Response of two Antarctic bryophytes to stratospheric ozone depletion

Abstract

We report a study which measured changes to the radiative environment arising from stratospheric O3 depletion at Rothera Point on the western Antarctic Peninsula (67°S, 68°W) and subsequent associations between these changes and the pigmentation and maximum quantum yield of photochemistry (Fv/Fm) of two Antarctic bryophytes, the liverwort Cephaloziella varians and the moss Sanionia uncinata. We found a strong relationship between O3 column depth and the ratio of UV‐B to PAR irradiance (FUV‐B/FPAR) recorded at ground level. Weaker, but significant, associations were also found between O3 column depth and noon irradiances and daily doses of unweighted and biologically effective UV‐B radiation received at ground level. Regression analyses indicated that FUV‐B/FPAR and daily dose of unweighted UV‐B were best predictors for concentrations of total carotenoids and UV‐B screening pigments extracted from bryophyte tissues. Concentrations of these pigments were loosely but significantly positively associated with O3‐dependent irradiance parameters. HPLC analyses of carotenoids also suggested that both species increased the synthesis of neoxanthin during periods of O3 depletion. Violaxanthin, lutein, zeaxanthin and b,bββ‐carotene concentrations were also apparently influenced by O3 reduction, but not consistently across both bryophyte species. Concentrations of chlorophylls a and b were apparently unaffected by O3 depletion. No direct associations between Fv/Fm and O3‐dependent irradiance parameters were found. However stepwise multiple regression analyses suggested that the production of UV‐B screening pigments conferred protection from elevated FUV‐B/FPAR on Fv/Fm in both species and that carotenoids conferred protection on Fv/Fm in Sanionia. Our data suggest that changes to the radiative environment associated with stratospheric O3 depletion influence the pigmentation of two Antarctic bryophytes, but that Fv/Fm is unaffected, at least in part because of rapid synthesis of protective pigments.

Sequential reduction of UV-B radiation in the field alters the pigmentation of an Antarctic leafy liverwort

“…It also corroborates previous data showing positive associations between concentrations of UV-B screening pigments in C. varians tissues and daily doses of UV-B BE received at Rothera Point (Newsham et al, 2002). The data reported by Newsham et al (2002) were based upon correlations between plant pigmentation and UV-B exposure over 60 days, increasing the degrees of freedom in statistical analyses to an order of magnitude greater than in the present study. It is hence difficult to make a direct comparison between these data and those from the current study.…”

“…This observation corroborates those from previous experiments into the effects of UV-B radiation on Antarctic vascular plants: higher concentrations of UV-B screening pigments have been consistently recorded in tissues of C. quitensis and Antarctic Hairgrass (Deschampsia antarctica) exposed to near-ambient or ambient UV-B radiation, relative to plants exposed to reduced UV-B (Ruhland and Day, 2000;Ruhland and Day, 2001;Xiong and Day, 2001). It also corroborates previous data showing positive associations between concentrations of UV-B screening pigments in C. varians tissues and daily doses of UV-B BE received at Rothera Point (Newsham et al, 2002). The data reported by Newsham et al (2002) were based upon correlations between plant pigmentation and UV-B exposure over 60 days, increasing the degrees of freedom in statistical analyses to an order of magnitude greater than in the present study.…”

“…Further research suggests that other pigments in C. varians tissues also respond to UV-B exposure: concentrations of UV-B screening pigments, which, along with anthocyanins, are products of the phenylpropanoid biosynthesis pathway, correlate significantly in C. varians tissues with rapid between-day fluctuations in UV-B doses received by plants at Rothera Point on the Western Antarctic Peninsula (Newsham et al, 2002). This observation implied that these pigments respond within 24 h of exposure to UV-B radiation, demonstrating a remarkably rapid response to an environmental factor in such a cold habitat (Newsham et al, 2002).…”

Biological invasions in the Antarctic: extent, impacts and implications

“…This anthropogenic feature has existed only since the early 1980s (Farman, Gardiner & Shanklin, 1985) and, as yet, shows no sign of recovery. Though no link has yet been proposed with the biology of alien species, subtle biological consequences for indigenous biota are beginning to be reported, including dynamic changes in patterns of use of biochemical pathways associated with protective pigment production (Newsham et al, 2002) and negative effects on population sizes of microarthropods (Convey et al, 2002 b).…”

Spatial and temporal variability across life's hierarchies in the terrestrial Antarctic

“…Rapid responses have also been reported in field studies of pigment biochemistry of species of moss and liverwort on maritime Antarctic Adelaide Island. Non-manipulated plants, exposed to naturally varying levels of ultraviolet B radiation associated with the dynamically changing depth of the Antarctic ozone hole, showed rapid changes in the concentrations of some screening pigments that were best correlated with the levels of UV-B experienced within the previous 24 h rather than any longer period (Newsham et al 2002;Newsham 2003). It is recognized that any such rapid biochemical and ecophysiological responses carry clear implications in terms of the diversion or trade-off of energy resources, an important factor determining life-history strategies (Convey 1996a(Convey , 1998(Convey , 2003a), but to date little or no effort has been directed towards quantifying these shifts in energy budgets.…”