Sand supplementation favors tropical seagrass Thalassia hemprichii in eutrophic bay: implications for seagrass restoration and management

Abstract

Background Sediment is crucial for the unique marine angiosperm seagrass growth and successful restoration. Sediment modification induced by eutrophication also exacerbates seagrass decline and reduces plantation and transplantation survival rates. However, we lack information regarding the influence of sediment on seagrass photosynthesis and the metabolics, especially regarding the key secondary metabolic flavone. Meanwhile, sulfation of flavonoids in seagrass may mitigate sulfide intrusion, but limited evidence is available. Results We cultured the seagrass Thalassia hemprichii under controlled laboratory conditions in three sediment types by combining different ratios of in-situ eutrophic sediment and coarse beach sand. We examined the effects of beach sand mixed with natural eutrophic sediments on seagrass using photobiology, metabolomics and isotope labelling approaches. Seagrasses grown in eutrophic sediments mixed with beach sand exhibited significantly higher photosynthetic activity, with a larger relative maximum electron transport rate and minimum saturating irradiance. Simultaneously, considerably greater belowground amino acid and flavonoid concentrations were observed to counteract anoxic stress in eutrophic sediments without mixed beach sand. This led to more positive belowground stable sulfur isotope ratios in eutrophic sediments with a lower Eh. Conclusions These results indicated that coarse beach sand indirectly enhanced photosynthesis in T. hemprichii by reducing sulfide intrusion with lower amino acid and flavonoid concentrations. This could explain why T. hemprichii often grows better on coarse sand substrates. Therefore, it is imperative to consider adding beach sand to sediments to improve the environmental conditions for seagrass and restore seagrass in eutrophic ecosystems.

Association Analysis of Seagrass Coverage and Human Activities in Nusa Lembongan

“…This condition predicted due to substrate in the LMB02 that consist of sandy and mud. This is in accordance with Hans (1996) who stated that Thalassia hemprichii lives better on a slightly sandy muddy substrate, then Jiang et al ( 2017) and Jiang et al (2022) explained that Thalassia hemprichii grows better on coarse sand substrate or in the coral substrate. Besides Thalassia hemprichii, Enhalus acoroides also lives quite well on this type of substrate.…”

The Suitable Sites for Seagrass Transplantation in Lae-Lae Island and Sandbar According to Sediment Characteristics

“…She found that E. acoroides seed settlement and seedling establishment can readily occur at sites with fine sand substrate and lower wave exposure. Another recent study by Jiang et al (2022) also reported sediment's importance on seagrass's growth and survival. According to Jiang et al (2022), seagrass Thalassia hemprichii often grows better on coarse sand substrates because coarse beach sand indirectly enhances photosynthesis in T. hemprichii by reducing sulfide intrusion with lower amino acid and flavonoid concentrations.…”

In-vitro study of cytotoxic and apoptotic potential of Thalassia hemprichii (Ehren.) Asch. And Enhalus acoroides (L.f.) Royle against human breast cancer cell line (MCF-7) with correlation to their chemical profile

“…Marine seagrasses are a rich source for secondary metabolites, mainly, phenolic compounds [ 11 ]. Thalassia hemperchii is a widespread species of seagrass in the genus Thalassia that is indigenous to the shore of the Red Sea [ 12 ].…”