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

Effects of UV radiation on five marine microphytobenthic Wadden sea diatoms, isolated from the Solthörn tidal flat (Lower Saxony, southern North Sea) – Part II: changes in carbohydrate, amino acid and fatty acid composition

“…by scavenging free radicals) is unclear, our data indicate a direct correlation between UV exposure and accumulation of these sugars. For example, the highest antioxidant capacity was found in Achnanthes exigua in the first part of this study (Scholz et al, 2014), correlating in the present study with relatively high amounts of mannose and galactose, at least in the combined UV-A+UV-B assay (Fig. 3B).…”

“…The relationships between the growth rates obtained from the different UV treatments (given in Scholz et al, 2014) and physiological characteristics (e.g. concentrations of amino acids, glucose, mannose, glycerol, saturated (SFA) and unsaturated fatty acids (UFA)) were evaluated using non-parametric Spearman rank correlation (r s ) to avoid problems associated with non-normal data distribution.…”

“…In this context, it is necessary to distinguish between short-and long-term UV effects in our results. In the first part of the study (short-term exposure) the specific growth rates of the five diatom taxa did not show significant differences in comparison to the PAR control (P > 0.05), whereas 4 hours of daily exposure to UV-B and UV-A+UV-B for 30 days led to decreasing cell numbers in all tested species (Scholz et al, 2014). Thus, the observed increase in carbohydrates after long-term UV exposure in our data may be linked to the decline in cell division found for the five taxa in the first part of the study.…”

“…The taxa were isolated according to the method described in Scholz & Liebezeit (2012a). Details about sampling stations and dates as well as purification of species are given in Scholz et al (2014).…”

“…The taxa were isolated from the Solthörn tidal flat in summer 2008, when relatively high levels of UV were recorded on the sediment surface (up to 118 Wm −2 in June 2008; Scholz & Liebezeit 2012c). Whereas the first part of our study (Scholz et al, 2014) dealt with the influence of UV on growth and antioxidative defence strategies, the main objectives of the present study were to determine (1) variations in carbohydrate and lipid content, which might give evidence on the overall physiological status of the cells; (2) carbohydrate composition, particularly with regard to EPS production and the possible role of particular carbohydrates as compatible solutes; (3) differences in fatty acid composition including likely changes in membrane composition; and (4) amino acid composition, with special emphasis on proline, including the activities of enzymes involved in proline metabolism.…”