The condition of megabenthos and reef fish in coral reef ecosystems in Aru Islands National Conservation Area, Southeast Maluku, Indonesia

. The waters of the Aru Islands are part of the National Marine Protected Areas (MNR), and have extensive coral reefs with high biodiversity. The study was conducted in October 2016 at twelve stations to determine the status of coral cover, composition, and density of megabenthos and reef fishes. Coral reef data collection refers to the Underwater Photo Transect (UPT), and data processing uses Coral Point Count for Excel (CPCe). The Benthos Belt Transect (BBT) method was used for megabenthos data, and the Underwater Visual Census (UVC) method was used for reef fish observations.The result of the benthic component analysis showed that the proportion of live corals at each station ranged from 10.60% to 54.27%, with an average cover value of 31.21%, which fell into the “fairly good” category. Megabenthos density analysis revealed that Drupella cornus had the highest density value (0.29 individuals/m 2 ) and Holohuria edulis (0.01 individuals/m 2 ) had the lowest density. Analysis of the reef fish community revealed that the indicator fish were 168 individuals from the family Chaetodontidae. The group of herbivore fish recorded 116 individuals from threee families: Acanthuridae, Scaridae, and Siganidae. Acanthurus auranticavus and Acanthurus pyroferus are common species found in the waters of the Aru Islands.


INTRODUCTION
Marine ecosystems vitality and continued viability are essential to the rich biodiversity they support and the economic and social well-being of dependent human communities.In this sense, the Aru Islands National Conservation Area in Southeast Maluku, Indonesia, is a vital region that requires thorough scientific investigation.The nature reserve covers an extensive land and sea area of around 114,000 hectares.In 1991, the official recognition of the area's ecological importance came from the Indonesian Ministry of Forestry (Decree No. 72 of the Ministry of Forestry (MoF).Kpts-II/1991) [1,2].This formal designation was fueled by research highlighting the islands as notable habitats for several species of sea turtles.
In March 2009, by Handover Protocol No. BA.01/Menhut-IV/2009BA.108/MEN.KP/III/, managing the region's marine nature reserve, was officially transferred to the Ministry of Maritime and Fisheries Affairs (MMAF) 2009.Subsequently, the MMAF formalized this Marine Natural Reserve (MNR) through Decree Number: Kep.63/MEN/2009 and designated the National Marine Protected Area Authority of Kupang as the competent administrative authority.As outlined by Dangeubun [3], the MNR operates under the terms of Ministerial Order No. Per.02/Men/2009, which focuses on forming marine protected areas through zoning strategies.The main objectives include (i) the protection and conservation of marine fish populations and essential marine ecosystems to maintain their ecological functions; (ii) facilitating the sustainable use of fish stocks and associated habitats; (iii) preservation of indigenous knowledge systems in the management of marine fisheries resources in the designated areas; and (iv) raising the standard of living of communities in the vicinity of the marine reserve.
Over the years, establishing the Marine National Reserve in the Aru Islands has been controversial.Although established, the reserve management has yet to produce desirable outcomes.There is also a need for more data regarding the various marine species that live in the region's coastal ecosystems.For instance, more information should be given regarding reef fish populations and megabenthos.This suggests the need for a more effective and targeted conservation strategy.The current management practices of the marine reserve have raised concerns about its sustainability, and it has jeopardized the biodiversity within it, which includes important species such as reef fish and the megabenthos, whose fate still needs to be discovered due to the lack of data.
To address the issues related to the reserve's conservation, the government should immediately implement rigorous research programs to fill the data gaps.These studies would not only provide a deeper understanding of the reserve's current condition, but they would also help guide future conservation efforts.Through the research, the government can establish a more community-oriented management model that would benefit the local population and the environment.
There is also a need for more collaboration among various groups to improve marine reserve management.This can be achieved through the involvement of government agencies, environmental groups, and local communities.Such engagements can help develop sustainable solutions that meet the unique needs of the region's marine reserve.The Aru Islands' marine reserve has existed for a long time.Still, its current management has yet to be able to effectively conserve its natural resources or provide the necessary benefits to the local communities.This is why the government and the various stakeholder groups must work together to improve the management of this resource.
Positively, the Marine National Reserve (MNR) in southeast Aru has been identified as one of the key sites for implementing the Coral Reef Rehabilitation and Management Program Coral Triangle Initiative (COREMAP-CTI).This initiative includes the start of baseline studies to assess the health of coral reefs and associated ecosystems.Therefore, the main focus of the present study is to study the biodiversity and population densities of fauna in these coral ecosystems, with a particular emphasis on megabenthos and reef fish.In addition, the study compares these results to data from other Marine Protected Areas (MPAs) or MNRs.

MATERIAL AND METHODS
This activity was carried out following the baseline study conducted by the Coremap program in October 2016 in the MNR of the southeastern Aru Islands situated between the south latitude of 6.8177° to 7.1375° and the east longitude of 134.3919° to 134.8189°.Observations were conducted on six small islands at 12 stations: the station ARC02 (Mar Island), ARC03 and 04 (Rataan Terumbu/Coral Reef), ARC05 and ARC06 (Jerudin Is), ARC07 (Jin Is), ARC09 and ARC10 (Jeh Is), ARC11 and ARC12 (Karang Is) and ARC13 and ARC14 (Enu Is).(Figure 1; Table 1).The coral reef condition was observed using Underwater Photo Transect" (UPT).The UPT method is carried out by photographing underwater substrates using a digital camera equipped with a protector (underwater casing).Pictures were taken along a 50 m rolling rule parallel to the coast at a depth between 5-7 meters.The objects were taken at a distance of ± 60 cm from the bottom, starting from the first object at the first meter with a length of 1 meter until the end of the transect line at 50 meters, so that the number of shooting results is 50 frames (photos).The technique of taking pictures is done by placing a frame made of iron with a size of 48 x 54 cm, placed on the first number (odd number) by touching the tape towards the flat coral (top) and then the second meter (even number) is placed on the video, towards the edge (bottom).The results of photo shooting will then be analyzed using a computer program (application) called CPCe 4.1, which will later be transferred to an Excel program (Microsoft) to obtain more accurate results.The data is exported to an Excel program so that the condition of the components inhabiting the coral reef ecosystem can be seen as a percentage (%) cover.Identifying rock coral species using the books of [4].
Megabenthos data were carried out using the Benthos Belt Transect (BBT) with the help of SCUBA diving equipment.This method is done by drawing a 70-meter line parallel to the shoreline at a depth of 5-7 meters.An observation width is around one meter on the left and right of the transect line.So, the area of Megabentos data is 70 x 2 = 140 m 2 .All Megabentos found in the transect recorded their species name and the number of each individual, especially those that became the target of this study.The criteria of megabenthos chosen as a research target are economically valuable and ecologically important biota, and their presence is closely related to coral health conditions [5].Megabenthos monitoring targets consisted of eight species: the Acanthaster planci (thousand feather star), Diadema spp.(black sea urchin), "Holothurian" (sea cucumber), Linckia laevigata, Lobster (barong shrimp), Drupella spp.(gastropod/snail species that live in coral crevices), Tridacna spp.(clams) and Trochus spp.(Lola).Species identification was referred to in the identification books of [6] and [7].
Reef fish data were collected using the underwater visuals census (UVC) method.The observation was made on a 70-meter transect line parallel to the beach or shoreline, with a 2.5 m observation area on the left and right of the transect line at depths ranging from 5-7 meters.So, the observation field for reef fish is 70 m x 5 m = 350 m 2 .The reef fish found along the transect line were counted for species diversity and the number of each species.Reef fish species identification refers to the identification books of [8] and [9].
Data analysis included species diversity and fish abundance, or density (individuals/m 2 ) of megabenthos and reef fish species found during the observation.For coral cover (benthic habitat), data derived from photos of coral transects were used and analyzed using CPCe software.The percentage of coral cover was used to categorize the conditions into four groups: very good, good, medium, and bad if the coral cover was >75%, 50-75%, 25-50%, and <25%, respectively.Correspondence analysis (CA) was also used to determine the relationship between the abundance of target reef fishes and live coral cover.Analyze the relationship between megabenthos, target reef fish, and biotic components using free software R [10].

RESULTS AND DISCUSSION
The results showed that the percentage of live coral cover at each station in the MNR southeast Aru Islands ranged from 10.6 to 54.37%, with an average of 31.2% or in medium condition [11].The highest percentage of live coral cover was found at two stations, ARC04 and ARC02, with percentage covers of 53.2 and 54.3%, respectively, or coral at these stations was in good condition.Seven stations were categorized as the medium condition, with percent cover ranging from 26.5 to 50.3% (ARC03, ARC 06, ARC 09, ARC11, ARC12, ARC 13, and ARC14), while the worse condition < 25% were found in 2 stations (ARC05) with the lowest one of ARC07 with percent cover of 10.6% (Figure 2).
In addition to the percentage of live coral cover (HC), other benthic categories that influence coral reef communities, such as rubble (R), sandy (S), silt (SI), and dead coral with algae (DCA), have a reasonably high percentage at several stations.The percentage of rubble covered at each station ranged from 1.13-52.53%,with an average cover of 23.33%.The highest rubble cover was found at station ARC05 and the lowest at station ARC07.The sand (S) component ranged from 0.07 to 43.13%, with the highest percentage covered at station ARC07 (43.13%), followed by Silt (SI) ranging from 1.87 to 47.80%.The percentage of DCA in the Aru Islands ranged from 0.54 to 18.40%, with an average value of 5.52%.The highest DCA was found at station ARC07, close to settlements and open, while the lowest DCA was found at station ARC05.The average cover percentage of these four component categories can affect the growth of live coral colonies in the Aru Islands.This can be seen from the high level of these four components found at several stations (stations ARC03, ARC05, ARC07, ARC09, ARC12, ARC13, and ARC14), thus affecting the percentage of live coral cover (HC).The low coral cover (HC) and the high number of other components (R, S, SI, and DCA) are influenced by several factors, such as stormy wave conditions, coral collected for building materials, and destructive fishing resources (dismantling coral reefs and the use of bombs and potash).Other components, such as dead coral (0.01%), soft coral (3.00%), and sponge (0.97%), have a low average percentage cover values.Generally, the percentage cover of these components at each station is lower than live corals, and their presence does not affect the growth of live coral colonies.Coral reefs in any coastal area are vulnerable to change (damaged) and require a long time to recover and return to good condition.Many studies report that anthropogenic influences (increased activities on land due to population growth and direct human interactions) accelerate the rate of physical damage to coral reefs.Impacts caused by human recreational activities on coastal ecosystems have shown clear impacts on fish and coral communities [12,13].Turbid water conditions with high sedimentation due to community activities on small islands and their surroundings will affect the coastal ecosystems of mangroves, seagrass beds, and especially coral reefs.It will affect the growth of hard corals and other benthic components.Differences in diversity and species distribution of hard coral colonies of various growth types at each location are strongly influenced by the hydrological conditions of local anthropogenic waters and human activities on the coast.The result of this will affect the condition of the reef both biologically and ecologically [14].
Some previous research results in other waters in Indonesia using relatively the same sampling methods and equipment showed varying percentages of live coral cover, as shown in Table 2 [15].The results of this study have a relatively high rate of coral cover.They are slightly lower than observation sites located far from the shore or in fairly clear waters with good water circulation.Many factors can influence coral diversity and percentage cover at various locations, in addition to natural factors such as differences in water topography, storms, tsunamis, pollution, acidification, and climate change [16,17].Destructive human activities, using environmentally unfriendly fishing gear, and anthropogenic inputs into coastal waters can cause changes in microhabitats that will affect the rate of damage compared to the rate of coral recovery and growth.[18] Table 2. Percentage of live coral in several locations in Indonesia compared to this study [15].

No. Locations
Number Table 3 shows the megabenthos found during the observation.A total of 49 specimens belonging to 5 species were collected from 12 stations, which consisted of 2 taxa of Echinoderms, Diadema setosum (17 specimens) and Holothuria edulis (1 spesimen), and three taxa of Molluscs, Drupella cornus (34 specimens), Tridacna squamosa (13 specimens) and Trochus sp.(10 specimens).Thus, the species diversity of megabenthos in MNR of southeast Aru was shallow compared to the megabenthos in Buton Islands [19] in the east Sumba Regency waters [20], and Ternate islands [21], which found 7-8 species.The presence of each megabenthos group in each location cannot be separated from the condition of the coral reef as a living habitat for this various biota.Among the megabenthos diversity, Molluscs were dominated in the southeast Aru MNR than the Echinoderms, particularly the Drupella cornus (Muricidae), which has a relatively broad distribution with percentage of occurrence of 34% followed by Tridacna squamosa and Trochus sp.(25%).The distribution and presence of Drupella cornus are due to its attraction to coral polyps as food targets, but not all coral species are food targets for Drupella; in which they prefer the coral species of Acropora spp.Thus, It means that the more species of Acropora spp., the greater the chance of getting the Drupella genus in the coral reef ecosystem.Therefore, the genus and abundance of Drupella could indicate coral reef health since they become natural predators that can damage the coral reef ecosystems worldwide [22,23].
The percentage of individuals from the Echinodermata group found during the observation showed that Diadema setosum had a percentage value of 10.2% and Holothuria edulis 2.0%.While from the mollusk group, Drupella cornus was recorded to have a high percentage value of the number of individuals (40.8%), followed by Tridacna squamosa (26.5%) and Trochus sp.(20.4%).When viewed from the distribution of megabenthos species, D. cornus has a reasonably wide distribution compared to other species.Of the twelve stations observed, this species was present at five stations, with a percentage value of presence of 35.71%, followed by T. squamosa and Trochus sp. with 21.43% each.While H. edulis has the lowest percentage of company (7.14%), it is only found at 1 station.Holothuria edulis have a minimal distribution and are only found at station ARC10, with a low-density value (0.01 individuals/m 2 ).The limited distribution of sea cucumbers with low individual abundance in Aru Islands waters is suspected of overfishing by coastal communities or fishermen.Sea cucumbers have a high enough selling value to become a target catch for sale or self-consumption.In the research area and its surroundings, there are many collectors of marine products so that the community or fishermen can quickly sell their catch.Holothurian (sea cucumbers) are large and abundant members of the aquatic benthic community, but over-exploitation worldwide has caused concern because of their essential role in the ecosystem.Sea cucumbers play a significant role in bioturbation, deposit-feeding, reducing organic load, and redistributing surface sediments, serving as bioremediation for coastal mariculture and acidification controllers [24].Overexploitation can degrade sediment health and minimize nutrient recycling and the transfer of organic matter from detritus to higher trophic levels.
The limited presence of Tridacna squamosa at some stations is also due to high capture by local people for meat.The clinging way of life makes the species easy to catch during high and low tides.T. squamosa, found during this observation, has a reasonably large shell size (> 30 cm).The low number of Trochus sp. is due to the unsuitability of the coral reef environment and habitat type, which is generally dominated by sand.Trochus sp.always lives in coral reef areas dominated by coral, hard corals, live corals, and dead corals, and overgrown with green and brown algae, which are its leading food.This species actively forages at night and is rarely seen on the substrate's top of the reef or surface, and it always takes refuge in coral holes or behind rocks during the day.In some coral reef waters in Indonesia, the Tridacna family and Trochus sp. are increasingly challenging to find.So, all forms of capture/collection from nature or utilization and trade have been regulated and limited in Appendix II IUCN.
The mega benthos density value at each station varied, ranging from 0.01 to 0.11 individuals/m 2 (Figure 3).Station ARC04 had the highest relative density value, 0.11 individuals/m 2 .The high value of individual density at this station was influenced by the presence of T. squamosa, which amounted to 60% of the total individuals.The abundance of T. squamosa individuals at this station could have been caused by clear waters, coral reefs in reasonably good condition (54.27%), and having the highest percentage value of live coral cover in the coral reef area of the observation area.At the same time, the lowest individuals were found at stations ARC03 and ARC12 (0.01 individuals/m 2 ).The low density is found at stations ARC03 and ARC12, each with 0.01 individuals/m 2 .At these two stations, only one mega benthos species each was found, represented by T. squamosa and D. setosum.Benthic composition dominated by broken dead coral "rubble" (37.87% and 40.13%), fine sand (29%), macroalgae (16.80%), and turbid waters are thought to have influenced the species composition and abundance of individuals at both stations.In general, turbid, choppy water conditions and high human activity can affect the presence of "sessile" mega benthos associated with coral reefs.The density of Drupella cornus at all observation stations was in the relatively lowdensity range (0.29 individuals/m 2 ).The density of Drupella in the Aru Islands was lower than those from the waters of Perlang Village, Bangka Belitung [25], Kendari waters [26] or East Sumba waters [20].However, the density of Drupella snails in Senggigi Beach was slightly higher than the density of Drupella from nearby waters, namely in Sekotong Bay [27] or other areas such as Buton Island [19] and Waworaha waters [28].The presence of Drupella at low densities does not significantly impact damage to coral species targeted by their prey.[29] stated that although there is no significant relationship, the presence of Drupella strongly correlates with coral reefs as parasitic animals.Some studies say that the presence of Drupella in a coral colony is closely related to the health condition of the reef and generally tends to attach to unhealthy coral colonies.This means that if the target coral species is in good condition, Drupella will not stick to the coral.
Diadema setosum is usually found in quite a large number of individuals on sand substrates with clear water.However, in this observation, the genus Diadema was found in a deficient number of individuals with limited distribution and was only found in stations ARC10 and ARC12.The low abundance of D. setosum in Aru Islands waters is related to the low mean percentage of dead coral covered with algae (DCA) (5.2%) since the leading food of this species and other starfish is benthic algae [30].This group is a macroalgae and microalgae eater, capable of controlling the growth and spread of algae (Hernández et al., 2008), thus providing space for coral planula growth.The low diversity of species and the number of individual megabenthos can be caused by high human activities in coastal waters and hydrological factors such as currents and waves so that megabenthos living on the substrate will easily move to a quieter place or a protected place.
In terms of species diversity, Figure 4 shows the results of the UWS reef fish at 12 stations in the MNR southeast Aru Islands for three groups of reef fishes: the Corallivores or indicator fish (Chaetodontidae), the herbivores (Acanthuridae, Scaridae, and Siganidae), and the carnivores (Serranidae, Lethrinidae, Lutjanidae, Labridae, Mullidae, Haemulidae, Nemipteridae, and Holocentridae).The highest number of total reef fish was in the carnivore group, with 44 species (67%), followed by the corallivore group, with 11 species (18%), and the herbivore group, with nine species (15%).
The highest carnivore groups were found in the stations ARC05 and ARC13 (12 species), followed by ARC11 (11 species), ARC10 (10 species), ARC04 (9 species, ARC03, and ARC14 (8 species).In contrast, the species diversity at the rest of the stations were <8 species (Figure 4).The carnivores group was dominated by Lutjanus carponotatus, Scolopsis monogramma, and Choeronodon anchorago species.The highest corallivore groups were found limited in 2 stations, the ARC03 (7 species) followed by ARC04 (6 species), while other rest stations <5 species.The dominant species in this group is Chelmon rostratus.The other species of Chaetodon aurefasciatus and the Chaetodon sp2. that is suspected of being Chaetodon rainfordi was also found in the MNR southeast Aru Island.These species have a limited distribution in Indonesia's coral reefs and are only found around the waters of the Great Barrier Reef and southern Papua New Guinea [31].
The herbivore groups had the lowest species diversity; only 3 to 4 species were found in the stations of ARC07, ARC03, and ARC04.All the other stations have only about two species, with the dominant species being Acanthurus auranticavus.
In terms of reef abundance or density (Individual fish/m 2 ) (Figure 5), the herbivore fish dominated the density of reef fish with the density ranging from 12-31 fish/350m 2 with an average of 18.7 fish/350m 2, although in term of species diversity were low.The next abundance group was carnivores with density ranging from 4-40 fish/350m 2 and an average of 16.2 fish/350m 2 , while the lowest one was corallivores with density in the range of 5-26 fish/350m 2 and an average of 12.5 fish/350m 2 .Fig. 5.The density of corallivores, herbivores, and carnivores at each station.
The highest density of herbivores was in the stations ARC10 (40 fish/350m 2 ), followed by ARC11 (30 fish/350m 2 ) and ARC07 (28 fish/350m 2 ), while other stations < 20 fish/350m 2 .The species of Acanthurus auranticavus, Siganus lineatus, Scarus dimidiatus, and S. ghoban dominated the highest density of this group.The herbivorous fish group plays an essential role in the coral reef ecosystem as a controller of algae growth.It can provide a substrate for attaching new coral planula (reef recruitment).Several previous studies have shown that herbivorous fish are fast-growing and have a high density [32], [33] and play an essential role in the resilience of coral reef ecosystems [34].The large composition of herbivorous fish at these stations positively impacts the recovery of coral reef ecosystems by controlling and limiting the growth of algal communities [35].
The highest density of carnivores was in stations ARC10 (31fish/350m 2 ), followed by ARC13 (24 fish/350m 2 ), ARC04 and ARC11 (23 fish/350m 2 ), and ARC14 (20 fish/350m 2 ), while the rest other stations < 20 fish/350m 2 .The carnivore group's relatively high fish density is similar to the herbivore fish group.The highest density of carnivores reef fish was represented by the Lutjanidae family with Lutjanus carponotatus species, L. decussatus, and L. lemniscatus The highest density of the Chaetodontidae corallivores fish group is relatively evenly distributed at almost all stations.The highest density of this group was found at station ARC11 (26 individuals/m2) and the lowest at station ARC 09 (5 individuals/m 2 ).The presence of indicator fish groups (Chaetodontidae) with high species diversity can reflect the condition of coral health.[36] stated that Chaetodontidae is an indicator fish that eats coral polyps (corallivorous), which can be associated with predictions of coral reef health.The high and low density of corallivorous fish in a reef community can reflect the condition of corals under pressure or not.The observations at each station show that individual corallivorous species are relatively low and quite stable (20 individuals).This condition reflects that corallivorous fish species do not put significant pressure on live corals in the Aru Islands waters.
The results of the visual census show that the number of species and the number of reef fish individuals found in the MNR southeast Aru Islands waters is relatively low compared to several other locations in coral reef waters in Indonesia (Table 4).The diversity and composition of corals on a reef affect the diversity of reef fish species, meaning that the structure of the reef fish community is directly proportional to coral species and coral colony size [37].In general, hard corals (HC) were more influential than algae in the composition of associated biota (Table 5).Hard coral cover significantly correlated with Megabenthos abundance (p-value = 0.03) and herbivore species richness (p-value = 0.001).On the other hand, the algal cover was significantly correlated with herbivore species richness (p-value = 0.004).Other fish groups (corallivorous and carnivores) showed no significant correlation with either benthic category.Hard coral cover has the same interaction trend with megabenthos abundance and herbivore richness.In this case, megabenthos abundance and herbivore richness will generally decrease as hard coral cover increases (Figure 6a, b).However, a more robust interaction occurred between hard coral cover and herbivore richness (r 2 = 0.72).
The algal cover is generally positively correlated with herbivore richness (Figure 6c).However, the correlation was slightly weaker than the previous interaction (r 2 = 0.63).Therefore, herbivore richness was the category of associated biota most influenced by the benthic community.Reef fish abundance is not only influenced by the percentage of coral cover but also by biotic processes such as competition, predation, and distribution [43].In addition to different reef profiles and contours, substrate complexity [44], currents, depth and brightness [45], and exposure [56,47].The decreasing cover or loss of live corals can cause rapid declines in reef fish abundance across groups [48, 49, and [50].

CONCLUSIONS
In general, the percentage of live coral cover in the waters of the Aru Islands ranged from 10.60-54.27%,with an average cover value of 31.19%, and was included in the category of reasonably good cover.Megabenthos species from the mollusk group are relatively widespread compared to the echinoderm group.Utilization of megabenthos from economically valuable biota groups such as the genera Tridacna, Trochus, and Holothuria is relatively high.The composition of the largest reef fish group came from the carnivorous fish group (40 species, 11 families, and 244 individuals), followed by the herbivorous fish group from the Acanthuridae, Scaridae, and Siganidae families.The distribution and composition of benthic components that make up coral reefs in the waters of the Aru Islands affect the presence of megabenthos and reef fish.There is a relationship between Coral and Algae cover, Macrobentos, and Herbivore fish.Further Observation and monitoring are needed to update the coral reef ecosystem data in this Aru Marine Nature Reserve.

Fig. 1 .
Fig. 1.Map of MNR in southeast Aru showing study sites of coral reefs, megabenthos, and reef fish.

Fig. 4 .
Fig. 4. Species diversity of reef fish in each MNR Southeast Aru Islands station.

Table 1 .
Coordinates of transect in each station

Table 4 .
Species diversity and abundance of indicator and target reef fish in several observation sites in Indonesia.

Table 5 .
Interactions between benthic categories and associated biota with coral reefs.