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Information on the geological environment, accumulated by different branches of the earth sciences, demonstrates the complexity of the system of cause-and-consequence links formed in the Earth during its geological evolution..

Judging from the absolute age of the most ancient rocks, the geological cover of the Earth has been developing for about 4 billion years. The processes of origination and evolution of all forms of life on the planet are inseparably connected with two important media — geological and aquatic (oceanic) ones. First, about 1 billion years ago, life in the form of protozoa originated in an aquatic medium and then, with sophistication of the forms and accretion of populations, moved to the land. The geological matrix served always as a substrate for it.

The evolution of the geological environment proceeds through numerous physico-chemical and geodynamic processes and these directly influence the functioning of associated ecosystems. Modem geological processes and phenomena thus exert direct or indirect effects on biota and the overall environmental situation over large areas.

The physical structure of an estuary is governed by geological circumstance and shaped by a combination of river flows, tidal characteristics, current speeds and wave action. An over-riding constraint on estuarine biota is the nature of the variable salinity regime, since the capacity for ionic and osmotic regulation varies greatly between species and sets the limits for their distribution. Of equal importance, if the organism is to settle and survive, are the properties of deposits. Superimposed on these primary drivers are numerous other factors that influence estuarine biota, either directly or indirectly. These include light attenuation and oxygenation patterns (natural characteristics), together with an assortment of anthropogenic impacts. The current chapter focuses on the ways in which geological and geochemical features (substrate properties) impinge on estuarine ecosystems, including modifications made as a result of contaminant bioavailability and toxicity. We also consider ways in which biological activity can mobility in estuaries through processes such as bioturbation and biodeposition.

Planet Earth is but one large complex ecosystem. Indeed, every centimeter of the planet is itself an ecosystem, and yet part of a larger, interacting community of organisms and environment that give rise to the natural world (Pickett and Cadenasso, 2002). Habitats, the places where organisms live, are primarily fashioned by geologic processes. These processes started and still control the distribution of the earth’s major land biomes: tundra, desert, grassland, chaparral, forest and savanna. Of particular interest is chaparral, a shrub-dominated ecosystem found on several continents, including the Mediterranean, the African Cape region, central Chile, southwestern Australia, and California Though climate directly determines the distribution of these vegetation types and their related fauna, the climate itself is influenced by mountain building, and by the size, shape and location of landmasses. Accordingly, ecosystems from microscopic to greater than continental-size, generally depend on the magnitude and frequency of geologic processes affecting a given area. The importance of geologic and ecosystem interaction is reflected by increasing scientific recognition and new fields of university study now generally termed “geoecology,” “geobiology,” and “ecohydrology” (Bastian et al., 2002; Rodriquez-Iturbe, 2000; Safford, 2002).

Karst is a type of landscape found on carbonate rocks (limestone, dolomite, marble) or evaporites (gypsum, anhydrite, rock salt) and is typified by a wide range of closed surface depressions, a well-developed underground drainage system, and a paucity of surface streams. Karst is, therefore, a particular kind of landscape where landforms due to solution processes prevail over other kinds of landforms. It is estimated that karst landscapes occupy up to 10% of the Earth’s land surface, and that as much as a quarter of the world’s population is supplied by karst water. The karst system is sensitive to many environmental factors. Karst aquifers contain the most important water resources of mountainous countries: these resources have often a good quality because karst areas have currently a low technogenic pressure.

An idea of balanced development of the world, brought forward by the United Nations Organization and supported by 182 countries (Rio-92), implies satisfaction of today’s demands for mineral resources without any damage for future generations. Possible ways to achieve this goal were analyzed during recent years in a number of international projects taking account of political, economic, social and environmental factors. It is obvious that balanced development requires achieving a balance of interests in the system “state (S) - mining companies (MC) - community (C) - habitat (H)”. The first two elements in this system possess the strongest influences, whereas possibilities for cooperation community are considerably limited by the potential of democratic institutions for protest movements. The habitat is, in general, defenseless and passive, but only until critical situations creat a threat to mankind’s existence. Preventive measures for such situations comprise at the present only a small part of natureprotective actions; mankind struggles chiefly with adverse effects already accumulated and current influences upon the environment.

It has become obvious during recent decades that any type of anthropogenic activity (civil engineering, agriculture, deforestation, extraction of surface and ground waters, etc.) inevitably has an impact upon ecosystems. The main task in solving this problem is to predict possible changes in the geological environment and to provide scientifically sound recommendations for the prevention of negative anthropogenic influences on marine and terrestrial ecosystems.

Processes of continental water quality degradation stemming from the powerful anthropogenic pressure continue to figure prominently amongst current environmental problems. Particular attention has been paid to groundwater because it has been considered that it may show better quality indices compared to surface water sources. At the same time, rapidly accumulating water chemistry data indicate that such views may need fundamental revision, especially in areas where, due to a variety of circumstances, the natural condition of groundwater formation and factors influencing its quality are disturbed.

An important environmental problem is that of estimate risks and hazards of groundwater pollution in conditions of increasing negative impact on them from natural and anthropogenic factors. Risks and hazard are estimated in relation to groundwater as an ecosystem life support system and, more generally, to their economic significance for sustainable development of the investigated regions.