Karst Ecosystems
- PDF / 555,348 Bytes
- 11 Pages / 595.276 x 790.866 pts Page_size
- 49 Downloads / 212 Views
KARST ECOSYSTEMS Annette S. Engel Louisiana State University, Baton Rouge, LA, USA
Definition Karst. A landscape in and on the Earth’s surface produced by the natural processes of solution and leaching of soluble rocks, generally carbonate rocks (e.g., limestone), in which the ensuing topography is mainly characterized by sinkholes, sinking streams, underground drainage networks, and caves. Introduction Karst landscapes comprise 15–20% of the Earth’s icefree land surface. Because karst forms in soluble rocks, the global occurrence coincides roughly with the distribution of carbonate sedimentary rocks (e.g., Ford and Williams, 2007) (see Chapters Carbonates and Carbonate Environments). Karst landscapes link the Earth’s surface to the subsurface, being characterized by features such as sinking streams, sinkholes, caves, and extensive underground water flow systems. Caves, which can extend up to 100 m into the subsurface, are solutionally- or collapse-enlarged discontinuous openings in rock. Surface karst features neither have to be extensively developed, nor present, for subsurface karst development and aquifer processes to be operative. Approximately, 25% of the global population depends upon the health of karst terrains and karst aquifers for its water supply (Ford and Williams, 2007). Air, water, and rock within karst landscapes offer reactive interfaces for microbial activity. Considering the extent to which carbonate rocks comprise the rock record, and the depths to which subsurface carbonates can be karstified, the microbial biomass within karst settings
and at karst interfaces is potentially tremendous. Hence, microbial diversity and microbial processes are central to all of the karst-related sciences. Moreover, as some karst landscapes have remained relatively unchanged for thousands, if not millions, of years (e.g., Gale, 1992), the longevity of the karst habitat makes karst a potentially long-term reservoir for microbial communities and subsurface ecosystems (see Chapter Deep Biosphere of Continental Rocks). The goals of this review are two-fold: (1) to summarize the geobiology of karst ecosystems by describing the range of karst habitats that are important to maintain biological (and microbiological) diversity, and (2) to examine the range of geochemical, mineralogic, and ecological processes that are influenced by microbes in karst.
Types of caves and karst Karst development, and subsequently cave formation (speleogenesis), is primarily due to rock dissolution, mechanical weathering, volcanic activity, or the melting of glacial ice (Figure 1). Karst can be classified in a number of ways, including from determining the solid that a feature has developed within (e.g., limestone, dolomite, gypsum, basalt, granite), the proximity to the groundwater table (e.g., above, at, or below it), the origin of the feature, and the morphology of the feature (e.g., cave passage shape, cave length, passage arrangement, passage levels). As Figure 1 demonstrates, there are a number of karst, pseudokarst, and cave types.
Data Loading...
