Abstract
Subterranean ecosystems are regarded as the most extensive biome on earth, comprising
terrestrial and aquatic systems - the latter constituting freshwater, anchialine and marine
systems. This system plays a key role in the distribution and storage of freshwater, once it
contains 97% of the world’s total liquid freshwater (Chapter 1), which has been progressively
explored in quality and amount. Initial observation of the subterranean environment began
with speleological studies by the recognition of a typical fauna adapted to live inside caves.
The first studies to provide information about aquatic subterranean fauna commenced in
Slovenia, with the description of the Proteus aguinus by Laurenti in 1768. After an initial
faunal classification by the Danish zoologist Schiödte (1849), the Austrian naturalist Schiner
(1854) established the most commonly used classification for cave fauna and a great portion
of modern research dealing with ecobilogy of aquatic subterranean fauna has mostly evolved
from the European biospeleology (Chapters 1 and 3).
Studies in biospeleology have made a significant contribution to the progressive knowledge in
aquatic subterranean ecology, especially in those circumstances where the access of the
underground through smaller voids (e.g. crevicular spaces) is not possible. Accessibility to the
underground environment is in fact a negative factor that has led a large number of studies
consider about subterranean fauna initially being limited to caves. Spatial constraint was (and
still is) a limiting factor in accessing a diverse range of subsurface habitats, although during
the last decade, modern research has been using advance technology as a tool to overcome the
physical barriers to subterranean research.
For a long time the classification of subterranean aquatic organisms was an unclear subject,
with the classification subterranean fauna mostly related to terrestrial cave fauna
(troglofauna). The classification system dealing with aquatic subterranean groups
(stygofauna) is more recent. A few nomenclature schemes have been proposed to describe
these relationships, based on morphological, behavioural, and ecological adaptations of
animals to the underground life and their level of relationship with groundwater (Chapter 4).
The prefix “stygo” is suggested as the most descriptive to refer ecologically to a group of
animals related to groundwater habitats. Groundwater related fauna (stygofauna) is comprised
by groups of animals encompassing aquatic surface, intermediate and subterranean habitats.
They represent diverse group of animals that have different interactive relationships with the
groundwater habitat. Some may transact between surface water and groundwater systems,
while others spend the whole life cycle in the subterranean voids (Gibert et al., 1994). This
transition zone between surface streams and groundwater is recognized as a critically
important boundary or ecotone, constituted by a habitat that contains a reservoir of
invertebrate fauna biodiversity.
It is therefore from the study of karst systems that most information on groundwater
ecobiology is resourced, once the open structure of most karsts terrains promotes a number of
caves, streams, crevices, sinkholes, and springs to allow human access. Karst systems are well
fractured because of the relation between the rock mass and the action of meteoric water, as
well as the dissolution rate of calcium carbonate rocks that high. The latter increases with
time, producing a terrain with a great drainage potential (Chapter 2). Once porosity is high
and the flow of percolating water is fast, it allows good vagility for subterranean fauna and
nutrients, as well as penetration of contaminants. In subterranean karsts, much water saturates
some areas inside rock spaces. The saturation in the rock in turn promotes large water
pockets, known as aquifers. When these groundwater aquifers are found to be interconnecting
with the adjacent ecosystems, they became active eco-hydrological components, due to their
key participation in the surface-groundwater continuum.
Groundwater has different degrees of importance, depending on the available sources of
surface water. In many countries it supplies a significant proportion of urban and rural
drinking water, industrial, and agricultural. Yet, groundwater systems are “hidden”, difficult
in access and to study (Chapter 4, 5 and 7), consequently the recognition of the groundwater
aquifer as a natural resource that needs to be protected is largely ignored. Moreover, studies in
the ecobiology and distribution of stygobitic invertebrates (Chapter 5), and the need to
identify a frame of methods for quality assessment and the suitability of groundwater
invertebrates as bioindicative elements, has not been developed (Chapter 6).
Finally, strong management and public education programs are required to emphasize the
need for a better understanding of the nature of groundwater resources, their participation and
complexity (Chapter 8), with the conceptualization of the groundwater aquifer integrity as an
ecosystem still receiving little attention in South Africa.
Dr. J.F. Durand
Prof. G.J. Steyn