浒苔微观繁殖体与亚历山大藻相互作用的研究

INTERACTIONS BETWEEN MICROSCOPIC PROPAGULES OF ULVA PROLIFERA AND ALEXANDRIUM

连年暴发的浒苔绿潮灾害对我国近海生态安全造成了严重的危害,因此本实验选取了中国沿海常见赤潮藻种亚历山大藻以及浒苔微观繁殖体中的配子为研究对象,在室内控制条件下模拟了浒苔配子在发育早期两个重要阶段(固着和萌发阶段)与四株亚历山大藻之间的相互影响效应。研究发现:浒苔配子在固着阶段对四株亚历山大藻的生长无明显影响,但在随后的萌发阶段却显著抑制了塔玛亚历山大藻的生长,第7天的生长抑制率达到27%。而四株亚历山大藻均可强烈抑制浒苔配子的固着,24h ID50均小于50 cells/m L,但对随后浒苔配子的萌发并无影响。因此在两者的相互作用关系中,微藻的竞争优势主要体现在浒苔配子固着阶段,浒苔的竞争优势则体现在配子萌发阶段。进一步的研究发现,亚历山大藻对浒苔配子固着的抑制效应是通过分泌某些物质(非PSP毒素)产生的,该类物质可能由蛋白类和非蛋白类成分共同组成。而浒苔配子分泌的化感物质造成了其对塔玛亚历山大藻的抑制效应。

Large-scale outbreaks of green tides of Ulva prolifera threatened estuarine and coastal ecosystems in the Yellow Sea recent years. We studied interactions between common red-tide-causative microalgae Alexandrium and the microscopic propagules（unisexual gametes） of U. prolifera at settlement and germination stages in co-culture systems. The results show that U. prolifera gametes at settlement stage had no effects on growth of Alexandrium species; but the microscopic forms of subsequent germinated U. prolifera inhibited significantly the growth of Alexandrium tamarense, and the inhibition rate was 27% on Day 7. Inversely, all four Alexandrium strains inhibited settlement of U. prolifera gametes at an ID50 less than 50 cells/m L in 24 h, but had no adverse influence on germination of U. prolifera propagules. Therefore, the competitive advantage of microalgae took effect mainly at the settlement stage due to possible allelechemicals of non-PSP allelopathic substances released from Alexandrium. These substances might be composed of both protein and non-protein components, while the allelochemicals secreted from U. prolifera gametes might take competitive advantage at the germination stage.