Biofilm formation at warming temperature: acceleration of microbial colonization and microbial interactive effects

Abstract

River biofilms that grow on wet benthic surface are mainly composed of bacteria, algae, cyanobacteria and protozoa embedded in a polysaccharide matrix. The effects of increased river water temperature on biofilm formation were investigated. A laboratory experiment was designed employing two temperatures (11.1-13.2°C, night-day; 14.7-16.0°C, night-day) and two nutrient levels (0.054 mg P l(-1), 0.75 mg N l(-1); 0.54 mg P l(-1), 7.5 mg N l(-1)). Biofilm formation at the higher temperature was faster, while the biomass of the mature biofilm was mainly determined by nutrient availability. The specific response of the three microbial groups that colonized the substrata (algae, bacteria and ciliates) was modulated by interactions between them. The greater bacterial growth rate and earlier bacterial colonization at the higher temperature and higher nutrient status was not translated into the accrual of higher bacterial biomass. This may result from ciliates grazing on the bacteria, as shown by an earlier increase in peritrichia at higher temperatures, and especially at high nutrient conditions. Temperature and ciliate grazing might determine the growth of a distinctive bacterial community under warming conditions. Warmer conditions also produced a thicker biofilm, while functional responses were much less evident (increases in the heterotrophic utilization of polysaccharides and peptides, but no increase in primary production and respiration). Increasing the temperature of river water might lead to faster biofilm recolonization after disturbances, with a distinct biofilm community structure that might affect the trophic web. Warming effects would be expected to be more relevant under eutrophic conditions.

Interactive climate change and runoff effects alter O<sub>2 fluxes and bacterial community composition of coastal biofilms from the Great Barrier Reef

“…When calculating percentage changes of each factor from the control treatment (26°C and 0.5 µM NO 3 − ), a high temperature of 31°C reduced 24 h net O 2 production by 17%, and additive effects with 1.4 µM NO 3 − reduced that production by an additional 28% (thus, a total reduction of 45%). Similarly, warming effects became more pronounced under elevated nutrient conditions in river biofilms, suggesting that high temperatures may promote faster biofilm re-colonisation after disturbances (Diaz Villanueva et al 2011). As also demonstrated in the present study, higher nutrient availability did not result in higher biomass.…”

Functional diversity of algal communities from headwater grassland streams: How does it change following afforestation?

“…However, a previous study in the area found that water chemistry was similar between grassland and afforested streams and that nutrient content was low and similar in both stream types during two successive years (on six dates covering fall, winter and spring) (Farley et al 2008). Water temperature could be acting in the same way as current velocity, accelerating biofilm formation and stimulating metabolism (Díaz Villanueva et al 2011;Romaní et al 2014). In our study, although water temperature did not differ between stream types, it was higher during the high water period, which coincided with summer.…”

Factors affecting algae biofilm growth and lipid production: A review

“…Organic and inorganic carbon concentrations in the growth medium will affect the abundance and proportions of algae compared to bacteria -high inorganic and low organic carbon results in algae dominated cultures [55]. In addition to carbon species concentrations, Villanueva et al [63] and Kebede-Westhead et al [35] demonstrated that increases in nitrogen and phosphorus loading rates cause significantly greater photosynthetic biomass accumulation compared to bacteria. With adequate nutrients and light, photosynthetic biofilms will be greater than 75% algae biomass [56,57]; however, when biofilms become too thick, or light intensities insufficient, light limitation will occur and the biofilm layer furthest from the light source (light limited) may become dominated by bacteria, EPS, and other non-photoautotrophic materials, as was demonstrated by Kuhl et al [64] and Guariento et al [65].…”