The influence of light attenuation on the biogeomorphology of a marine karst cave: A case study of Puerto Princesa Underground River, Palawan, the Philippines

摘要: Karst caves are unique biogeomorphological systems. Cave walls offer habitat for microorganisms which in-turn have a geomorphological role via their involvement in rock weathering, erosion and mineralisation. The attenuation of light with distance into is known to affect ecology, but the implications this processes forms seldom been examined. Here we describe semi-quantitative microscopy study comparing extent, structure, thickness biocover depth endolithic penetration samples from Puerto Princesa Underground River system Palawan, Philippines, natural UNESCO World Heritage Site. Organic growth at entrance cave was abundant (100% occurrence) complex, dominated by phototrophic organisms (green microalgae, diatoms, cyanobacteria, mosses lichens). Thickness layer 0.28 ± 0.18 mm active endolith limestone (mean = 0.13 0.03 mm). In contrast, phototrophs were rare 50 m biofilm cover significantly thinner (0.01 0.01 mm, p < 0.000) spatially patchy (33% occurrence). Endolithic here also shallower (< non-uniform. Biofilm found 250 cave, complete absence no evidence bioerosion. We attribute these findings light-induced stress gradients, showing that influence on phototroph abundance has knock-on consequences development morphological features. marine includes notches, most well-developed sheltered our site, variability formation rates between locations currently poorly understood.