浮游植物生长与固碳之间存在紧密的联系,相关机制的研究有助于更好了解海洋碳循环的过程。一般认为,水华发生时由于浮游植物大量繁殖,溶解有机碳(dissolved organic carbon,DOC,采用高温燃烧法测定)相应增加,然而,现场调查发现,长江口和珠江口夏季中高盐度(盐度10~30)水华区DOC浓度与非水华区相近,水华区总有机碳(total organic carbon,TOC)浓度较非水华区显著增加,其中,长江口水华区TOC比DOC增加60~140μmol/L,珠江口水华区TOC较DOC高出~110μmol/L以上,显示固碳主要以颗粒有机碳(particulate organic carbon,POC)存在。培养结果表明藻菌混合培养条件下DOC增加只占固碳~10%(即固碳的~90%为POC),相反,无菌培养条件下DOC增量可占固碳的~80%(即固碳的~20%为POC),两个河口水华区DOC未显著增加的机制可能是由于浮游植物产生的DOC易被细菌降解所致。 There is a close relationship between phytoplankton growth and carbon sequestration. Studies on related mechanisms will help to better understand the process of ocean carbon cycle. It is generally believed that due to the large numbers of phytoplankton blooms, dissolved organic carbon (DOC) is increased correspondingly with the high-temperature combustion method. However, the field survey found that the summer salinity (salinity 10 ~ 30) DOC concentration in the water area was similar to that in the non-water area, and the total organic carbon (TOC) concentration in the water area was significantly higher than that in the non-water area. The TOC was 60 ~ 140μmol / L. The TOC of the Pearl River Estuary watershed was ~ 110μmol / L higher than that of DOC, indicating that the carbon sequestration mainly existed in the particulate organic carbon (POC). The results of the cultivation showed that the increase of DOC in the mixed culture of algae only accounted for 10% of the carbon fixation (ie ~ 90% of the carbon fixation was POC). On the contrary, the DOC increment could account for -80% of the carbon fixation under the aseptic culture ~ 20% of carbon sequestration is POC). The mechanism by which DOC did not increase significantly in the two estuarial bloom areas may be due to the biodegradation of DOC by phytoplankton.