Ulva prolifera

Lore & Background

Ulva prolifera occurs worldwide, found in Europe (Bulgaria, France, Great Britain, Greece, Ireland, Portugal, Romania, Slovenia, Spain, and Lolland island of Denmark), African islands (Canary and Madeira), US states (Alaska, California, Florida, Texas, Washington), Central American countries (Costa Rica, El Salvador, Panama, Cuba), and occasionally on the Pacific side of Mexico. It mostly occurs as wild algae, though some are cultivated in Japan, Korea, China, and other countries. The species is notable for causing green tides in the Yellow Sea of China every summer since 2007, with the largest recorded bloom in 2013 off the coast of Qingdao. These green tides are a major environmental concern involving natural, anthropogenic, physicochemical, and algae factors, along with warming local water. Analysis supports the hypothesis that blooms originate off the Jiangsu coast, driven by monsoons and ocean currents, and are linked to Porphyra yezoensis aquaculture activities, where thalli of U. prolifera are scraped and thrown away after harvesting.

Reader's Guide

Ulva prolifera is significant primarily for its role in recurring green tides in the Yellow Sea of China, which have occurred every summer since 2007. These blooms caught additional attention in 2008 when the sailing games of the Beijing Olympics were hosted in Qingdao, as green tides cause great economic and ecological impacts. The overgrowth of this alga at the seawater surface blocks sunlight, creating a shallower aphotic zone that can be fatal for plants and organisms requiring sunlight, and reduces phytoplankton photosynthesis, devastating the local food web. Increased algal respiration during blooms depletes oxygen, harming all living organisms. Accumulated algae washed ashore degrade and release noxious smells, harming the environment, underwater biome, and tourism. Traditional treatments include collecting algae from the coast or setting up nets offshore; research is being done on microbial complex formulation spray to promote rapid degradation. The species is also cultivated in some countries and has common names in Chinese, Hawaiian, Japanese, Korean, and Swedish.

Did You Know?

• Ulva prolifera was previously classified as Enteromorpha prolifera.
• The largest recorded bloom of this alga occurred in 2013 in the Yellow Sea off Qingdao, China.
• Green tides from U. prolifera have occurred every summer in the Yellow Sea since 2007.
• The species is known as 'gasiparae' in Korean and 'suji-aonori' in Japanese.