Enteromorpha

Enteromorpha is a name historically used for a group of green macroalgae in the family Ulvaceae. Molecular studies showed that species once placed in Enteromorpha are nested within Ulva, and as a result Enteromorpha is now generally regarded as a synonym of Ulva in modern taxonomy. A well-known representative formerly placed in Enteromorpha is Enteromorpha intestinalis, commonly called gutweed; in updated classifications it is typically named Ulva intestinalis.

Morphology: The thallus of Enteromorpha is typically hollow and tubular, lacking the flat, sheet-like lamina characteristic of Ulva. Tubes are green, flexible, and may be branched or uniseriate. The length can reach several tens of centimeters, while the diameter commonly ranges from a few millimeters to about a centimeter.

Habitat and distribution: This group occurs in temperate to subtropical coastal waters worldwide, especially where nutrients are abundant. It is common in intertidal and shallow subtidal zones, estuaries, and brackish lagoons, growing on substrata such as rocks, sediment, seagrasses, or floating freely as mats.

Ecology and significance: Enteromorpha/Ulva intestinalis responds rapidly to nutrient enrichment and can form dense mats that shade other flora and fauna. Its abundance is frequently used as an indicator of eutrophication in coastal ecosystems. Localized use in traditional diets or as fodder exists in some regions, reflecting regional practices.

Related taxa include Ulva, with Ulvaceae as the broader family. The taxonomic status of Enteromorpha reflects historical classification rather than a distinct lineage in modern systematics.