halophila ovalis

12 09 2008

Common name: Spoon seagrass/ Paddle weed
Halophila Ovalis

Kingdom: Plantae
Phylum: Magnoliphyta
Class: Liliopsida
Order: Alismatales
Family: Hydrocharitaceae
Genus: Halophila
Species: Ovalis

Description: Halophila Ovalis is a small herbaceous plant. 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 are covered in fine root hairs. It is also connected by a series of interconnecting rhizomes as in grasses.

Habitat: This plant occurs in sea beds and other saltwater environments. It is also frequently seen in reefs, estuaries, islands, inter-tidal areas, on soft sand or mud substrates. It can dominate a sand bank or other patches of the sea bed and is thus often found in meadows.


ulva lactuca

12 09 2008

Ulva Lactuca

Kingdom: Protista
Phylum: Chlorophyta
Class: Ulvophyceae
Order: Ulvales
Family: Ulvaceae
Genus: Ulva
Species: Lactuca

Description: Ulva lactuca is a thin flat green alga growing from a discoid holdfast. The margin is somewhat ruffled and often torn. It may reach 18cm or more in length, though generally much less, and up to 30 cm across. The membrane is two cells thick, soft, translucent and grows attached, without a stipe, to rock by a small disc-shaped holdfast. Green to dark green in color this species in the Chlorophyta is formed of two layers of cells irregularly arranged, as seen in cross section. The chloroplast is cup-shaped with 1 to 3 pyrenoids. There are other species of Ulva which are similar and not always easy to differentiate.

Habitat: This sea lettuce is found in all levels of the intertidal. However, in more northerly latitudes and brackish habitats, it is found in the shallow sub littoral. In very sheltered conditions, the plants that have become detached from the substrate can continue to grow, forming extensive floating communities. Ulva lactuca can be found on suitable substrata in estuaries. It is particularly prolific in areas where nutrients are abundant.