We provide a comprehensive list of microorganisms (algae, Archaea, bacteria,
cyanobacteria, fungi, and Protista) inhabiting cryoconite holes on glaciers
throughout the world, giving an updated taxonomy accompanied by geographic
coordinates and localities. The list consists of 370 taxa reported from
cryoconite holes (mostly from Arctic and Antarctic regions and European Alps).
However, most of the taxa were not identified to the species level. Until now
only 39 identified species or subspecies of bacteria and Archaea, 11 fungi, 17
cyanobacteria, 62 algae, and 13 Protista are known from cryoconite holes, which
are only about 38% of total number of taxa reported from these ephemeral
environments. Almost 62% of the taxa were marked as cf.
(confer) or were identified only to the genera or even to
the higher taxonomic units (such as families or orders). This wide and detailed
review assists other scientists to identify the gaps in our knowledge about
cryobionts and indicates directions for further zoogeographical and taxonomical
studies in this unique freshwater habitat.
Due to their small area and shallow depth ponds are usually treated as a single sampling unit, while various microhabitats offer different environmental conditions. Thus, we tested the effect of different habitat types typically found within small ponds on the microalgae and zooplankton communities. We found that submerged macrophytes have the strongest impact on microalgae and zooplankton communities out of all the analysed habitats. Some epontic diatoms (e.g. Fragilaria dilatata, Cymbella affinis) and littoral-associated zooplankton species (e.g. Simocephalus vetulus, Lecane bulla) were significantly related to elodeids. However, pelagic species (e.g. bosminids) preferred less complex helophytes, which suggests that the most heterogeneous elodeid habitats were not an anti-predator shelter for cladocerans. Selection of different macrophyte types by taxonomically various organisms suggests that it is not only macrophyte cover that is desired for healthy aquatic environment but that a level of habitat mosaic is required to ensure the well-being of aquatic food webs. Species-specific preferences for different types of macrophytes indicate the high ecological value of macrophyte cover in ponds and a potential direction for the management of small water bodies towards maintaining a great variation of aquatic plants. Moreover, the type of surrounding landscape, reflecting human-induced disturbance (28 field ponds) and natural catchment (26 forest ponds), significantly influenced only zooplankton, while diatoms were affected indirectly through the level of conductivity. Nutrient overload (higher content of TRP) and increased conductivity in the field landscape contributed to a rise in microalgae (e.g. Amphora pediculus, Gomphonema parvulum) and zooplankton (e.g. Thermocyclops oithonoides, Eubosmina coregoni) abundance. An awareness of the responses of both components of plankton communities to environmental factors is necessary for maintaining the good state of small water bodies in various types of landscape.
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