养马岛附近海域藻华期间有色溶解有机质的生物可利用性研究

Bioavailability of chromophoric dissolved organic matter in the coastal waters adjacent to Yangma Island during an algal

本研究利用吸收光谱和荧光激发-发射矩阵光谱-平行因子分析(EEMs-PARAFAC),研究了养马岛附近海域海水中有色溶解有机质(CDOM)的浓度、组成、来源和生物可利用性,并估算了浮游植物生长繁殖对CDOM及具有生物可利用性CDOM的贡献。结果表明,表、底层海水中CDOM浓度(以吸收系数a350计)平均值分别为1.62±0.42 m^(-1)和1.30±0.47 m^(-1),光谱斜率(S275-295)平均值分别为0.022±0.003 nm^(-1)和0.023±0.003 nm^(-1)。利用PARAFAC模型识别出4种荧光组分,分别为陆源类腐殖酸C1、类色氨酸C2、类酪氨酸C3和微生物源类腐殖酸C4。荧光指数(FIX)、腐殖化指数(HIX)和生物指数(BIX)显示,CDOM受陆源输入和海洋自生源的综合影响。降解实验结果显示,表、底层海水中生物可利用性CDOM百分比(%∆a_(350))平均值分别为(23.36%±17.94%)和(8.93%±20.30%)。C1、C2和C4组分的荧光强度在培养之后降低,而C3组分的荧光强度上升。各荧光组分生物可利用性依次递减的顺序为:%ΔC1(23.75%±8.96%)>%ΔC4(20.83%±11.71%)>%ΔC2(11.67%±38.87%)>%ΔC3(-29.61%±39.90%),显示培养之后CDOM的平均分子量和腐殖化程度降低。表层海水中a_(350)、%Δa_(350)与Chl a之间存在显著线性相关关系,据此可以估算出浮游植物生长繁殖对CDOM的贡献为36.9%,对具有生物可利用性CDOM的贡献为85.0%。

The concentrations,composition,and sources of chromophoric dissolved organic matter(CDOM)in the coastal waters adjacent to Yangma Island were studied by measuring the absorption spectra and fluorescence excitation-emission matrix-parallel factor analysis(EEM-PARAFAC),and the contribution of phytoplankton growth and reproduction on CDOM and its bioavailability were estimated.The results revealed that the average concentrations of CDOM reflected by a_(350) in the surface and bottom seawater were 1.62±0.42 m^(-1) and 1.30±0.47 m^(-1),and the spectral slopes S_(275-295) were 0.022±0.003 nm^(-1) and 0.023±0.003 nm^(-1),respectively.Four fluorescence components were identified by the PARAFAC model,namely,terrestrial humic-like C1,tryptophan-like C2,tyrosine-like C3,and microbial humic-like C4.The fluorescence,humification,and biological indexes indicated that CDOM was influenced by terrestrial input and marine autochthonous sources.Degradation incubation experiments indicated that the percentages of bioavailability CDOM(%Δa_(350))were(23.36%±17.94%)and(8.93%±20.30%)in the surface and bottom seawater,respectively.The fluorescence intensities of C1,C2,and C4 decreased while that of C3 increased.The bioavailability of fluorescent components decreased in the following order:%ΔC1(23.75%±8.96%)>%ΔC4(20.83%±11.71%)>%ΔC2(11.67%±38.87%)>%ΔC3(-29.61%±39.90%),which indicates that the mean molecular weight and humification degree of CDOM decreased after microbial degradation.a_(350) and %Δa_(350) had significant linear correlations with Chl a,based on which phytoplankton growth and reproduction were estimated to contribute 36.9% and 85.0% to CDOM and bioavailable CDOM,respectively.