Utilisation of organic compounds by osmotrophic algae in an acidic lake of Patagonia (Argentina)

Abstract

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Global change‐driven effects on dissolved organic matter composition: Implications for food webs of northern lakes

“…A subgroup of phytoplankton (primarily phytoflagellates, mixotrophic flagellates, and cyanobacteria) that benefit from the mixotrophic potential that DOM provides, populates DOM-rich waters. Their ability to use this alternate form of energy will enable these cells to outcompete strict autotrophs in waters with low concentrations of inorganic nutrients (Beamud, Karrasch, & Diaz, 2014;Flynn et al, 2013;Glibert & Legrand, 2006;Gran eli, Carlsson, & Legrand, 1999;Monchamp, Pick, Beisner, & Maranger, 2014;Ou, Lundgren, Lu, & Gran eli, 2014), or to use alternative sources of N such as DON to satiate the N needs of the otherwise autotrophic cells. DON-containing organic materials as simple as urea have been recently implicated as an alternative source of N linked to an increase in cyanobacteria blooms over the past decade (O'Neil et al, 2012).…”

Peer Review #1 of "Osmotrophic glucose and leucine assimilation and its impact on EPA and DHA content in algae (v0.1)"

“…The uptake velocities of different algae may vary for different compounds (North and Stephens 1972) and depending on the growth mode (Wheeler et al 1974), and thus it is possible that even though our cultures were on stationary phase and assumingly depleted by nutrients, our 30 min incubation time was not sufficient enough for assimilation for some of the algae used in this study. We did the incubations in light, which also could have affected the results, since in some cases algae have shown higher osmotrophic assimilation in dark than in light for glucose (Beamud et al 2014) and leucine (Ruiz-González et al 2012). However, many algal species are reported to enhance their osmotrophic uptake in light (Tittel et al 2009;Beamud et al 2014).…”

“…We did the incubations in light, which also could have affected the results, since in some cases algae have shown higher osmotrophic assimilation in dark than in light for glucose (Beamud et al 2014) and leucine (Ruiz-González et al 2012). However, many algal species are reported to enhance their osmotrophic uptake in light (Tittel et al 2009;Beamud et al 2014). Additionally, our experiments were done in nutrient-rich AF6 or MWC medium, but inorganic nutrient limitation could have triggered rapid osmotrophic uptake .…”

“…The detection of mixotrophic behavior can be challenging both in laboratory and field conditions, and thus, for example, radioactive isotope labelling has been applied to study the osmotrophic nutrient uptake Tittel et al 2009;Beamud et al 2014).…”

“…glutamine, leucine, thymidine, aspartic acid) and other organic compounds (e.g. acetic acid, coumaric acid, glycerol), which they use as carbon and nitrogen sources, and which are commonly released by the algae themselves or by bacteria (Hellebust 1965; Tittel et al 2009;Beamud et al 2014;Dąbrowska et al 2014).…”