Long‐term pigment dynamics and diatom survival in dark sediment

Abstract

In order to investigate survival of diatoms and long-term pigment dynamics in dark sediment, we incubated samples of homogenized, sieved, tidal-flat sediment for 1 yr in darkness. Microscopic observations revealed that some diatoms survived the full year in darkness and retained their pigments. Concentrations of the diatomspecific phospholipid-derived fatty acid (PLFA) 20:5v3 indicate that these survivors represented only a small fraction of the original diatom community, probably no more than a few percent. Consequently, the effect of pigment retention in living diatoms on the overall pigment dynamics was negligible. The photosynthetic potential of the surviving diatoms was further investigated by re-exposing the sediment to light in the presence of 13 Cbicarbonate. Rapid 13 C fixation into algal PLFAs at a level similar to that in sediment freshly collected from the field indicates that surviving diatoms fully retained their photosynthetic capacity. Concentration dynamics of photosynthetic pigments generally reflected degradation of two different pools with clearly different loss rates. Losses during the first 1-2 months of the experiment (half lives of 6-22 d) reflected degradation of fresh algal material, while losses during the rest of the experiment reflected much slower degradation of more refractory pigment pools (half lives of $ 1 yr). Individual pigments showed distinctly different labilities, with losses ranging from 0% to 86% over the full year. The order of overall loss was fucoxanthin . chlorophyll c . chlorophyll a . diadinoxanthin . pheophorbide . pheophytin . diatoxanthin.

Dark survival in a warming world

“…although the proportion of surviving cells is very low [42]. Survival is facilitated by spore production, although there is also some evidence for heterotrophy [42,43].…”

Effects of prolonged darkness and temperature on the lipid metabolism in the benthic diatom Navicula perminuta from the Arctic Adventfjorden, Svalbard

“…Veuger and van Oevelen (2011) observed during the first weeks of a 12 months dark incubation period a degradation of chlorophyll a and c, fucoxanthin and other carotenoids in benthic diatoms, followed by much slower or even completely reduced degradation rates at the end of the dark period. Schlie et al (2011) mentioned for the benthic diatom Surirella sp.…”

“…Consequently, phototrophic algae can be exposed up to about 10 months to darkness or very low light conditions (Chapman and Lindley 1980;Dunton 1990). Diatom taxa from different polar habitats, such as sea ice, pelagial and microphytobenthos (MPB), are known to survive long periods of complete darkness (Bunt and Lee 1972;Palmisano and Sullivan 1983;Peters and Thomas 1996;Zhang et al 1998;Schlie et al 2011;Veuger and Van Oevelen 2011). The species-specific maximum survival periods range from 3 months to 3 years, whereby benthic diatoms showing the longest survival times (Antia 1976).…”

A seasonal study of particulate organic matter composition and quality along an offshore transect in the southern North Sea

“…The POM quality was explored in terms of OM degradation and microbial reworking based on the timescales of molecule degradation rates Hedges, 1994, Veuger andvan Oevelen, 2011;Veuger et al, 2012). We considered three time scales:…”

“…To investigate the seasonal variation of the POM quality three time scales were defined in terms of OM degradation and microbial reworking, based on molecule degradation sensitivities Hedges, 1994, Veuger andvan Oevelen, 2011;Veuger et al, 2012).…”