Identification Technology Of Green Tides Forming Algae Along The Coast Of Qingdao

"Green tides" are harmful phenomena refering to fast growth and vast accumulated biomass of green macroalgae, which often occur in estuaries, inner bays, lagoons and on urbanized seacoasts in different scales. This kind of phenomena has increased over the past four decades all over the world. Species forming green tides are mainly Ulvaceae, especially Ulva. They often become abnormally free-floating instead of normally attached during the occurence of green tides. Our government has raise concerns about the Yellow sea green tides since the year of 2008 when Ulva prolifera overgrowth occurred. During the year of 2009, green tides formed by Ulva occured for many times on the coasts of Qingdao as well. They all had negative impacts on the marine ecological environment. Our work is to identify these free-floating green algae and find out their orgin, in order to provide theoretical basis for subsequent analyzations and controls of green tides.With digoxin labeled DNA probes technology, we set up a rapid method of identifying Ulva prolifera, which is the yellow sea green tides forming algae. By means of DNA extraction, amplification of determinands' DNA sequences and detection with two DNA probes, precise identifation of Ulva prolifera is done. The entire process is very simple and convenient, which could be accomplished within 24-36h.From May to July of 2009, there were large amount of free-floating green algae assembling in the inner bays of Qingdao. By amplifying and analyzing ITS DNA sequences(internal transcribed spacer) and 5SS DNA sequences(5S rDNA spacer), we managed to estimate the biomass of this green algae bloom and identify the species forming the bloom, which refered to Ulva linza. The thalli of free-floating Ulva linza were quite different from thalli of the attached ones in shape. Since late July of 2009, Ulva linza disappeared gradually; other free-floating Ulva species became dominant simultaneously.By amplifying and analyzing rbcL DNA sequances (ribulose-1,5- bisphosphate carboxylase/oxygenase large subunit), we managed to make out the species forming the new algae blooming, which were majority of Ulva pertusa and minority of Ulva rigida. According to our outdoor survey and. common traits of the three species, we conclude that Ulva linza, Ulva pertusa and Ulva rigida don't have the morphological characteristic by which they can drift for long distance with the help of seawater current, so the three species are all locally originated and not from other regions. A phenomenon of cell wall thickening of free-floating Ulva specimens can be observed microscopically, which may be explained by their adaptions to the change of their living environment.DNA barcoding is a species identification technology based on the analysis of sequence diversity in small segments of DNA. We choose ITS DNA sequences as candidates to test whether it could be eligible for DNA barcode of Ulvaceae. The results told us that the minimum interspecific genitic distance of ITS DNA sequences involving a few species of Ulvaceae was less than their maximum intraspecific distance, so ITS DNA sequences haven't made the grade to be DNA barcodes. But it can be learned from the molecular phylogenetic tree that data of ITS DNA sequences are still good references for Ulvaceae taxonomy study.