| The Yellow Sea is semi-enclosed shelf sea located between the mainland of China and the Korea Peninsula.It is one of the world's 50 so-called 'large marine ecosystems' and one of the most important fishing areas.An algal bloom is defined as a relatively rapid increase in the biomass of phytoplankton in an aquatic system.The twice bloom in spring and autumn every year is common for mid-latitude phytoplankton annual cycle.Phytoplankton bloom has great effect on the primary production level and biological variable cycle of the whole area region.The main purpose of this paper is 1) to simulate the seasonal variation of phytoplankton by using a three-dimension biological dynamic model,2) to analyze the characteristic phytoplankton bloom in the Yellow Sea,3) to discuss the variations of phytoplankton spring bloom which affected by the change of environment factors.Based on the observation data which were obtained from bloom cruise on April, 2007 in the Yellow Sea,analyze and discuss the characteristics of different biological variables during the bloom process and the reason for rapidly decrease of the bloom. During the bloom process,the nutrient concentration doesn't restrict the phytoplankton growth.Combined with the remote sensing data,the spatial variation of the phytoplankton bloom appears in shore region at first.Then it extends to the central part of the Yellow Sea.After the central region bloom declined,the chlorophyll concentration has another small peak in the shore region again.The distribution of the phytoplankton bloom reveals the patchiness characteristic which has a wide range of spatial and temporal scales.The horizontal convection is speculated to be responsible for the abrupt decrease in the concentration of chlorophyll at anchor station.A three-dimension biological model is established to simulate the phytoplankton bloom process in the Yellow Sea.The model has two groups of phytoplankton(diatom, flagerlate) and three kinds of nutrients.It could reveal the succession between the two groups during the bloom and the different restriction effect on the two groups from different nutrient.The results are similar to the observation data.The model could reveal the seasonal variation of phytoplankton well.From the simulation results,the phytoplankton concentration has two peaks every year in the Yellow Sea.The bloom appears in spring and autumn separately.The intensity and range of the autumn bloom is weaker and smaller than the spring bloom's.In general the spring bloom happens in March,strengthens in April and decreases in May due to the consumption of the nutrient.The spatial variation of the phytoplankton bloom process from simulated data coincides with the result from remote sensing data.The distribution of the phytoplankton also has the patchiness characteristic.The spatial scale is ten to tens of kilometers.It is mainly affected by the convergence and divergence of the current field.The horizontal convection is responsible for the rapidly variations of the patch scale,location and concentration.Through analyzing the environment variation,the growth of phytoplankton is mainly restricted by the solar radiation in February.The water temperature has effect on the phytoplankton growth in March.In spring,intensified the radiation could make the bloom happen in advance and the lasting time increase.The temperature could affect the phytoplankton growth through the relationship between the temperature and growth rate.The increase or decrease of the temperature could lead the bloom to happen in advance or delay.The lasting time of the phytoplankton bloom also increases or decreases a little correspondingly.The intensified mixing effect could weaken the water stabilization,therefore the happening time of the bloom will be delayed.The suspended particulate matter could intensify the diffusion the radiation in water column and change the bloom timing and range obviously.The primary production and the phytoplankton community will change correspondingly.
|
PDF Full Text Request