Dissertation
The resilience of tropical intertidal seagrass meadows, grazed by dugongs, and the impact of anthropogenic stressors
Seagrass is a marine flowering plant with special adaptations to coastal and marine environments, playing a crucial role in providing a wide range of ecosystem services.
- Author
- A.A.B. Aditya
- Date
- 23 September 2025
- Links
- Thesis in Leiden Repository
Its main functions include supporting complex trophic food webs, stabilizing sediments, filtering nutrients, and serving as spawning and nursery grounds for fish and various marine organisms. However, seagrass ecosystems face multiple pressures, including sedimentation, nutrient runoff, physical disturbances, oil pollution, commercial fishing practices, grazing by marine herbivores, algal blooms, and global warming.
Balikpapan Bay, one of the important tropical bays in Indonesia, serves as a concrete example of such conditions. The bay has a strategic role as a major commercial port, an industrial hub, and a shipping gateway to the new national capital, Nusantara. Despite high anthropogenic pressures, Balikpapan Bay still supports significant biodiversity, including protected species such as the dugong (Dugong dugon), the Irrawaddy dolphin, and other dolphin species, which are sustained by mangrove, seagrass, and coral reef habitats. Although coral reefs have degraded due to turbidity and sedimentation, seagrass meadows persist in the intertidal zone, dominated by Halodule, Thalassia, and Enhalus. These meadows are vital for dugong survival, serving as grazing areas and possibly as nursery grounds.
Nevertheless, Balikpapan Bay also faces serious threats due to its role as a center of the national oil industry. An oil spill in 2018, caused by an underwater pipeline leak, resulted in extensive damage to seagrass ecosystems, with the loss of above-ground biomass and the cessation of dugong grazing activity for more than a year. Although pioneer seagrass species showed recovery capacity, biomass imbalance remained long after the incident, highlighting the ecosystem’s vulnerability to pollution. In addition, intertidal seagrasses in Balikpapan Bay must adapt to extreme environmental conditions such as high turbidity, sediment loads, and desiccation from sun exposure during low tide. Physiological adaptations, such as rhizome and root elongation, play an important role in nutrient distribution under such extreme conditions.
This study highlights the resilience of tropical intertidal seagrass communities, while at the same time underscoring their vulnerability to anthropogenic pressures. Therefore, future coastal management, particularly in Balikpapan Bay, should pay greater attention to the protection of intertidal seagrass meadows by controlling sedimentation and chemical pollution, as well as utilizing dugongs as indicators of seagrass ecosystem health.