Seagrass beds are among the most efficient carbon absorption systems on Earth, but our understanding of blue carbon shouldn't be limited to the plants' carbon sequestration capabilities alone. The true value of these underwater oases lies in how their complete ecosystem and rich biodiversity collectively maintain this highly efficient carbon storage system.
We can learn from the seagrass survey of Dongsha Atoll National Park and the publication "Glittering Green: Dongsha Seagrass Beds." Seagrasses are the only vascular plants that can flower and bear fruit in seawater, distributed in temperate to tropical shallow seas worldwide. They fix carbon dioxide through photosynthesis, demonstrating their carbon sequestration ability via the sediments beneath them. The dense blades of seagrass slow down water currents, allowing organic and inorganic matter to settle. In anoxic environments, these materials decompose slowly, forming long-term "blue carbon" storage. Of course, different species of seagrass distributed in tropical and temperate regions vary in morphology and biomass, so we cannot consider their carbon sequestration equal. However, if we view seagrass bed ecosystems from the perspective of biodiversity, then seagrass beds around the world share a common characteristic: they are rich, diverse, healthy, and vibrant carbon cycling reservoirs.
In addition to their carbon sequestration function, seagrass beds are home to countless marine organisms, providing food, shelter, and nurseries for diverse species such as fish, crustaceans, and mollusks. They even support coastal fishery resources. In a healthy and intact seagrass bed ecosystem, dugongs are one of the most representative large residents.These gentle marine mammals need to consume large amounts of seagrass daily to survive, which might seem destructive. However, they act like gardeners, maintaining ecological balance. The selective foraging of dugongs influences the competitive relationships among different seagrass species, balancing them and maintaining ecosystem stability. Their excretions convert organic matter into easily decomposable forms, accelerating localized nutrient cycling, which also benefits seagrass growth.
Various benthic invertebrates living in seagrass beds influence sediment structure, oxygen content, and the decomposition rate of organic matter through bioturbation. Moderate disturbance also aids in deeper carbon burial. Bacteria in the sediments decompose organic matter, striking a balance between carbon release and retention. Generally, higher biodiversity leads to more stable and efficient carbon cycling processes. Organisms moving between different ecological niches bring in external nutrients and contribute organic carbon, while indirectly affecting sediment bioturbation through predation.
From a holistic ecological perspective, the carbon sequestration value of seagrass beds is not merely the photosynthesis of seagrasses; it is the result of the entire ecosystem, from microorganisms to dugongs, working together. Biodiversity ensures the stability and resilience of ecological functions, making seagrass beds more reliable "blue carbon" warehouses that are more resistant to environmental changes.
Therefore, when understanding blue carbon, we need to move beyond the simple notion that "seagrasses can sequester carbon." We should view seagrass beds as complete ecosystems. Protecting seagrass beds is not just about protecting the plants themselves, but also about protecting all the life within them. Promoting blue carbon conservation should adopt a comprehensive ecosystem management approach, including reducing pollution, preventing habitat destruction, and maintaining the health and population stability of biodiversity and key species. Only then can seagrass beds maintain their rich and diverse ecological functions while continuing to store carbon effectively.
“Glittering Green: Dongsha Seagrass Beds.”
Dongsha Seagrass Beds.