ABSTRACT: Solar radiation leads to hydrogen peroxide (H₂O₂) accumulation in shallow intertidal surface waters during daytime tidal emersion periods. The lugworm Arenicola marina irrigates its sedimentary tubes with surface water containing variable H₂O₂ concentrations. We studied aspects of the antioxidant status of the intertidal polychaete A. marina in response to seasonal variations of oxidative stress in its environment. Antioxidant enzyme activities [superoxide dismutase (SOD), glutathione reductase (GR) and catalase] and vitamin E were concentrated chiefly in the chloragog and to a lesser extent in body wall tissue. Response to experimental H₂O₂ exposure (5 µmol l^-1) was confined to the chloragog tissue and consisted of elevated catalase activity. On a subcellular level, the major part of enzymatic antioxidants examined was found in the cytosolic (77% of SOD activity, 60% of GR activity, 41% of catalase activity, 87% of total glutathione) and the peroxisomal (56% of catalase activity) fractions, whereas the same antioxidants were virtually absent in mitochondria. Gradual acclimation of winter A. marina (5°C) to higher ambient temperatures (20°C) over 20 d resulted in a doubling of chloragog SOD activities, while catalase activity was not affected. Elevated in situ concentrations of photoproduced H₂O₂ during summer (1.7 µmol l^-1) coincided with a significant increase of chloragog catalase activities in young (winter: 317.97 ± 78.3 U mg^-1 protein, summer: 783.41 ± 192.7 U mg^-1 protein, means ± SD) and in adult (winter: 480.09 ± 160.1 U mg^-1 protein, summer: 1165.5 ± 207.5 U mg^-1 protein) lugworms. Seasonal differences in the SOD activities of adult worms (winter: 16.06 ± 4.69 SOD units mg^-1 protein; summer: 23.29 ± 3.31 SOD units mg^-1 protein) were attributed to the elevated sediment temperatures in intertidal areas during summer.

KEY WORDS: Arenicola marina · Hydrogen peroxide · Enzymatic antioxidants

Published in MEPS Vol. 143 (1996) on November 14
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1996