Effects of environmental factors and halophyte distribution on spatiotemporal variability of dominant mollusc species (Glauconome chinensis Assiminea lutea) in the Donggeom salt marsh, Korea

Abstract

We examined the effects of environmental factors and halophyte distribution on spatiotemporal variation of two dominant mollusc species (Glauconome chinensis Gray, 1828 class Bivalvia and Assiminea lutea A. Adams, 1861 class Gastropoda) in the Donggeom salt marsh on Ganghwa Island, off the west coast of Korea. Macrobenthos and halophytes were collected monthly between July 1997 and June 1998 using a can corer (0.025 ㎡), and halophyte coverage was evaluated in quadrats of 50 ㎠. Halophyte coverage in the salt marsh was positively correlated with exposure time (p<0.01) and negatively correlated with salinity and silt content (p<0.01). Halophytes a positive correlation with G. chinensis (p<0.001) and A. lutea (p<0.01) were the most dominant species in mixed halophyte communities (Triglochin maritimum, Juncus haenkei, Phragmites communis) in the central part of the salt marsh. G. chinensis infauna among halophyte roots showed no significant correlation with environmental factors. A. lutea epifauna on the surfaces of sediments and halophyte leaves/stems which widely distributed in tropical and temperate brackish water zones, as well as coastal and wetlands affected by tides showed significant positive correlation with Gravel/sand content and exposure time, but a negative correlation with salinity (p<0.01). The formation of patches in high water content, halophyte life/death cycles, and increased organic matter due to decreased flow rate have been reported to affect A. lutea distribution and density. These results indicate that the habitat difference are important determinants on the spatiotemporal distribution of two mollusc species in salt marsh.