Influence of Temperature on the Effects of Artificially Enhanced UV-B Radiation on Aquatic Bryophytes Under Laboratory Conditions

Abstract

We examined, under laboratory conditions, the influence of temperature (2 ºC vs. 10 ºC) on the physiological responses of two aquatic bryophytes from a mountain stream to artificially enhanced UV-B radiation for 82 d. These organisms may be exposed naturally to relatively low temperatures and high levels of UV-B radiation, and this combination is believed to increase the adverse effects of UV-B radiation. In the moss Fontinalis antipyretica, UV-B-treated samples showed severe physiological damages, including significant decreases in chlorophyll (Chl) and carotenoid (Car) contents, Chl a/b and Chl/phaeopigment ratios, Chl a fluorescence parameters F v /F m and Φ PS2 , electron transport rate (ETR max ), and growth. In the liverwort Jungermannia cordifolia, UV-B radiation hardly caused any physiological change except for growth reduction. Thus, this liverwort seemed to be more tolerant to UV-B radiation than the moss under the specific experimental conditions used, maybe partly due to the accumulation of UV-B absorbing compounds. The influence of temperature on the effects of UV-B radiation depended on the species: the higher the UV-B tolerance, the lower the influence of temperature. Also, different physiological variables showed varied responses to this influence. Particularly, the lower temperature used in our study enhanced the adverse effects of UV-B radiation on important physiological variables such as F v /F m , growth, and Chl/phaeopigment ratios in the UV-B-sensitive F. antipyretica, but not in the more UV-B-tolerant J. cordifolia. Thus, the adverse effects of cold and UV-B radiation were apparently additive in the moss, but this additiveness was lacking in the liverwort. The Principal Components Analyses (PCA) conducted for both species with the physiological data obtained after 36 and 82 d of culture confirmed the above results. Under natural conditions, the relatively high water temperatures in summer might facilitate the acclimation of aquatic bryophytes from mountain streams to high levels of UV-B radiation. This may be relevant to predict the consequences of concomitant global warming and increasing UV-B radiation.

Biodiversity monitoring: some proposals to adequately study species’ responses to climate change

“…OTCs, Klein et al 2004;Zavaleta 2006). Open garden experiments are using (semi)-natural areas (Stenstrom and Jonsdottir 2004), while experiments in microcosms are conducted in fully artificial environments (Núñez-Olivera et al 2004;Santos 2007). In the two cases, the logistics of an experimental protocol may be difficult to implement (because of expensive experimental design and biases involved by use of an artificial environment; Table 2).…”

Spatial genetic structure of aquatic bryophytes in a connected lake system

“…For instance, Fontinalis antipyretica is used to monitor aquatic pollution (Vieira et al. 2009), to reveal the effects of UV‐B radiation (Nunez‐Oliveira et al. 2004) and to discover radionuclide contamination (Bolsunovsky 2004).…”

Photosynthetic Characteristics of Marestail Using PAM Fluorometry

“…But, F v /F m of GL and ABL did not show full recovery at 17:00. These results suggest that low temperature may exacerbate the adverse effects of UV-B on important physiological variables such as F v /F m [7]. Furthermore, many plant species display slow recovery from photoinhibition at low temperature, possibly because of slow rate of repair of the D-1 protein in PSII [8].…”