Effects of temperature on growth rate and gross growth efficiency of an Antarctic bacterivorous protist

Abstract

The effects of temperature on the growth rate and gross growth efficiency (GGE) of the heterotrophic nanoflagellate, Paraphysomonas imperforata, cultured from the Ross Sea, Antarctica were investigated using five experimental temperatures (range ¼ 0-20 1C). This bacterivorous protist exhibited measurable growth over the temperature range examined, although temperature exerted a significant effect on its growth rate. There was no evidence for an effect of temperature on GGE. The growth rates and GGE of our Antarctic P. imperforata isolate were compared to values reported for other cultures of species from this genus. A wide range of growth efficiencies have been reported for different strains of Paraphysomonas spp., but our estimates were comparable to mean/median values reported in the literature. The growth rates of our Antarctic P. imperforata were similar to rates obtained for an Arctic conspecific at low temperatures (0-5 1C), among the highest reported rates for any Paraphysomonas species at intermediate temperatures (10-15 1C) and similar to rates reported for temperate congeners and conspecifics at 20 1C. Q 10 values of 15, 2.2, 3.6 and 0.93 were calculated for growth rates at 5 1C intervals between 0 and 20 1C, respectively. Results indicated that our Antarctic P. imperforata grew at rates comparable to other polar isolates at ambient polar temperatures, but these low temperatures may be outside the physiological optimum for the isolate.

Temperature effects on the heterotrophic bacteria, heterotrophic nanoflagellates, and microbial top predators of the NW Mediterranean

“…Edwards & Richardson 2004), as temperature led to positive effects on bacterial secondary production and bacterial losses to grazing, while heterotrophic nano flagellates and ciliates reduced their production. This finding is counter-intuitive because of the known general positive effect of temperature on the growth rates of protists (Rose & Caron 2007, Rose et al 2009). However, it is plausible if the growth efficiencies of protists decrease with temperature (Rivkin & Legendre 2001) and/or if the in creases in protist growth rates related to warming are tightly top-down controlled by the copepod nauplii present in the samples (Vidussi et al 2011), which, furthermore, could have enhanced their metabolic rates by the positive effect of temperature on their metabolism (Huntley & Lopez 1992, Weisse et al 2002, Montagnes et al 2008.…”

“…Production (P) and respiration (R) are metabolic processes affected by temperature (Brown 2004); its effect on P and R rates has been shown in both heterotrophic bacteria (Shiah & Ducklow 1994, Morán et al 2006, Vázquez-Domínguez et al 2007) and protists (Rose et al 2008(Rose et al , 2009. Temperature can also decrease the ratio between primary production and bacterial secondary production (Hoppe et al 2008), as was observed in mesocosms deployed in Kiel Fjord, where warming increased the recycling of dissolved organic matter (Wohlers et al 2009).…”

“…However, there are few studies inspecting the effects of temperature on the transfer of carbon between heterotrophic bacteria and protists, at least in natural microbial communities. Those available show a positive effect of temperature on bacterial grazing rates (Marrasé et al 1992, Rose & Caron 2007, Rose et al 2009). …”

Temperature and phosphorus interacts in controlling the picoplankton carbon flux in the Adriatic Sea: an experimental versus field study

“…On the other hand, under experimental conditions, grazing on autotrophic picoplankton (PROC and SYN) increased at higher rates than their production. This is supported by studies reporting that the mortality rate of autotrophs showed higher sensitivity to warming in comparison with their growth rate (Allen et al, ; Brown et al, ; López‐Urrutia et al, ; Rose et al ., ).…”

Elevated temperature alters proteomic responses of individual organisms within a biofilm community

“…Many microbial community studies have evaluated the effect of warming on overall community structure and on specific metabolic processes such as respiration (for example, Zogg et al, 1997;Finke and Jørgensen, 2008;Rose et al, 2009;Yergeau et al, 2012;Lindh et al, 2013;Wu et al, 2013;von Scheibner et al, 2014). Far fewer studies have comprehensively assessed functional responses across the entire community (for example, using 'omic' approaches (Luo et al, 2013;Toseland et al, 2013) or functional gene arrays (Yergeau et al, 2012;Tu et al, 2014)).…”