Effect Of Spartina Alterniflora Invasion On Community Vertical Structure Of Macrobenthos

We made a study of macrobenthic vertical structure in Spartina alterniflora tidal flats (HH) and in Natural tidal flats (ZR) in tidal wetlands of Xuanmen Bay, Yuhuan in August2012. The content of this research contains two parts, part one is about the vertical structure of macrobenthos in different mud depth; part two is about the vertical structure of macrobenthos in different offshore distances in tidal wetland. The main research results are as follows:1. We obtained40kinds of macrobenthos in total, which belong to six Phyla, eight Classis and twenty five Families. Among them, there are13Arthropoda,18Mollusca and4Annelida, the total kinds were35, and they took the87.5%of the total number of species. There are30kinds in Spartina alterniflora tidal flats (HH), and31kinds in Natural tidal flats (ZR). There are21species live in both HH and ZR.10kinds of species lives only in HH, including:C.largillierti,-Zeuxis scalaris, Natica vitellus, Littorinopsis intermedia, Bullacta exarata, Tegillarca granosa, Uca arcuata, Sesarma haematocheir, Hemigrapsus penicillatus, Betaeus yokyai kubo. There are9kinds of species only live in ZR, including:Natica tigruna roding, Onchidium verruculatum, Odostomia subangulata, Moerella iridescen, Philyra pisum, Paguristes pusillus zhejiangensis, Exopalaemon annandalei, Corophium sinensis, Mcinereus.2. In this survey, the average biomass of Spartina alterniflora tidal flats (HH) is39.23g/m2, and the average density of Spartina alterniflora tidal flats (HH) is222.6ind./m2. The average biomass of Natural tidal flats (ZR) is19.19g/m2, and the average density of ZR is1052.8ind./m2. We analyze different distance far from shore and different environment (HH and ZR) in the way of non-repeated two-factor variance analysis. The result showed that:density and biomass are not differences between HH and ZR. There are significant differences in the density between parts of different distance far from shore. Biomasses between different offshore distances were not significantly different. Along the mud depth, in the same mud depth, the numbers of species in ZR is higher than the numbers of species in HH. And the deeper mud depth is, the numbers of species is less. The density is as like as numbers of species, in the same depth, the density of species in ZR is higher than the density in HH. And the deeper mud depth is, the density is smaller. The numbers of species and density of macrobenthos in HH and ZR in different depth of mud are significant differences.3. According to analyze the main depth of the habitat, we found that the same species almost had the same in the main depth of the habitat in HH and ZR. We can infer that after the invasion of Spartina alterniflora, the macrobenthic living environment of vertical distance was shorten, but the macrobenthic main depth of habitat was not affected.4. In this research, the biodiversity index, including:Margalef, Shannon-Wiener, Pielou index, in HH are higher than the same offshore distances in ZR; the simpson index is reversed, in ZR is higher than the same offshore distances in HH, the higher the simpson index is, the lower the biodiversity is. so, the level of biodiversity in HH is higher than in ZR. According to the statistical analysis, there are significant differences between HH and ZR. There are no significant differences between different offshore distances. In different mud depth, the biodiversity index, including: Margalef, Shannon-Wiener, Pielou, Simpson index, in0-20cm in HH are higher than the same depth in ZR. In20-25cm, the result is the opposite. In0-20cm depth, the Simpson index in HH is lower than the same depth in ZR, in20-25cm, the result is the opposite. In20-25cm in HH, the Simpson index is the biggest, but the other three indexes are the smallest in20-25cm. In0cm in ZR, the Simpson index is the biggest, but the other three indexes are the smallest in0cm.5. We use hierarchical cluster in different offshore distances of macrobenthos in HH and ZR, the result shows that the macrobenthos can divided into two categories. The MDS result well supported this result, and this result is consistent with the result of statistical analysis. In the research of different mud depth, Ocm and0-5cm are quite similar in HH and ZR, in the depth of5-25cm in both HH and ZR, they are quite similar, which indicates that though the habitat is different, the same mud depth are quite similar. But it is not similar among0cm,0-5cm,5-20cm; it shows that it is quite different in different mud depth, which means macrobenthos is highly affected by mud depth. Meanwhile, the result of cluster and MDS is quite consistent with the result that macrobenthos showed a high density distribution at the surface.