盐沼植物对大型底栖动物群落的影响

2005年5月下旬在崇明东滩中潮区相同高程上的裸地(ld)、海三棱藨草(Scirpus×mariqueter)地(hs)、芦苇(Phragmites australis)地(lw)、互花米草(Spartinaalterniflora)地(hh)里取样研究了大型底栖动物群落。ld物种数、总个体数、Shannon-Wiener指数、Margalef物种丰富度指数、平均密度和平均生物量都是最低的;平均密度在裸地和3种盐沼植物地间都存在显著差异(P<0.05,LSD检验);平均生物量在海三棱藨草地与裸地间存在极显著的差异(P<0.01,LSD检验);等级聚类分析(Cluster)表明,裸地和盐沼植物地间大型底栖动物群落差异明显。hs、lw、hh中的优势种都是底上附着型的软体动物,而ld中则以穴居型的甲壳动物占优势;hs、lw、hh、ld的面上群与面下群的比值分别为0.56、0.63、0.63、0.75。3种盐沼植物地间大型底栖动物群落相似性程度较高,但非度量多维标度(MDS)排序仍然揭示出可以区分的差异。这些差异体现了盐沼植物对大型底栖动物群落的明显影响。盐沼植物是通过直接改变生境结构或间接影响水动力和沉积物扰动等作用进而明显地影响大型底栖动物群落,盐沼植物也是影响潮间带大型底栖动物群落的重要生态因子。

Effects of saltmarsh on the benthic macroinvertebrate community in Yangtze Estuary

On intertidal mudflats, invertebrate communities often respond strongly to biogenic species that form emergent structures. This hypothesis was tested by collecting benthic macroinvertebrates from four distinct habitat types, which occurred in a saltmarsh mosaic at an equivalent tidal elevation at Dongtan, Yangtze Estuary, Shanghai, China. Habitat types were: a) Scirpus × mariqueter saltmarsh (hs), b) Phragmites australis saltmarsh (lw), c) Spartina alterniflora saltmarsh (hh), and their contrasting type, d) unvegetated mudflat (ld). Within every habitat type, six quadrats (25cm×25 cm, 20cm deep) were taken from independent patches in late May, 2005 and sieved (1 mm mesh).
Communities in different habitats were compared in terms of numbers of species, total individuals, Shannon-Wiener index value, Margalef index value, mean density and mean biomass (fresh weight) of the macrofauna. All of these values were lowest on unvegetated mudflat. There were significant differences (P<0.05, LSD tests) in the mean macrofaunal density between the three saltmarshes and the ld type, and extremely significant difference (P <0.01, LSD tests) in the mean biomass between patch types hs and ld; CLUSTER showed that the macrofauna in type ld were quite different from those in the three saltmarshes.
In patch types hs, lw and hh, the dominant life forms were all adhering Mollusca, whereas that in patch type ld was caving Crustacea. This difference was reflected in the ratios of group of surface to group of surface below in patch type hs (0.56), lw (0.63), hh (0.63), and ld (0.75). Though the macrofauna in the three saltmarshes were relatively similar, they were distinguished from each other by MDS.
Differences in macrofauna between unvegetated mudflat and the three saltmarshes suggest the obvious effects of saltmarsh on the benthic macroinvertebrate community. These effects may be direct, such as alteration of habitat structure, providing resources of food, or may be indirect through shifts in hydrodynamic and deposition regimes. The saltmarsh is thus an important ecological factor which can influence the benthic macroinvertebrate community in the intertidal zone.