Specialized aquatic subterranean communities are probably most species-rich in the thickest epikarst

Stygobionts are aquatic troglobionts, i.e., organisms that are specialized for living in subterranean environment. It has been demonstrated that the epikarst above caves harbors a stygobiont fauna that is as rich as that in deeper caves. The abiotic parameters affecting the aquatic fauna in drip water have been relatively well explored, while aquatic troglobionts alone are not frequently the focus of such studies; consequently, many crucial questions remain insufficiently studied. We hypothesized that the epikarst stygobiont fauna may occur locally in deeper zones of the epikarst, since environmental conditions are more stable there. For this purpose, we studied the composition and annual dynamics of the epikarst stygobiont community from ten water drips in the cave Zguba jama in Slovenia. Copepoda predominated among eight stygobiont taxa. The high total and between-sites dissimilarity of stygobiont communities among the drips was mainly the consequence of species turnover. We found that the greater the distance from the entrance and the ceiling thickness, and the higher the water temperature, the greater was the chance of finding aquatic troglobionts and the higher thier diversity. Our study suggests that locally, owing to specific lithology and geomorphology, epikarst stygobionts can extend from the shallow layers into deeper epikarst layers, where voids with more suitable environmental conditions exists.     

沉积物孔隙空间天然气水合物微观分布观测

在高分辨率工业型X射线层析扫描仪上（X-CT,X-Ray Computerized Tomography）,研制了适用于沉积物中水合物微观赋存状态研究的CT原位探测装置,可通过模拟天然气水合物生成/分解过程,直接观测水合物在沉积孔隙中的微观分布特征.对粒径为0.425~0.85 mm沉积物中水合物形成过程进行了CT观测研究,结果表明,沉积孔隙中水合物呈混合分布模式,但在水合物不同形成阶段,以某种分布模式为主导：在水合物形成初期,仅有极少量水合物悬浮在流体中,水合物主要以接触或胶结模式为主;在水合物形成中期（如饱和度为24.6%、35.0%时）,水合物倾向于在孔隙流体中以悬浮状形态生成;在水合物形成后期（如饱和度为51.4%之后）,悬浮状的水合物慢慢生长聚拢在一起,水合物又重新胶结沉积物颗粒.