The number of large populations of seagrasses is in serious decline. Seagrasses are plants that in the course of evolution have recolonised the sea. Despite their name, they are not grasses but plants with flowers and seeds that provide a habitat for marine animals along the ocean coasts. In addition, seagrass beds attract international attention for the many ecosystem services they provide. They store carbon much faster than tropical forests and protect the coast against erosion. VUB PhD student Jasper Dierick is studying offshore seagrass beds in Southeast Asia with partner scientists from local universities.
He uses genetics to understand how sexual reproduction (via seeds) and asexual reproduction (via clonal rhizome growth) contribute to the conservation of seagrass beds in disturbed areas. This disturbance may be related to more intensive use of the coast and to changing land use inland. There, a shift is increasingly visible from forestry to intensive agriculture. His research shows that some of these seagrasses are centuries-old clones that are resistant to intense disturbance. In Vietnam, where the coasts have undergone a major change over the past 30 years due to human land use, Dierick observes that sexual reproduction is declining and large, resistant seagrass clones can be seen.
“Those clones can sometimes be very old, literally hundreds of years,” says Dierick. “The clonal vs sexual reproduction ratio differs from habitat to habitat. Thus, in undisturbed areas, the focus is on flower pollination and seed dispersal via ocean currents. By contrast, in disturbed coastal areas, almost exclusively old clones remain, which is significant. The study should estimate the longer-term resistance and survival of seagrass beds in the affected coastal areas and quantify the impact of nutrient-rich water, which runs off fields along the coast almost directly into the ocean.”
The results of his research will provide essential information for the design and implementation of effective management measures to ensure the long-term protection and recovery of seagrasses. Dierick received an award for his research in the recent VLIZ Marine Science Day 2023 in Bruges, where his presentation was chosen as the Best Oral Talk.