筼筜湖绿潮期间颗粒有机物及沉积有机物的来源研究

以原子碳氮比C_at/N_at、TOC/Chl a、δ13C和δ15N等为指标,分析了筼筜湖绿潮爆发期间悬浮颗粒有机物(POM)和沉积有机物(SOM)的来源。结果显示,筼筜湖的POM主要以外源输入为主。在靠近海水入口的引水渠,POM主要来自厦门西海域的陆源有机碎屑;位于筼筜湖上游的干渠,生活污水及餐饮业废水的有机质是其POM的主要贡献者;内、外湖POM的C_at/N_at(6.94~7.08)与浮游植物接近,但它们并不以浮游植物为主,而主要来自引水渠和干渠有机质的输入。以内湖为例,它们对内湖POM的联合贡献高达54%~97%。筼筜湖SOM的潜在来源多样,但不同湖区差异显著:在大型海藻覆盖区,主要以大型海藻和POM为主,而在无海藻覆盖的区域,则主要来自POM的自然沉降或与底栖微藻的联合贡献。结果表明,在来源复杂的潟湖系统,有机物的化学组成并不能很好的指示有机物的来源和成因,它在有机质的示踪方面并不如稳定同位素来得有效可靠。不过,基于多种指标的分析结果可能更准确。

The source of particulate organic matter and sedimentation organic matter during macroalgal bloom in Yundang Lagoon

On the basis of the chemical indexes(C_at/N_at and TOC/Chl a) and stable isotope composition (δ13C and δ15N), suspended particulate organic matter (POM) and sedimentation organic matter (SOM) were analyzed during macroalgal bloom in Yundang Lagoon. The results showed that POM in the lagoon was mainly from the terrestrial origin inputs. In diversion canal close to coastal water, POM was largely composed of terrestrial organic matter from Xiamen Western Sea, while in main canal located in upper reaches of the lagoon, domestic sewage was the largest contributor of POM. Although POM in inner and outer lagoon was close to phytoplankton in atom C∶N ratio (C_at/N_at), phytoplankton was only a small part of POM. The results from ISOSOURCE linear mixing model indicated 54%-97% of combined contribution of the input from diversion and main canal to POM in inner lagoon. SOM had many potential sources in the lagoon, but displayed significant spatial difference. SOM was mainly from seaweed and POM in the areas with seaweed canopy, while mainly from POM deposition or benthic microalgae in those areas without seaweed. Our results showed that, in the lagoons where there are many potential organic sources, the chemical composition of organic matter (OM) could not work well in tracing the source of OM compared with stable isotope tracing. However, the analysis based on a variety of indicators may be more accurate and reliable.