Indonesian Journal of Limnology

Impact of the Southern Oscillation Index on Surface Water Variability in Floodplain Lake Semayang, Kalimantan, Indonesia: A Satellite Time-Series Approach

2025-10-16T09:42:11+07:00

ENSO is an important driver of hydroclimate variability in Indonesia and is strongly suspected to influence the dynamics of floodplain lakes. However, no study to date has combined the ENSO index (SOI) and satellite permanent water area time series for Lake Semayang. This study examines these linkages using 30 m resolution satellite image time series for 2000-2020. Permanent water area was obtained from JRC Global Surface Water, while SOI from NOAA. Monthly series were aligned and aggregated annually; the SOI-PWA relationship was analyzed by Pearson correlation and monthly lead-lag exploration (cross-correlation). The trend of the original annual series was tested nonparametrically with Mann-Kendall and the slope was estimated using Theil-Sen. Results showed a significant positive relationship between annual SOI and permanent water area of Semayang Lake (r = 0.591; p = 0.0048; r² ? 0.35). Monthly explorations displayed peaks at small positive breaks, but at the annual scale the strongest relationships were contemporaneous (same year). The original annual series show no significant monotonic trend over 2000-2020 according to the Mann-Kendall test, and the Theil-Sen estimates are small with confidence intervals that include zero. This finding confirms that La Niña trending conditions are associated with permanent water area expansion, while El Niño trending conditions are associated with shrinkage, making interannual variability the main driver of lake area change. The practical implications are that SOI information can be utilized for seasonal perspectives in navigation, fisheries and flood preparedness, and integrated into regional-level water resources management and climate adaptation planning in lowland wetlands in the region.

Investigation Effects of Methylene Blue Exposure on Behavior and Adsorption in Baramundi (Lates calcarifer)

2025-10-08T21:20:41+07:00

This study aims to investigate the effect of Methylene Blue (MB) exposure on the behavior and adsorption in the body of Baramundi (Lates calcarifer). The fish were kept for 28 days in aquariums with five levels of MB concentration (1-5 ppm) and one control group without exposure. The parameters observed included behavior, morphology, water quality, and MB concentration in the tissue through spectrophotometric analysis. The results showed a decrease in absorbance values in the 500–800 nm wavelength range in the treated fish compared to the control, indicating degradation or a reduction in MB concentration in the tissue. Water quality remained stable across all treatments, as indicated by relatively constant salinity, conductivity, salt content, pH, and ammonia values. Variations were only seen in lower Total Dissolved Solids (TDS)in some treatment aquariums and a decrease in phosphate compared to the control. Behaviorally, fish in the control group exhibited normal swimming activity, rapid response to feed, and stable social interactions. Meanwhile, fish exposed to MB, especially at higher concentrations, showed slower movements, decreased feeding responses, a tendency to remain at the bottom, and signs of mild stress. The treatment aquarium environment also appeared cleaner with minimal algae or other biota, unlike the control. Overall, the use of MB did not disrupt the stability of environmental quality but affected behavioral responses.

Assessing Fish Alpha Diversity in Relation to Water Quality Parameters in Mendelang River, Merangin, Jambi

2025-10-29T10:50:12+07:00

Information regarding the ecological evaluation of the Mendelang River from abiotic and biotic components is still limited. This study aims to determine species richness and abundance, assess diversity indices, and determine the effect of water quality on fish abundance in the Mendelang River, Mekar Jaya Village, South Tabir Subdistrict, Merangin Regency. The research method used was a survey with participatory observation techniques. The data collected included fish catches using ambat net fishing gear and water quality parameters (temperature, pH, dissolved oxygen, transparancy, and current). The results showed that there were 21 species with a total of 1541 individuals. The most dominant species were Seluang and Nilem. The Shannon-Wiener diversity index (H’) value of 2.10 indicates a moderate category, the evenness index (E) of 0.69 is classified as high, and the Simpson dominance index (C) of 0.18 is in the low category. The water quality conditions of the Mendelang River were measured based on the water quality parameters. Meanwhile, Principal Component Analysis (PCA) shows that Seluang fish are strongly associated with temperature and pH, while Nilem fish are associated with pH and current. Based on the fish diversity index and water quality parameters, the Mendelang River ecosystem can be classified as ecologically stable. This ecological assessment serves as a foundation for evaluating and monitoring aquatic habitats, thereby supporting sustainable fisheries management.

Riparian Landscape Suitability for Urban Tourism : A Case Study At Ciliwung River in Central Jakarta, Indonesia

2025-11-05T11:24:41+07:00

To meet community needs, riparian zones of rivers are widely developed as recreational areas in major cities. Jakarta has the potential for riparian tourism development as it is traversed by 13 rivers. However, before being developed as riparian recreation areas, several assessments of the site are required. This study aimed to assess three distinct segments of the Ciliwung River in Central Jakarta for their potential as urban tourism sites. The evaluation was carried out by incorporating several parameters related to the suitability of riparian areas for tourism, including vegetation cover percentage, accessibility, and water quality. These parameters were measured using the Riparian Strip Quality Index (RSQI), proximity to public transportation hubs, and the Pollution Index, then categorized into four scoring levels. High scores indicate the suitability of riparian areas as tourist locations. Segments 1, 2, and 3 received scores of 6, 7, and 7 respectively out of 12, indicating that the riparian areas are still far from being ideal urban tourism sites. The findings also highlight weak land use regulations in these riparian zones and poor water quality in the Ciliwung River in Central Jakarta. The originality of this study lies in its combination of terrestrial ecosystem assessment parameters (vegetation cover percentage, accessibility) and aquatic ecosystem indicators (water quality), resulting in a comprehensive evaluation of the riparian landscape management.

Analysis Production and Technical Efficiency of Tilapia (Oreochromis niloticus) In Freshwater, Tasikmalaya

2025-12-10T18:54:03+07:00

The fisheries subsector plays a significant role in the national GDP. In 2023, its contribution reached 2.66%, increasing from 2.58% in 2022. In the second quarter of 2024, the subsector contributed 2.54%, higher than the 2.34% recorded in the first quarter. One of its leading commodities is tilapia (Oreochromis niloticus), a freshwater species valued for its high economic potential and strong adaptability. In 2021, West Java reported the highest national tilapia production at 270,925 tons, with Tasikmalaya City contributing the largest share at 2,189 tons. This study analyzes the technical efficiency of tilapia farming in Tasikmalaya using the Cobb–Douglas Stochastic Production Function. The research was conducted from July - September 2024 in the districts of Bungursari, Kawalu, Purbaratu, and Cibeureum. Locations were selected purposive, and a snowball sampling technique yielded 52 respondents. The results indicate that seed and pellet feed exert a statistically significant effect on production, whereas bran, EM4, cultivation duration, and labor inputs do not show a significant influence. The technical inefficiency model demonstrates that farmer experience and education have a significant impact on efficiency. Experience contributes to technical inefficiency, while education mitigates it.