Effects of UV-B Radiation on the Structural and Physiological Diversity of Bacterioneuston and Bacterioplankton

Abstract

The effects of UV radiation (UVR) on estuarine bacterioneuston and bacterioplankton were assessed in microcosm experiments. Bacterial abundance and DNA synthesis were more affected in bacterioplankton. Protein synthesis was more inhibited in bacterioneuston. Community analysis indicated that UVR has the potential to select resistant bacteria (e.g., Gammaproteobacteria), particularly abundant in bacterioneuston. Global changes over the next decades are expected to increase the exposure of aquatic organisms to damaging UV wavelengths, particularly UV-B (280 to 320 nm), with far-reaching ecological consequences (5). Therefore, a thorough understanding of the effects of UV radiation (UVR) on the diversity and function of bacterial communities, key players in nutrient cycling in aquatic ecosystems, is necessary.The effects of UV-B on aquatic organisms depend on the dose of harmful radiation to which they are exposed, which is, in turn, determined by the positioning of the organism in the water column (19). The surface microlayer (SML) represents a unique microbial niche in which the bacterial community (bacterioneuston) is exposed to high doses of solar UVR (2). The higher abundances of microorganisms in the SML than in underlying waters (UW) (e.g., 1) could indicate that bacterioneuston may have adapted to this "extreme environment," making it an interesting model system for the assessment of UV effects on aquatic organisms by testing the hypothesis that bacterioneuston and bacterioplankton respond differently (in terms of abundance, activity, and structural and functional diversity) to UV-B radiation.Sampling and experimental setup. Samples from the SML and UW were collected in triplicate (n ϭ 9) from an estuarine system (Ria de Aveiro, Portugal, latitude 40°38=N, longitude 08°46=N) on three consecutive days in June 2008. Samples were collected around noon, with a clear sky, minimum wind (Ͻ2 m s Ϫ1 ), and solar radiation levels ranging from 30 to 35 kJ m Ϫ2 (climetua. fis.ua.pt/legacy/main/current_monitor/cesamet.htm). Water properties of the original samples are presented as supplemental material. Bacterioneuston was sampled with glass plates (9). Samples from underlying water were taken at a depth of 20 cm. A total of three irradiation experiments (one on each day), with triplicate subsamples, were conducted using unfiltered water samples, since

Away from darkness: a review on the effects of solar radiation on heterotrophic bacterioplankton activity

“…Note the logarithmic scales of the ratio on the Y axes. (1) Aas et al, 1996; (2) Sommaruga et al, 1997; (3) Ziegler and Benner, 2000; (4) Straza and Kirchman, 2011; (5) Amon and Benner, 1996; (6) Lindell and Edling, 1996; (7) Bullock and Jeffrey, 2010; (8) Santos et al, 2011a; (9) Santos et al, 2012b; (10) Carrillo et al, 2002; (11) Medina-Sánchez et al, 2002; (12) Medina-Sánchez et al, 2006.…”

The organic sea-surface microlayer in the upwelling region off the coast of Peru and potential implications for air–sea exchange processes

“…Earlier studies showed that some bacteria may be adapted to UV radiation in the SML as well as in the ULW (Agogué et al, 2005;Carlucci et al, 1985). Amino acid consumption by bacterioneuston under UV-B stress may be reduced (Santos et al, 2012), which may give an explanation for the higher concentrations of FAA and DHAA in the SML during M91. However, no significant correlation between bacterial abundance and UV radiation or between UV radiation and amino acid concentrations in the different pools was observed during this study, suggesting that at most stations history rather than instantaneous UV radiation, if at all, responsible for controlling bacteria and organic matter components in the SML.…”

Study on organic matter fractions in the surface microlayer in the Baltic Sea by spectrophotometric and spectrofluorometric methods

“…The surface microlayer is almost ubiquitous and covers most of the surface of the ocean, even under high turbulence conditions (Cuncliffe et al, 2013). Surface active molecules present in the SML may modify a number of physical processes occurring in the sur-face microlayer: surfactants affect the solar radiation penetration depth (Santos et al, 2012;Carlucci et al, 1985), exchange of momentum between atmosphere and ocean by reducing the sea surface roughness (Nightingale et al, 2000;Frew et al, 1990) and gas exchange between ocean and atmosphere, impacting production of aerosols from the sea surface (Vaishaya et al, 2012;Ostrowska et al, 2015;Petelski et al, 2014). Therefore, research on the influence of surfactants on the sea surface properties becomes an important task, especially in coastal waters and in the vicinity of the river mouths (Maciejewska and Pempkowiak, 2015).…”