Giant clams in Nha Trang Bay: A look into the IMARCS Foundation's research on reef restoration
Working with researchers from the University of Barcelona and Nha Trang University, the IMARCS Foundation has begun a novel research project to determine the effects that giant clams have on reef health and biodiversity in Nha Trang Bay, Vietnam. Giant clams are found in many areas of Vietnam, including Phu Quoc and Con Dao, but the reefs surrounding Nha Trang are ideal for utilizing the methodologies that will best determine the effects that reintroducing giant clams will have on reef environments. Below is a summary of what the current status of giant clams looks like in Vietnam and how IMARCS is working alongside partners to carry out important research in the area.
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Giant clam habitats and ecosystem roles
Vietnam’s coral reefs offer ideal conditions for giant clams, particularly within shallow lagoons where sunlight reaches depths that support zooxanthellae. These algae live symbiotically within the clams' tissues, enabling them to photosynthesize and produce essential nutrients that support the clam's growth. The clams’ large size and filter-feeding behavior help to clear the surrounding water, thus enhancing light penetration, which benefits the coral and algae in their ecosystems (Neo et al., 2015). This unique role makes them critical for maintaining the ecological balance within reefs and supporting overall biodiversity. Current research suggests that giant clams can significantly contribute to reef resilience, as their shells provide microhabitats for various marine organisms (Singla, 2023), and IMARCS is looking to expand on this to determine the extent to which biodiversity is enhanced and reef health is improved through novel surveying techniques and environmental DNA analysis.
Vietnam’s coral reefs offer ideal conditions for giant clams, particularly within shallow lagoons where sunlight reaches depths that support zooxanthellae. These algae live symbiotically within the clams' tissues, enabling them to photosynthesize and produce essential nutrients that support the clam's growth. The clams’ large size and filter-feeding behavior help to clear the surrounding water, thus enhancing light penetration, which benefits the coral and algae in their ecosystems (Neo et al., 2015). This unique role makes them critical for maintaining the ecological balance within reefs and supporting overall biodiversity. Current research suggests that giant clams can significantly contribute to reef resilience, as their shells provide microhabitats for various marine organisms (Singla, 2023), and IMARCS is looking to expand on this to determine the extent to which biodiversity is enhanced and reef health is improved through novel surveying techniques and environmental DNA analysis.
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Conservation status and threats
The populations of giant clams in Vietnam, much like elsewhere in Southeast Asia, have been severely impacted by unsustainable harvesting for food, traditional medicine, and the ornamental trade. For example, a study conducted by TRAFFIC (Lee, M. and Wong, R., 2023) highlighted that high local demand in Southeast Asia has led to the decline of several Tridacna species, pushing some to the brink of extinction. In addition, coastal development and pollution from tourism and agriculture have degraded many coral reefs, where these clams play an essential role. Increased sedimentation from construction along Vietnam’s coastlines has smothered reefs and disrupted the clams’ ability to photosynthesize, compromising their growth and survival (Le, 2020).
Climate change further exacerbates these threats through rising sea temperatures and ocean acidification, both of which pose a direct risk to clams' calcium carbonate shells. Acidification weakens their shells, making them more vulnerable to predation and environmental stressors (Watson, 2015). Additionally, coral bleaching—a result of increased ocean temperatures—affects reef health overall, and giant clams are indirectly impacted by the reduced structural integrity and biodiversity of these ecosystems.
Conservation efforts in Vietnam
In response to these threats, Vietnam has implemented several conservation strategies to protect its giant clam populations. Marine Protected Areas (MPAs) in regions such as Nha Trang Bay and Con Dao restrict fishing and harvesting activities, providing safer zones for marine life, including giant clams. Restoration projects have also been initiated in these MPAs, which include reintroducing juvenile clams grown in controlled environments back into natural reef systems. IMARCS will be looking to add to these efforts by recording improvements in local biodiversity and ecosystem resilience where clam populations were successfully restored. This approach has already proven beneficial for stabilizing clam populations, allowing them to resume their ecological roles; this research will focus on the extent to which giant clams improve or increase total biodiversity of reef ecosystems.
Furthermore, sustainable mariculture practices are also being explored by IMARCS (as well as projects such as Martin Selch's project in Kosrae, FSM) to meet market demand while minimizing impacts on wild populations. By cultivating giant clams in controlled environments, researchers from Nha Trang University in Vietnam have already helped reduce the need for wild harvesting, alleviating pressure on natural populations. Additional collaborations with international conservation organizations are also helping to establish monitoring programs to track clam populations and assess the effectiveness of protection measures.
Furthermore, sustainable mariculture practices are also being explored by IMARCS (as well as projects such as Martin Selch's project in Kosrae, FSM) to meet market demand while minimizing impacts on wild populations. By cultivating giant clams in controlled environments, researchers from Nha Trang University in Vietnam have already helped reduce the need for wild harvesting, alleviating pressure on natural populations. Additional collaborations with international conservation organizations are also helping to establish monitoring programs to track clam populations and assess the effectiveness of protection measures.
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The future of giant clams in Vietnam
In parallel to the ongoing research being carried out by the IMARCS Foundation, the University of Barcelona, and Nha Trang University, the survival of giant clams in Vietnam hinges on continued conservation efforts, sustainable practices, and community engagement. Local communities are becoming increasingly involved in these initiatives, participating in reef restoration and learning about the significance of clams to reef health. Creating conditions that are ideal for balancing economic interests with conservation goals should provide hope that giant clam populations can be preserved, contributing to healthier and more resilient coral reefs in the region.
Stay up to date about our research in the area by reaching out to us at relationships@imarcs.org
Stay up to date about our research in the area by reaching out to us at relationships@imarcs.org
References
Neo, M. L., Eckman, W., Vicentuan, K., Teo, S. L., & Todd, P. A. (2015). The ecological significance of giant clams in coral reef ecosystems. Biological Conservation, 181, 111-123. doi:10.1016/j.biocon.2014.10.012
Singla, G. (2023). Organism Communities on Giant Clam Shells as Compared to the Surrounding Substrate in Reefs Around Lizard Island, Queensland. Independent Study Project (ISP) Collection. 3752. https://digitalcollections.sit.edu/isp_collection/3752
Watson, S. (2015). Giant clams and rising CO₂: Light may ameliorate effects of ocean acidification on a solar-powered animal. PLoS ONE, 10(6), e0128405. https://doi.org/10.1371/journal.pone.0128405
Lee, M.A. and Wong, R. (2023). Trading Giants: A rapid assessment of giant clam Tridacninae seizures implicating Southeast Asia 2003-2022. TRAFFIC, Southeast Asia Regional Office,
Petaling Jaya, Selangor, Malaysia
Le, D. (2020). The status of coral reefs in central Vietnam’s coastal water under climate change. Aquatic Ecosystem Health & Management, 23(3), 323-331. https://doi.org/10.1080/14634988.2020.1819715
Neo, M. L., Eckman, W., Vicentuan, K., Teo, S. L., & Todd, P. A. (2015). The ecological significance of giant clams in coral reef ecosystems. Biological Conservation, 181, 111-123. doi:10.1016/j.biocon.2014.10.012
Singla, G. (2023). Organism Communities on Giant Clam Shells as Compared to the Surrounding Substrate in Reefs Around Lizard Island, Queensland. Independent Study Project (ISP) Collection. 3752. https://digitalcollections.sit.edu/isp_collection/3752
Watson, S. (2015). Giant clams and rising CO₂: Light may ameliorate effects of ocean acidification on a solar-powered animal. PLoS ONE, 10(6), e0128405. https://doi.org/10.1371/journal.pone.0128405
Lee, M.A. and Wong, R. (2023). Trading Giants: A rapid assessment of giant clam Tridacninae seizures implicating Southeast Asia 2003-2022. TRAFFIC, Southeast Asia Regional Office,
Petaling Jaya, Selangor, Malaysia
Le, D. (2020). The status of coral reefs in central Vietnam’s coastal water under climate change. Aquatic Ecosystem Health & Management, 23(3), 323-331. https://doi.org/10.1080/14634988.2020.1819715