Using Dissolved Organic Matter Fluorescence to Signal Changes in Carbon Cycling During a Cave Stream Experiment

Cover Photo: Cave salamanders (Eurycea lucifuga) are often found in the "twilight zone " area. This zone is near the entrance of the cave where a small amount of natural light still falls. E. lucifuga feed mainly on various insects and spiders. In the fall one might find their eggs in little crevices of rocks that have water/moisture in them or along rimstone pools. This particular specimen was found in Bluff River Cave scrambling around popcorn formations on the rocks. About the Photographer: Amy Hinkle (Sunguramy Photography) holds a Master of Science and specializes in biochemistry and neuroscience research. She is also an avid caver and photographer and develops techniques to bring light to these pitch-black underground systems without the use of massive amounts of camera gear. Having always enjoyed the worlds of both art and science, she endeavors to join the two in both her photography and graphic design work. Both have appeared on covers of multiple scientific journals including Neuroscience, biotech company advertisements, and other publications. All rights to the articles presented in this journal are retained by the authors. Permission must be granted for replication by any means of any of the material. Disclaimer: The views of the authors do not necessarily reflect those of the staff of JOSHUA or The University of Alabama. Introduction Some of the most biologically unique places on Earth are found in underground cave systems. Because caves do not receive any sunlight they do not harbor any photosynthetic primary producers and instead rely on secondary production by heterotrophic organisms. This heterotrophic production is performed by microbial communities in the stream and is passed up the food web to invertebrates (i.e. chironomids) and vertebrates (i.e. cave salamanders) when these animals eat the detritus (coarse dead organic matter and its associated microbes) with the bacteria and fungi (microbes) living on them. The cave food web is thus ultimately reliant upon detritus and dissolved organic matter (DOM) reaching the cave from the surface as a source of energy and carbon for growth [5]. One study found that dissolved organic matter (DOM) was the most important factor controlling the flux of energy in a cave system [3]. The lack of high quality sources of carbon has created a shortage of energy in cave systems, and this lack of energy may control the trophic dynamics, the composition of communities , and even the evolution of native organisms …