Changes of seagrass area in Beralas Pasir and Beralas Bakau Island observed from Sentinel-2 Satellite and verified by Unmanned Surface Vehicle (USV)

Today, the area of seagrass ecosystems in Indonesia is estimated to have shrunk significantly. Bintan Island has quite a large seagrass ecosystems area. Along with the development of satellite technology, monitoring of conditions and changes to a coastal ecosystem can be carried out effectively through remote sensing technology. One satellite image that is relatively new and has good spatial quality is Sentinel-2 with a spatial resolution value of 10×10 m2 / pixel. Field data retrieval is facilitated by the use of Unmanned Surface Vehicle (USV). This research went through several stages such as image pre-processing, water column correction, masking, unsupervised classification, and detection of changes of seagrass area. The data obtained from the USV becomes the data for the accuracy-test in the supervised classification. Seagrass area was obtained in Beralas Pasir and Beralas Bakau Island is 84.27 ha (2016), 81.3 ha (2019) and 77.4 ha (2021). Detection of seagrass to non-seagrass area changes resulting 31.35 ha (2016-2019) and 30.91 ha (2019-2021). On the other hand non-seagrass to seagrass area is 24.84 ha (2016-2019) and 27.98 ha (2019-2021). The accuracy test of 2019 image classification and Unmanned Surface Vehicle data resulting overall accuracy at 62.20%.

Estimation of soil carbon storage under mono-specific Enhalus acoroides meadows in Pari Island, Indonesia

Large seagrass meadows in Indonesia are predicted to have a significant ability in capturing and storing carbon and are useful to mitigate global climate change. However, most of the available data are derived from short-term carbon storage of living biomass, whereas data on long-term carbon storage in the soil is still limited. This study, therefore, aims to measure soil carbon storage in mono-specific Enhalus acoroides meadows in Pari Island. A total of nine soil cores was collected in a 100×100 m2 area. The parameters were soil depth, dry bulk density (DBD), and Corg content. We applied a PVC corer with 7.4 cm in diameter and 80 cm in length to collect the soil. The length of the soil core varied between 8 and 67 cm. The mean (±SE) of soil dry bulk density is 0.98±0.04 gr/cm3 and the median is 1.1 gr/cm3, while Corg content is 2.1±0.1% soil DW (mean±SE) and 1.9% (median). E. acoroides vegetation in Pari Island stores around 63 Mg Corg/ha organic carbon in 8-67cm or 34cm (mean depth) of topsoil. Carbon storage of these mono-specific meadows is comparable to soil carbon storage in the seagrass ecosystems per hectare areas on national, regional, and global levels.

Country-specific emission factor for developing a tier 3 system of Indonesia’s seagrass carbon inventory

Climate action regarding carbon inventory requires baseline assessment, data regarding annual changes, and evaluation of reductions in carbon emissions. However, many studies of seagrass ecosystems have focused only on carbon stock and sequestration, neglecting the importance of the carbon emission factor. It is known that emission factors for land-use change, including those in seagrass ecosystems, can be derived from biomass and sediment carbon stock. Since currently Indonesia only has data for biomass carbon stock, we propose the measurement of province-based emission factors. This study combines the available carbon stock data reported in national or international publications and conducts a meta-analysis to obtain emission factor values. The results show that the biomass standing carbon stock of Indonesia’s seagrass meadows ranges from 0.30 tC/ha (i.e., Special Region of Yogyakarta) to 16.51 tC/ha (i.e., Gorontalo province), while emission factor ranges from 0.012 tC/ha/yr to 0.661 tC/ha/yr (equal to 0.05 t CO2/ha/yr to 2.42 t CO2/ha/yr). These findings will be beneficial for developing Tier 3 carbon inventory since they allow country-specific emission factor for the seagrass ecosystem to be measured.

Seasonal Dynamics of Bathyarchaeota-Dominated Benthic Archaeal Communities Associated with Seagrass (Zostera japonica) Meadows

Little is known about the seasonal dynamic of archaeal communities and their potential ecological functions in temperate seagrass ecosystems. In this study, seasonal changes in diversity, community structure, and potential metabolic functions of benthic archaea in surface sediments of two seagrass meadows along the northern Bohai Sea in China were investigated using Miseq sequencing of the 16S rRNA gene and Tax4Fun2 functional prediction. Overall, Crenarchaeota (mainly Bathy-15, Bathy-8, and Bathy-6) dominated, followed by Thermoplasmatota, Asgardarchaeota, and Halobacterota, in terms of alpha diversities and relative abundance. Significant seasonal changes in the entire archaeal community structure were observed. The major phyla Methanobacteria, Nitrosopumilales, and genus Methanolobus had higher proportions in spring, while MBG-D and Bathyarchaeota were more abundant in summer and autumn, respectively. Alpha diversities (Shannon and Simpson) were the highest in summer and the lowest in autumn (ANOVA test, p < 0.05). Salinity, total organic carbon, and total organic nitrogen were the most significant factors influencing the entire archaeal community. Higher cellulose and hemicellulose degradation potentials occurred in summer, while methane metabolism potentials were higher in winter. This study indicated that season had strong effects in modulating bsenthic archaeal diversity and functional potentials in the temperate seagrass ecosystems.

Evaluation Methods of Change Detection of Seagrass Beds in the Waters of Pajenekang and Gusung Selayar

Knowledge about coastal and small island ecosystems is increasing for the monitoring of marine resources based on remote sensing. Remote sensing data provides up-to-date information with various resolutions when detecting changes in ecosystems. Studies have defined a shift in marine resources but were limited only to pixel or object classification in changes of seagrass area. In the present study, two classification method analysis approaches were compared to obtain optimum results in detecting changes in seagrass extent. It aimed to determine the dynamics of a seagrass ecosystem by comparing two classification methods in the waters of Gusung Island and Pajenekang, South Sulawesi, these methods being pixel-based and object-based classification methods. This research used SPOT-7 satellite imagery with 6 m2 of spatial resolution. Accuracy assessment using the confusion matrix showed optimum accuracy in object-based classification with an accuracy value of 87 %. Meanwhile, pixel-based classification showed an accuracy value of 78 % around Gusung Island. Pajenekang Island had accuracy values of 69 % with object-based classification and 65 % with pixel-based classification. A comparison of both classification methods revealed statistically high accuracy in mapping the benthic habitats of seagrass ecosystems. The results of the classifications showed a decline in the area of seagrass populations around Gusung Island from 2016 - 2018 and around Pajenekang Island from 2013 - 2017, with a change rate of 11.8 % around the island of Gusung and 7.6 % around the island of Pajenekang. This can explain the reason for the temporal method of object-based research classification having the best potential to process data changes in areas of seagrass in South Sulawesi waters and remote sensing information for the mapping of coastal area ecosystems. HIGHLIGHTS Information on coastal ecosystems globally with remote sensing data is currently very easy to access, but information related to ecosystem management and seagrass ecology in certain areas is still limited Analysis of seagrass benthic changes in shallow water requires data processing methods with high accuracy The OBIA (Object Based Image Analysis) method is one of the analytical methods that can provide optimal results in observing changes in seagrass ecosystems in the waters of South Sulawesi, Indonesia GRAPHICAL ABSTRACT

Association patterns of seagrass with gastropods types in the intertidal zone of coastal waters, Suli village, Salahutu district, Ambon island

Seagrass beds play an important role in coastal aquatic ecosystems and are one of the tidal areas that are widely used by the community as a forum for the interests of educational institutions in research activities, conservation of various marine biota. Ecologically, the seagrass ecosystem acts as a shelter and a place to eat various marine biota, including gastropods. The purpose of this research is not only to explore the diversity of gastropods, but also to examine the interactions of gastropod species, both between the same species and between different species in a community of seagrass ecosystems. The diversity index calculation shows the diversity index value H = 3.982 > 3, this means that the diversity of gastropod species is quite good. The results of the basic analysis obtained the calculated X2 value of 0.656, > X2 table with a significant level of 0.05%. There is an association relationship between seagrass ecosystems and the types of gastropods that live in seagrass ecosystems in coastal waters of Suli Village, Ambon. Keywords: Gastropods, Seagrass meadows, Association

Feeding ground indications are based on species, seagrass density and existence of Dugong dugon in Hiri Island Sea, North Maluku, Indonesia

Seagrass ecosystems are located between mangrove ecosystems and coral reefs. Seagrass ecosystems are habitats and foraging area for many marine organisms. Eco-biological cycles in seagrass ecosystems are important for maintaining populations of many organisms. Seagrass at Hiri Island is distributed horizontally along the coast. This island is also a location where Dugong dugon is found North Maluku. Dugong dugon is a vurneable species that has been included in the IUCN and Appendix I Cites. This study aimed to identify species, density of seagrass and existence of Dugong dugong. The survey method used quadratic transect method to collect seagrass data. The Results found 6 species of seagrass at Hiri Island. Five species of those seagrass (Cymodocea serrulata, Cymodecea rotundata, Halodule uninervis, Halodule pinifolia, Halophila spinulosa) are known as food of Dugong dugon. The highest species density was shown by Halodule uninervis. The presence of Dugong dugon and its feeding trail was found during field survey. Information on seagrass species and Dugong dugon sightings location can be used for endangered species conservation policies. Management and conservation efforts need to be done to maintain seagrass ecosystem and Dugong dugon potential habitat at Hiri Island.

Biomasa dan Simpanan Karbon pada Ekosistem Lamun di Perairan Batulawang dan Pulau Sintok Taman Nasional Karimunjawa, Jepara

Ekosistem lamun memiliki fungsi ekologi dan ekonomi yang tinggi. Peran ekosistem lamun dalam penyimpanan karbon akan tetapi masih belum menjadi sorotan. Tujuan dari penelitian ini yaitu untuk mengetahui nilai biomassa dan estimasi simpanan karbon pada ekosistem lamun di Perairan Batulawang, Pulau Kemujan serta Pulau Sintok, Taman Nasional Karimunjawa. Penelitian ini dilaksanakan pada 7 – 14 Noevmber 2019 di Perairan Batulawang dan Pulau Sintok, Taman Nasional Karimunjawa. Metode penelitian di lapangan menggunakan metode SeagrassWatch, sementara nilai biomassa dan nilai estimasi simpanan karbon dihitung menggunakan metode Metode Loss of Ignition (LOI) di laboratorium. Data yang diperoleh berupa pengukuran berat kering untuk menghitung biomassa dan analisa kandungan karbon pada lamun dan sedimen. Hasil penelitian didapatkan empat jenis lamun di Perairan Batulawang yaitu Enhalus acoroides, Thalassia hemprichii, Cymodocea serrulata, dan Thalassodendron ciliatum sedangkan di Pulau Sintok terdapat tiga jenis lamun yang ditemukan yaitu Thalassia hemprichii, Cymodocea rotundata, dan Halophila ovalis. Nilai total biomassa lamun terbesar pada Perairan Batulawang yaitu Enhalus acoroides dengan nilai 849,75 gbk/m2 dan nilai total biomassa lamun terkecil Thalassodendron ciliatum dengan nilai 29 gbk/m2. Nilai total biomassa lamun terbesar pada Pulau Sintok yaitu Cymodocea rotundata dengan nilai 177,75 gbk/m2dan nilai total biomassa lamun terkecil Halophila ovalis dengan nilai 4,75 gbk/m2. Hasil pengukuran karbon lamun pada Perairan Batulawang yaitu 12,97 – 359,87 gC/m2­ dan 258,20 – 541,51 gC/m2 pada sedimennya. Hasil pengukuran karbon pada lamun di Pulau Sintok yaitu 2,35 – 85,80 gC/m2 dan 204,92 – 765,92 gC/m2 pada sedimen. Kandungan karbon paling besar terdapat pada bagian bawah substrat (below ground). Kandungan karbon pada bagian bawah substrat tidak terganggu oleh faktor lingkungan (gelombang, arus, dan ulah manusia) sehingga terakumulasi baik. Seagrass ecosystems have high ecological and economic functions. The role of seagrass ecosystems in carbon storage, however, has not yet been highlighted. The purpose of this study was to determine the value of biomass and estimated carbon storage in seagrass ecosystems in Batulawang waters, Kemujan Island and Sintok Island, Karimunjawa National Park. This research was conducted on 7 − 14 November 2019 in Batulawang waters and Sintok Island, Karimunjawa National Park. The research method in the field uses the SeagrassWatch method, while the biomass value and the estimated value of carbon storage are calculated using the Loss of Ignition (LOI) method in the laboratory. The data obtained were measurements of dry weight to calculate biomass and analysis of carbon content in seagrass and sediments. The result shows that there are four species of seagrass in Batulawang Waters, they are Enhalus acoroides, Thalassia hemprichii, Cymodocea serrulata, and Thalassodendron cliatum meanwhile in Sintok Island there are three species, they are, Thalassia hemprichii, Cymodocea rotundata, and Halophila ovalis. The measurement of carbon is done by using Loss on Ignition Method. The highest total seagrass biomass in Batulawang waters is Enhalus acoroides with a value of 849.75 gbk/m2 and the lowest total seagrass biomass is Thalassodendron ciliatum with a value of 29 gbk/m2. The highest total seagrass biomass on Sintok Island is Cymodocea rotundata with a value of 177.75 gbk/m2 and the lowest total seagrass biomass is Halophila ovalis with a value of 4.75 gbk/m2. The results of measurements of seagrass carbon in Batulawang waters are 12,97 – 359,87 gC/m2­ and 258,20 – 541,51 gC/m2 on the sediments. The result of seagrass carbon measurement in Sintok Island is 2,35 – 85,80 gC/m2 and 204,92 – 765,92 gC/m2 on the sediments. The largest carbon content is at the bottom of the substrate (below ground). The carbon content at the bottom of the substrate is not disturbed by environmental factors (waves, currents, and human activities) so that it accumulates well.