Settlement of vegetative fragments of Ulva prolifera confirmed as an important seed source for succession of a large‐scale green tide bloom

Abstract

Ulva prolifera green tides in the Yellow Sea of China in the past 3 yr are among the largest macroalgal blooms ever recorded. Satellite images, as well as wind and current patterns, provide a clear picture of the formation of these green tides; however, their place of origin remains unclear. Terrestrial investigation along the coastline of the Jiangsu Province and two shipboard surveys in the Yellow Sea in 2009 showed that filamentous Ulvaceae algae were prevalent in various environments in Jiangsu Province including floating rafts for Porphyra cultivation, land‐based bivalve culturing ponds, estuaries, embankments, intertidal stones, wharfs, and hard muddy coasts. Vegetative fragments in sediment samples were found in both shipboard surveys during the bloom and postbloom periods, and all of the samples were U. prolifera. Phylogenetic analysis of 5S spacer sequences showed that the green tide in the Yellow Sea was not of terrestrial origin. However, settled vegetative fragments of U. prolifera were an important seed source for the successive and more serious green tide blooms.