Highlights
- Sporophytes and gametophytes differed in germ cell release.
- Sporophytes and gametophytes differed in physiological responses.
- The different responses lead to Ulva sp. green tide outbreak.
Abstract
The Ulva sp. green tide is one global marine ecological disaster, and its prevention and control have drawn global attention. However, existing control strategies based on ecological mechanisms of Ulva sp. green tide without distinguishing sporophytes from gametophytes have yielded limited success, suggesting that the green tide outbreaks are driven by intrinsic biological mechanisms. Ulva australis Areschoug gametophytes and sporophytes differ in chromosome number; hence, it is inferred that their reproductive strategies respond differentially to environment factors, which explains the biological mechanism of Ulva sp. green tides from the perspective of the origin of germ cells. To verify this hypothesis and for effective control of green tides, the sporophytes and gametophytes of U. australis Areschoug were respectively cultivated and exposed to the conditions of nutrient salts, salinity and carbon dioxide (CO2) superimposed in a uniform design experiment for 48 h to observe the release of germ cells (spores or gametes). The spore release rate of sporophytes was positively correlated with salinity (p<0.05). The gamete release rate of gametophytes had a positive correlation with the interaction between NH4-N and PO4-P (p<0.05), and a negative correlation with CO2 concentration (p<0.05). The difference in responses of sporophytes and gametophytes to environmental factors ensures the availability of germ cells of U. australis Areschoug, which facilitates the green tide outbreak. Thus, the sporophyte and gametophyte respond differently to environmental factors, suggesting that they can adapt to different habitats, which implies that the green tide outbreak of the Ulva sp. has an inherent biological promoting mechanism. Moreover, it is understandable that the effect of a single control strategy in dealing with Ulva sp. green tides is not satisfactory.
Wang Y., Gu W., He Q., Tan Q., Yang Q., Zhang H. & Ge C., 2027. Response of spore or gamete release of Ulva australis Areschoug to the superimposition of nutrients, salinity and ocean acidification: Implication for Ulva sp. green tide outbreak. Aquatic Botany 208: 104066. doi: 10.1016/j.aquabot.2026.104066. Article.
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