An assessment of hydrogen sulfide intrusion in the seagrass Halodule wrightii

Abstract

Hydrogen sulfide (H2S, “sulfide”) is a naturally occurring component of the marine sediment. Eutrophication of coastal waters, however, can lead to an excess of sulfide production that can prove toxic to seagrasses. We used stable sulfur isotope ratio (δ34S) measurements to assess sulfide intrusion in the seagrass Halodule wrightii, a semi-tropical species found throughout the Gulf of Mexico, Caribbean Sea, and both western and eastern Atlantic coasts. We found a gradient in δ34S values (−5.58 ± 0.54‰+13.58 ± 0.30‰) from roots to leaves, in accordance with prior observations and those from other species. The results may also represent the first values reported for H. wrightii rhizome tissue. The presence of sulfide-derived sulfur in varying proportions (15–55%) among leaf, rhizome, and root tissues suggests H. wrightii is able to assimilate sedimentary H2S into non-toxic forms that constitute a significant portion of the plant’s total sulfur content.