Effects of gilvin on the composition and dynamics of metalimnetic communities of phototrophic bacteria in freshwater North-American lakes

Abstract

SUMMARY The spectral distribution of light reaching the populations of phototrophic bacteria in the metalimnion of stratified lakes is a selective factor determining the community composition. At deep metalimnia, light spectra are enriched in photons of the central part of the spectrum (500–600 nm) and benefit Chromatiaceae, brown‐coloured Chlorobiaceae and phyco‐erythrine‐containing cyanobacteria. Their carotenoids (okenone, spiriloxanthine, isorenieratene) and phycoerythrines allow these phototrophic bacteria to use light from the narrow central spectral wavebands. Otherwise, shallow metalimnetic communities receive light from a wide range (400–800 nm) and their composition is more diverse and usually enriched in green‐coloured Chlorobiaceae, which are unable to take advantage of the central part of the spectrum. Gilvin compounds (humic substances dissolved in water), have strong effects on light absorption, especially at shorter wavelengths. Therefore, light spectra in lakes with high gilvin contents are enriched in photons of long wavelengths (> 600 nm). Several Wisconsin lakes with different gilvin contents were studied during the period of summer stratification in 1994. Spectral distribution of light reaching their metalimnia changed with increasing gilvin contents (measured as g440). In the latter, phototrophic metalimnetic bacterial communities were absolutely dominated by green‐coloured Chlorobiaceae. Intermediate lakes could experiment changes on their community composition depending on variations in gilvin content, as happened in Little Long lake. The dynamics of this lake was studied during summer 1995. The ratio of green‐coloured species in respect to brown‐coloured species increased after a sudden increase of gilvin due to strong rainfall. These results agree with the photosynthetic advantage of green‐coloured Chlorobiaceae under red‐light illumination, inferred from laboratory experiments, and suggest a bacteriochlorophyll‐dependent, light‐harvesting strategy of these phototrophic sulphur bacteria.

Direct and context‐dependent effects of light, temperature, and phytoplankton shape bacterial community composition

“…Light attenuation has been well described in Trout Bog (e.g., this study, Vila et al. , Read and Rose ). Since dissolved organic carbon concentration is correlated with how quickly PAR attenuates with depth (Read and Rose ), we can infer that light attenuates slightly less rapidly in SSB than it does in TB.…”

“…As our study lakes have high humic content, light spectra are enriched in long‐wavelength photons (>600 nm) and light attenuates rapidly with increased depth, creating potential opportunities for spectral niche partitioning across modest changes in depth (e.g., 0.5 m; Vila et al. ). Photoheterotrophic bacterial cells can comprise a sizable portion of lake bacterial communities, and change in abundance with depth (Mašín et al.…”

“…Organisms that harvest light energy are adapted to use specific wavelengths of light and, as a result, phototroph distribution within the water column has been observed to reflect the available light spectrum Abella 2001, Haverkamp et al 2008). As our study lakes have high humic content, light spectra are enriched in long-wavelength photons (>600 nm) and light attenuates rapidly with increased depth, creating potential opportunities for spectral niche partitioning across modest changes in depth (e.g., 0.5 m; Vila et al 1998) additionally, direct effects of light may have been caused by ultraviolet radiation. Based on the transparency properties of borosilicate glass, plankton were exposed to a fraction of longwave ultraviolet A radiation, but none of the ultraviolet B and shorter wavelengths of light, penetrating to their respective incubation depths (D€ ohring et al 1996).…”

Bacterial communities in Chinese grass carp (Ctenopharyngodon idellus) farming ponds

“…DOC) in the water (Yannarell & Triplett ). The relationships between bacterial community composition and SD were reported in many studies (Yannarell & Triplett ; Wu, Zwart, Wu, Kamst‐van, Liu and Hahn (), and the influence of SD on bacterial community composition might be attributed to the influence of intensity and spectrum of light (Vila, Abella, Figueras & Hurley ; Vila, Cristina, Abella & Hurley ).…”

Geographic and Environmental Sources of Variation in Lake Bacterial Community Composition

“…Thus, the identification of Secchi depth as important in these models does not suggest an immediate mechanistic explanation for variation in BCC. Secchi depth may indicate that light levels or spectral composition had a direct influence on BCC in these lakes, as shown in several studies (76,77). However, water clarity can also be influenced by particulate (e.g., organisms) and dissolved (e.g., DOC) matter in the water.…”