I. Ecosystems A. Most aquifers do not support traditional aquatic ecosystems. 1. No light, no photosynthesis (for plants) 2. No nutrients 3. No dissolved O 2 to support aerobic life. 4. Survivors include: bacteria, protozoans, and other unicellular organisms. B. Karst aquifers support a more complex aquatic ecosystem in underground cave habitats. 1. Invertebrates, fish and amphibians make up the majority of the organisms. 2. Nutrients are recycled among the organisms due to the lack of producers. 3. Have a very low carrying capacity. 4. Adaptations a. Absence of eyes b. Many devoid of color c. Increased sensory development including, antennae, chemoreceptors and touch receptors. d. Consistent water temperature supports a lower metabolism which means less food require. e. Environment stable and predictable. C. Nutrient Support from the outside 1. Cave-dwellers depend on the plant and animal material washed into the caves. 2. Feces dropping from bats and mice provides nutrients for fungal growth which many insects eat. 4 3. Food chain: Fungi insects insect larva invertebrates blind salamander toothless blindcat (catfish). Death of the catfish would provide nutrients and cycle continues 5 D. Spring Ecosystems 1. Food provided by aquatic plants and algae 2. Isolated habitats of many springs contain species found only in that particular location. 3. Consistent water temperatures near the springs the cave openings prevent organisms from wandering to the streams and rivers associated with the spring. 6 4. Ecosystems are small providing limited numbers of any one species population to survive. 7 E. Changes Impact the Habitat 1. Decrease in ground water flow or drought reduces habitat and stresses many species. 2. Invasive species enter native springs and take over often eliminating the indigenous species of the spring. 3. Human impact on springs vary; from building dams across the springs to building recreational pools destroying the native species. 8 II. Water Supply Problems for Aquifers and Springs A. Water Supply Problems 1. Water Quantity a. Spring runoff is highly dependent on rainfall b. Not enough recharge times between drought c. Edwards aquifer holds a huge amount of water but: At less than 95% capacity, the springs run dry. d Wide spread fauna and flora inhabit springs and caves and are vulnerable to extinction if water levels get too low. 2. Water Quality - a. Vulnerable because aquifer is relatively shallow b. Little reaction time in case of a spill c. Clean-up of local threats almost impossible Aquifer has a low self-cleaning ability (natural remediation ) 11 3. Sources of Pollution a. Solid waste 1. Wild depositions in dolines (sink-holes) are common in many area 2. Strong precautions for sealing dump-sites b. Waste water 1. high risk from leaking sewers 2. used water infiltrates aquifer 3. no surface drainage system c. Agricultural use d. Industrial contamination e. Hydrocarbons-explosive f. Liquid waste injection III. Environmental Impact A. Eight species in the Edwards Aquifer, Comal Springs, and San Marcos Springs ecosystems are currently listed by the U.S. Department of Interior, Fish and Wildlife Service, as either threatened or endangered species. Endangered Comal Springs Dryopid Beetle Comal Springs Riffle Beetle Fountain Darter Pecks Cave Amphipod San Marcos Gambusia Texas Blind Salamander Texas wild-rice Threatened San Marcos Salamander 14