Tourism impact on wastewater-derived nitrogen pollution on the tropical small island Gili Trawangan, Indonesia.
by Sarah Zwicker | Marie Fujitani | Nils Moosdorf | Matthias Birkicht | Nurliah Buhari | Doni Putra | Sian Williams
ZMT, Uni Bremen | ZMT, Uni Bremen | ZMT, Uni Kiel | ZMT | University of Mataram | University of Gadjah Mada | Gili Eco Trust
Mass tourism sustains livelihoods on the Indonesian small island of Gili Trawangan but presents a sustainability challenge in wastewater management. In the absence of an advanced wastewater treatment system, most of the approximately 400 hotels discharge untreated wastewater into open-bottom septic pits. From there, wastewater infiltrates the groundwater and subsequently reaches the marine environment, transferring nutrient pollution from land to sea.
The COVID-19 pandemic drastically reduced global tourism and temporarily interrupted the flow of tourism-generated wastewater on the island. This study leveraged this quasi experimental situation to assess the impact of tourism on nutrient pollution. Monthly measurements of dissolved inorganic nutrients in six coastal groundwater wells—three in the urban hotel district and three in remote areas—were conducted between March 2022 and September 2023, covering the period before, during, and after the tourism recovery. Additionally, bi-monthly measurements of δ15N in marine macroalgae (Padina) were taken from six marine sites near the groundwater wells.
A seasonal comparison revealed that NOx concentrations in groundwater increased significantly in hotel-dense areas following the return of tourism, while remote control sites showed consistently and statistically lower levels with no comparable increase. Similarly, δ15N values in Padina near hotel districts exceeded 6 ‰, clearly indicating wastewater as the primary nitrogen source, and again showed a notable rise in nitrogen levels after tourism resumed.
These findings highlight the rapid resurgence of nitrogen pollution associated with tourism and underscore the urgent need for improved wastewater management to protect Gili Trawangan’s marine ecosystems from eutrophication. On a positive note, the reduced nutrient levels observed during the period of minimal tourism indicate that the aquifer has a natural capacity for self-purification when wastewater discharge is halted. This offers an encouraging outlook, as it suggests that with effective wastewater management, long-term aquifer recovery is achievable, paving the way for sustainable improvements in groundwater quality.
Nursery Site Systems influence Growth Performance of Juvenile Holothuria scabra in Earthen Ponds
by Lisa Fajar Indriana | Andreas Kunzmann | Matthew James Slater
ZMT | ZMT | Alfred Wegener Institute (AWI)
The high-value sea cucumber Holothuria scabra experiences a population decline due to over-exploitation, making aquaculture crucial for its conservation and market supply. Indoor nursery systems are limited by space, feeding, and costs, requiring juvenile transition to outdoor environments to optimize the rearing process. The aims of this research are to determine the influence of various nursery sites on the growth and survival of juvenile H. scabra in earth ponds. The study was carried out in Lombok, Indonesia, and was conducted over 84 days in various settings within earthen ponds, utilizing a completely randomized design with five replicates. Four different treatment sites including a reservoir (N1), a stirred pond (N2), a non-stirred pond (N3), and the main inlet sluice (N4) were implemented. Juveniles (mean wet weight of 1 g, n=50) were distributed into replicate floating hapa units. The results showed that the main inlet sluice N4 is the most effective location for promoting the Growth Rate (mean±SD 0.083±0.011 g d-1) and Specific Growth Rate (2.360±0.145 % d-1). Survival exhibited no significant differences across the treatments, ranging from 64.00±2.37 to 74.80±5.82%. The main inlet sluice is most suited for growth of juvenile H. scabra, presumably owing to its nutrient availability, phytoplankton composition, and efficient water exchange.
Keywords: sea cucumber nursery, floating hapa unit, earthen ponds, main inlet sluice
Urban change dynamics at an e-waste site in Accra, Ghana: Insights from satellite imagery
by Alexandra Nozik | Nils Moosdorf | Hildegard Westphal | Paul Botwe
ZMT | ZMT | ZMT | ZMT
The poster visualizes the approach to reconstruct the recent historical development of one of the world’s biggest electrical waste (e-waste) sites, Agbogbloshie, located in Ghana’s capital Accra, by detecting land cover changes (LCC) using satellite imagery. The current work in progress shows the technical workflow and our expectations on how this approach can support social sciences research. Along with first results, the poster invites to discuss the potential and limitations of this approach.
Harmful e-waste recycling practices are increasingly recognized as a health risk for workers and nearby populations. Agbogbloshie, once a coastal wetland with mangroves around the Odaw river and Korle lagoon, became an informal settlement in the late 20th century. Over the past two decades, it has turned into a major scrapyard where the informal sector processes e-waste and scrap metals. Studies link these activities to severe environmental pollution and health risks from persistent organic pollutants (POPs) and heavy metals.
While there is a general understanding of the history of the e-waste site based on local knowledge, news reports, and existing research, reconstructing changes over the last 20-30 years in detail remains a challenge. One way to address this is through satellite imagery.
The poster presents intermediate results derived from Landsat imagery from 2000 to 2015, selected for its ability to reveal major land cover changes (LCC). Landsat’s temporal resolution aids in reconstructing time frames, while its spectral resolution is used to test methods for detecting potential burning sites using index calculations, such as the normalized burn ratio (NBR). These findings can support transdisciplinary research and interviews addressing specific LCC dynamics, including issues related to management, settlement, and the future land use of this and other poorly regulated waste sites worldwide.
Tourism, Gender, and Climate Change Adaptation: A Mental Models Perspective from Kenya’s Coast
by Lucy Atieno | Marie Fujitanii
ZMT, University of Bremen | ZMT, University of Bremen
This study examines the interplay between gender, tourism, and climate change, from the perspective of a tourism dependent community at Kenya’s coast. Tourism is predicted to represent the largest segment of the ocean economy by 2030, according to the Organization for Economic Cooperation and Development. Through mental modeling interviews, the study uncovers how this interplay is conceptualized across respondent groups. Such conceptualizations help to frame knowledge about climate change, aiming to feed into decision processes in marine environments. The study focuses on coastal tourism as representative of blue economy sectors requiring such decision processes. Results from Kenya’s coast show subtle differences between female and male respondents, and between those with a policy background compared to those with practitioner’s background. These differences suggest knowledge mismatches between respondent groups. Upon examination of micro interactions at the study site through qualitative interviews, the differences appear to be linked to distinct places where respondents are predominantly associated with. This association arises from conception of place in coastal tourism, where status quo is who has access to sea or shore, or whose occupational role is anchored to work or home realms. The analysis takes an interpretive lens of Feminist Political Ecology to show that mismatches in climate change knowledge among study respondents, lead the flow of knowledge into decisions for climate change solutions. Thus, we come to the important question of whose knowledge matters. This work highlights the link between knowledge sovereignty and the conception of place. It further points to ideologies behind this conception of place, singling out where they reinforce gender related inequality in economic opportunities and governance processes. This revelation is important in efforts to advance gender equality in marine environments, which are shown by previous research to be female spheres.
Mapping Gaps in Mangrove Forests Using Deep Learning and Remote Sensing: Correlation Between Gap Frequency and Canopy Height
by Dominic Wrieden | Daniel Schürholz
ZMT | ZMT
Mangrove forests are important ecosystems that provide habitats for wildlife, protect coastlines from erosion, sequester carbon, and offer valuable resources. Canopy gaps are a natural part of the renewal process in mangrove forests, caused by factors such as pests, senescence, and lightning strikes, as well as anthropogenic influences, including pollution and forestry.
Canopy gap characteristics—such as size, shape, height of the original canopy, and recovery duration—offer insights into the factors driving their formation.
Field campaigns to study these gaps are challenging due to the intertidal location of mangroves, making satellite imagery a promising alternative for research. Previous studies have successfully used commercial very-high-resolution (0.3 m) satellite imagery combined with machine-learning models to map canopy gaps and classify their recovery stages. However, the high cost of such commercial imagery limits its feasibility for large-scale or long-term applications.
Norway’s International Climate and Forest Initiative (NICFI) provides open-access multispectral satellite imagery of tropical regions at a 4.77 m resolution, available biannually from 2015 to 2020 and monthly from 2020 onwards. Our study proposes a method to map mangrove canopy gaps using NICFI imagery. By applying machine-learning models trained on gap annotations provided by Kyei et al., we aim to delineate canopy gap contours across larger spatial and temporal scales. Additionally, we explore whether gap appearance correlates with the original canopy height to better understand the underlying drivers.
Key challenges include the relatively coarse resolution of NICFI imagery compared to the diameter of annotated gaps (3.45 m to 110.44 m), misalignment between annotations and imagery, and misalignment among NICFI satellite images at different times. Our study addresses these issues to improve mangrove monitoring, potentially serving as an early warning system, and enhancing understanding of canopy gap dynamics in these critical ecosystems.
Species Composition And Performance Of Estuarine Seagrass In Madagascar: Seasonal Variation And Regional Pattern
by Tsiaranto Fanoro | Ranivoarivelo Lantoasinoro | Martin Zimmer
ZMT | IH.SM | ZMT
Seagrass ecosystems along the African coasts are vital for supporting fisheries and adjacent habitats such as reefs and mangroves. Despite their importance, these ecosystems remain poorly studied in that bioregion. Seagrasses in estuarine regions face increasing sedimentation threats from coastal development and climate change. The research investigates the species composition of seagrass meadows in four estuaries of Madagascar: Irodo, Lokia, Androka, and Morombe. Sampling was conducted during both the dry and the rainy seasons, adapting the SeagrassWatch methodology to the estuarine hydrological condition of the sites.
Sampling data were analyzed using three performance metrics: (1) traditional measures (biomass, species richness, shoot density, canopy height, accumulated organic matter in the sediment); (2) the biomass ratio approach; and (3) the space occupation efficiency metric, dgrass.
The analysis aims to explore site-specific and seasonal variations in seagrass performances. This study compares whether each metric offers consistent or distinct interpretations across different ecological contexts. By providing baseline data on Madagascar’s estuarine seagrass ecosystems, this research lays the foundation for future investigations into sedimentation impacts and offers insights into species-oriented conservation and restoration strategies under climate change.
Mangrove Ecosystem Restoration in Pasarbanggi: Species Diversity, Environmental Conditions, and Management Implications
by Aulia Rahim | Tri Retnaningsih Soeprobowati | Jumari Jumari | Lilih Khotimperwati
Doctoral Program of Environmental Science, School of Postgraduate Studies, Diponegoro University, Semarang, Indonesia; Cluster for Paleolimnology (CPalim), School of Postgraduate Studies, Diponegoro University, Semarang, Indonesia; ZMT | Department of Biology, Faculty of Science and Mathematics, Diponegoro University, Semarang, Indonesia; Cluster for Paleolimnology (CPalim), School of Postgraduate Studies, Diponegoro University, Semarang, Indonesia | Department of Biology, Faculty of Science and Mathematics, Diponegoro University, Semarang, Indonesia; Cluster for Paleolimnology (CPalim), School of Postgraduate Studies, Diponegoro University, Semarang, Indonesia | Department of Biology, Faculty of Science and Mathematics, Diponegoro University, Semarang, Indonesia; Cluster for Paleolimnology (CPalim), School of Postgraduate Studies, Diponegoro University, Semarang, Indonesia
The mangrove ecosystem in Pasarbanggi, Rembang, has expanded from 3 hectares in 1960 to 60 hectares through community and government restoration initiatives. Recognized for its ecological and socio-economic importance, it was designated as an Essential Ecosystem Area under the Governor of Central Java Decree No. 552.52/31 of 2020. This study examines the vegetation structure, species diversity, and environmental conditions of the mangrove ecosystem. Five true mangrove species—Rhizophora mucronata, Rhizophora stylosa, Rhizophora apiculata, Avicennia marina, and Sonneratia alba—were identified, all classified as Least Concern by the IUCN. Primary forests exhibited higher species diversity, while restored secondary forests demonstrated greater sapling and seedling densities. Rhizophora stylosa dominated across growth stages, as indicated by the Important Value Index (IVI). Environmental parameters, including pH (5–7), salinity (18–25 ppt), temperature (29–33°C), and dissolved oxygen (4–7 mg/L), were within ranges conducive to mangrove growth and resilience. However, slight deviations in pH and dissolved oxygen levels in certain locations may indicate localized stress. Beyond its ecological function, the mangrove ecosystem plays a critical role in supporting local livelihoods through eco-tourism and product diversification. These activities not only enhance economic welfare but also reinforce conservation efforts. The findings highlight the ecological and socio-economic significance of Pasarbanggi’s mangroves and underscore the necessity of sustainable and adaptive management practices to mitigate anthropogenic pressures and ensure long-term ecosystem resilience.
How Does the Decomposition of Mangrove Fine Roots Influence ‘Blue Carbon’ Accumulation?
by Chenxi Yu | Tim Jennerjahn
ZMT | ZMT, University of Bremen, Faculty of Geoscience
In the context of global climate change, this study highlights the critical role of fine roots in tropical mangrove ecosystems as the most dynamically active component of root systems, characterized by rapid turnover and direct contributions to soil processes that drive carbon accumulation and stabilization. By systematically analyzing fine roots decomposition, the research examines how these short-lived roots structures transform organic matter, stimulate microbial activity, and regulate soil carbon pools, providing key insights into biogeochemical mechanisms of carbon fixation. Utilizing advanced modeling approaches, this study offers a robust framework for quantifying fine roots contributions to ‘Blue Carbon’ dynamics, enhancing our understanding of carbon sequestration processes and supporting precise climate change mitigation strategies in coastal ecosystems.
Evolving research data management needs: Insights from the 2021 and 2024 ZMT Surveys
by Birte Hemmelskamp-Pfeiffer
ZMT
Effective research data management (RDM) is essential for advancing scientific discovery, ensuring data integrity and fostering collaboration. To align its services and products with the evolving needs of researchers, the ZMT Research Data Service conducted comprehensive surveys at ZMT in 2021 and 2024. These surveys aimed to identify the practices, challenges and requirements of researchers in relation to RDM.
This poster presents a comparative analysis of the results from both surveys, highlighting trends in researchers’ needs, changes in RDM practices and emerging priorities. The poster also outlines next steps for service development and invites feedback to ensure continued alignment with researchers’ goals.