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High-Resolution Seagrass Species Mapping and Propeller Scars Detection in Tanjung Benoa, Bali through UAV Imagery

Karang I. Wayan Gede Astawa, Pravitha Ni Luh Putu Ratih, Nuarsa I. Wayan, Basheer Ahammed K. K., Wicaksono Pramaditya

Journal of Ecological Engineering

2024

Vol. 25, nr 1

161--174

As a part of the marine ecosystem, seagrass plays a significant role in the coastal environment. However, due to increased threats from natural causes and anthropogenic pressures, seagrass decline will likely begin in many areas of the world. Therefore, several studies have been carried out to observe seagrass distribution to help resolve the issue. Remote sensing is often used due to its ability to achieve high accuracy when distinguishing seagrass distribution. Still, this method lacks in species classification because not all satellites and similar aerial vehicles have fine spatial resolution to distinguish distinct species of seagrass. In this study, we aim to address the issue by utilizing unmanned aerial vehicles (UAV), which are known for providing finer resolution and better imagery. Samuh Beach at Tanjung Benoa, Bali, Indonesia, was chosen as the study site location because it experiences high levels of marine tourism and anthropogenic activities. From the UAV flight mission, the images obtained were processed. The result’s accuracy was also tested with an error matrix. The species found in this study are Enhalus acoroides, Halodule pinifolia, Thalassia hemprichii, Cymodocea rotundata, and Syringodium isoetifolium, with 65% overall accuracy of the species classification map. This result indicates that UAVs can be a strong option for similar studies in the future. In addition to that, this study was able to observe the scars on the seagrass beds left by boat propeller activities from marine tourism. However, further research is needed to gain a better understanding of these objects.

Developing Beach Litter Monitoring System Based on Reflectance Characteristics and its Abundance

Antara I Made Oka Guna, Nuarsa I Wayan, Sudarma I Made, Hendrawan I Gede, Cordova Muhammad Reza

Ecological Engineering & Environmental Technology

2024

Vol. 25, iss. 5

61--78

Marine litter is a major global problem; it originates on land and enters the ocean via rivers, coastal erosion, and extreme events. Over time, marine litter collects in coastal areas. As a result, the research on litter dispersal and buildup is critical for successful coastal area management. Addressing the knowledge gap is critical for establishing successful solutions to fight that problem. In recent years, a variety of remote sensing techniques have been used to better understand litter abundance, distribution patterns, and dynamics in marine as well as coastal ecosystems. Marine litter detection and quantification are carried out using aircraft-based imaging systems, satellite images, and unmanned aerial vehicles (UAVs). The purpose of this study was to create a beach litter monitoring system or technical reference using a small UAV and geographic information system (GIS), with the test location at Batu Belig Beach, Badung Regency, Bali, Indonesia. The box-plot approach was used to determine the reflectance threshold on the orthophoto. GIS is used to determine the regions with and without litter based on the set threshold values. To verify the model, Slovin’s Formula was used to collect the sample, with a confusion matrix indicating an accuracy of 80%. This monitoring system provides a simple approach for identifying and measuring litter, even with only one person handling the entire operation. The outcomes of this analysis indicated that the majority of litter at the study location was made up of white plastic bags and styrofoam. As a last step, portraying litter abundance as a percentage per square meter was considered.

Investigation of Microplastic Contamination in Sediments, Water and Aquatic Biota in Lake Beratan, Tabanan Regency, Bali Province – Indonesia

Watiniasih Ni Luh, Hendrawan I. Gede, Nuarsa I. Wayan, Wiradana Putu Angga

Journal of Ecological Engineering

2023

Vol. 24, nr 3

323--332

Microplastics (MPs) has become a very serious global threat, especially to the health of animals, humans and the environment. In this study we aim to investigate the contamination of MPs in sediment, air, and aquatic biota collected from the waters of Lake Beratan in Bali Province, Indonesia. Lake Beratan is one of the strategic areas that continues to develop as a tourist destination, agriculture and fisheries, as well as a source of water for daily needs. Sediment, water, and aquatic biota samples were collected from 4 stations that represent the Beratan Lake area. Each sample obtained was then followed by the pre-treatment stage using 5 M NaCl solution. Furthermore, the extraction process for each sample used wet oxidation peroxidation (WPO) with the addition of Fe (II) catalyst. The highest average weight of MPs in the sediment samples was obtained at the 1st sampling point of 2.53% which was dominated by soft fragments. The percentage of MPs weight in the water samples was varied at each sampling point with the highest obtained at the 4th point of 99.2% and was dominated by hard-shaped fragments at all sampling points. The collected aquatic biota was also contaminated by MPs of 68% in fish and 36.40% in shrimp. The types of MPs found in the digestive tract of aquatic biota are in the form of fragments, filaments, films and foam. These results indicate that the aquatic environment of Lake Beratan, Bali has MPs content that varies in sediment, water and aquatic biota which are often consumed by the local community. This must be of particular concern and further investigation, especially regarding the environmental management of the lake area and the relevant authorities in formulating regulations to reduce the harmful effects of MPs contamination.