Assessing the validity of making a new designation of seaweed tide forming Ulva ohnoi and Sargassum horneri nonindigenous population as ecosystem disturbing and harmful organisms

Abstract

Recurrent outbreaks of drifting seaweed biomasses, called seaweed tides or macroalgal bloomings, such as “green- and golden tides”, are nuisance phenomena worldwide, as they pose a serious threat to local biodiversity in coastal ecosystems and also cause severe damage to the local economy by disturbing tourism, aquaculture, and fisheries. The green tide forming seaweeds, primarily the genus Ulva and the golden tide seaweeds, the genus Sargassum are particularly notorious for the formation and inundation of drifting seaweed biomass along the coastlines. In recent years, green algal massive growth forming ‘green carpets’ have readily been detected all year round along the shorelines on Jeju Island, especially for the Shinyang beach on the northeastern coast. A subtropical species, Ulva ohnoi is suggested to be one of the major green tide forming species in Jeju Island. Moreover, Sargassum horneri that bloomed in the eastern coast of China has drifted in a large biomass with oceanic currents and accumulated along the southern coast of Korea including Jeju Island. In the current study, we discuss and evaluate the validity of making a new designation of Ulva ohnoi and S. horneri nonindigenous population as marine ecosystem disturbing and harmful organisms, in order to effectively manage the green- and golden tides seaweeds in the future.