Application Of Active Fluorescence Of Chlorophyll In Yangtze Estuary

The active fluorescence of chlorophyll a (Chl a) is very important ecological factor in estuary, and it can help us to get more information about the temporal and spatial changes of Chl a, the distribution and abundance of phytoplankton, the changes of the primary productivity, the relationship between phytoplankton growth condition and the environment factors, the cause of the red tide and the changes during its process in estuary.Based on the data from the 2009 and 2010 cruises, this paper studied the active fluorescence of Chl a in the Yangtze estuary and its adjacent sea area. With the measurement of the active fluorescence of Chl a, we mainly focuses on the chlorophyll a temporal and spatial changes as well as its responses to the environment factors, the environment stress influence on phytoplankton growth condition and so on. From the cruise 2009, we studied the changes of the active fluorescence of c Chl a in plume front and the adjacent sea area in Yangtze estuary, compared with the vertical and horizontal changes of environment factors. During the cruise, we also did the sea water preliminary evaluation to measure the "healthy water" level. And the cruise 2010 is about the typhoon. We measured the sea water layer before and after the typhoon pass Yangtze estuary, and to find the influence on the Chl a concentration, the mass of the phytoplankton and its growth condition with the change of the mixed water layer. Several major conclusions are shown as follows:1. The relationship between Fo, Fm and Chl aThe analysis about Fo and Fm distribution of the cruises found that they were very dimilar to Chl a, ane the correlation analysis showed that the value of Fo and Fm were significantly correlated to Chl a concentration. This means both Fo and Fm can be a good indicator to Chl a, and can be used for Chl a concentration and distribute research in the sea where the suspension is low. The Chl a fluorescence can performs well especially in Chl a quick measure.2. Use active fluorescence of Chl a to indicate the phytoplankton growth conditionFrom the difference of Fv/Fm, Fv/Fo in and out the plume front and between the changes before and after the typhoon pass Yangtze estuary, it noticed that Fv/Fm, Fv/Fo could reflect the environment stresses in the phytoplankton growth sensitively. But when use the parameter as the indicator, it is important to distinguish the primary factor from others.3. The health evaluation of water quality As a key index of water health evaluation system of water quality, Chi a concentration was significant correlate with the water health level. Now, the healthy or sub-healthy water can be distinguished effectively through Fo, Fm, Fv/Fm and Fv/Fo measure. As the result, the water with Fm<6000, Fv/Fm>0.6 was thought healthy, which had high transparency and low biomass, and the phytoplankton could growth well without environment limits. Though this evaluation method has some demerits, but it was thought that it still could be good for the quick evaluation of water quality.4. The application to red tide Observation in the seaChlorophyll fluorescence could reflect the red tide event accurately. From the research in Yangtze estuary, it was noticed that the red tide would be occred in the plume ftont where the fresh water mixed with sea water as well as upwelling current with water temperature around 26℃.5. The influence of typhoon on phytoplankton distribution and biomassTyphoon process can relief the problems such as nutrient stress and unbalance. Chi a rapidly increased to a high level after the typhoon event, and the growth condition of phytoplankton also became better than before. After typhoon, the Chi a concentration changed significantly, but it still based on the concentration and the distribution before the typhoon event.