互花米草入侵对大型底栖动物群落垂直结构的影响

Effect of Spartina alterniflora invasion on the vertical structure of macrobenthic community

2012年8月,在浙江省玉环县漩门湾国家湿地公园,利用自制分层采样器,以5 cm为单位对0—25 cm泥层进行分层取样,研究潮间带互花米草滩涂和自然滩涂两种生境中大型底栖动物的垂直分布情况,以及互花米草入侵对大型底栖动物垂直结构的影响。两种生境中共获得大型底栖动物40种,其中软体动物18种,甲壳动物13种,环节动物4种,其他类群5种。在自然滩涂生境中获得的物种数为30种,互花米草生境为31种,两种生境的共有种有21种。互花米草和自然滩涂生境平均栖息密度分别为222.6株/m2和1052.8株/m2。研究结果表明:(1)大型底栖动物主要栖息在0—10 cm泥层深度;(2)大型底栖动物群落沿泥层深度存在分层分布现象;(3)互花米草入侵缩短了底栖动物的垂直分布距离,但对其主要栖息深度影响不大;(4)互花米草入侵改变了原来生境特征,导致大型底栖动物的群落结构发生变化。

A Spartina alterniflora tidal fiat （HH）, （coverage 25%--30%） and a natural tidal fiat （ZR） were studied to determine the impact of a S. alterniJTora invasion on the vertical structure of a macrobenthic community. Macrobenthos field sampling was carried out in the HH and ZR areas in Xuanmen Bay National Wetland Park, YuHuan County, Zhejiang Province, China, in August 2012. The tidal flat was reclaimed in 2005 and its current width is approximately 200--250 m. The study area was divided into HH and ZR habitat types, which are defined by geomorphologieal features and vegetation distribution. Within each habitat type, three sample lines were selected. Each sample line was composed of five sites, which were 50 m, 100 m, 150 m, 200 m, and 250 m from the coast. Four quadrats （25 ~ 25 ~ 25 cm） were taken from independent patches in each site and sieved （ 1 ram）. Macrobenthos samples were collected from depths of 0 cm, 0--5 cm, 5--10 era, 10--15 cm, 15--20 cm, and 20--25 cm, with a newly designed, stratified macrobenthos sampling device. We analyzed the numerical data using several biodiversity indices, e.g., the Shannon-Wiener （H＇）, Pielou （J）, Margalef （Doa ）, and Simpson （D） indices. Community structure was determined by hierarchical cluster and multidimensional scaling analyses. Significance testing for differences in macrobenthic species and density between sample lines and sediment depth was undertaken. Based on the data collected from three sample lines in the ZR and three in the HH, a total of 40 species were obtained, of which 18 species were Mollusca, 13 were Crustacea, 4 were Polychaeta, and the remaining five were members of various other taxonomic groups. Thirty species were obtained in the ZR, 31 were obtained in the HH, and 21 were found in both habitats. In both HH and ZR, the macrobenthic species numbers were highest at 0--5 cm depth and lowest at 20--25 cm depth. The average density in the HH and ZR was 222.6 ind./m2and 1052.8 ind./m2, respectively. The main habitat depth coincidence rate was more than 50% when the quantities of species were more than 1% of the total species. When the quantities of species were more than 10% of the total species, then the coincidence rate was more than 75%. In the 0--20 cm deep HH sediment, the Margalef, Shannon-Wiener, and Pielou indices were higher than at the same sediment depth in ZR, but the Simpson index showed an opposite trend. In the 20--25 cm deep HH sediment, the Margalef, Shannon-Wiener, and Pielou indices were lower at the same depth in ZR. Again, the Simpson index showed an opposite trend. The results revealed that （ 1 ） In I-IH and ZR, macrobenthos mainly inhabit the 0--10 cm deep sediment category; （2） different macrobenthic communities are distributed at different sediment depths in both habitats ; （3） the invasion of S. alterniflora reduced the vertical macrobenthos distribution depth, but had little effect on its main habitat depth; and （4） the S. alterniflora invasion altered the original habitat characteristics, which caused changes to the macrobenthic community structure.