2种潮间带大型海藻种间竞争作用对UV-B辐射增强的响应

Response of Interspecific Competition Between Ulva pertusa and Grateloupia filicina to UV-B Irradiation Enhancement

选择2种代表性的潮间带大型海藻孔石莼(Ulva pertusa)和蜈蚣藻(Grateloupia filicina),采用单独培养和共同培养的方法,以生物量为主要测定指标,研究了二者种间竞争关系及这种关系在UV-B辐射增强时的响应趋势.结果表明,孔石莼和蜈蚣藻二者的种间竞争同时包含营养竞争和相生相克2种机制,试验中营养充足及营养限制的共养处理下孔石莼特定生长率是蜈蚣藻相应值的2.54和2.47倍,蜈蚣藻在竞争关系中处于劣势;UV-B辐射对单独培养的孔石莼和蜈蚣藻的生长均有抑制作用,且随着UV-B胁迫时间延长及辐射剂量的增加,抑制作用愈加显著;共同培养条件下,低剂量[1.6kJ·(m2·d)-1]、中剂量[4.8kJ·(m2·d)-1]的UV-B辐射时孔石莼虽占据竞争优势,但其种群竞争能力有弱化趋势,孔石莼和蜈蚣藻的生物量比共养对照分别下降6.81%、3.88%和10.47%、6.98%,二者的种间竞争趋向均衡;12d时高剂量[9.6kJ·(m2·d)-1]UV-B辐射使孔石莼的生物量下降13.09%,而蜈蚣藻生物量降低更多达14.72%,从而导致孔石莼在高剂量辐射处理中的优势地位更趋于明显,因此UV-B辐射增强可改变共培养体系中孔石莼和蜈蚣藻种间竞争的关系,且对应于不同UV-B辐射剂量其表现不同;长期UV-B辐射可能会影响孔石莼和蜈蚣藻产生克生物质的代谢过程.

The interspecific competition between Ulva pertusa and Grateloupia filicina and it＇s response to the UV-B irradiation enhancement were analyzed using mono-culture and co-culture methods. The study adopted reasonable experimental design and took biomass as the main examined index. Results showed that the relation of interspecific competition included both allelopathy effect and nutrient competition. Specific growth rates of U.pertusa under treatment with abundant nutrition and limited nutrition was 2.54 and 2.47 times of those of G .filicina .Thus, compared to U. pertusa, G.filicina was in inferior position. UV-B irradiation could inhibit the growth of U. pertusa and G .filicina under the condition of mono-culture. The higher the dosage and the longer exposure of UV-B irradiation were, the more significant the inhibitive effect was. When they were cultured together, low dosage [ 1.6 kJ·（ m^2·d）^-1] and medium dosage [ 4.8 kJ·（ m^2·d）^-1] of UV-B irradiation reduced the competitive ability of U. pertusa, and weights of U. pertusa and G.filicina declined 6.81% and 3.88% in low dosage, and 10.47 % and 6.98 % in medium dosage, respectively. So the relation of interspecific competition tended to be at a balanced level even though U.pertusa was still the dominant algae. However, on the 12th day, weight of U.pertusa decreased by 13.09%, but the value of G .filicina was 14.72%, which was higher than that of U. pertusa. Therefore, high dosage [9.6 kJ·（ m^2·d）^-1] of UV-B irradiation had more serious inhibitive effect on G .filicina, and competitive dominant position of U. pertusa tended to be more obvious. Thus, UV-B changed the relation of competitive balance of U. pertusa and G.filicina, which changed along with the dosage of UV-B. Moreover, UV-B irradiation might influence the metabolism of the allelochemicals produced by U. pertusa and G .filicina in a long time.