桑沟湾春季有色溶解有机物(CDOM)吸收光谱特性及空间分布特征

有色溶解有机物(CDOM)是水生态系统中碳的重要来源,其光学性质可示踪海水中溶解有机物组分的动态信息。利用紫外可见吸收光谱手段,分区域测定了桑沟湾春季水体及表层沉积物间隙水中CDOM的吸收光谱特征,探讨了CDOM的来源组成、空间分布特征、迁移转化过程及其与养殖活动的关系。结果表明,(1)波长为355_的吸收系数(a(355))范围为0.23~9.09 /m,不同水层空间分布差异显著,表层和底层均从近岸区向贝藻区逐渐降低,之后在海带区升高后向外海逐渐降低；海带区从表层向底层先降低后升高,高密度、规模化的海带养殖释放了大量的CDOM,各区域沉积物间隙水a(355)是其表中底之和的1.3~2.5倍,CDOM在沉积物间隙水中富集并逐渐累积。(2)光谱斜率(S_275-295)范围为0.013~0.036,外海区和海带区S_275-295均值显著高于其他各区,海带区和外海区CDOM中海源有机质占主要成分,而近岸区以陆源有机质为主；近岸区CDOM中的腐殖酸类物质含量从表层到底层逐渐降低,沉积物中积累的富里酸类物质含量较高,海带区和外海区呈相反趋势。(3)比紫外吸光度(SUVA₂₅₄)范围为4.60~14.10 L/(mg.m),贝类区、贝藻区和藻类区SUVA₂₅₄均呈现出从表层到底层逐渐增大的趋势,CDOM的芳香性逐渐增强并在沉积物间隙水中达到最大；海带区和外海区沉积物间隙水中的SUVA₂₅₄显著高于其他各区,表明海带区的规模化养殖活动向养殖海区及邻近海域贡献了较多的惰性溶解有机物,暗示着海带养殖活动有较强的碳汇效应并通过海流作用向外海输送。

Spectral and distribution characteristics of colored dissolved organic matter (CDOM) in Sungo Bay in spring

Colored dissolved organic matter (CDOM) is an important source of carbon in aquatic ecosystems, the optical properties of dissolved organic matter (DOM) can be used to trace water masses and provide information about the dynamics of the dissolved organic fraction in seawaters. The ultraviolet-visible absorption spectrum was applied to investigate the chemical composition, sources, spatial distribution characteristics and migration and transformation processes of the CDOM in both the water column and interstitial water in Sungo Bay, a representative semi-enclosed and mariculture bay in Shandong Province, China. The results indicated that: (1) The range of absorption coefficient (a(355)) was 0.23~9.09 /m in Sungo Bay, there are significant differences in the spatial distribution of different water layers, both the surface layer and bottom layer gradually decreased from the nearshore zone to the bivalves kelp zone, then it rised in the kelp zone and gradually decreased towards the outer sea zone. The a(355) in the kelp zone decreased from surface to bottom and then increased, high-density and large-scale kelp mariculture had released a large amount of CDOM into the seawater. The a(355) of sediment interstitial water in each region is 1.3~2.5 times of the sum of the surface, middle and bottom layer, and it was enriched and gradually accumulated in the sediment interstitial water. (2) The range of spectral slope (S_275-295)was 0.013~0.036 in Sungo Bay, the mean values of S_275-295 in outer sea zone and kelp zone were significantly higher than that in other zones, the main components of CDOM are marine organic matter in kelp zone and outer sea zone, and terrigenous organic matter is predominant in the nearshore zone. The content of humic acids in CDOM in the nearshore zone was gradually decreased from the surface layer to the bottom layer, the accumulation of fulvic acid in sediments is high, and kelp zone and outer sea zone showed opposite trend. (3) The range of specific UV absorbance (SUVA₂₅₄)was 4.60~14.10 L/( mg.m) in Sungo Bay, the SUVA₂₅₄ of the shellfish zone, the bivalves kelp zone and the kelp zone showed a trend of increasing gradually from the surface to the bottom layer, and the aromaticity of CDOM was gradually increased and reached the maximum in the sediment interstitial water. The SUVA₂₅₄ in the sediment interstitial water of kelp zone and outer sea zone were significantly higher than that in other zones, it showed that large-scale suspended cultivation activities from kelp zone contributed more refractory dissolved organic matter to the mariculture zone and adjacent seawaters, it implied that kelp mariculture had a strong carbon sequestered effect and this sequestration was exported to the offshore waters through the current.