Ciliates as bioindicators of CO2 in soil

Abstract

The effect of controlled sub-surface CO2 emissions on edaphic ciliate communities was examined in experimental mesocosms and then compared with the effect of natural CO2 emissions from natural vents on edaphic ciliate communities to analyse the potential of ciliates as bioindicators of soil CO2 increments. The relative abundance of each taxonomic family formed the basis for developing the metrics of the ciliate assemblages in order to obtain a quantitative soil quality bioassessment, the edaphic ciliate bioindex. Twenty-four mesocosms filled with soil and equipped with controlled CO2 injection were built for the experiment. To evaluate the potential of soil ciliates as bioindicators, the same CO2 fluxes were analyzed in both study conditions, from 0 to more than 150mlCO2d−1. Several diversity indices and other group ratios and percentages of community structure were calculated.Biodiversity of ciliates (Equitability, Margalef and Shannon indices) decreased with the increase in CO2 fluxes, and Colpodid/Polyhymenophorean ratio increased. This indicated adverse conditions for the ciliates in the soil. There was a positive significant relationship between the observed CO2 values measured in the test set and the values expected according to their inhabiting ciliate community. The weighted averaging of taxonomic group indicator method supported the experimental results attesting to the potential of edaphic ciliates as bioindicators of CO2 flux increments. The ecological profiles estimated within the training test, based on the taxonomic level of family, were reliable and provided a basis for the use of ciliates to monitor soil CO2 flux increments in a wide range of ecological conditions.