AN ASSESSMENT OF USING AQUATIC SUBTERRANEAN ORGANISMS AND FLUORESCENT PROTEINS AS BASIC TRACERS IN THE CUMBERLAND VALLEY KARST REGION OF SOUTH CENTRAL PENNSYLVANIA

The organisms of subsurface systems are significantly understudied and largely unknown. Many subterranean systems are comprised of diverse communities, members of which may be used for monitoring groundwater quality and source tracing. Karst recharge may also induce microbial growth traceable as fluorescent proteins. This study focused on four karst groundwater systems and several surface streams in south central Pennsylvania. Objectives were to document subsurface diatoms, algae, and invertebrates, explore whether abundances of organisms are affected by hydrologic conditions, and to assess the feasibility of using aquatic organisms and fluorescent dissolved organic matter (DOM) as basic tracers. The presence of organisms and microbially derived DOM varied with hydrologic condition and source waters where known. The diffuse flow of Dykeman Spring contained no organisms or protein fluorescence, the conduit systems of Welsh Run and Green Spring contained many organisms and high protein fluorescence, and the intermediate system of Big Spring contained very few organisms and very low protein fluorescence. There were two distinct surface contributors to the Welsh Run Cave shown by diatoms and algae, one of which was previously traced with fluorescent dyes. Diatoms in Green Spring revealed a surface water contribution during baseflow, and there were high microbial proteins during spring melt. Three diatom types were found in the Green Spring resurgence, two of which also occurred in up-gradient surface waters. This study confirms that organisms and microbial proteins as basic tracers may corroborate and complement fluorescent dye traces in elucidating surface water sources to karst flow systems.