Community Structure and Health Status of Mangrove Ecosystem in Anambas Islands Marine Tourism Park, Indonesia

. Mangroves are one of the coastal ecosystems that can adapt to tidal areas with highly saline environments. This community plays a crucial role in ecological and economic functions, such as prevention of abrasion and seawater intrusion, providing habitat for biotas, nutrient recirculation, carbon sinking and storage, and mangrove educational tourism. The climatic changes and anthropogenic activities affect the mangrove ecosystem and thus need protection and conservation. The novelty of this research is that it is conducted in a marine protected area and was carried out at several stations consisting of zones such as the core zone, utilization, and others. This research does provide scientific literation about the community structure and health index of the mangrove ecosystem in the Anambas Islands as one of the first steps for ecosystem protection and management. This study was conducted at twelve stations using the squared line transect (10x10 m; 5x5 m; 1x1 m) to calculate vegetation density, and hemispherical photography method to calculate the percentage of canopy cover. The results showed that nine mangrove species were found at the study site: Rhizophora mucronata, Rhizophora apiculata, Bruguiera gymnorhiza, Xylocarpus granatum, Ceriops tagal, Rhizophora stylosa, Rhizophora lamarckii, Avicennia marina , and Aegiceras floridum . The status of mangrove ecosystem in Anambas Islands is categorized as good and dense condition with a percentage of canopy cover of 85.18% and a density of 2797 ind/ha. The result shows that management of this coastal ecosystem has been carried out well and can develop other potential to support the


Introduction
Anambas Islands Marine Tourism Park is one of the National Marine Conservation Areas established by the Minister of Marine Affairs and Fisheries.This area has a total area of 1,262,686.2ha.Marine conservation areas are managed to protect communities, resources, and biodiversity to increase the welfare of humans in and around the areas.One of the communities managed on Anambas Islands is the mangrove forest with an area of 1156.66 ha.
Mangroves are coastal vegetation communities that have a distinctive identity and can grow in tidal areas.This plant can adapt and survive in extreme environments with high water salinity and muddy substrates [1].Mangrove ecosystems have a high productivity and organic matter content [2], which decomposes with the help of microbes and becomes a source of nutrients such as phosphate and nitrate [3].The content of organic matter in the mangrove ecosystem plays an important function in supporting the availability of nutrients for maintenance, spawning, and food sources [4].
The mangrove ecosystem is a transitional ecosystem with ecological, social, and economic functions.Mangroves function as the protector of land areas from ocean waves and can reflect the energy of tsunami waves [5].Mangroves can also prevent sedimentation by binding dissolved sediment from rivers and suppressing the rate of seawater intrusion toward the mainland [6].In addition, mangrove ecosystem has the function as a carbon sink and storage [7] [43].The potential of carbon storage can be analyzed in the stand structure of mangroves and sediments.Carbon storage in mangrove stands has a value of 190,257 tons of carbon/ha, while in mangrove sediments, it has a value of 480,608 tons/ha [8].
Mangroves ecosystem plays a crucial function in coastal conservation.Unfortunately, the various climatic [5] and anthropogenic-induced including waste pollution [9], conversion of mangrove areas [10], and sea level rise changes affect the mangrove ecosystem [11].National Marine Protected Area Agency of Pekanbaru, as the Anambas Islands area manager, aims to protect, preserve and utilize the area sustainably to realize the welfare of the local community.Mangrove forests that are managed properly can be developed and provide ecologically and economically benefits.There has been no published research regarding the health status of mangroves in this area, so this research was carried out to provide scientific literation about the mangrove ecosystem's community structure and health status in the Anambas Islands Marine Tourism Park, Riau Islands, Indonesia.

Materials and Methods
This research was conducted at the Anambas Islands Marine Tourism Park in 2021.Primary data were obtained from environmental parameters, diameter at breast height (DBH) field surveys, canopy cover, and mangrove density.

Sampling area
The research location was determined by considering environmental conditions and the zoning in the field to represent the whole location [12].

Environmental conditions
Environmental parameters are important aspects that support mangrove life and greatly affect mangrove plants' health conditions.The water quality parameters measured in this study were the type of substrate, pH, temperature, salinity, dissolved oxygen, conductivity, and turbidity.

Percentage of mangrove (canopy) cover
The canopy cover was calculated using the hemispherical photography method [13], which is a method by calculating the canopy cover area using a camera from under the tree canopy.This method uses a 10x10 m2 transect divided into four small 5x5 m2 plots, and 12 phototaking points were selected on each transect [14] (Figure 2).The results were analyzed to determine the percentage of mangrove cover in the area.

Mangrove density
Mangrove ecosystem data collection was carried out using the line transect method, plotting a certain area into three quadrants measuring 10x10 m.Each quadrant is divided into three sub transects, namely 5x5 m and 1x1 m [15] The stem diameter is calculated by measuring the stem diameter at breast height (DBH) with a trunk circumference of at least 16 cm.The number of trees and their trunk circumference were calculated on each plot to determine mangrove density and importance value index.Identification of mangrove species at the observation site was carried out visually by looking at the characteristics of roots, leaves, fruits, and flowers [16][17] [18].

Vegetation Analysis
The analysis consists of density, frequency, dominance, importance value index, and percentage canopy cover.Calculation of the data is done using Microsoft Excel software.

Percentage of Canopy Cover
The percentage of mangrove cover was analyzed using Image J. software [13] and calculated from the comparison of the number of pixels with a value of 255 (P255) with the total number of pixels (ƩP) multiplied by 100% [22].

Environmental condition
Environmental conditions are important aspects of supporting mangrove life.This parameter affects the health condition of mangrove plants because each species has different characteristics and levels of adaptation to environmental parameters (Table 1).The results showed that the pH value ranged from 6.15 -8.26, DO values ranged from 2.64 -5.26 mg/l, the temperature ranged from 28.3 -31.9 °C, salinity had an average value of 25.15, conductivity had an average value of 8.03 s/m, and turbidity had an average value of 6.28 NTU.
The pH value of water shows the balance between acid and base.The average pH value in the research locations is 7.68 and categorized as good conditions, which is between 7 and 8.5 (Minister of Environment Decree number 51 of 2004).Fluctuations influence the high pH in the content of O 2 and CO 2 [23].Changes in pH can impact the amount of carbon dioxide, the availability of macro & micronutrients, and their absorption.The pH value will affect the balance of carbon dioxide content used for photosynthesis [24].Dissolved oxygen is a basic need for life-living things in the ocean for respiration.Dissolved oxygen is generally obtained from oxygen diffusion, currents, or water flow through rainwater and photosynthesis [25].The average value of DO is 3.59 mg/l.The low DO content is thought to be due to the high mud substrate at the study site.The presence of currents and tides causes an increase in the carried mud substrate, thus causing an increase in turbidity.Turbid waters will cause phytoplankton not to be able to photosynthesize optimally, so the amount of dissolved oxygen will be lower [26].
The results showed that the average salinity and temperature value in the mangrove community waters were 25.15 ppt and 30.63˚C.This range is still within the tolerance limit for mangrove growth, ranging from 10-30 ppt [27], and the temperature value is still in good condition based on the Seawater Quality Standard, which is between 28˚C to 32˚C.The average turbidity value in the mangrove community waters is 6.28 NTU.This value tends to be above the standard quality value (<5 NTU).The high turbidity value is related to the substrate dominated by mud and the inclusion of material from the mainland.Another environmental parameter measured is the type of substrate.The substrates at 12 station points are muddy sand and sandy mud substrates.The type of substrate usually found in river mouths and rehabilitation mangroves was sandy substrate, while in natural mangroves, it was a muddy substrate [28].Areas with a muddy sand substrate are in the seaward zone, while areas with sandy mud substrate are in the landward and middle zones.The grain size of the sediment obtained will be finer when approaching the coastal area [29].This indicates that the sediment source has been transported until it finally settled on the bottom.

Species and Important Value Index Analysis
The results showed that nine mangrove species were found in the research plot: Rhizophora mucronata, Rhizophora apiculata, Bruguiera gymnorhiza, Xylocarpus granatum, Ceriops tagal, Rhizophora stylosa, Rhizophora lamarckii, Avicennia marina, and Aegiceras floridum.The results showed that Rhizophora apiculata had the highest relative values of frequency, density, and dominance.The value of species and relative frequency were 0.83 (F) and 25.79% (FR), respectively.This value indicates that Rhizophora apiculata has a high level of presence in each plot compared to other species because the frequency is one of the parameters that can show the distribution species in the ecosystem [21].The frequency value of mangroves was influenced by the number of species found at each research location; the more mangroves found, the higher the frequency of mangrove presence [1].The highest relative density was also found in Rhizophora apiculata, with a value of 33.88%.This value indicates that Rhizophora apiculata has a higher density than other species.The difference in the density value of each species is due to differences in reproductive ability, distribution and adaptability to the environment [30].The relative dominance value in Rhizophora apiculata is 31.47%,indicating that Rhizophora apiculata has a large diameter in each plot.The high relative density of R. apiculata is caused by the high level of adaptation in mangrove Rhizophora sp., so they can develop well and spread widely throughout the areas [21].

Fig. 3. Importance Value Index
IVI is calculated to determine species dominance in mangrove vegetation.The graph (Figure 3) shows that Rhizophora is the most common group of mangrove species or genera in the area.Rhizophora apiculata is the species that has the highest importance value index compared to other species found in the plot [31].
Stations with a high level of species diversity are ANBM03 and ANBM08, with six mangrove species found in the plot, while the least number of species found is ANBM04.ANBM03 in Muntai and ANBM08 on Penesan Island had the highest diversity, presumably because the location still has a natural mangrove area.The number of species found in natural mangrove forests is more than the number of species found in rehabilitated mangrove forests [32].It also happens because natural mangrove forests are still slightly influenced by human activities.The existence of shrimp ponds, expansion of settlements, and excessive taking of firewood and household waste in the mangrove area have reduced the mangrove forest area [33].In addition to environmental parameters, the condition of unspoiled mangroves and anthropogenic activities are other factors that affect the composition of the mangrove ecosystem.
The research location was dominated by three species: Rhizophora apiculata, Rhizophora mucronate, and Brugueira gymnorhiza.These three species are the major components and are species that are easily adapted to the mud or muddy sand substrate found at the study site.Species of Rhizophora apiculata were found in almost all study sites with muddy and sand substrates.Rhizophora apiculata can dominate because this species is the major component, and lives in two zones.In addition, the substrate in several research locations is in the form of soft mud and slightly sandy.This substrate is a suitable habitat for Rhizophora apiculata and several other dominant mangrove species, such as R. mucronata and B. gymnorhiza .This is in accordance with further research, which shows that the most dominant substrate in family Rhizophoracea is mud [34].

Percentage of Mangrove Cover
The results of the analysis using the hemispherical photography method and the Image J application showed that the percentage of mangrove cover at twelve stations had different results (Figure 4).

Importance Value Index
Ra Rm Bg Ct Xg Rs Rl Am Af

Fig. 4. Percentage of Mangrove Cover
The mangrove cover graph (Figure 4) shows the percentage value of mangrove cover had an average of 85.18% and is included in the dense category (> 75%).The highest value of mangrove cover was found at ANBM03 station, 89.10% and is thought to be caused by the substrate condition, which contains a lot of organic matter so that the supply of nutrients for mangrove growth and development is adequate.The same thing was reported that the mud substrate had a positive relationship with mangrove vegetation [35].The station with the highest density level has a high percentage of cover.This condition proves that the percentage of mangrove cover is related to the density level of mangrove vegetation.

Mangrove Density
Mangrove density is distinguished by three categories: tree, sapling, and seedlings.Treelevel mangrove density was used to determine the status of the mangrove community by the Minister of Environment Decree No. 201/2004.The mangrove density value at the research site has an average of 2797 Ind/Ha and is in the very dense category (>1500 ind/ha) (Figure 5).The highest density value was found at ANBM03 station (Dusun Muntai), which was 4333 Ind/Ha, while the lowest value was found at ANBM07 station (Teluk Besuh), which was 1400 Ind/Ha.Tree species influence the density or sparseness of a stand in a plot.Trees with tall stands with relatively large trunk diameters will cause space competition between individuals, so trees with large diameters will have low density [36].
In addition, the type and condition of the environment at the study site also support the success rate of mangrove growth [37], so the density is still relatively dense.

Fig. 5. Tree-level Mangrove Density
The condition of the mangrove community in Anambas Islands is generally dominated by sapling levels.It is influenced by the condition of the substrate as a source of nutrients.The type of substrate greatly affects the composition of the type and density of mangrove vegetation that lives on it.The suitability of the substrate for certain types of mangrove vegetation can be seen from the number of stands of these vegetations in their living areas [38].The analysis of the sapling level at the study site showed it had a higher value than the tree-level density, with an average of 3025 Ind/Ha (Figure 6).These results indicate a good regeneration rate in the mangrove community, supported by seed health factors and substrate fertility conditions.The high level of sapling is a very favorable condition for the formation of trees [39], where the natural regeneration of mangroves is very dependent on the readiness of seedlings to grow and develop independently in the surrounding environment [37].The highest sapling-level density was found at the ANBM04 station (Kr.Salahnama), which was 5133 Ind/Ha, while the lowest density value was found at the ANBM11 station (Telapan), which was 967 Ind/Ha.This illustrates the characteristics of small island mangrove vegetation, which is dominated by sapling-level mangroves compared to tree-level mangroves Fig. 6.Sapling-level Mangrove Density The average Seedling-level density of mangroves at the study site was 2208 Ind/Ha.ANBM09 station has the highest number of seedlings, which is 5733 Ind/Ha, while ANBM04 is the station with the lowest seedling-level density, which is 800 Ind/Ha (Figure 7).ANBM04 has a low seedling density, presumably because this station is a station with a high tree-level density and is dominated by Rhizophora mucronata so that the substrate is filled with roots.Seedling growth is limited because a dense canopy covers the seedling and sapling under the stand, filling the substrate with roots.Dense mangrove conditions with large diameters will result in space competition for seedling growth and development [40].Seedling growth is also influenced by sunlight to carry out photosynthesis; the higher percentage of canopy cover, the less sunlight will enter, so that the seedlings cannot grow optimally [41].

Fig. 7. Seedling-level Mangrove Density
In addition, the substrate found at this station is muddy sand, so the probability of propagules sticking is less than the mud substrate.The mangrove growth, especially at the propagule stage into seedling, was strongly influenced by several factors such as salinity, water temperature, tidal currents, tidal height, waves/tidal waves, turbidity.water, the intensity of sunlight, and substrate type [42].The graph of mangrove density at the tree level and the seedling level in Anambas shows a correlation.Stations with a high tree-level density level will have a low seedling density, whereas stations with a low tree-level density will have a high seedling density.The number of seedlings growing at all stations is expected to be a potential for recovery to replace dead stands [39].

Health Status of Mangrove Ecosystem
The health condition of the mangrove ecosystem can be determined by the percentage value of tree cover and the tree-level density at the research site (Table 3).The health status is relatively in a good condition with a percentage canopy cover of 85.18%, and mangrove density (2797 ind/ha) at the research site.Based on the Decree of Minister of the Environment Number 201 of 2004, the status of the mangrove ecosystem is categorized as good and dense based on and has a high species diversity (heterogeneous).
The result shows that management of this coastal ecosystem has been carried out well and can develop other potential to support the area's conservation function.

Conclusion
The results showed that nine mangrove species were found in the research location.The mangrove ecosystem in Anambas Islands is in good and dense condition, with a mangrove cover percentage of 85.18% and a density of 2797 ind/ha, and has a high species diversity (heterogeneous).The result shows that management of this coastal ecosystem has been carried out well and can develop other potential to support the area's conservation function.

Table 1 .
Environmental parameters in the research location

Table 2 .
Result of mangrove vegetation analysis

Table 3 .
Health status of the mangrove ecosystem