Mahakam Delta Research Articles

Air and noise pollution analyses near oil and gas fields in the Mahakam Delta, Kalimantan, Indonesia

The Mahakam Delta is a strategic industrial area in East Kalimantan, Indonesia, in which oil and gas industries reduce ambient air quality and generate excessive noise. This research aimed to analyze the ambient air and noise pollution attributed to oil and gas production activities in the delta. Relevant parameters at five sampling points (UA-02 to UA-06) were measured and further analyzed in the laboratory, including total suspended particulate (TSP), SO2, Pb CO, NO2, O3, temperature, humidity, wind direction, wind speed, and noise. Indonesia’s air pollutant standard index (locally abbreviated as ISPU) with four parameters (CO, NO2, SO2, and O3) was used to determine the ambient air quality, and provisions written in the Decree of the Minister of Environment No. 50 Kep-48/MENLH/11/1996 were consulted for the noise quality assessment. Results showed ISPU values in the range of 0–50 at the five sampling points, suggesting good ambient air quality and compliance with Government Regulation No. 22 of 2021. In addition, it was revealed that the noise parameter was lower than the upper threshold set in the Ministerial Decree, namely 65 dB. Nevertheless, monitoring air and noise quality at the main pollutant sources should be regulated through policies and implemented to protect the public from exposure to potential pollutants.

Identification of the pest outbreak in the coastal mangrove ecosystem of Mahakam Delta, East Kalimantan, Indonesia

Abstract. Harmonis, Haqiqi MT, Fahroni MFA, Jefry, Gunawan S, Sekedang MA, Rahmat D, Azhar NF, Putra MOPS, Kusuma FD, Hapsari MT, Muhammad FA, Diana R, Sudarmadji T, Amirta R, Ariyanto, Saud OR, Sofyan FPM, Fajriansyah, Asngari AMS, Bulo YS, Salman I, Rizaldi R, Lubis KM. 2024. Identification of the pest outbreak in the coastal mangrove ecosystem of Mahakam Delta, East Kalimantan, Indonesia. Biodiversitas 25: 829-835. Mangrove ecosystems are considered the most essential areas in the wetland since they sequester carbon more efficiently than terrestrial ecosystems. Thus, they have received significant attention as a nature-based solution to achieve the Naturally Determined Contributions in the commitment to global climate change mitigation. Currently, the degradation of mangroves has been linked to serious threats, including pest outbreaks. Our primary objective was to assess the pest outbreaks that occurred in the coastal mangroves of the Mahakam Delta, Indonesia. This study was conducted in two areas in Tanjung (R1 and R2) and one area in Pulau (R3). A total of 19 observation plots with a size of 10 × 10 m2 were made. The water quality was further measured to identify the natural conditions affecting the outbreaks. In the present study, it was found that significant disturbance of the mangrove plants occurred due to invasions by Amphibalanus amphitrite Darwin, 1854 and Sphaeroma terebrans Spence Bate, 1866. The dangerous attack from S. terebrans has only been found at the R1 site, where we found environmental conditions such as high dissolved oxygen (DO), high total dissolved solids (TDS), and high salinity. In this area, it could affect the death of adult Avicennia alba Blume and Sonneratia alba Sm. The results obtained from this study are expected to provide preliminary data to design the best management practices in order to enhance the effectiveness of the mangrove rehabilitation strategy in the Mahakam Delta.

Characterizing deep groundwater using evidence from oil and gas exploration wells in the Lower Kutai Basin of Indonesia

Groundwater at depths exceeding 500 m can be an important source of freshwater. However, the characteristics of deep groundwater in many regions of the world, including Indonesia’s sedimentary basins, remain vaguely defined. This study investigates the pressure regimes, hydraulic head distributions, salinity, and hydrochemical facies of deep groundwater using available evidence from oil and gas exploration wells in the Lower Kutai Basin of Indonesia. Pressure measurements and wireline log data reveal three pressure regimes within the basin: hydrostatic, overpressure, and underpressure. The top of the overpressure varies, from close to the surface onshore to depths of ~4.5 and ~3.8 km in the Mahakam Delta and offshore, respectively. Computed hydraulic heads at the top of the overpressure range from ~191 m above sea level onshore to ~71 m below sea level offshore, and are indicative of regional groundwater flow. The observed salinity of deep groundwater within the basin indicates predominantly brackish or saline conditions. Fresh (total dissolved solids < 1 g/L) groundwater to a depth of ~2 km is found at a small minority of wells onshore and in the delta; no fresh groundwater is found offshore. Four hydrochemical facies are observed: Na+/Cl–, Ca2+/Cl–, Na+/HCO3–, and Na+–Ca2+/HCO3–. This study indicates that deep fresh groundwater in the Lower Kutai Basin is of localized occurrence. Recharge from meteoric water may replenish deep fresh groundwater within the hydrostatic zone and sustain water supplies, whether brackish or fresh. Water produced from clay diagenesis is also cited as a possible process of freshening deep groundwater.

Observation of waterbirds in mangrove forest: The need for habitat rehabilitation to maintain and utilize the bird species community in the Mahakam Delta

Waterbirds are relatively permanent inhabitants of mangrove forests and can come from either the mainland or very distant regions as migrant species. These birds serve as an important indicator for preserving biodiversity in general by maintaining mangrove forests through rehabilitation and restoration activities. Additionally, some species have good economic potential to improve community welfare, as well as current pond products such as fish and shrimp. This study aimed to observe bird species diversity in the mangrove area to understand its function and recognize the migratory species that can be the basis for strengthening preservation or conservation. The research sites were in the Mahakam Delta, which is located in Muara Jawa and Sepatin, Kutai Kartanegara, Indonesia. More than 60 birds were successfully identified. Only one species was classified as CR (critically endangered), namely Thalasseus Bernstein. Meanwhile, bird species that were classified as VU (vulnerable) included Leptotilus javanicus, Fregata minor, and Egretta eulopheutes. Four species, including Anhinga melanogaster, Ichtyopaga ichtyaetus, Macronus ptilosus, and Numenius arquata, were identified as NT (near threatened) species. Most of the species found were characterized as having LC (least concern) status.

Soil organic carbon stores in the mangrove forest restoration of ex-ponds in the Salo Palai Village of Kutai Kartanegara

Mangrove forests in the Mahakam Delta have traditionally been used by people for a variety of purposes, including fuel, hut construction, and charcoal production. Such use is still acceptable as long as it does not reach commercial scale. Where mangrove forests have greater potential for carbon absorption when compared to dry land. In this study, several analyses of bulk density, soil carbon (%), total soil organic carbon (g/cm2), total soil organic carbon (tonnes/ha) were analysed from 3 points with 3 depths (0-50.50-100.100- 150). Then an analysis was carried out using the t test to test whether there was a very significant difference or not. The results of this study showed that ponds without rehabilitation had a total bulk density value of 7.16 g/cm2 with a total soil organic carbon store of 0.34 tons/ha. In the former ponds the rehabilitation area has a total bulk density value of 8.64 g/cm2 with a total soil organic carbon store of 1.01 tons/ha. Based on the results of the t test analysis, it shows that t count > t (0.01) so that it can be said that rehabilitated former ponds provide a very significant difference to carbon storage.

Arbuscular mycorrhizal colonization of pioneer mangrove species in Mahakam Delta, East Kalimantan

Arbuscular mycorrhizal fungi (AMF) are symbiotic, with more than 80% of plant species in terrestrial and mangrove ecosystems. This study aimed to determine the level of AMF colonization on Avicennia lanata and its correlation with soil chemical properties. Sampling was conducted in Sepatin Village, located in Mahakam Delta. There are four sampling locations, three were mangrove rehabilitation areas (A, B, and C), and one was a mangrove natural forest (MNF). Root samples were taken from four A. lanata seedlings purposively selected at each location. The roots were stained with 0.05% trypan blue, and the mycorrhizal structures of the roots were observed using a compound microscope. The results showed that the percentage of AMF colonization with A. lanata in MNF was higher (97%) than in other locations. Internal hyphae were the dominant structure found in the root of A. lanata in all locations, with a percentage of 76.61%. AMF root colonization negatively correlated with N-total, C-organic, and available P. In contrast, Ca, Mg, K, Na, and CEC positively correlated with AMF root colonization. The colonization of AMF in the root of A. lanata may promote the early growth of seedlings, and the application of AMF can support rehabilitating mangrove degraded.

Relief (Recursive Elimination of Feature) method for Solar Home System (SHS) analysis in Delta Mahakam

The area of Delta Mahakam has not been accessible by an electricity network for a long time and has been relying on gasoline as a source of electric power generation for daily and economic activity. The community uses the Solar Home System (SHS) unit for their home and public facility. The provision of these SHSs units was an activity of a community development program from a company having industrial activity in the area. This research aims to identify the SHS unit’s condition and the attributes relevant to the condition of the SHS unit. An SHS condition was determined by gathering data on the technical specification such as unit power size and battery capacity, electricity utilization, and its financing model. Data is collected using field survey, data collection, and interviews with respondents. The data was then analysed by the Recursive Elimination of Feature (Relief) method to select features sensitive to the condition of the SHS unit. The result of this study showed that the majority of SHS units are still functional to satisfy the electricity need. The set of attributes used in this research were accurate for the intended classes of SHS condition. This result provides information beneficial to improve the existing program and impact the community.

Sedimentary Environments and Paleoclimate Control of the Middle Miocene Balikpapan Group, Lower Kutai Basin (Indonesia): Implications for Evaluation of the Hydrocarbon Potential

Sedimentary organic matter concentrated in source rocks forms the main source for the formation of hydrocarbons. Its deposition and preservation are strongly controlled by the depositional environment and paleoclimate. This study evaluates the paleoenvironment and the paleoclimatic controls of sediments in the Middle Miocene Balikpapan Group, Mahakam Delta of the Lower Kutai Basin, Indonesia. The sedimentary succession of the Mentawir Formation, encountered in three wells (MHK 1, MHK 3, and MHK 4), contains interbedded sandstones, siltstones, shales, and coal. Gamma ray log analysis has revealed four facies associations: (a) funnel-, (b) bell-, (c) cylindrical-, and (d) bow-shaped patterns, which, together with sedimentological and mineralogical analysis, suggest a fluvio-deltaic depositional environment during the Middle Miocene in the study area. Sedimentary successions from wells MHK 1 and MHK 3 comprise interbedded sandstone and siltstones and are interpreted to represent repeatedly occurring delta plain, delta front, and prodelta deposits. The succession encountered in well MHK 4 mostly consists of amalgamated sandstones and indicates a predominantly fluvial to upper delta plain environment with distributary channels and crevasse splays interbedded with only thin delta front deposits. X-ray diffraction–clay fraction analysis shows that the &lt;2 μm clay-sized fraction consists of kaolinite (38%–67%), illite (14%–29%), chlorite (2%–17%), and mixed-layer illite/smectite (I/S) (14%–30%). Kaolinite formation and abundance indicates a hinterland climate classified as type Af (tropical rainforest) and intensive chemical weathering conditions in the source areas related to tropical to sub-tropical climates with high precipitation. Under such climatic conditions, kaolinite and I/S mixed-layer minerals are preferentially formed because the characteristic ions, K+, Na+, Ca2+, and Fe2+, are leached away. Thus, the production, transport, distribution, and preservation of sedimentary organic matter in the onshore Mentawir Formation of the Balikpapan Group are predominantly controlled by the humid tropical climate and fluvio-deltaic processes.

Traditional polyculture as a mangrove restoration solution in Delta Mahakam, East Kalimantan Indonesia

The Mahakam Delta is a large mangrove ecosystem in East Kalimantan with a precious ecosystem and a massive mangrove species. Because of the conversion to shrimp aquaculture, the mangrove ecosystem has been devastated. This study looks at shrimp pond management in Salo Palai, Muara Badak, Kutai Kartanegara, East Kalimantan, using the traditional polyculture concept to increase pond productivity. The current shrimp pond condition was decreased water quality, substrate infertility, and natural food availability crisis. This model focused on traditional management, with a particular emphasis on pond preparation, polyculture, and used plant extracts. For 100 days, Penaeus monodon, Chanos chanos, Litopenaeus vannamei, Lates calcarifer, Scylla spp., and Gracilaria verrucosa were grown in the same time and pond. The yield from the pond was thrived: 332.14 kg/Ha. This concept can be used to restore mangroves, preserve the mangrove ecosystem, increase shrimp pond production, and protect the sea ecosystem; thus, this method achieves sustainable aquaculture.

Training on Making Antiseptic Liquid Soap for Mangrove Type Pedada (Sonneratia cassiolaris) to the Community in Tani Baru Village, Anggana District, Kutai Kartanegara Regency, East Kalimantan Province

One of the efforts to increase public awareness of the importance of preserving mangrove ecosystems in the Mahakam Delta is by developing the capacity of the community to be able to take advantage of the potential of existing mangroves in the Mahakam Delta region. When the community is able to obtain economic value from the utilization of non-timber mangrove forest products, it is hoped that public awareness of the existence and sustainability of mangrove forests will increase. One of the mangrove products that has economic value and is a daily need for the community is an antiseptic liquid soap with the addition of pedada (Sonneratia cassiolaris) mangrove fruit extract. Antiseptic liquid soap with pedada fruit extract can be utilized and meet the sanitation needs of the community in Tani Baru Village, Anggana District, Kutai Kartanegara Regency as one of the villages in the Mahakam Delta region in particular. With the training on making bacada fruit antiseptic liquid soap, the aim is for the community to be able to increase their creativity in exploring pedada-type mangroves into a product that provides added value and high economic value. The results that have been achieved in this training are that the community is able to make their own antiseptic liquid soap for their daily needs and can open up business opportunities in entrepreneurship

ASSESSING THE IMPACT OF MANGROVES IN TRADITIONAL SHRIMP FARMING IN THE MAHAKAM DELTA USING A COST BENEFIT ANALYSIS

Mangroves began rapidly converting into shrimp-farming ponds in the Mahakam Delta, East Kalimantan, Indonesia. In 2000, the government launched the mangrove reforestation project, but the expected outcome was not achieved. Evaluation and recommendations are needed to attain the economic and environmental sustainability benefits of ponds with planted mangrove plants mandated by the government. This study examined the feasibility indicators of ponds with and without mangrove systems and analysed the feasibility of aquaculture pond performance. The results showed that the polyculture ponds with mangroves were more beneficial than the other pond systems, accruing more than 3.55 million IDR/ha/yr in net income. The polyculture pond with 10% mangroves showed the highest feasibility and benefits. The NPV, IRR, BCR, and PP were IDR72 million/ha/yr, 22%, 2 and 4.8 years, respectively. Therefore, the polyculture ponds with 10% mangroves were the best recommendation for farmers for the next 25 years. Government policy should facilitate improving environmental quality and sustainability in the Mahakam Delta.

Soil carbon stock in different of mangrove ecosystem in Mahakam Delta, East Kalimantan, Indonesia

Mangrove forests serve as a buffer against sedimentation from the mainland into the sea, protect the area from coastal erosion, and prevent seawater intrusion in some ecological types of coastal environments. Additionally, because soil and below-ground biomass retain a significant quantity of carbon, they are essential for carbon sequestration. The current study seeks to estimate the soil organic carbon stock of mangroves associated with natural regeneration, mangrove rehabilitation areas and abandoned shrimp ponds, in Mahakam Delta, East Kalimantan, Indonesia. A 125-meter-long transect line was used to collect data, with three sampling points representing the length of the transect line. Each soil sample was taken at three different depths: 0-50 cm, 50-100 cm, and 100-150 cm. After that, the samples were taken to the laboratory for carbon analysis. The mangrove rehabilitation area had the highest bulk density at 8.64 gr/cm3, followed by natural mangroves along the river border at 7.67 gr/cm3, and abandoned ponds had the lowest at 7.16 gr/cm3. The rehabilitation area had the highest soil carbon stock at 1120 tons/ha, followed by natural mangroves along the riverside at 686 tons/ha and abandoned ponds at 383 tons/ha. In accordance with the study, mangrove rehabilitation regions had larger soil carbon stocks than natural regeneration along the riverside and abandoned ponds. In order to protect the ecologically significant mangrove ecosystem and minimize the effects of climate change, mangrove restoration and rehabilitation are necessary.

Technology Focus: Reserves Management (December 2022)

We continue to live in volatile times. While there has been an easing of the global pandemic, geopolitical issues and conflicts have been increasing. There is also ever-increasing pressure to sanction and maintain oil and gas projects in a socially and environmentally sustainable manner. These projects can no longer be considered part of an isolated or independent petroleum sector but as part of the whole resource base of an area, country, or region. There needs to be visibility of the linkages among company vision; national, regional, and global targets; and the project attributes in meeting sustainable development goals and maintaining good governance. Paper SPE 205603 is a good example of a systematic approach to managing oil and gas reserves and resources data that has been assessed using the SPE Petroleum Resources Management System (PRMS). It is important for entities to accurately capture the information gathered during resource evaluation to use for strategic planning and sound resource management. We have been encouraged with the ongoing adaption of PRMS and many of the recommendations of the system, including the use of project-maturity subclasses. We would like to provide a cautionary note that several papers in the 2021–22 cycle highlight the need to ensure that management of resources complies with the requirements of PRMS when they say they do—for example, that when modifications are made to the system, the project still meets the requirements for inclusion in a particular class, such as discovery for contingent resources; and that discovered unrecoverable resources are not contingent resources. Paper SPE 207801 is a case study in trying to apply the principles of sustainable resource management by repurposing oil and gas wells for geothermal production. The paper follows a systems approach to testing the principles of the circular economy (though this term is not used in the paper). A circular economy is a systems approach that enables the resource to maintain its highest value for as long as possible. Critical considerations in implementing circularity are reducing and rethinking resource use and pursuing longevity, renewability, reusability, reparability, replaceability, and upgradability for resources and value-added products. Paper SPE 208483 discusses the challenge of decommissioning oil and gas equipment in Australia. The paper is a comprehensive discussion that highlights the importance of good regulation and the development of visible and robust decommissioning plans by industry titleholders. This important issue will resonate at a global scale and underlines the importance of a lifecycle focus on decommissioning rather than a just-in-time approach, which may not optimize costs or engender safe and environmentally responsible practices. Finally, we encourage you to seek out the additional reading material. Topics include good governance in exploration planning, testing pathways to decarbonization for remote offshore gas fields, an integrated subsurface study, and an example of the complementary use of PRMS and the United Nations Framework Classification. Recommended additional reading at OnePetro: www.onepetro.org. IPTC 21458 The Dusk of the Minimum Economic Field Size in the Digital Era of Exploration Value Creation by Dmitry Surovtsev, Schlumberger, et al. OTC 30941 Pathway to Decarbonization and Maximum Value Recovery for Remote Offshore Gas Fields by Lee Thomas, Intecsea, et al. SPE 205688 Integrated Subsurface Study To Convert Upside Intrabeta Subzone Stakes Into Additional Main Targets in Tunu Gas Field, Mahakam Delta, Indonesia by Dwiki Drajat Gumilar, Pertamina Hulu Mahakam, et al. SPE 207055 The United Nations Framework Classification Concept and the Possibility of Its Application in Azerbaijan by Narmina Garayeva, Baku Higher Oil School, et al.

Analisis kelimpahan plankton dan pertumbuhan kerang kepah Polymesoda erosa (Solander, 1786) yang dipelihara pada tambak di Delta Mahakam

This study was aimed to analyze the prospects of development of the This research was aimed to analyze the relationship between plankton abundance and morphometric growth of Mud Clam (Polymesoda erosa). The study was located in an idle brackish water pond in Mahakam Delta, by culturing Polymesoda erosa in small scale. Grouping random design was applied for sampling. Treatment was divided into factor A and B. Factor A is related to shell size: size I (40 – 60,99 mm), II (61 – 80,99 mm) and size III (81 – 100 mm). Factor B is indicating to study location with vegetation (Rhizophora sp) and no vegetation. In order to analyze plankton abundance, a quantitative descriptive analysis was applied, in addition of ANOVA test to analyze the growth. The result indicated that between two study ponds is different. The number of plankton per liter water from vegetated pond has more plankton individual than the sample from non-vegetated pond. The applied treatment on study ponds and shell size determined the morphometric growth and biometric. The growth of shell length is faster than that on height and thickness. The growth of mud clam in vegetated ponds relatively better that the pond without vegetation.

The diversity of plant species in the proboscis monkey’s habitat as a species reference for habitat restoration

Most of the Proboscis monkey (Nasalis larvatus) habitat is outside the protected area, so the potential for destruction is high. One of the efforts to improve its habitat is habitat restoration. This study aims to determine plant species for proboscis monkey habitat restoration based on reference habitats. The research was conducted at eight locations in East Kalimantan, Indonesia i.e. Kuala Samboja, Mahakam Delta, Suwi River, Ohong River, Berau Delta (mangrove and riverine), Sungai Wain, and Kutai National Park. Vegetation analysis with line-plot sampling method with a total sample of all locations of 11.7 ha. The results showed that the habitat included three main types: mangrove, riverine, and riverine-near coastal. A total of 152 tree species, 41 of which were potential proboscis monkey feed. The highest plant species diversity value was in the riverine forest-Berau Delta of 1.25, while the lowest was in the mangrove forest-Berau Delta of 0.54. Species that are a food source and have good adaptation in riverine habitat are Vitex pinnata, Dillenia excelsa, Garcinia spp, Heritiera littoralis, Ilex cymosa, Cerbera manghas, Hevea braziliensis, and Sonneratia caseolaris. Whereas in mangrove habitat are Avicennia alba, A. officinalis, Bruguiera gymnorrhiza, B. parvifolia, Rhizophora apiculata, and S. alba. They are recommended for habitat restoration.

A Kinetic Explanation for Combined Potassium Gains and Radiogenic 40Argon Losses of Diagenetic Illite-Rich Clay Separates

In this study, a kinetic model sketches the concomitant K gain and radiogenic 40Ar loss of clay separates recovered from progressively buried sediments. Published K-Ar ages of clay separates from the Mahakam Delta, the Texas Gulf Coast, and the North Sea were used to constrain the modeling. As compared with analytical results, the model simulates changes relative to depth or to deposition time of the K-Ar ages from fine- and coarse-grained clay crystals. The decrease in the K-Ar ages of detrital-rich coarse-grained fractions (&gt;2 μm) is bracketed with depth by K addition rates between 0.2 and 3.5%/Ma and slightly higher 40Ar release rates between 0.5 and 4.5%/Ma. The former rate varies from 3.5 to 6%/Ma in the fine-grained fractions (&lt;0.4 μm) and the latter rate varies from 0.7 to 6%/Ma in the same fractions. In fact, the K addition and the radiogenic 40Ar release rates record independent processes on different material sizes and types. Small K addition and 40Ar escape rates of about 1%/Ma also simulate analytical cases in which the mean K-Ar ages of the finer grained fractions remain about constant with increasing depth, confirming that the relationship between K-Ar age and stratigraphic depth cannot represent a temporary “steady state”, but a continuing dynamic process at a smaller rate. In turn, the modeled results help quantifying the illitization reactions in size separates consisting of authigenic and detrital clay materials from sediments covering stratigraphic intervals from 10 to 1000 Ma.

Involvement and roles of stakeholders in Mahakam delta management to support mitigation and adaptation effort of climate change in East Kalimantan

East Kalimantan provincial government supports Nationally Determined Contribution (NDC) commitment by developing Green Growth Compact (GGC) initiative. This initiative emphasizes participatory and collaborative efforts among stakeholders at different levels and roles in forest management. One of the prototype initiatives currently under development is the management of mangrove forest areas in Mahakam delta. This paper aims to provide information on the process of involving the parties by identifying more details about the role, importance and influence of stakeholders on the Mahakam delta area in order to support the initiative. Data collected through interviews, observation, documents study and using stakeholder analysis. The analysis showed that stakeholders concerned have a direct and influential role can be broadly divided into three main sub-groups: those who provide services needed for the sustainable use and management of these resources (mainly government, NGOs); KPHP (Production Forest Management Unit/FMU) Mahakam delta, Mangrove Lestari Foundation, and Planete Urgence/Bioma Foundation; those who are directly involved in production and trade of oil and gas: Pertamina Hulu Mahakam Company, Pertaminan Hulu Sanga-Sanga Company and Chevron Indonesia; those who are directly involved in production and trade of marine products: Conventional Shrimp Farmers Group and Sustainable Shrimp Farmers Group. Also, there are several parties or stakeholders are classified in the secondary and key stakeholders. This paper supports and provides information and inputs for such initiatives and better management efforts of FMU Mahakam delta.

Waterbirds roosting on gas drilling platforms in Mahakam Delta, East Kalimantan: the Unexpected Impact of Landscape Transformation

Since 2014 some offshore gas platforms operated by Pertamina Hulu Mahakam near Mahakam Delta has been used by hundreds of egrets as roosting sites, causing nuisance to the platform and hampering the duty of workers/operator. The objective of this paper was to analyse the situation of the waterbirds’ nuisance, analyse the possible causes, and provide some recommendations. Field visits were conducted in August 2019 and February 2020 to three unmanned platforms (Ax, D, C) that suffered the most from the bird roost. Birds that infested the platforms were identified as great egret and intermediate egret, both are very similar in appearance and ecological requirements. The maximum number of egrets visiting C-Platform (the worst platforms) was 671 birds. These birds roost at night in the platform and leave the platform in the morning to forage for fish, eel, and shrimps in the wetlands of Mahakam Delta, about 2-4 km from the platform. The root cause of the infestation was believed to be the landscape transformation in the Mahakam Delta. Mangrove forest has been diminished and heavily converted into shrimp-ponds. The egrets’ foraging areas became ubiquitous, while the roosting/nesting site greatly decreased, forcing the egrets to roost on gas platforms. In the short-medium term, platforms need to be managed as bird tolerated-zone and bird-free zone (using deterrent), while in the long term, land-use in Delta Mahakam need to be restored.

Species diversity and estimation of carbon stock in abandoned shrimp pond of mangrove ecosystem in East Kalimantan

The mangrove forest ecosystem plays an absorbent and carbon sink to reduce CO2 levels in the atmosphere, including in degraded mangrove areas. This research was conducted precisely on abandoned shrimp ponds in mangrove areas in the Mahakam Delta. Four different locations are locating on Sepatin ponds, ponds, ponds, and ponds Bayur headland. The purpose of this study was to estimate the above-ground carbon stock in abandoned shrimp ponds. Carbon stock measurement methods create a 125 m transect and quadrant divided into six plots at each location. These measurements were conducted on living vegetation and dead wood from felling vegetation. Measurement of above-ground biomass was done by measuring the tree diameter at breast height (1.3 m) on each tree diameter> 5 cm in radius quadrant plot 7 m. Vegetation has a diameter <5 cm categorized in seedling criteria and measured 30 cm from the ground within the quadrant plot radius of 2 m. The vegetation diversity experienced a succession calculated using the diversity index by calculating the dominance index, diversity index, and similarity index of vegetation. While the calculation of above-ground biomass accumulation using allometric equations according to the species. The results showed that vegetation analysis in the fourth study sites obtained a high dominance index value at each location. The study is inversely proportional to the value of diversity and similarity index. The highest total carbon stock at Tanjung Nipah location was 11.599 Mg C. Ha -1, followed by Sepatin 6.248 Mg C. Ha -1, Benati Dalam 3.579 Mg C. Ha -1, and lowest carbon stock at Bayur location 1.460 Mg C. Ha -1.

Land-use dynamics associated with mangrove deforestation for aquaculture and the subsequent abandonment of ponds

The objective of this study was to evaluate the spatiotemporal dynamics of large area mangrove deforestation, aquaculture pond building, and the subsequent abandonment of ponds in a large delta in Indonesia, namely the Mahakam Delta. So, we developed and applied a novel methodology for exploring the lifespan of aquaculture ponds. Using historical multispectral and radar data, the lifespans of aquaculture ponds across the delta were estimated via a chronological analysis of the landscape into four different states: primary mangroves → deforested mangroves → ponds → abandoned/inactive ponds. Specifically, a combination of sequential classification and rule-based techniques were used to: 1) produce a time series of land cover maps from 1994 to 2015 and 2) quantify lifespans of aquaculture ponds in the delta. Results show that of the 110,000 ha of primary mangrove forests in the delta in 1994, 62% had been deforested by 2015, with a 4.5% annual rate of loss on average. The lifespan of aquaculture ponds in the delta varied between 1 and 22+ years, with most of the ponds having productive lifespans of 10 to 13 years. Ponds with relatively longer lifespans were located near the existing settlements in the delta. This study showed that the productive lifespan of most aquaculture ponds in deforested mangrove lands of Mahakam delta is relatively short, information that should be useful for developing appropriate management plans for the delta or similar coastal mangrove ecosystems. The abandoned ponds can potentially be rehabilitated for shrimp and fish production after applying appropriate restorative treatments or be targeted for mangrove restoration projects.