Seasonal carbon budget and growth of Laminaria solidungula in the Alaskan High Arctic

Abstract

Larninaria solidungula is the dominant member of an arctic kelp community subjected annually to 8 mo of darkness under a turbid ice canopy. Seasonal changes in total tissue carbon were measured for 24 sporophytes incubated in situ for 1 yr. Net annual production was calculated from these measurements and compared to carbon fixation rates from in situ "C uptake experiments. During rapid linear growth, from November to late Apnl, L. soljdungula has a carbon deficit. About 25 % of the plant's original carbon content is depleted before photosynthet~c production begins at ice breakup in June or early July. Daily rate of carbon loss (0.7 pg mg-' of frond dry weight) is greatest between November and late February, and least (0.2pg C mg-' d-') between February and late Apnl due to photosynthesis at extremely low hght levels. Summer carbon fixation rate measured by I4C uptake experiments was 0.09pg rng-' h-'. This rate of production, when extrapolated for the summer openwater period, matched net carbon production for experimental plants grown in situ, with no assimilatory surplus. L. soLidungula reallocates stored reserves to produce new frond tissue during ice-covered periods that replaces about 80 % of the previous year's carbon content.