Influence of solar UV‐B radiation on peatland microbial communities of southern Argentinia

SUMMARY • Stratospheric ozone depletion occurs over Tierra del Fuego, Argentina, in the austral spring and summer due to the Antarctic ‘ozone hole’ and the general erosion of the ozone layer. Thus, we investigated the responses of microbial communities to manipulations of solar UV‐B radiation. • Results reported here are for field plots receiving either near‐ambient or reduced solar UV‐B using plastic filters in a Sphagnum peatland and a Carex fen during the second and third years of UV‐B manipulations. • The total number of testate amoebae (Protozoa, Rhizopoda) inhabiting the upper centimeter of Sphagnum magellanicum was greater under near‐ambient solar UV‐B than under reduced UV‐B. No response to UV‐B manipulation was apparent for rotifers, nematodes, bacteria, microfungi, and a common microalga (Euglena mutabilis) inhabiting the S. magellanicum. On leaves of small Nothofagus antarctica trees, the ratio of upper: lower leaf‐surface fungal populations for the genus Aureobasidium and for total fungi indicated lower populations on the upper, relative to the lower, surface under near‐ambient solar UV‐B. • When responses to modifications of the solar UV‐B flux were detected, these involved both direct UV‐B inhibition and indirect consequences of UV‐B manipulation.