Classification, composition, and sources of marine litter on beach sediment of Kondang Merak Coast, Malang, Indonesia

Marine litter pollution has been examined extensively as a significant environmental concern. Beaches are particularly vulnerable to this form of pollution since it is located between land and sea. Malang is one of the cities on Java Island, with a long coastline and numerous beautiful beaches facing the Indian Ocean. Kondang Merak Beach is a popular tourist destination among locals. However, it is under constant threat from marine litter pollution. The beach is divided into two distinct areas: the foreshore, which is influenced by sea waves and currents, and the backshore, which is significantly impacted by tourist activity. Therefore, this study aimed to examine marine litter on beach sediment and to distinguish the composition of marine litter between foreshore and backshore areas. Quadrat transects of 5 x 5 m and 50 x 50 cm were used to collect bigger and micro-size marine litter, respectively. Of the 895 litter items, 61 % were collected from the backshore and 39 % from the foreshore areas. Bigger-sized litter found in the backshore area was the result of tourism activities. On the other hand, micro-size litter in the foreshore area resulted from fragmentation from bigger-size litter.


Introduction
The National Oceanic and Atmospheric Administration (NOAA) describes marine litter as any persistent solid material processed directly or indirectly, intentionally or unintentionally, and discarded into marine areas [1].Marine litter is tenacious polluting materials that interfere with water bodies, including aquatic habitats and freshwater [2].Most marine litter comes from anthropogenic activities such as sea-based sources like fisheries and vessel traffic and land-based sources such as tourism activities or river run-off.The rising use of single-use materials, unmanaged disposal of debris, and poor waste management and recycling processes are the main reasons for hoarding litter in the sea [3], [4].Data obtained from the International Coastal Clean-up Day depicts that the most recaptured debris includes plastic bottles, cigarette butts, food wrappers, plastic bags and lids, plastic straws, plastic bottle caps, stirrers, foams, and beverage bottles [5].
Based on scientific research, there is a lot of information that plastics are the primary source of marine litter.Marine anthropogenic debris causes damage to a wide range of aquatic biota and habitats.Fishes, turtles, marine mammals, and seabirds suffer from entanglement and ingestion of marine debris, especially the plastic form, as portrayed by lots of animal images of strangled and injured by discarded fishing gear in the public media [4] [6].Moreover, bigger-sized plastic could degrade into smaller particles called microplastics and bring harm to marine ecosystems and biotas [7][8] [9].The amount of marine litter is strongly connected to the management of solid waste worldwide, wastes that are kept in the environment for a very long period, and wastes carried for long distances by rivers, winds, rain, and marine currents [10].
The research related to marine litter studies has been developed extensively in Indonesia.Beach areas are specifically of high interest since tourism activity highly influences marine litter.This study was conducted on Kondang Merak Beach in the southern area of Malang region of East Java, Indonesia.Kondang Merak Beach is well-known as a tourist destination for locals and visitors.Furthermore, this location became an economic site for locals, many selling their products such as foods, handmade items, and others.Those types of anthropogenic activities could influence the presence of marine litter.Therefore, this study was conducted to examine marine litter on beach sediment and to distinguish the composition of marine litter between foreshore and backshore areas.

Study and Sampling Area
Sampling was conducted in July 2023 on the beach sediment along the Kondang Merak coast (Figure 1).The litter was sampled through a 20 m line transect placed parallel to the shoreline along the coastline, and a 5 x 5 m quadrat transect was placed within the line to collect marine litter.Another 50 x 50 cm quadrat transect was placed inside a bigger transect to collect micro-size debris.Litter was collected from both foreshore and backshore areas.The foreshore area is influenced by sea waves and currents, while the backshore area is significantly impacted by tourist activity.There were 14 transects from each foreshore and backshore.All litter collected within the quadrate transects was identified and counted based on categories: plastic, paper, rubber, fabric, processed wood, metal, glass, ceramic, and others.The litter abundance measured as in Equation 1.Meanwhile, the percentage for litter categories as in Equation 2.

Result and Discussion
Marine litter was identified in 895 items collected from foreshore and backshore areas of Kondang Merak Beach.Backshore areas captured a higher percentage of marine litter than foreshore areas, at 61% and 39%, respectively (Figure 2).Another study found that the number and size of litter in the coastal environment increased from the waterline to the backshore, implying that vegetated backshore areas should be considered a primary sink for marine litter, particularly larger items [13].The litter found on foreshore and backshore areas was classified into micro-size, meso-size, and macro-size.Macro-size was the dominating type of litter in both foreshore and backshore areas (Figure 3).Micro-size abundance in the foreshore and backshore areas were 0.67±0.72 and 0.23±0.42piece/m 2 respectively.Meanwhile, the meso-size numbers were 0.23±0.27and 1.36±0.98piece/m 2 respectively.Macro size was recorded as the highest litter found both on the foreshore and backshore, with 5.82 ± 5.56 and 8.14 ± 4.70 piece/m 2 , respectively.
The abundance of meso-size and macro-size litter was higher in the backshore area, while the abundance of micro-size litter was higher in the foreshore area.Bigger-sized litter found in the backshore area was the result of tourism activities.The litter, usually discarded directly on the beach, was often found on the backshore area, where locals and tourists stay most of the time [14].On the other hand, micro-size litter in the foreshore area from fragmentation from bigger-size litter.Meanwhile, litter was less abundant in the foreshore area because of the low tide water level that can vary from place to place [14].

Conclusion
The result of this study highlighted that the composition and origin of beach litter differed between the foreshore and backshore areas.Marine litter from backshore areas is influenced by anthropogenic activities such as fisheries, vessel activity, and tourism.foreshore areas are affected by sea waves and currents.As Kondang Merak Beach has recently become well-known as a tourism destination, most marine litter has been recorded coming up from the backshore rather than the foreshore area.

Figure 1 .
Figure 1.Map of sampling sites in the Kondang Merak Beach East Java, Indonesia

Figure 2 .
Figure 2. Percentage Litter Found in Backshore and Foreshore areas

Figure 3 .
Figure 3. Abundance of marine litter in the foreshore and backshore area

Figure 4 .
Figure 4. Percentage of marine litter found in Kondang Merak Beach