01547nas a2200145   4500008004100000245012200041210006900163300001300232490000700245520097800252100001801230700001501248700001401263856012401277       1996                        eng d00aMicrocosms for aquifer research: Application to colonization of various sized particles by groundwater microorganisms0 aMicrocosms for aquifer research Application to colonization of v  a756 -7590 v343 aFlow-through microcosms were constructed to conduct ecological experiments on aquifer organisms. The two 5-channel microcosms were simple to construct, were fed by an artesian spring, and maintained close to in situ temperature and O2 concentrations. They were used to test relative microbial colonization of three substrate sizes: silt (0.063 mm), sand (0.9 mm), and gravel (3 mm). After 96 days of incubation, O2 microelectrode measurements revealed the lowest O2 tension in the silt, the highest in the gravel, and intermediate values in the sand. Microbial activity (3[H]-thymidine incorporation) was greatest in the gravel, followed by sand and then silt. Denitrification was greatest in the silt, followed by sand and then gravel. Microbial activity may be greatest with the largest particle size because of increased water exchange through pores, and denitrification may be greatest with the smallest particle sizes because of the occurrence of anaerobic microzones.1 aDodds, W., K.1 aRandel, C.1 aEdler, C.  uhttp://knz.lternet.edu/content/microcosms-aquifer-research-application-colonization-various-sized-particles-groundwater