Self-shading protects phytoplankton communities against H2O2- induced oxidative damage

Self-shading protects phytoplankton communities against H2O2- induced oxidative damage
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Journal Article
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Barros MP, Pedersen M, Colepicolo P, Snoeijs P

Aquatic Microbial Ecology
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oxidative stress, eutrophication, phytoplankton, mesocosm, hydrogen peroxide, SOD, catalase, lipoperoxidation, Zingst marine station, Rostock, 1.4 m3, Germany


The aim of this study was to investigate whether increased phytoplankton growthrates and biomass caused by higher nutrient availability will result in lower oxidative stress inmicroalgae by reducing effective-light exposure, a process called self-shading. This hypothesis wastested by a 6 d mesocosm experiment carried out at the Zingst Marine Station, Germany (southernBaltic Sea, 8 to 9 psu) in June 2001. Out-door mesocosms filled with 1400 l of natural seawatersieved through a 100 ?m plankton net were manipulated by daily additions of nitrate and phosphate(NP treatment), and nitrate, phosphate and silicate (NPSi treatment). Oxidative stress parametersmonitored daily were H2O2 concentrations in the seawater and concentrations of superoxidedismutase (SOD) activity, catalase activity and lipoperoxidation products (thiobarbituric acid-reactivesubstances, TBARS) in the phytoplankton. Chlorophyll a (chl a) concentration, pH and photosynthesis(O2 evolution) were measured throughout the experiment to describe the physiologicalstatus of the phytoplankton. Our data suggest that fast growth of nutrient-saturated microalgaestrongly limits oxidative stress by self-shading. This was shown by significantly lower SOD andcatalase activities in the nutrient treatments than in the control treatment without nutrient additions.No differences were observed between the 2 nutrient treatments (with or without Si), despitehigher photosynthetic rates in the diatom-rich mesocosms (NPSi). Our findings may contribute to abetter understanding of the close relationships between eutrophication, the occurrence of algalblooms and antioxidant activity in microalgae.

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