Characteristics and distribution of stranded plastic pollution in Bali conservation areas.

Plastic pollution threatens vulnerable conservation areas such as West Bali National Park (TNBB) and Nusa Penida Marine Protected Area (NPMPA), which play a crucial role in supporting marine biodiversity and the economy through tourism and fisheries activities. This study aims to investigate the characteristics, density, and distribution of marine debris in Bali's conservation areas. Surveys were conducted at 37 locations around TNBB and NPMPA, with approximately 94 % of the total samples consisting of plastic debris. Sampling effects related to substrate type, sea bottom gradient, and backshore type were significant and correlated with local debris load. Effects associated with land-based sources (such as population, distance to the nearest rivers, settlements, and tourist spots) were also significant. Statistical patterns suggest that illegal waste disposal is also an important driver. Understanding drivers of waste mismanagement, coupled with place-based approaches can help identify approaches likely to be successful in reducing plastic pollution in the environment. We suggest emphasizing citizen awareness, public policies, and their implementation as actions that can help prevent debris pollution in TNBB and NPMPA conservation areas, as well as in similar high-value areas around the world.

Evaluating the collection and composition of plastic waste in the digital waste bank and the reduction of potential leakage into the ocean.

Most ocean plastic pollution results from leakage from waste management activities on land, mainly in coastline communities. In this research, the digitalization of waste management will be evaluated to improve the prevention of leakage. The digitalization means introducing mobile apps into the waste bank that can improve waste management efficiency while providing reliable data. The data on waste management were gained from Griya Luhu App which has been used in 13 villages around Gianyar, while the waste generation was calculated from 97 samples. Then, the villages were categorized by their potential risk of waste leakage based on their distances from the shore. First, the growth of digital waste banks based on the number of units, the number of customers and the amount of waste-managed was analyzed. Second, the composition of waste collected was evaluated. Last, inorganic waste generation (IWG) from digital waste banks was reduced. The results showed that digital waste banks and the customers had grown rapidly in 1 year. The number of waste bank units grew from 0 to 80 with an increase to a total of 5500 customers during the same period with a maximum of 20 tons of waste managed per month. In general, digital waste banks have shown promising performance in preventing waste leakage into the ocean with a 54.04% reduction of IWG. Compared to this reduction percentage, Tulikup as a high-risk village has a considerably low reduction (30.30%) and should be prioritized. Furthermore, the ability to manage a village with a high population/number of customers should be improved.

Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park.

Background: The reef manta ray (Mobula alfredi) is a globally threatened species and an iconic tourist attraction for visitors to Indonesia's Komodo National Park (NP). In 2013, manta ray fishing was banned in Komodo NP and its surroundings, preceding the nationwide manta ray protection in 2014. Over a decade ago, a previous acoustic telemetry study demonstrated that reef manta rays had high fidelity to sites within the park, while more recent photo-identification data indicated that some individuals move up to 450 km elsewhere. Characterization of manta ray demographics, behavior, and a focused assessment on site use of popular tourism locations within the park is vital to assist the Komodo NP Management Authority formulate appropriate manta ray conservation and management policies. Methods: This study uses a long-term library (MantaMatcher.org) of photo-identification data collected by researchers and citizen scientists to investigate manta ray demographics and habitat use within the park at four sites frequented by tour operators: Cauldron, Karang Makassar, Mawan, and Manta Alley. Residency and movements of manta rays were investigated with maximum likelihood analyses and Markov movement models. Results: A total of 1,085 individual manta rays were identified from photographs dating from 2013 to 2018. In general, individual manta rays displayed a higher affinity to specific sites than others. The highest re-sighting probabilities came from the remote southern site, Manta Alley. Karang Makassar and Mawan are only ~5 km apart; however, manta rays displayed distinct site affinities. Exchange of individuals between Manta Alley and the two central sites (~35.5 km apart) occurred, particularly seasonally. More manta rays were recorded traveling from the south to the central area than vice versa. Female manta rays were more mobile than males. Similar demographic groups used Karang Makassar, Mawan, and Manta Alley for foraging, cleaning, cruising, or courtship activities. Conversely, a higher proportion of immature manta rays used the northern site, Cauldron, where foraging was commonly observed. Fishing gear-related injuries were noted on 56 individuals (~5%), and predatory injuries were present on 32 individuals (~3%). Tourism within the park increased from 2014 to 2017, with 34% more dive boats per survey at Karang Makassar and Mawan. Discussion: The Komodo NP contains several distinct critical habitats for manta rays that encompass all demographics and accommodate seasonal manta ray movements. While the present study has not examined population trends, it does provide foundational data for such work. Continued research into manta ray abundance, long-range movements, and identifying and protecting other critical aggregation areas within the region is integral to securing the species' recovery. We provide management recommendations to limit undue pressure on manta rays and their critical habitats from tourism.

What's in the soup? Visual characterization and polymer analysis of microplastics from an Indonesian manta ray feeding ground.

Plastics in marine environments vary in their physical and chemical properties, influencing their risk to biota once ingested. Manta rays are large filter-feeders that ingest plastics. To assess this risk, we characterized the plastics in a critical feeding habitat off Nusa Penida, Indonesia. We examined the color and polymer composition of sampled small-sized plastics (<30 mm). Plastics were mostly secondary microplastics and transparent (46%), white/off-white (24%), and blue/green (22%). Fourier transform infrared spectroscopy of plastics grouped according to type (films, fragments, foam, or lines) and color indicated that most plastics were polyethylene (PE) or polypropylene (PP) (99%), with the remainder polystyrene and polyester. Visual characterization aligned with single polymer composition in seven out of ten groups. Although PE and PP have relatively low toxicity compared to other plastics, their composing monomers and associated pollutants and microbes are of concern to manta rays and other marine biota.

It's not all black and white: investigating colour polymorphism in manta rays across Indo-Pacific populations.

Intraspecific colour polymorphisms have been the focus of numerous studies, yet processes affecting melanism in the marine environment remain poorly understood. Arguably, the most prominent example of melanism in marine species occurs in manta rays (Mobula birostris and Mobula alfredi). Here, we use long-term photo identification catalogues to document the frequency variation of melanism across Indo-Pacific manta ray populations and test for evidence of selection by predation acting on colour morph variants. We use mark-recapture modelling to compare survivorship of typical and melanistic colour morphs in three M. alfredi populations and assess the relationship between frequency variation and geographical distance. While there were large differences in melanism frequencies among populations of both species (0-40.70%), apparent survival estimates revealed no difference in survivorship between colour morphs. We found a significant association between phenotypic and geographical distance in M. birostris, but not in M. alfredi. Our results suggest that melanism is not under selection by predation in the tested M. alfredi populations, and that frequency differences across populations of both species are a consequence of neutral genetic processes. As genetic colour polymorphisms are often subjected to complex selection mechanisms, our findings only begin to elucidate the underlying evolutionary processes responsible for the maintenance and frequency variation of melanism in manta ray populations.

Underwater noise from airplanes: An overlooked source of ocean noise.

The effects of underwater noise pollution on marine life are of increasing concern. Research and management have focussed on the strongest underwater sound sources. Aerial sound sources have understandably been ignored as sound transmits poorly across the air-water interface. However, there might be situations when air-borne noise cannot be dismissed. Commercial passenger airplanes were recorded in a coastal underwater soundscape exhibiting broadband received levels of 84-132 dB re 1 µPa rms. Power spectral density levels of airplane noise underwater exceeded ambient levels between 12 Hz and 2 or 10 kHz (depending on site) by up to 36 dB. Underwater noise from airplanes is expected to be audible to a variety of marine fauna, including seals, manatees, and dolphins. With many of the world's airports lying close to the coast, it is cautioned that airplane noise not be ignored, in particular in the case of at-risk species in small, confined habitats.