17 Green Algae II

Ulvophyceans

Ulvophyceans include some of the largest and most conspicuous of the green algae. A number of genera are notable for forming nuisance growths that interfere with human activities or harm other organisms. Examples include tubes of Enteromorpha that foul the hulls of oceangoing ships and form “green tides” along rocky marine shorelines affected by nutrient pollution. Codium, the seaweed aptly known as “dead man’s fingers,” can wreak havoc in shellfish beds. By growing on their surfaces, this heavy seaweed weighs shellfish down, thereby preventing their escape from predators. Vast lawns of a giant form of Caulerpa taxifolia have become notorious for smothering corals and other sea life in the Mediterranean Sea. Overgrowths of gray-green Dictyosphaeria occur on Hawaiian coral reefs as a result of human disturbances. In freshwaters, surface blankets of Pithophora may clog boat motors, and shoreline thickets of Cladophora generate terrible odors after washing up onto beaches and rotting there. On land, the ulvophycean genus Cephaleuros becomes a pest in tropical plantations, producing rusty spots on the leaves of tea and other plants.

Other ulvophyceans play more positive roles, providing food and habitat for aquatic animals. Beautiful tropical green seaweeds such as the mermaid’s wine cup Acetabularia attract snorkelers and divers, while the lacy blades of Anadyomene decorate both coral reefs and the cover of this book. This chapter surveys the relationships, diversity of body forms, and reproductive cycles of ulvophycean green algae.