Presence, abundance and bacterivory of the mixotrophic algae Pseudopedinella (Dictyochophyceae) in freshwater environments

SAAD, J. F.; GASOL, J.; GEREA, M.; QUEIMALIÑOS, C.; IZAGUIRRE I.; UNREIN, F.

AQUATIC MICROBIAL ECOLOGY

INTER-RESEARCH

Lugar: Oldendorf/Luhe; Año: 2016 vol. 76 p. 219 - 232

0948-3055

The genus Pseudopedinella has been described as mixotrophic; however, ecologicalinformation about this algal stramenopile (Heterokonta) is unclear. We investigate the environmentalconditions that determine the presence, abundance and bacterivory rates of this genus infreshwater systems. To this end we analyzed 54 water bodies with different limnological featuresdistributed along a latitudinal and trophic gradient in northern Patagonia (Argentina) and theAntarctic Peninsula. In addition, 14 grazing experiments were carried out in order to estimate ingestionrates and impact on the bacterioplankton. Our results indicate that this genus is exclusivelyfound in oligotrophic environments, and that it develops well in a wide range of temperatures.Average cell-specific grazing rate was 2.83 bacteria cell?1 h?1, with a maximum value of 6.74bacteria ml?1 h?1. Interestingly, grazing increased with prey abundance and decreased with increasingnutrient availability. These patterns are common in highly bacterivorous protists that usephagotrophy as a main source of nutrient acquisition. Despite their usually low abundance (avg.182 cells ml?1), this single genus was responsible for up to 24% (avg. 10%) of the total grazing impactexerted by all phagotrophs in these lakes. Overall, our results support the idea that Pseudopedinellais a highly bacterivorous group of freshwater protists, with the ability to develop well inoligotrophic conditions and with a potentially significant impact on bacterioplankton.