两种赤潮藻对汞富集和甲基化影响的研究

研究塔玛亚历山大藻(Alexandrium tamarens)和锥状斯式藻(Scrippsiella trochoidea)两种赤潮藻对海水中汞的富集和甲基化的影响, 探讨赤潮藻对硫铁还原地杆菌 Geobacter sulfurreducens PCA (G. sulfurreducensPCA)汞生物甲基化的抑制作用。实验结果表明, 不同种类藻对汞的耐受性不同, 高浓度HgCl₂ (≥25 μg/L)抑制锥状斯式藻的生长, 而对塔玛亚历山大藻的影响较小。两种藻均可有效地富集无机汞, 但直接进行汞甲基化的效果不显著。FTIR分析发现, 藻细胞表面分泌的大量羧基、氨基和羟基等官能团是富集汞的主要位点。汞-藻-菌实验中, 当HgCl₂初始浓度为10 ug/L时, G. sulfurreducens PCA驱动的汞生物甲基化效率可达 (6.38±0.4)%, 在G. sulfurreducens PCA与塔玛亚历山大藻共存的实验组中, 汞甲基化效率为 (1.04±0.44)%,G. sulfurreducens PCA与锥状斯式藻的实验组中汞甲基化效率低至 (0.76±0.05)%, 两种赤潮藻的加入抑制了G.sulfurreducens PCA的汞生物甲基化。

Study on the Effect of Two Red-Tide Algae on MercuryBiocondensation and Methylation

The effect of two red-tide algae of Alexandrium tamarens and Scrippsiella trochoidea on mercury (Hg)adsorption and methylation were investigated. The inhibitory effect of two algae on biomethylation of GeobacterSulfurreducens (G. sulfurreducens) PCA were demonstrated. The growth of Scrippsiella trochoidea was inhibitedunder exposure to high concentration of HgCl₂ (≥25 μg/L), but less affecting Alexandrium tamarens. Significantadsorption of Hg²⁺ was observed onto algal cells, whilst negligible amount of methylmercury (MeHg) wasproduced by two algae directly. FTIR spectra revealed that hydroxyl, carboxyl and amino groups were majorbinding sites for Hg²⁺ adsorption. In Hg-algae-bacteria tests, at initial HgCl₂ concentration of 10 μg/L, a maximummercury methylation efficiency of (6.38±0.4)% was obtained by pure G. sulfurreducens PCA culture as a control,but the efficiency reduced to (1.04±0.44)% with G. sulfurreducens PCA and Alexandrium tamarens coexisting, anda much lower efficiency of (0.76±0.05)% was detected with G. sulfurreducens PCA and Scrippsiella trochoideacoexisting. These results suggested that two red-tide algae inhibited mercury biomethylation of G. sulfurreducensPCA.