LIMNOTEK Perairan Darat Tropis di Indonesia

Growth of the water fleas Daphnia magna (Straus, 1820) at different trophic levels of two small urban lakes in Indonesia

2023-08-30T16:05:46+07:00

Nutrient enrichment in waters that has become a major environmental problem is related to excessive loading of nutrients into aquatic ecosystems. This nutrient enrichment, called eutrophication, favors phytoplankton growth, which can function as a natural daphnid feed. This study examined the growth performance of the water fleas Daphnia magna in water collected from small lakes (ponds) of different trophic levels. The water was taken from Situ Rawa Kalong, considered eutrophic from its dark green color, and the less eutrophic Situ Cibuntu with relatively clear water. Daphnids were grown in six aquaria filled with water from both ponds without artificial feeding with an initial density of five individuals/L. Samples of daphnids were taken every three to four days to observe their growth and reproduction, along with water samples to analyze the chlorophyll content and total suspended solids (TSS). The result showed that the eutrophic water of Situ Rawa Kalong favored phytoplankton growth, indicated by a consistently higher chlorophyll content in the water ranging from 35.3 to 140.7 μg/L compared to less eutrophic water of Situ Cibuntu with chlorophyll content ranging from 1.4 to 13.2 μg/L throughout the experiment. A much higher daphnid density of 151.7 individuals/L was achieved with more water chlorophyll content, meaning phytoplankton availability became a controlling factor for daphnid growth in the pond waters. This study reveals the functional relationships in the food chain between the water trophic level, the abundance of phytoplankton as the primary producer, and daphnids as the first-order predator. It also suggests that the open water trophic level can be managed to favor the daphnid growth, which can then be harvested for use as natural feed.

A biological perspective for the fishery management of a small urban lake in Indonesia: a case study on the reproductive stage of the red devil (Amphilopus citrinellus) in Situ Cilodong, West Java, Indonesia

2023-10-17T10:52:32+07:00

The presence and establishment of invasive alien fish species is one of the biggest threats to aquatic biodiversity. The red devil, Amphilopus citrinellus, is one of the emerging invasive species and its occurrence is massively detected in common water bodies in tropical areas such as Indonesia. However, the topic remains under-reported from the small urban lakes. This study aims to present the reproductive characteristics of the fish in Situ Cilodong, a small urban lake in the country, that can be used as a principal reference for population control. The sampling was conducted in June 2021 and May 2022 using a mix of seven mesh-sized gillnets. The results of the length-weight relationship reveal that both the female and male fish perform isometric growth type. The calculated Gonad Somatic Index (GSI) and the histological analysis confirmed that the fish is a multi-spawner species. The results imply that sustainable population control efforts must include intensive catch and engage a participatory approach between the legal authority and the local fishers.

Sorption kinetics of heavy metals from aqueous solution using Spirogyra sp.: a microcosm study

2023-09-14T11:14:08+07:00

Understanding the mechanisms by which algae communities respond to disturbances in the lotic aquatic environment that is polluted by heavy metals is important, considering that algae is a biotic component of waters that acts as a producer in the aquatic food chain which has the potential to bio-magnify. This study examines the influence of time, biomass weight, heavy metal concentration, sorption capacity, and efficient removal on epilithic periphyton as a bio-accumulator of Cr, Pb, and Ni. The experiment was conducted on a laboratory scale using a canal system with a length and width of 1.2 and 1.0 meters, respectively. The canal system contains 132 L of water, has a 1.2 m² substrate and periphyton area, a depth of 0.09 – 0.10 m, and a current flow rate of 0.04 – 0.06 m/s. The dissolved Cr⁶⁺ initial concentration in the medium was 1.64 mg/L, Pb²⁺ and Ni²⁺ concentrations were 1.4 mg/L, and the adsorption process was studied for 24 hours. Based on microscope observations and functional group interpretation utilizing infrared spectra (FTIR), the periphyton community is dominated by Spirogyra sp., which has hydroxyl (O-H), carboxyl (C-H), and carbonyl (C-C and C=O) functional groups with the ability to binding heavy metals. The remaining quantities of Cr, Pb, and Ni in water were 0.43 mg/L (removal 69.29%), 0.05 mg/L (96.43% removal), and 0.03 mg/L (97.86% removal). Periphyton has a maximal sorption capacity of 1.019 mg Cr/g, 1.97 mg Pb/g, and 1.92 mg Ni/g. The sorption kinetics of Cr, Pb, and Ni follow a pseudo-second-order model with k₂ = 1.686 x 10^-2 g/mg.min for Cr, 4.516 x 10^-3 g/mg.min for Pb, and 2.259 x 10^-2 g/mg.min for Ni, with R² of 0.965 for Cr and 0.971 for Pb and 0.972 for Ni. Periphyton can potentially play a role as a bio-accumulator in lotic habitats, adsorbing Cr, Pb, and Ni ions, according to this study.

Sediment capping technology for eutrophication control and its potential for application in Indonesian lakes: a review

2023-11-02T16:53:44+07:00

Eutrophication occurs when the lakes become enriched with nutrients. Some nitrogen and phosphorus fractions will settle in sediment, and others will be released back into the overlying water column. Excess nutrients in water bodies resulting in hypoxic to anoxic conditions that can cause a mass fish death. Hence, we need a sediment management strategy to minimize resuspension and transport of sediment back into the water column. Sediment capping is a containment technology to reduce the release of nutrients from sediment as a strategy for eutrophication control. This study aims to provide insight into sediment capping technology, including several considerations in capping design, as well as information on several active materials that have been applied as capping materials and their efficiencies. Capping materials such as calcite, zeolite, bentonite, activated carbon, sludge, biochar, and gypsum from previous studies showed the efficiency of 54–99 % nutrient reduction with capping duration of 10–300 days in some eutrophic lakes. Sediment capping technology has successfully promoted lake ecosystem restoration in other countries, and this technology has the potential to be applied in Indonesian eutrophic lakes as a strategy for eutrophication control and sustainable management of lake ecosystems by considering the selection of the most effective, efficient, easy, inexpensive, and eco-friendly capping materials.

Assessment of Flash Flood Vulnerability Index in a tropical watershed region: a case study in Ciliwung Hulu watershed, Indonesia

2023-09-05T15:42:18+07:00

Flash floods, an unpredicted swift climatological disaster, frequently occur in Indonesia. However, there are limited vulnerability assessments, especially in urban and vital regions such as Bogor District. The study aims to assess the vulnerability index of Ciliwung Hulu Watersheds as one of the most susceptible areas in the district. Flash flood vulnerability index (FFVI) is selected to be calculated as the indicator. Data were obtained from the official government offices and processed using the FFVI formula referring to the work of Nasiri et al., (2019) and Perka BNPB No. 2/ 2012 and then mapped using ArcGIS 10.3. The results and the maps show that the study area is categorized as highly to very highly vulnerable to flash flood disasters. The attained results help facilitate the governance interplay processes in building a more disaster-ready management plan and to construct a more resilient society.