Quantifying the Biotic Enhancement of Mineral Weathering by Moss
Addressing the paucity of reliable, robust studies into the weathering effect exerted by biota onto rocks and minerals: mineral weathering by the moss Physcomitrella patens was measured in a novel in vitro microcosm study. A sterile technique was maintained in order to ensure that P. patens was the only organism exerting weathering affects within the microcosms, control microcosms were devoid of biota entirely. After the weathering period (mean = 112 days) the moss and aqueous solutions resulting from microcosms were analysed for Al, Ca, Fe, K, Mg, Na and Si using Inductively Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES) and for PO4(3-) and SiO4(4-)using a Nutrient Auto-Analyser. Results show strong biotic enhancements for all ICP analytes and PO4(3-) (except Na). Biotic enhancements were strongest for Fe on most substrates, reaching levels of <625x abiotic weathering in andesite microcosms (population mean = 330.7x) and <493.6x on granite (all significant at P<0.01). Aqueous phase biotic enhancements for PO4(3-) were 5.3x on vermiculite and 4.2x on granite. Experimental substrates were analysed using X-Ray Fluorescence Spectroscopy (XRF) in order to ascertain their petrologies and to enable comparison with weathering results to determine whether ions were being preferentially weathered over their baseline levels. Weathering of plant macronutrients is enhanced over the baseline stoichiometries, but biotic influence on this effect appears negligible. This study has a bearing upon hypotheses linking the effects of increased land-surface weathering to the Ordovician glaciation due to the proliferation of bryophyte organisms across the land surface. Furthermore this study finds that P. patens is an excellent model bryophyte for studies of weathering as well as its more common use as the model bryophyte in genetic studies. Keywords: Biogeochemistry, Enhancement, Microcosm, Mineral, Moss, Weathering.
MSc by Research Thesis, UEA, Norwich, 194