Seagrasses

Large, perennial, seagrass meadows of the Poseidon’s ribbon weed and the wire weed (Amphibolis antarctica) dominate much of the marine ecosystem in the UNESCO World Heritage Site of Shark Bay, Australia.

Two years ago, scientists discovered some of the seagrass there was a clone of a Poseidon’s ribbon weed (Posidonia australis) that had 40 chromosomes instead of the typical 20. They think half those chromosomes may come from the ribbon weed and half from an unknown species.

Seagrasses need nutrients to thrive, particularly nitrogen (N). Up to now, it has been assumed that the nitrogen is taken up by the seagrasses through leaves and roots from the surrounding seawater and sediment.

However, in many of the regions where seagrasses are most abundant, there is little nitrogen to be found. Furthermore, while nitrogen is abundant in the sea in its elemental form (N₂), seagrasses cannot use it in this form. 

Admittedly, the idea of protecting seagrass is not as “glamorous” as protecting the rainforest, but this marine vegetation is essential to both marine life and humans. A new study by scientists from Cardiff University, Swansea University and Stockholm University, and published in the Fish and Fisheries journal, highlights the global importance of seagrass to fisheries.

“Wherever you find seagrass and people, there is most certainly fishing,” said Dr Leanne Cullen-Unsworth, from Cardiff University’s Sustainable Places Research Institute.