Other Surveys

Ground Truthing Seagrass Habitats

In 2022, our surveys team conducted seagrass rapid assessment surveys at 250 locations across TRS and Amaala. The resulting data greatly improve our understanding of the distribution of seagrass habitats, and of species composition.

Halodule and Halophila species are particularly important as food for dugongs and Green turtles. Those genera are small, fast-growing and pioneer species that are able to recover faster after disturbances (e.g., burial by sediment, grazing) than larger grasses. Cymodocea rotundata is also fast-growing, although of larger size, and is a food alternative for dugongs when Halophila and Halodule spp. are not available.

Larger species such as Enhalus acoroides, Thalassia hemprichii and, especially, Thalassodendron ciliatum, contribute to substrate stabilization and sediment accumulation and hence to enhanced carbon sequestration. Those species have extended root systems that trap sediment and allow them to withstand wave action in mud substrate. Ephiphytes that grow on all species, especially on T. hemprichii and T. ciliatum, are a food source for small grazing organisms, such as snails.

As shown in the image on the right below, grazing dugongs leaves characteristic ‘feeding trails’. These are distinct tracks within seagrass beds left after dugongs have consumed seagrass within that track. The presence of these trails is one indication of a dugong feeding ground.

Overall, 10 of the 12 seagrass species found in the Red Sea basin have been encountered in TRS area and seven in Amaala. Halodule uninervis, Halophila decipiens, Halophila ovalis, Halophila stipulacea, Cymodocea rotundata, Thalassia hemprichii, and Thalassodendron ciliatum were recorded at both sites, whereas Halodule pinifolia, Cymodocea serrulata and Enhalus acoroides were recorded only in TRS.