| In the Yellow Sea of China, large-scale green tides have broken out for sixconsecutive years from2007to2012, which was thought to be originated in the Subei(northern Jiangsu) shoal patch. After generating, green tide drifts toward the northunder the winds and wind-driven circulation. During the drifting process, green tidegathers together and growes as a group. The accumulational green tide has a greateffect on the gas exchange and incoming light through insulating the floating channelfrom the air. Meanwhile, under the impact of wind and tide, green tide accumulates ina huge range along the coastal water, which destroies the marine ecosystem ulteriorly.Morphological and phylogenetic analysis demonstrates the homology of Ulvaprolifera in the2008green tide with the U.prolifera from Porphyra yezoensisaquaculture rafts. This paper not only analyses the effects of nutrients on U.proliferagrowth through an indoor incubated experiment using the samples from P.yezoensisaquaculture rafts, and also analyses the absorptive capability of U.prolifera ondifferent nitrogen sources through an indoor incubated experiment using the samplesfrom Maidao seacoast in Qingdao. In addition, according to the Key Project ofChinese National Programs for Fundamental Research and Development (973Program)“Evolution mechanism and ecological safety of China coastal algal bloomshazard” U.prolifera voyage, the field investigation in south yellow sea (120oE~123.5oE，32oN~36oN) was carried out. We have made three important progresses asfollowing:1. The former indoor incubated experiment results show that the high NO3-Nconcentration has an advantage in absorbing PO4-P by U.prolifera. The absorptionrate of PO4-P by U.prolifera is greater than that of NO3-N, and the demand for N isgreater than that for P. The optimal nutrient condition for the growth is that the ratioof N/P is from16to32and the NO3-N concentration is lower than160μmol·L-1. Meanwhile, both of the growth rate, μ, and NO3-N concentration are fit to Monodequation. The maximum growth rate, μm, is0.0581d-1, and half satulation constant,Ks, is4.51μmol·L-1.2. The later experiment results indicate that the affinity for urea by U.prolifera isgreater than that for inorganic nitrogen, and the affinity for NH4-N is greater than thatfor NO3-N. The maximum absorbing rate of nutrient is NO3-N, and then is NH4-N,and the minimumrate is urea.3. According to the remote sensing observations and the four field inverstigations,we find that green tide firstly appears in yellow sea in late April, and drifts toward thenorth in early May, and could reach to the nearshore of Qingdao in early June. Fromlate May to late July, the variation characteristic of the cover area and distributionarea of U.prolifera in the Yellow Sea is from incease to decrease The biomass ofU.prolifera reaches to the maximum in the middle of June.The NO3-N and DIN concentration increases with time until29thMay, and thedecreases. The NH4-N concentration has a trend of “increase to decrease to incease”,while the urea concentration inceases always. In the early June, even though thebiomass has a maximum value, but the special growth rate, μ, decreases to zero. Itlags the absorbing rate of a week, which coincides with the indoor experiment result.The divation between the estimated distribution area and the investigation isabout17%, while the divation between the estimated cover area and investigation isabout19%, which indicates that the special growth rate of U.prolifera in the studyarea is close to the value of0.0728d-1derived from the indoor experiment. |
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