EFFECTS OF FIRE SUPRESSION ACTIVITIES ON KARST AQUIFERS: RESULTS FROM THE HIDDEN FIRE, SEQUOIA NATIONAL PARK, CA

In the fall of 2008, a lightning caused wildfire burned over a major karst region within Sequoia National Park. During initial fire fighting efforts, large amounts of fire retardant, chemicals known to be harmful to aquatic invertebrates, were dumped on the upper reaches of these surface drainages. The drainages downstream of the retardant drops is home to approximately half of the known habitat for the endemic Big Spring Isopod (Bowmanulus sequoiae). To determine the effect of these fire suppression activities on the aquatic karst ecosystems, water chemistry data was collected both during and after the fire from karst springs and surface creeks. Additionally, biological inventories of karst springs and subsurface streams were conducted prior to and after the winter rains. These inventories show no statistical change in isopod populations within the basin, suggesting minimal negative effects of the retardant chemicals. Water chemistry data also supported this finding with no statistical change in cation concentrations or nutrient levels associated with fire retardant. This suggests a series of potential buffers: (1) the karst groundwater systems provide buffering of the negative effects of fire retardant on aquatic species, (2) the combination of distance of the fire retardant drops from streams and vegetation uptake of nutrients reduced its effect on the aquatic system, or (3) large rainfall events through the winter diluted the concentration of these chemicals enough to negate the effects.