温度变化对铜绿微囊藻(Microcystis aeruginosa)生长和光合作用的影响

Effects of temperature variation on the growth and photosynthesis of Microcystis aeruginosa

近年来,随着水体富营养化的加剧,在世界各地经常发生微囊藻水华,并且因有些微囊藻品系能够产生毒素和异味物质,从而严重影响饮用水安全并威胁人类健康。自然水体中的微囊藻水华通常由产毒品系和非产毒品系微囊藻共同引发,并且很多研究表明气候变暖将使蓝藻水华进一步扩张。研究铜绿微囊藻产毒品系FACHB-905(Microcystis aeruginosa FACHB-905)和非产毒品系FACHB-469(M.aeruginosa FACHB-469)在不同温度下适应10天后的生长、光合作用以及对强光胁迫耐受性的差异。结果发现两品系在15℃下都基本没有生长,在40℃下甚至无法存活。而在20至30℃间,两品系的比生长速率均随着培养温度的升高而增大,当温度进一步升高到35℃,其又开始降低。在20至35℃之间,铜绿微囊藻产毒品系FACHB-905比非产毒品系FACHB-469的比生长速率略高,但是尚未达到显著差异水平。在20至35℃下适应10天后,产毒品系FACHB-905的最大光合作用速率(P_(max))和暗呼吸速率(Rd)均显著高于非产毒品系FACHB-469。将两品系转移至强光下(600μmol·photons·m^(–2)·s^(–1))照射4小时后,两者的最大光化学效率(F_v/F_m)都显著降低,但是产毒品系FACHB-905的F_v/F_m在30和35℃时显著高于非产毒品系FACHB-469。总之,在适应了不同温度梯度10天后,与非产毒品系FACHB-469相比,产毒品系FACHB-905表现出较高的生长、光合作用潜能以及耐光性。根据以上研究结果,我们推测气候进一步变暖有可能使产毒品系微囊藻处于优势地位,从而加剧其水华危害。

As the eutrophication of freshwater system becomes an increasingly widespread phenomenon during the last few decades, toxic Microcystis blooms are occurring all over the world. Therefore, the water supply security and human health are threatened because some Microcystis stains can produce malodorous compounds and microcystin. Microcystis blooms in natural freshwater system are usually caused by the combination of toxic and non-toxic Microcystis species. Furthermore,climate warming is thought to lead to the expansion of these blooms. To investigate whether the competitive ability of toxic M. aeruginosa FACHB-905 is higher than the non-toxic ones under global warming background, we studied the growth, photosynthesis and light resistance of non-toxic M. aeruginosa FACHB-469 and toxic M. aeruginosa FACHB-905 after they had been cultured for 10 days at temperatures ranged from 15 to 40 ℃. The results showed that both non-toxic M. aeruginosa FACHB-469 and toxic M. aeruginosa FACHB-905 grew little at 15 ℃ and could not survive for a long time at 40 ℃. However, the average specific growth rate of both strains increased with increased temperatures ranged from 20 to 30 ℃, and then began to decrease when temperature was further increased to 35 ℃. Moreover, the specific growth rate of toxic M. aeruginosa FACHB-905 was slightly higher than that of non-toxic M. aeruginosa FACHB-469 at temperatures ranged from 20 to 35 ℃ though the difference was not statistically significant. However, the maximal photosynthetic rate （Pmax） and dark respiration （Rd） of toxic M. aeruginosa FACHB-905 were significantly higher than non-toxic M. aeruginosa FACHB-469 after both strains had been grown at temperatures ranged from 20 to 35 ℃ for 10 days. The maximal photochemical efficiency （Fv/Fm） of both strains decreased significantly when they were exposed to stressful irradiance （600 μmol·photons·m^-2·s^-1） for 4 h, however, the Fv/Fm of toxic M. aeruginosa FACHB-905 was significantly higher than that of non-toxic M. aeruginosa FACHB-469 at 30 and 35 ℃. In brief, the toxic M. aeruginosa FACHB-905 showed higher potentialities of growth, photosynthetic capacity and resistance to stressful irradiance compared with non-toxic M. aeruginosa FACHB-469 after they had been acclimated to temperatures ranged from 20 to 35 ℃ for 10 days. The results indicated that global warming may favor the predomination of the toxic Microcystis species in natural waters, which would further aggravate the ecological risk of Microcystis blooms.