The 24 hour recovery kinetics from n starvation in Phaeodactylum tricornutum and Emiliania huxleyi

Abstract

The response of N (nitrate) starved cells of the diatom Phaeodactylum tricornutum and the coccolithophore Emiliania huxleyi to a pulse of new N were measured to investigate rapid cellular and photosynthetic recovery kinetics. The changes of multiple parameters were followed over 24 h. In P. tricornutum, the recovery of Fv /Fm (the maximum quantum yield of PS II) and σPSII (the functional absorption cross-section for PSII) started within the first hour, much earlier than other parameters. Cellular pigments did not recover during the 24 h but the chlorophyll (chl) a/carotenoid ratios increased to levels measured in the controls. Cell division was independent of the recovery of chl a. In E. huxleyi, the recovery of Fv /Fm and σPSII started after an hour, synchronous with the increase in cellular organic N and chl a with pigments fully recovered within 14 h. P. tricornutum prioritized the recovery of its photosynthetic functions and cell divisions while E. huxleyi did not follow this pattern. We hypothesize that the different recovery strategies between the two species allow P. tricornutum to be more competitive when N pulses are introduced into N-limited water while E. huxleyi is adapted to N scarce waters where such pulses are infrequent. These findings are consistent with successional patterns observed in coastal environments. This is one of only a few studies exploring recovery kinetics of cellular functions and photosynthesis after nitrogen stress in phytoplankton. Our results can be used to enhance ecological models linking phytoplankton traits to species diversity and community structure.

Impact of nitrogen availability upon the electron requirement for carbon fixation in Australian coastal phytoplankton communities

“…The observed reduction in ETR PSII per Chl a is consistent with physical constraints associated with pigment packaging effects upon light harvesting (Morel and Bricaud ), which can lead to an inverse relationship between PSU size and photosynthetic efficiency per Chl a (Perry et al ). However, the apparent insensitivity of C‐fixation to N‐amendment we observed for December and January would appear contrary to recent studies demonstrating that Chl a normalized C‐assimilation generally increases with N‐availability for diatoms (Zhao et al ; Berg et al ).…”

“…Nevertheless, it is would be highly desirable to utilize NPQ NSV as a predictor of K C in Australian coastal waters, following on from recent attempts to do so elsewhere (Schuback et al 2015(Schuback et al , 2016(Schuback et al , 2017Zhu et al 2016). We revisit this point later in this discussion.…”

“…These processes provide sinks for excess electrons and simultaneously build proton motive force (pmf), which may be used to drive additional ATP generation or play a regulatory role in the activation of nonphotochemical quenching (NPQ) to protect PSII from photodamage (Kanazawa and Kramer, 2002; see also Nawrocki et al 2015). Growing evidence also suggests that K C fundamentally varies as a function of the prevailing taxa (Suggett et al 2009a;Robinson et al 2014) in addition to environmental conditions (Lawrenz et al 2013;Schuback et al 2015Schuback et al , 2017Zhu et al 2016). A recent meta-analysis encompassing > 10 yr of FRRf retrieved K C values reported broad correlations between K C and nutrient availability (Lawrenz et al 2013), yet was not able to isolate the specific influence of any single environmental factor and/or phytoplankton taxa upon K C variability.…”

Primary Productivity Dynamics in the Summer Arctic Ocean Confirms Broad Regulation of the Electron Requirement for Carbon Fixation by Light-Phytoplankton Community Interaction

“…When grown at higher and/or fluctuant irradiances, warmer temperature and without nutrient limitation, diatoms tend to express higher F v /F m values (Cermeño et al, 2005b;Suggett et al, 2009b), which inherently increases the transfer of excitation energy to the PSII reaction center to sustain electron transport activity compared to other species (Owens, 1986;Ott et al, 1999;Nymark et al, 2009;Brunet and Lavaud, 2010). Higher F v /F m values lead to higher Chl-a normalized C-assimilation rates (Falkowski, 1980;Zhao et al, 2015). Such inherent physiology may explain the lower K C observed for f micro than for f pico+nano , especially when daily PAR was relatively high (i.e., >20 mol quanta m −2 d −1 , Figure 4D).…”

Effect of CO2-induced seawater acidification on growth, photosynthesis and inorganic carbon acquisition of the harmful bloom-forming marine microalga, Karenia mikimotoi

“…Samples for measurements of cellular carbon (C), nitrogen (N) and phosphorus (P) were filtered onto glass microfiber membranes (GF/F, Whatman), which were pre-combusted at 500°C for 4 h, and then stored at -20°C in a refrigerator before analysis. Cellular C and N content were determined using a Perkin-Elmer 2400 CHNS analyzer following the method of Zhao et al [ 36 ]. Cellular P content was measured as in Fourqurean et al [ 37 ].…”