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Ulva is a genus of green algae known commonly as sea lettuce or green laver. Ulva seaweeds are found worldwide in nitrogen-rich marine habitats attached to rocks in the mid to low intertidal zone (Lee 2008; Kirby 2001). The fronds of Ulva usually grow as sheets, but some species exist in a hollow cylindrical form. These cylindrical species were previously classified as a distinct genus, Enteromorpha, but are now included in Ulva. (Lee 2008; Hayden et al 2003). The blades can grow up to 40 cm long, but are very thin—only 2 cells thick (Lee 2008).
Ulva is eaten by humans in soups, salads, and sushi (Lee 2008 and references within; Kirby 2001).
Ulva is found worldwide.
Lives in marine environments, and sometimes found in brackish waters in estuaries, however, Ulva needs nitrogen-rich waters. Ulva attaches to rocks in the mid to low intertidal zone (Lee 2008; Kirby 2001).
Ulva goes through an isomorphic alternation of generations. Adult gametophytes produce only female or male gamets, which are positively phototactic, and move with flagella. They are released in swarms coordinated by lunar cycles and tides. When the zygote is formed it becomes negatively phototactic and swims to the bottom to settle, and germinates within a few days. The haploid phase of the life cycle (the sporophyte), produces sporophytes which, like the gametes, are also motile using a set of four flagella to swim (Lee 2008; Guiry and Guiry 2011).
The fronds of Ulva usually grow as sheets, but some species exist in a hollow cylindrical form. These cylindrical species were previously classified as a distinct genus, Enteromorpha, but have been synonymized with Ulva. The blade morphology of Ulva is dependent on bacterial composition in the environment (Lee 2008; Hayden et al 2003).
Ulva is considered the main component of "green tide" events in bays especially near large cities in Japan and elsewhere. Its prolific growth becomes a nuisance, especially in run-off waters containing high nutrient levels. In these environments it can outcompete other organisms and reduce diversity in benthic communities. It also creates a nuisance on beaches when it is washed up and decomposes in large amounts as the rotting algae produces hydrogen sulfide gas (Lee 2008; Yabe 2009).
The blades can grow up to 40 cm long, but are very thin - only 2 cells thick (Lee 2008).
Ulva is eaten by humans, although the literature has some disagreement about how tasty and digestible it is. It is eaten in soups, salads and sushi (Lee 2008 and references within; Kirby 2001).
