共培养体系中石莼和江蓠对赤潮异弯藻生长的影响

研究共培养体系中2种大型海藻石莼(Ulva pertusa)和江蓠(Gracilaria lemaneiformis)的鲜组织和培养液滤液对赤潮异弯藻(Heterosigma akashiwo)生长的影响.结果发现:①石莼和江蓠均能明显影响赤潮异弯藻生长,鲜组织的作用更明显,能在短时间内完全灭杀共培养的赤潮异弯藻;石莼对微藻的影响强于江蓠的作用.②除菌作用和补充充足的碳酸盐不能消除或缓解石莼和江蓠对赤潮异弯藻生长的影响,说明细菌和碳限制不是导致大藻对微藻作用的原因.③对共培养体系中硝酸盐和磷酸盐的跟踪测定结果显示,营养盐限制不是造成石莼对赤潮异弯藻影响的原因,但却在江蓠的作用中起重要作用.当向江蓠体系中补充f/2营养盐后发现,充足的营养盐能够减轻但不能完全消除江蓠对赤潮异弯藻生长的影响.另一方面,石莼的起始浓度与其对赤潮异弯藻的生长影响之间存在明显的相关性,石莼的起始浓度越高,对赤潮异弯藻的影响越明显.④实验初步说明,石莼可能通过相生相克作用影响共培养体系中赤潮异弯藻的生长,而相生相克和营养竞争的共同作用是导致江蓠作用的根本原因.

Effects of Ulva pertusa and Gracilaria lemaneiformis on Growth of Heterosigma akashiwo(Raphidophyceae) in Co-Culture

We studied the effects of fresh tissue and culture medium filtrate of two species of macroalgae,Ulva pertusa(Chlorophyta) and Gracilaria lemaneiformis(Rhodophyta) on growth of Heterosigma akashiwo(Raphidophyceae) in coculture.Both U.pertusa and G.lemaneiformis,and especially their fresh tissues,significantly impede the growth of H.akashiwo.Carbonate limitations and the presence of environment bacteria are not necessary for the negative effects of macroalgal on H.akashiwo.The simultaneous nutrient assays show that nitrate and phosphate are almost exhausted in the G.lemaneiformis co-culture system,but remain at acceptable levels in the U.pertusa system,when all cells of H.akashiwo are completely dead.When f/2 medium is supplied daily to G.lemaneiformis culture, the growth of H.akashiwo is greatly inhibited but not completely terminated.Furthermore,different amounts of fresh seaweed tissue,and culture medium filtrate prepared from different macroalgal concentrations are analyzed to determine their effects on the growth of H.akashiwo.The results show a positive correlation between the initial macroalgal concentration and the negative effects they exert on the co-cultured microalgae.Results suggest that the allelopathic effects ofU.pertusa may be essential for negative effects on H.akashiwo;however,the combined roles of allelopathy and nutrient competition may be responsible for the negative effect of G.lemaneiformis the release of allelochemicals by U.pertusa.