Studies On The Distribution And Origins Of Biogenic Matters In The ECS Sediments Of High-frequency HABs Areas

In the past few years, the Harmful Algae Blooms happened frequently. The Changjiang Estuary Adjacent area and the coastal area of Zhejiang are one of the main Harmful Algae Blooms areas. For the inshore areas, the main component of the sediment is the oddments from the continent. Other parts are biogenic matters mainly composed of biogenic CaCO3, biogenic silica, organic carbon, organic nitrogen and so on. Even though their content are very low, they can reflect the situation of the water in the specific time. So the study on biogenic matters is very important to study the situation in spatial and temporal changes. In this study, the biogenic silica, carbonate, organic carbon and organic nitrogen were analyzed completely, their origins were also discussed. The conclusions have been reached as follow:1. The content of biogenic silica in the sediments sampled in the year 2005 and 2006 from the East China Sea was analyzed, and the results are that the content of biogenic silica in the sediment ranges from 0.72% to 1.64%. The distribution of biogenic silica takes on higher content offshore and lower inshore, and also higher in this south and lower in the north. The content of biogenic silica in the surface sediments associated with the previous concentration of chlorophyll. In this study, three considered factors was used to explained the regulation of distribution, which are the effect of dilution by river, the production of diatoms in the seawater, and the rate of deposition. The distribution of biogenic silica in the cores was discussed. With the increase of depth, the content of biogenic silica in HB08 sediments increases at first and then decrease. The vertical changes reflect the changes of seawater.2. The content of carbonate, organic carbon and organic nitrogen in the sediments sampled in the year 2005 and 2006 were analyzed. The change of carbonate is high, from 0.01% to 0.95% for carbonate. from 0.043% to 0.82% for organic carbon, and from 0.045% to 0.11% for organic nitrogen. The changes of organic carbon and organic nitrogen were associated with the concentration of chlorophyll. The content of them in the vertical samples was discussed and the results implicated the relationship existed among them. The content of total carbon in HB08 was stable, and the ratio of organic carbon and carbonate (mol/mol) is high that means the buried efficiency of carbonate is low.3. The syntheses analysis was taken among all the parameter in the sediments. Results are reached as follow: the relationship of the biogenic silica and the carbonate is negative, as well as organic carbon. The relationship of organic carbon and organic nitrogen is positive. The ratio of organic carbon and organic nitrogen is high, which means the organic matter in the sediments came from the phytoplankton in the seawater. In general, when the content of biogenic silica is high, and the content of organic carbon is high as well as organic nitrogen, and when the content of carbonate is low, there were lots of diatoms in the seawater at that special time, because the biogenic silica is produced by diatoms, and because it's organism is the source of organic matter.