Physiological responses of polar benthic algae to ultraviolet radiation

Abstract

Stratospheric ozone depletion and the concomitant increase in ultraviolet (UV) B radiation at the earth's surface represent major threats to polar marine ecosystems. Whereas in coastal rocky shore environments macroalgae constitute an assemblage of particular significance to ecosystem function, benthic diatoms dominate microphytobenthic assemblages, which typically grow on shallow-water sediments as highly productive and stabilising phototrophic biofilms. This review summarises present knowledge on how UV radiation affects the physiology of polar benthic algae with an emphasis on cell biological and structural changes, molecular targets and repair mechanisms, induction of reactive oxygen species and antioxidative strategies, photosynthesis and growth, photoprotective mechanisms, interactive effects between UV radiation and other abiotic factors, and finally ecological consequences. Although available data indicate that there are specific characteristics and adaptations in polar benthic micro- and macroalgae that explain their ecological success and limits under environmentally extreme conditions, much more research is needed to understand the underlying mechanisms. In particular, more ecosystem approaches and studies on interactive effects, as well as modern genomic, proteomic and metabolomic approaches could help address all open questions and depict a more holistic picture.

Induction of phlorotannins through mechanical wounding and radiation conditions in the brown macroalgaLaminaria hyperborea

“…At the organismal level, growth and/or reproduction may be inhibited (Karsten et al, 2009). At the cellular level, biological molecules such as DNA may be damaged with deleterious effects (Dring et al, 1996;Hanelt et al, 1997;Aguilera et al, 1999;Roleda et al, 2004).…”

“…Since the middle of the 1980s, overall ozone levels in the stratosphere have decreased, with high regional and seasonal variations. The decrease in ozone results in a shift of the solar spectrum in the direction of shorter UV-B (280-320 nm) wavelengths (Franklin & Forster, 1997), resulting in damage to biologically important molecules and structures, in particular DNA, membrane lipids and the photosynthetic apparatus (Franklin & Forster, 1997;Karsten et al, 2009). There are, Correspondence to: H. Halm.…”

Photoprotective Effect of a <i>Polyopes affinis</i> (Harvey) Kawaguchi and Wang (<i>Halymeniaceae</i>)-Derived Ethanol Extract on Human Keratinocytes

“…Phlorotannins possess antioxidant properties, in addition to anti-allergic, anti-bacterial, and anti-tumour properties [15]. Of importance to the current study, phlorotannins are also capable of absorbing UV radiation, thereby protecting cells against photodamage [16] and animals against UVB-induced skin carcinogenesis [17]. In addition, phlorotannins can inhibit melanogenesis and protect cells against photo-oxidative stress induced by UVB radiation [18].…”

Photosynthetic UV stress tolerance of the Antarctic snow alga Chlorella sp. modified by enhanced temperature?

“…Apparently, exposure to enhanced UV radiation in snow living populations of Chlorella stimulates the activity of antioxidant enzymes, such as catalases and superoxide dismutase [23,41] or enhance the synthesis of protective compounds like secondary carotenoids (e.g. in Chlorella zofingiensis) or mycosporine-like amino acids (MAAs) [14]. However, when algae were exposed to higher temperatures, repair processes in Antarctic strains increase significantly [27].…”

“…DNA, photosynthetic apparatus, lipid membranes, etc. ; reviewed by [14]) and also cell motility [15]. However, some snow algae downregulate their photochemical processes via a series of dissipative mechanisms such as the violaxanthin cycle, synthesis and accumulation of astaxanthin, turnover of D1 proteins, antenna quenching, cold induced transcripts and cold-adapted proteins, etc.…”