Physiological responses of intertidal marine brown algae to nitrogen deprivation and resupply of nitrate and ammonium.

Intertidal macroalgae Fucus and Laminaria experience seasonally fluctuating inorganic N supply. This study examined the effects of long-term N deprivation, recovery following N resupply, and effects of elevated ammonium and nitrate exposure on N acquisition in intertidal algae using manipulations of N supply in tank culture. Over 15 weeks of N deprivation, internal N and nitrate reductase activity (NRA) declined, but maximum quantum yield of PSII was unaffected in Fucus serratus and Fucus vesiculosus.

Cadmium tolerance and adsorption by the marine brown alga Fucus vesiculosus from the Irish Sea and the Bothnian Sea.

Cadmium (Cd) uptake capacities and Cd tolerance of the marine alga Fucus vesiculosus from the Irish Sea (salinity 35 psu) and from the Bothnian Sea (northern Baltic, 5 psu) were quantified. These data were complemented by measurements of changes in maximal photosynthetic rate (P(max)), dark respiration rate and variable fluorescence vs. maximal fluorescence (F(v):F(m)).

Seasonal variations in nitrate reductase activity and internal N pools in intertidal brown algae are correlated with ambient nitrate concentrations.

Nitrogen metabolism was examined in the intertidal seaweeds Fucus vesiculosus, Fucus serratus, Fucus spiralis and Laminaria digitata in a temperate Irish sea lough. Internal NO(3) (-) storage, total N content and nitrate reductase activity (NRA) were most affected by ambient NO(3) (-), with highest values in winter, when ambient NO(3) (-) was maximum, and declined with NO(3) (-) during summer. In all species, NRA was six times higher in winter than in summer, and was markedly higher in Fucus species (e.