The overall diatom and testate amoeba diversity is much lower
than what can be expected in undisturbed terrestrial or aquatic
environments. However, this low diversity is not
surprising. Testate amoebae are considered to be mostly K strategists
and therefore would be expected to be especially sensitive to
repeated perturbation such as plowing, cutting or grazing and
diatoms are very sensitive to desiccation because they live at the
surface of the soil where moisture content is frequently very low.
Therefore, the different degree of soil disturbance [29] and potential
differences in soil moisture between the conventional and
organic fields might explain at least one part of the differences
observed among treatments. The number of species reported in this
study is quite likely underestimated. Indeed, our morphologybased
approach does not allow us to rule out the presence of
cryptic species within diatom and testate amoeba morphotaxa
[46e48]. Moreover, several morphotaxa in this study as well as inother comparable works could not be assigned a precise name and
might therefore represent new species . Molecular studies
may allow for a better resolution for both species identification and
diversity estimates. Generally, soil protists remain poorly known
and many species are still undescribed .