Review of Allelopathy in Green Tides: The Case of Ulva prolifera in the South Yellow Sea

Abstract

The proliferation of large green macroalgae in marine environments has led to the occurrence of green tides, particularly in the South Yellow Sea region of China, where Ulva prolifera has been identified as the primary species responsible for the world's largest green tide events. Allelopathy among plants is a critical factor influencing the dynamics of green tides. This review synthesizes previous research on allelopathic interactions within green tides, categorizing four extensively studied allelochemicals: fatty acids, aldehydes, phenols, and terpenes. The mechanisms by which these compounds regulate the physiological processes of green tide algae are examined in depth. Additionally, recent advancements in the rapid detection of allelochemicals are summarized, and their potential applications in monitoring green tide events are discussed. The integration of advanced monitoring technologies, such as satellite observation and environmental DNA (eDNA) analysis, with allelopathic substance detection is also explored. This combined approach addresses gaps in understanding the dynamic processes of green tide formation and provides a more comprehensive insight into the mechanisms driving these phenomena. The findings and new perspectives presented in this review aim to offer valuable insights and inspiration for researchers and policymakers.

Keywords: Ulva prolifera; allelochemicals; allelopathy; green tide; marine monitoring; physiological mechanism.

Figure 1

Green tide of U. prolifera in the South Yellow Sea in 2022. From May to July each year, large-scale green tides move northwards from Jiangsu to the Shandong Peninsula. Satellite images cited from previous work [17].

Figure 2

Fatty acids, aldehydes, phenols, and terpenoids in U. prolifera: known mechanisms of their allelopathic actions. Allelochemicals’ effect on U. prolifera’s physiology is shown by blue arrows; algae’s physiological processes’ effect on allelochemical content is shown by red arrows. (By BioRender).

Figure 3

With the confluence of developing technology, ecological adaptation strategies for green tide algae will be better understood. Satellite technology tracks the emergence of green tides regionally; eDNA technology quickly monitors species distribution and community structure; and allelochemical detection greatly fills the gap in the unknown interactions between species. This changes the research emphasis from the traditional nutrient and hydrometeorological factors to the in-depth study of ecological dynamics and structure during green tides.