Effects of UV‐A Radiation on Desmodesmus armatus: Changes in Growth Rate, Pigment Content and Morphological Appearance

Abstract

Laboratory cultures of Desmodesmus armatus (R. CHOD.) HEGEW. were grown under different levels of photosynthetically active radiation (PAR) supplemented with 3.75 mW · cm -2 UV-A radiation. Growth rate was monitored daily, chlorophyl-a concentration, total carotenoid content, cell number and the relative abundance of different coenobial forms was determined at the end of each experiment. Exposure to UV-A radiation resulted in an increasing inhibition of growth towards higher PAR levels, reaching 100% at 400 µmol · m -2 · s -1 . Cellular carotenoid content was higher in the presence of UV-A radiation, on the other hand no differences were observed in cellular chlorophyll-a concentration. UV-A radiation also induced changes in coenobium formation with a decreasing proportion of 4-celled coenobia and an increase in the abundance of 2-celled and teratologic coenobia, suggesting that high intensity UV-A radiation may influence cell cycle events or morphology development.

Potential effects of UV radiation on photosynthetic structures of the bloom-forming cyanobacterium Cylindrospermopsis raciborskii CYRF-01

“…For instance, UVB induces a reduction in the metabolism of heterotrophic bacteria (e.g., Amado et al, 2015 ), as well as aquatic primary producers, such as cyanobacteria, mainly due to DNA damage ( Buma et al, 2001 ; Helbling et al, 2001 ; Rastogi et al, 2010 ). Furthermore, detrimental effects by UVA on phytoplankton have been observed on primary production, pigment degradation and changes in nitrogen metabolism ( Kim and Watanabe, 1994 ; Döhler and Buchmann, 1995 ; Palffy and Voros, 2006 ).…”

Increasing Temperature Counteracts the Negative Effect of UV Radiation on Growth and Photosynthetic Efficiency ofMicrocystis aeruginosaandRaphidiopsis raciborskii

“…Surprisingly, at 28°C, the percentage of UVB inhibition increased to 48% and 38% in MYRF and CYRF, respectively. The adverse effect of UVA (315‐400 nm) on primary producers can be attributed, mostly, to pigment degradation (69‐71), and damage in the PSII complex, especially to the D1 protein (72). The attenuation of the PAR + UVA+UVB effect on PSII efficiency at 28°C found in our results indicates that the increase of the temperature primarily reduced the photoinhibition by UVA.…”

EFFECTS OF ULTRAVIOLET‐A RADIATION AND NUTRIENT AVAILABILITY ON THE CELLULAR COMPOSITION OF PHOTOPROTECTIVE COMPOUNDS IN GLENODINIUM FOLIACEUM (DINOPHYCEAE)1

“…1997), further justifying study of UVA effects in isolation. UVA radiation has been shown to enhance chl a (Kim and Watanabe 1994) and carotenoid (Palffy and Voros 2006) synthesis in different species of phytoplankton. Carotenoids can scavenge oxygen radicals, neutralize the singlet excited state of oxygen ( 1 O 2 ), and inhibit lipid peroxidation (Banaszak 2003), which is pertinent since UVA can stimulate lipid peroxidation in phytoplankton via the production of active oxygen species (Rijstenbil 2002).…”