UV-B Radiation Suppresses the Growth and Antioxidant Systems of Two Marine Microalgae,Platymonas subcordiformis(Wille) Hazen andNitzschia closterium(Ehrenb.) W. Sm

Abstract

This study investigated whether increased solar UV-B radiation (280−315 nm) could suppress the growth of marine microalgae through effects on their antioxidant systems. Two marine microalgae species, Platymonas subcordiformis (Wille) Hazen and Nitzschia closterium (Ehrenb.) W. Sm, were exposed to a range of UV-B radiation and both showed reductions in their growth rates, and the chlorophyll a (Chl a) and carotenoid (Car) contents when UV-B radiation dose increased. Superoxide anion radical (O 2 -. ) production and the concentration of hydrogen peroxide (H 2 O 2 ) and malodiadehyde (MDA) also increased with the increasing of UV-B radiation. Antioxidant systems, non-enzymic components (Car and glutathione content) and enzymic components (superoxide dismutase (SOD) and catalase (CAT) activity), decreased as a result of enhanced UV-B radiation. When the exogenous glutathione (GSH) was added, the effects of UV-B radiation on the growth of the two species were alleviated. These results suggest that enhanced UV-B radiation suppressed the antioxidant systems and caused some active oxygen species to accumulate, which in turns retarded the development of the marine microalgae.Increased solar UV-B radiation (280−315 nm) reaching the Earth's surface because of stratospheric ozone depletion have raised concerns its impact on plants (Caldwell et al. 1998). UV radiation at low doses affects the growth and the circadian rhythms of many microorganisms; recent measurements in Antarctic water indicated a reduction in photosynthesis by as much as 25% in the top 10−20 m of sea water because of increased UV-B radiation (Hader and Worrest 1997). The photosynthetic pigments were affected and consequently, production of ATP and NADPH decreased, hampering CO 2 incorporation into organic molecules (Hader and Worrest 1997). High levels of ultraviolet light are very effective in inducing lipid peroxidation of biological membranes (Kochevar 1990), polyunsaturated fatty acids (Yamashojis et al. 1979) and phospholipid liposomes (Pelle et al. 1990). Other studies have shown that in the presence of UV radiation, photosynthesis is impaired (Strid et al. 1990), pigment composition was altered (Hahlbrock and Scheel 1989), and the expression of the genes encoding antioxidants was induced (Strid 1993).Increased UV-B radiation inhibited photosynthesis of aquatic ecology phytoplankton by approximately 50% (Nilawati et al. 1997), and caused up to 80% loss of photosynthetic capacity during one-day simulated surface exposure (artificial light) and up to 40% loss during half-day exposures (natural light). These results are quantitatively consistent with reported responses of marine phytoplankton (Furgal and Smith 1997).

Effects of UV radiation on five marine microphytobenthic Wadden sea diatoms isolated from the Solthörn tidal flat (Lower Saxony, southern North Sea) – Part I: growth and antioxidative defence strategies

“…Differences in all growth responses measured during the exposures occurred mainly after long-term exposure to PAR+UV-A+UV-B. Nielsen & Ekelund (1995) and Zhang et al (2005) have reported similar results for some phytoplankton diatoms, but due to differences in the experimental set up, their results are difficult to compare with ours. In plants, UV-B damage has been observed at low radiation doses, causing a general decrease in protein synthesis and mRNA transcripts for proteins involved in chloroplasts and photosynthesis (Strid et al, 1994).…”

“…Data are expressed as mg 100 g Jaleel et al, 2009). One of the important features of antioxidant enzymes is their inducibility under conditions of oxidative stress, and such induction could be an important adaptation to UV-B radiation stress (Rijstenbil, 2002;Zhang et al, 2005). Furthermore, microalgae are damaged when the UV-B dose is relatively high and the production of protective enzymes is reduced, so the antioxidant systems cannot scavenge the excess active oxygen (Rijstenbil, 2002).…”

Physiological responses of bermudagrass (Cynodon dactylon) to submergence

“…The concentration of MDA reflects the extent of lipid peroxidation in the cell membrane under stress conditions (Zhang et al 2005). In the current research, the injury of biological lipids by ROS, as indicated by MDA content, was clearly detected in the submerged and non-submerged plants (Fig.…”

Effect of UV-B radiation on the growth and antioxidant enzymes of Antarctic sea ice microalgae Chlamydomonas sp. ICE-L

“…It has been shown that the detrimental effects of UV-B radiation on microalgae are always mediated by free radicals which induce oxidative stress (Janknegt et al 2008;Wang et al 2007). Fortunately antioxidant systems in microalgae can scavenge reactive oxygen species (ROS), including the antioxidant molecules such as carotenoids, tocopherols, ascorbate, and reduced glutathione, and antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) (Janknegt et al 2008;Zhang et al 2005). Our previous studies showed that the exposure of Antarctic ice microalgae to UV-B under laboratory conditions, affected their morphology and ultrastructure (Liu et al 2004), main biochemical composition ) and UV-B induced substances (Miao et al 2002).…”