Biotic interaction between protists and viruses are also known and have been shown [64]. Viruses specifically infect protists, e.g. the Coccolithovirus and it’s host, the calicifying haptophyte Emiliania huxleyi[65]. Additionally, viruses can also have

an an indirect influence on protists by infecting the bacteria on which the protistan grazers feed or protistan grazers can even feed directly on viruses even though the carbon transfer to the higher trophic level is of minor importance [66]. Furthermore, different bacterioplankton communities can produce a bottom-up control on grazing Talazoparib concentration protists. Namely, the growth efficiency of protists can relate strongly to the available bacterial prey [63, 67]. This is highly likely because differences in bacterial community composition in DHABs have been shown before [68, 69]. That leads to the assumption that different bacterial communities support different phagotrophic protists that show strong preferences for particular prey species [63, 67, 70, 71] or morphotypes [72, 73]. Other possible

explanations are founder effects, which describe a genetic deviation of an isolated find more population or founder population (on an island for example) compared to the original population based on a low number of alleles within the founders individuals [74], random effects or genetic drift is the change in the frequency of a gene in a population due to random sampling [75] and random extinctions that describe when a gene causes its carriers to have a deviating fitness from unity, its frequency will be determined by selection [76] in different basins. For protists in particular there is no literature available on this topic to our knowledge. At last, the Monoplization Hypothesis by De Meester et al. [77] could be relevant to protist biogeography Chlormezanone stating that a fast population growth and local adaptation

and colonization of a new habitat result in the monopolization of resources, which yields a strong priority effect. The effect is even enhanced when a locally adapted population can provide a ‘large resting propagule bank’ as a strong buffer against new genotypes invading. This holds true especially for species that reproduce asexually and form resting stages. Even though mass effect and dispersal [78] cannot be ruled out, these are unlikely alternatives to explain the observed community patterns. The habitats of the water column above the DHABs represent a potential source habitat with ‘high quality’. In comparison, the narrow interphase and the brine show ‘low quality’ conditions because these habitats harbor high gradients of change, anoxia, high salt concentration up to saturation and therefore require a high degree of physiological adaptation for microbial colonization. Chances for highly specialized organisms to cross environmental barriers outside their habitat and to disperse beyond their specific habitat are very low.