RESUMEN
The mixotrophic dinoflagellate Akashiwo sanguinea frequently forms harmful algal blooms around the world and has caused massive deaths of shellfish, finfish and birds, yet its toxic mechanism is still unclear. In this study, toxic effects of A. sanguinea on co-culturing phytoplankton and zooplankton were investigated. The results showed that sonicated cultures of A. sanguinea JX13 and JX14, isolated from the Pearl River Estuary, had a significant lethal effect on the rotifer Brachionus plicatilis, with the highest mortality rate of 80%. The highest inhibition rates of A. sanguinea cultures JX13 (90%) and JX14 (80%) on R. salina were much higher than that of AS2 (20%). Toxicity varied with the growth stage, during which A. sanguinea cells in the exponential stage showed the highest toxicity (40%), while A. sanguinea filtrate had the highest toxicity (10%) in the decline stage. The action mode of A. sanguinea toxicity on plankton was explored through an osmotic membrane culture device. It was found that A. sanguinea JX13 displayed an inhibitory effect on coexisting phytoplankton, whether they had contact or not, but the inhibition rate increased by 25% with contact. A lethal effect of A. sanguinea JX13 on rotifer Brachionus plicatilis was observed only in contact treatment. This study suggests that direct contact is the key action mode to trigger the release of toxins and induce toxic effects of A. sanguinea on co-occurring plankton.
Asunto(s)
Dinoflagelados , Animales , Estuarios , Floraciones de Algas Nocivas , Fitoplancton , ZooplanctonRESUMEN
Antialgal compounds from plants have been identified as promising candidates for controlling harmful algal blooms (HABs). In our previous study, luteolin-7-O-glucuronide was used as a promising algistatic agent to control Phaeocystis globosa (P. globose) blooms; however, its antialgal mechanism on P. globosa have not yet been elaborated in detail. In this study, a liquid chromatography linked to tandem mass spectrometry (LC-MS/MS)-based untargeted metabolomic approach was used to investigate changes in intracellular and extracellular metabolites of P. globosa after exposure to luteolin-7-O-glucuronide. Significant differences in intracellular metabolites profiles were observed between treated and untreated groups; nevertheless, metabolic statuses for extracellular metabolites were similar among these two groups. For intracellular metabolites, 20 identified metabolites showed significant difference. The contents of luteolin, gallic acid, betaine and three fatty acids were increased, while the contents of α-Ketoglutarate and acetyl-CoA involved in tricarboxylic acid cycle, glutamate, and 11 organic acids were decreased. Changes in those metabolites may be induced by the antialgal compound in response to stress. The results revealed that luteolin played a vital role in the antialgal mechanism of luteolin-7-O-glucuronide on P. globosa, because luteolin increased the most in the treatment groups and had strong antialgal activity on P. globosa. α-Ketoglutarate and acetyl-CoA were the most inhibited metabolites, indicating that the antialgal compound inhibited the growth through disturbed the tricarboxylic acid (TCA) cycle of algal cells. To summarize, our data provides insights into the antialgal mechanism of luteolin-7-O-glucuronide on P. globosa, which can be used to further control P. globosa blooms.