Ecophysiological characterization of two life forms, resting spores and resting cells, of a marine planktonic diatom, Chaetoceros pseudocun/isetus, formed under nutrient depletion

Abstract

Ecophysiological characteristics of 2 life forms, resting spores and resting cells, produced from vegetative cells of the marine d~a t o m Chaetoceros pseudocurvisetus (Mangin) under nitrogen depletion were ~nvestigated. Carbon and sillcon were concentrated In resting spores to a greater extent than nltrogen and chlorophyll a (chl a) although the levels of nitrogen and chl a were similar to those in vegetative cells. Resting cells were similar in appearance to vegetative cells but with weakly pigmented, shrunken and fragmented chloroplasts, and contained slightly more slllcon, reduced nitrogen and chl a and similar amounts of carbon in comparison with the vegetative cells. Respiratory and photosynthetic activity was depressed In both resting spores and resting cells. Net photosynthesis was slightly positive in resting spores and slightly negative In resting cells. Both resting spores and r e s t~n g cells accumulated neutral lipids mainly composed of myristic (C,, "), palmitic ( C l e 0 ) and palmtoleic (C,,; ,) acids as a stored energy source with increased unsaturation of fatty acids. Resting spores also stored large amounts of glucose in reserved polysacchandes These charactenstics indicate that each life form represents a different degree of the adaptive restlng stage for survival under nutnent depletion

Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

“…The seasonal evolution of the BSi:POC ratio is similar at P2 and P3 (except in summer) and reflects comparable diatom community composition. However, the lower BSi:POC ratio in summer at P3 can be attributed to the sinking of carbon-rich diatom resting spores containing neutral lipids (Doucette and Fryxell, 1983;Kuwata et al, 1993). These findings support an emerging view (Salter et al, 2012;Rembauville et al, 2015a) that the flux of carbon rich resting spores/stages are of particular importance in setting the Si:C export stoichiometry characterizing naturally-fertilized island systems in the Southern Ocean.…”

“…Rynearson et al, 2013), which can exhibit variability among species (MendenDeuer and Lessard, 2000) and life cycle stages (Kuwata et al, 1993). In the present study we tried to minimize this artifact by using species-specific relationships and where necessary distinct values for vegetative and resting stages (for Chaetoceros Hyalochaete and Thalassiosira antarctica).…”

“…Numerous experimental studies have demonstrated the role of macronutrient and trace metal limitation for resting spore formation in diatoms in laboratory experiments (Garrison, 1981;Sanders and Cibik, 1985;Kuwata et al, 1993;Oku andKamatani, 1997, Sugie et al, 2010). Chaetoceros Hyalochaete vegetative stages were observed in the summer upstream and downstream of South Georgia (Korb et al, , 2008, although only present in export assemblages downstream.…”

“…For Chaetoceros Hyalochaete resting spores (CRS) and Thalassiosira antarctica resting spores (TRS), 100 randomly selected individuals were measured. Biovolume was calculated and carbon content was estimated using the Kuwata et al (1993) carbon:volume relationship for CRS and the Menden-Deuer and Lessard (2000) formulation for TRS. The mean carbon content ( 7 standard deviation) was 2407101 pgC cell À 1 and 1018 7460 pgC cell À 1 for CRS and TRS, respectively.…”

Long time-series observations in population dynamics of the harmful diatom Eucampia zodiacus and environmental factors in Harima-Nada, eastern Seto Inland Sea, Japan during 1974^|^ndash;2008

“…Resting stage cells have been found for many dominant diatoms in Harima-Nada, such as Skeletonema costatum (Greville) Cleve (Itakura et al 1992), Chaetoceros spp. (Itakura et al 1993, Kuwata et al 1993 and Leptocylindrus danicus Cleve (Davis et al 1980, French & Hargraves 1986, and nitrogen depletion has been reported to be the most effective trigger for resting stage cell formation (Hargraves & French 1983). On the other hand, resting stage cells of E. zodiacus have not been found hitherto despite efforts in the Seto Inland Sea (Imai et al 1990.…”