Oxygenic Photosynthesis and Respiratory Activity in Microbial Mats of the Ebro Delta, Spain, by Oxygen Exchange Method

Abstract

Photosynthetic and respiratory activities at low light intensities (300 &mgr;E m-2 s-1) in the microbial mats of the Ebro Delta were measured by the oxygen exchange method in the laboratory. The response to H2S concentration, a significant factor in the dynamics of that ecosystem, was assessed. Total photosynthesis reached 23. 78-28.17 &mgr;g O2 cm-2 h-1. Photosynthetic activity was not significantly different at the two temperatures tested. Respiratory activity reached a consumption of 6.95-8.56 &mgr;g O2 cm-2 h-1 at 25 degreesC and 11.42-11.70 &mgr;g O2 cm-2 h-1 at 35 degreesC. The Q10 value for respiration was 1.37-1.64. Oxygen production in Microcoleus chthonoplastes, the most abundant cyanobacterium in those microbial mats, was highly resistant to sulfide inhibition. Concentrations less than 0.02 mM sulfide did not affect the rate of photosynthesis. Concentrations up to 0.1 mM sulfide caused different degrees of partially reversible inhibition, with a maximum of 67% at 0.78 mM sulfide. Primary production (g C assimilated/m2/year) in those microbial mats was also assessed and compared with data from other ecosystems.

Tools providing new insight into coastal anoxygenic purple bacterial mats: review and perspectives

“…Microbial mats are very productive ecosystems (e.g. about 200 gC.m -2 .y -1 in the Ebro Delta, Urmeneta et al, 1998). The Winkler titration method (Winkler, 1888), the incorporation of 14 C labeled bicarbonate, the fast-responding CO 2 microelectrodes (de Beer et al, 1997) or the measurements of total DIC fluxes (e.g.…”

Night Temperature has a Minimal Effect on Respiration and Growth in Rapidly Growing Plants

“…Ecological models and ecophysiological models assign the temperature-sensitive component only to the maintenance (or analogous) term, so that the total respiratory Q 10 is less than 2´0, but there is a lack of whole-plant measurements performed in long-term studies to validate these ecological models. Still, reported Q 10 values range from 1´2 to 4´0, and no mechanistic explanation for the variance is demonstrated (Larigauderie and Ko Èrner 1995;Boone et al, 1998;Chapman and Thurlow, 1998;Neven, 1998;Urmeneta et al, 1998;Nielsen et al, 1999;Quinlan and Lighton, 1999). Further confusing matters are researchers`correcting' for temperature differences in their studies by assuming a Q 10 of 2 for total respiration to calculate a basal respiration rate at a common temperature (Pearman et al, 1981;Wullschleger et al, 1992;Wullschleger and Norby, 1992;Witowski, 1997), which can mislead overall conclusions about the role of temperature on respiration.…”

The biomass dynamics of cyanobacteria in an annual cycle determined by confocal laser scanning microscopy

“…These studies have determined species composition and the spatial and temporal variations of the phototrophic anoxygenic bacteria (Esteve et al 1994, Martínez-Alonso 1997, Mir et al 1991, 2000, Sánchez-Cabeza et al 1999, Solé et al 1998, Urmeneta et al 1998. Various microscopic techniques have been applied to characterize the phototrophic populations (Esteve et al 1994, Mir and Esteve 1992, Mir et al 2000, Sole et al 1998.…”