The Effect Of Eutrophication On The Succession Of Two Kinds Of Red Tide Algae In East China Sea And The Growth Of Enteromorpha Prolifera In Yellow Sea

The ecological effect of eutrophication on offshore area of China is becomingmore and more serious. A series of experiments were conducted in order to study theeffect of eutrophication on the succession of two kinds of red tide algae in East ChinaSea and the growth of Enteromorpha Prolifera in Yellow Sea.Skeletonema costatum and Prorocentrum donghainese are the common red tidealgaes in high frequency HAB occurrence areas in East China Sea. Every year inspring, the causative red tide species was changed from diatom to dinoflagellate, andfinally became diatom. The experiments were conducted to find out how the changesof nutrients concentration and structure affect the succession of two kinds of red tidealgae. Indoor experimental show that, the growth of S. costatum and P. donghainesewere inhibition in the mixed cultivating system, which proved there was competitiveaction between two kinds of algae. Mesocosm experiment and outdoor experimentsshowed that phosphate concentration was the limiting factor for S. costatum in EastChina Sea and determine the length of index period, as well as the duration. Silicatewas potential limiting factor for S. costatum, limiting the biggest density. Highconcentrations of nitrates promoted the growth of of P. donghainese. The rise oftemperature (from16℃to18℃) promoted the growth of P. donghainese, andtemperature played an important role in succession process between S. costatum andP. donghainese.In recent years the outbreak of E.Prolifera in the Yellow Sea is also closelylinked with eutrophication. In order to research the influence of nutrients on E. prolifera growth, field investigation and mesocosm experiments were carried out inthe Yellow Sea in May2012. When phosphate level is appropriate, high dissolvedinorganic nitrogen (DIN) concentration could promote the growth of E. prolifera.The large-scale outbreak of E.Prolifera in Yellow Sea was probably because ofthe high content of DIN. Enough and continuous nutrient supplement is the materialbasis for E. prolifera green tide outbreak. Through the nutrient taking up by E.prolifera, the production of organics by photosynthesis could be estimated, which hasa good linear relationship with the increased wet weight of E. prolifera.