., 2023).

The variation in phytoplankton density in the waters is also influenced by the season (Benedetti et al., 2019), due to the different combinations of nutrient availability in each season (Damar et al., 2019). In this study, June represents the dry season period, while November marks the beginning of the rainy season. Higher temperatures, PO₄, and several nitrogen compounds in June are among the factors contributing to higher phytoplankton density in MPAs based on seasonal periods.

4.2 Composition and Proportion of Reef Fish

In this study, we observed three types of reef fish: major fish (small ornamental fish, generally 5–25 cm, with diverse color characteristics) such as Labridae and Ephippidae, target fish (economically important fish and catch targets for consumption) such as Caesionidae, Lutjanidae, Scaridae, Serranidae, and Siganidae; and indicator fish (reef fish that typically inhabit coral reef areas and serve as ecosystem fertility indicators) such as Chaetodontidae (See Figure 4). Target fish were the most commonly found, with a percentage rate of 90%, and the Caesionidae family had the highest dominance (69% or 108.83 kg ha^-1). Similar findings were observed in the MPAs of Southern Cebu, Philippines, where the Caesionidae family also exhibited high dominance (Corrales et al., 2015). The high dominance of target fish is attributed to the presence of suitable habitat variations, such as coral fragment substrates (Shabi et al., 2024). Furthermore, target fish like Scaridae and Siganidae, which are herbivores, play a crucial role in controlling macroalgae growth and preventing macroalgae dominance in coral reef ecosystems (Green and Bellwood, 2009). Other target fish, such as Lutjanidae and Serranidae, are carnivores with a high dependency on coral reefs (Sartori et al., 2021) for feeding and protection from predators (Kulbicki et al., 2005).

In contrast, major fish were only found in about 0-4.92% of the observed areas. This group was found in various habitats, including rocky substrates, sand, branching corals, and dead branching corals. The Chaetodontidae family, being coral predators and bioindicators of coral reef conditions, have a closer association with coral reefs than other reef fish species (Bellwood et al., 2010). This species was also found in the MPAs of Anambas, Indonesia (Putra et al., 2021). The biomass of reef fish increases with the rise in coral cover area. Conversely, a decline in coral cover area leads to a significant reduction in reef fish biomass, as observed in Batam and the Natuna Islands, Indonesia (Hadi et al., 2018). Establishing MPAs is expected to increase biomass, as MPAs are marine areas where fishing is legally prohibited in certain zones (full protection zones) (Abesamis et al., 2022). As a result, MPAs have the potential to harbor more than twice the biomass of coral fish compared to those in partially protected zones and open fishing zones (Hall et al., 2023).

4.3 State of Coral Cover

Recent bio-ecological research provides new insights into the condition of coral reefs. Our observations reveal variations in coral cover values across different observation stations, which are still classified as moderate, ranging from 31.2% to 49.3%, with an average of 40% (see Figure 3). Compared to previous research reports, these values indicate an increase in coral cover percentage, which was previously 35.30% (Irmadhiany et al., 2024), 38% (Kurniawan et al., 2021) and 37.6% (Abrar et al., 2018). Although the percentage of coral cover remains in the moderate category, the upward trend over the years suggests positive conditions for the health of the coral reefs on Bintan Island.

This increase in coral cover is a positive indicator for the marine ecosystem, as thicker coral cover correlates with the abundance of fish and other marine life. This supports a more complex ecosystem that is resilient to various disturbances. This positive dynamic reinforces the rationale for discussing and potentially expanding MPAs. Factors such as design, effective management, rule enforcement in MPAs, as well as support and involvement from local communities, although significant in conservation effectiveness, appear to be manageable. This is evidenced by the designation of Bintan Island as an MPAs in 2022, where this policy is expected to maintain the quality of the coral reef ecosystem by limiting human activities and therefore, is expected to continue increasing coral cover values annually. Such initiatives hinder coral loss and, over time, enhance coral cover. Conversely, without such protection, coral cover tends to decline (Selig and Bruno, 2010).

At station 2 specifically, there is an issue with a 19% fFS, which can reduce the resilience and recovery potential of the coral reefs to damage and hinder coral growth itself. This could explain why station 2 has a lower coral cover than the other two stations. An additional highlight of this study is that the levels of R and S at all stations are relatively low, which is actually beneficial, as an abundance of these elements tends to negatively impact productivity, such as lower fishery values compared to the presence of coral reefs, which tend to promote high fish abundance (Maina et al., 2015). Furthermore, the presence of rubble can impede the natural recolonization and recovery of coral reefs due to the lack of physical stability on the seabed (Hernández-Delgado et al., 2024).

4.4 Ecosystem Services Provided by MPAs on Bintan Island

Bintan Island, located at the southeastern boundary of Indonesia's maritime territory, exemplifies the complex interaction between environmental conservation and sustainable fishing practices. On this island, MPAs is divided into three zones: the Supporting Zone, the Fishing Zone, and the Core Zone, also known as the no-take zone. The Core Zone is exclusively designated for research and education activities, including case studies on protected area zoning aimed at achieving a balance between marine resource protection and production. In this context, MPAs are expected to have higher coral cover compared to other areas as part of ecosystem protection efforts. Our research indicates that live coral cover in MPAs is higher than outside MPAs, a condition also observed in other conservation areas such as the MPAs of Anambas Island, which have 30-60% live coral cover (BRIN, 2022). MPAs play a vital role in coral growth, given the vulnerability of coral reefs to environmental influences and destructive fishing activities (Hall et al., 2023; Nurdin et al., 2022). Additionally, MPAs are crucial for ensuring the provision of valuable environmental products and services to coastal communities (Nurdin et al., 2022), highlighting the significant role of MPAs in maintaining marine biodiversity and the sustainability of fish resources for local communities.

MPAs, as bastions of marine biodiversity, not only function to protect coral ecosystems and other often fragile marine habitats but also safeguard social aspects, such as the traditional way of life of fishermen who have adapted over generations in balance with natural resources. In Bintan Island, MPAs have become fishing grounds for traditional fishermen who use simple boats and manual fishing gear. We estimate the biomass of reef fish in Bintan Island MPAs to be 28 kg ha^-1, which is lower compared to the MPAs in Anambas (35 kg ha^-1) and significantly lower than the MPAs of Teluk Sebong, Bintan Island (221 kg ha^-1) (Kurniawan et al., 2021). However, this difference can be attributed to the fact that Anambas was designated as an MPA in 2014 based on the Decree of the Minister of Marine Affairs and Fisheries No. 37 of 2014, while Bintan Island was only designated as an MPAs in 2022. With industrial fishing restrictions based on quotas and the establishment of eight core zones totaling 1,797.62 ha, which are no-take zones, fish biomass is expected to increase over time. The fundamental concept in conservation, known as 'spillover' (Harman and Kim, 2024), emphasizes that biota stocks will thrive within protected areas, and the surplus from this growth will spread beyond the protected areas, which can then be sustainably harvested. These protected areas contribute to biomass enhancement, where healthy coral reefs support high fish abundance and biomass, while also providing necessary protection from predators or human disturbances, supporting essential processes for their survival (Kappes et al., 2021).

In 2019, approximately 600,000 tourists from various countries visited Bintan Island (BPS, 2019). This increase is largely due to its strategic geographic location, close to Singapore, a country experiencing rapid tourism growth and situated along major maritime trade routes (Vasagar, 2022). Coastal tourism activities, particularly snorkeling and diving, are major attractions that contribute to the local economy. It is estimated that if 5% of visitors engage in diving activities within the MPAs, the annual revenue from tourism could reach USD 12 million. Given this potential, tourism should be fully integrated into MPAs management, ensuring a balance between economic benefits and ecological integrity (Tranter et al., 2022).

While MPAs provide valuable ecosystem services, the growing tourism industry poses a challenge to conservation efforts. The designation of MPAs of Bintan Island as a Marine Tourism Park, which is one of the MPA types in Indonesia, underscores the need for sustainable management strategies. Achieving a balance between economic benefits and marine ecosystem protection is crucial, particularly in no-take core zones, where stricter conservation measures are required. Unregulated snorkeling and diving have been shown to contribute to coral reef degradation and marine life disturbance (So et al., 2023). To mitigate these risks, adaptive management strategies should incorporate seasonal closures, visitor quotas, and dynamic pricing mechanisms to regulate access and minimize cumulative environmental impacts.

Local community engagement plays a crucial role in ensuring sustainable tourism within MPAs. Traditional resource management practices, such as Sasi Laut in eastern Indonesia, demonstrate how community-led rotational closures can enhance fish stocks, support sustainable livelihoods, and foster marine ecotourism development (Prasetyo et al., 2023). Implementing a similar participatory model in Bintan could facilitate fair revenue-sharing from tourism while promoting habitat restoration initiatives. To effectively balance ecological thresholds with socioeconomic needs, a polycentric governance approach is recommended. This would integrate satellite monitoring, community patrols, and ecological certification schemes for tour operators, ensuring compliance with conservation guidelines. Such strategies can mitigate the impacts of mass tourism in conservation zones while encouraging low-impact ecotourism in buffer areas, ultimately supporting both biodiversity conservation and local economic resilience.

The maintenance and monitoring of MPAs, conducted by the Central Government, Local Government, and NGOs, have a total expenditure of USD 50,000 per year, without budget contributions from the Local Government. This condition highlights a significant disparity given the extensive conservation area but with low maintenance budgets. If MPAs are utilized for marine aquaculture, they have the potential to produce 1,300 floating net cage units with an economic value of approximately USD 2 million per year. This potential is lower compared to Pangkil Island, which can support 12,000 floating net cage units (Kurniawan et al., 2022). Despite Bintan Island’s limited potential, it should still be a priority for managers, particularly the Management Unit Organization (SUOP) by the Riau Islands provincial government, as outlined in Governor's Decree No. 710 of 2022. This decree is part of the Bintan MPAs and is responsible for improving MPAs management and monitoring, including enhancing biophysical ecosystem characteristics, fish stock assessments, and socio-economic assessments of communities in and around the core areas. Consequently, it is expected to promote sustainable marine resource utilization and improve the well-being of local communities.

Coral reefs are highly sensitive to environmental changes, and climate change is a major driver of coral degradation worldwide. One of the most significant threats is Annual Severe Bleaching (ASB), which results from prolonged thermal stress due to rising sea surface temperatures. Tropical regions, including Indonesia, are particularly vulnerable to ASB, as increasing ocean temperatures lead to more frequent and severe marine heatwaves (Napitupulu et al., 2025). However, our study found a relatively low frequency of coral bleaching in the waters of Bintan, suggesting that local oceanographic and climatic factors may be influencing thermal resilience. Analysis of sea surface temperature (Table 1) across the study sites shows relatively stable thermal conditions, indicating that Bintan’s MPAs may function as a thermal refugia. Climate projections estimate that this thermal stability could persist until approximately 2050 ±3.14 (De Clippele et al., 2023). One of the key factors supporting this resilience is seasonal upwelling, which is driven by monsoonal winds and seafloor topography, bringing cooler, nutrient-rich waters from the thermocline to the surface (Mayer et al., 2022; De Clippele et al., 2023). This process slows down temperature increases, reducing the accumulation of degree heating weeks (DHW), a key indicator of thermal stress in corals and thereby breaking the cycle that leads to mass coral bleaching (De Clippele et al., 2023).

In addition to local cooling mechanisms, regional oceanic circulation patterns influence Bintan’s thermal stability. The Indonesian Throughflow (ITF), a major component of global ocean circulation, transports warm Pacific waters into the Indian Ocean, primarily affecting central and eastern Indonesian waters (Hamzah et al., 2024; Wahyuni et al., 2024; Xu et al., 2025). While Bintan is not directly within the ITF pathway, it still experiences indirect effects from regional current dynamics, particularly through water mass exchanges with the South China Sea and Malacca Strait (van Sebille et al., 2014). These oceanographic factors help to disperse warm water, reducing the intensity of temperature spikes that trigger widespread coral bleaching. However, climate change is expected to alter these circulation patterns, potentially weakening seasonal upwelling and increasing bleaching susceptibility in the future (Bozec et al., 2025).

Although MPAs provide protection, past records indicate that coral bleaching events have occurred in other parts of the Riau Archipelago, signaling that even relatively stable reef systems may face increasing stress in the coming decades (Wouthuyzen et al., 2018; Putra et al., 2019; Gusviga et al., 2021). Additionally, marine heatwaves are projected to become more frequent and intense (Guibourd de Luzinais et al., 2025), which could disrupt the current stability of Bintan’s MPAs. Long-term climate trends also suggest changes in rainfall patterns and ocean currents, which may weaken seasonal upwelling, reducing the cooling effect that currently helps protect coral reefs (Boot et al., 2025; Datti et al., 2024). To preserve coral reef resilience, a multi-faceted conservation approach is needed. Scientific monitoring programs, climate adaptation strategies, and active restoration efforts should be prioritized to track early warning signs of thermal stress and implement targeted interventions. Additionally, public awareness campaigns and community engagement in coral monitoring initiatives will be critical in ensuring timely responses to emerging threats (Thiault et al., 2021). Involving local communities in routine reef monitoring and conservation training can enhance decision-making processes for MPA management (Gotama et al., 2023). While Bintan’s MPAs currently exhibit strong ecological resilience, proactive efforts are necessary to maintain their function as a climate refugia and safeguard coral ecosystems for the long term.

The total economic value of MPAs of Bintan Island, estimated at USD 13 million, far exceeds the annual expenditure (USD 50,000). However, based on 2021 data, the local government’s MPAs management budget is very minimal, about USD 0.35 ha^-1, significantly lower than the global conservation fund range (USD 100-1,000 ha^-1) (Cao et al., 2018). Funding is a key factor in sustaining both existing and future coral restoration programs (Sebastian et al., 2024). The ecological benefits derived from MPAs in supporting fisheries production, tourism sectors, and other supporting services are quite significant. Therefore, for the sustainability of MPAs, the government and stakeholders must give special attention to budgeting for coral reef maintenance and restoration. Although the indirect value of MPAs is higher than their direct value, maintaining their sustainability is crucial, given that both values are interrelated.

5. Conclusions

The MPAs of Bintan Island provide significant ecosystem services, particularly in fisheries production and tourism revenue generation. The economic value of fisheries production within the MPAs is estimated at USD 2 million, while tourism-related benefits contribute to an overall economic impact of approximately USD 14.96 million annually. This far exceeds the annual management cost of USD 50,000 in 2021. For sustainability the benefit of MPAs, government may increase the budget for maintained and coral transplantation programs.

Despite the economic benefits outweighing management costs, current funding levels remain insufficient for effective conservation efforts. According to a 2006 report by the Ministry of Environment of the Republic of Indonesia, the optimal funding required for MPAs management in Indonesia is estimated at USD 135.31 million annually. Given that MPAs of Bintan island cover 138,561 ha, the estimated annual conservation budget needed for monitoring, ecosystem restoration, and habitat protection is approximately USD 640,316. This funding gap poses a challenge to sustaining the ecological and economic value of MPAs, necessitating an increase in conservation investment from government agencies, local stakeholders, and external partners.

To address this financial responsibility, a multi-stakeholder funding approach is recommended. Public-private partnerships, ecotourism-based revenue-sharing mechanisms, and international conservation grants could supplement government funding. Additionally, involving local communities in conservation financing models, such as community-led coral restoration programs and sustainable tourism initiatives, could enhance long-term MPAs resilience. By ensuring adequate financial support, MPAs can continue providing ecological benefits, sustaining fisheries, supporting tourism, and strengthening coastal protection.

Acknowledgments

The authors extend their gratitude to the diving instructors, dive club managers, owners, and volunteers for their valuable insights in planning and implementing introductory dives. Appreciation is also given to the local government of Riau Kepulauan Province, the Directorate of Marine Biodiversity and Conservation, and the Directorate General of Marine Spatial Management of the Ministry of Marine Affairs and Fisheries for their support in data collection and discussions. This research was financially supported by Conservation Strategy Fund (CSF), whose contribution was instrumental in facilitating fieldwork and analysis.

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