Halophila ovalis, commonly known as paddle weed, spoon grass or dugong grass, is a seagrass in the family Hydrocharitaceae. It is a small herbaceous plant that occurs in sea beds and other saltwater environments in the Indo-Pacific.
The first description of the species was by Robert Brown as Caulinia ovalis, this was transferred to the genus Halophila by Joseph Dalton Hooker in Flora Tasmaniae (1858). The species name Halophila ovata is now regarded as a synonym of this species.
The plant occurs around reefs, estuaries, islands, inter-tidal areas, on soft sand or mud substrates. The leaves are ovate in outline, appearing on stems that emerge from rhizome beneath the sand. The roots get up to 800 mm long and covered in fine root hairs. It is often found in meadows that dominate a sand bank or other patch of sea floor. The arrangement of the plant, above and below ground, provides stability to the sea floor and habitat for other species. It is used as food by dugong, as is therefore known as dugong grass.
The two most prominent genera are Alpheus and Synalpheus, with species numbering well over 250 and 100, respectively. Most snapping shrimp dig burrows and are common inhabitants of coral reefs, submerged seagrass flats and oyster reefs. While most genera and species are found in tropical and temperate coastal and marine waters.
A very simple method of documenting bird tracks at seagrass area is to use Plaster of Paris (Calcium sulfate) as a liquid mixture poured into the bird tracks. The plaster cast is quick drying and easily stored for further ex-situ identification and documentation. Seen here is possibly the tracks of a small wader bird. Click here for steps on how to make your own plaster casts.