Abstract
Effects of nitrate availability in two culture media (von Stosch (VSES), and artificial ASP 12-NTA), and nitrogen sources (seawater enriched with nitrate, ammonium or urea in concentrations ranging from zero to 30 µM) were evaluated in two brown morphs (BR-1, BR-2), one light-green morph (LG) and one dark-green morph (DG) of Hypnea musciformis (Wulfen) J.V. Lamour. Higher growth rates of the four morphs were observed in VSES medium. However, artificial ASP12-NTA medium induced tetrasporangium development in DG morph. Growth rates of the four colour morphs followed kinetic of saturation-type nutrient uptake in treatments with urea. In contrast, growth rates of BR-1, BR-2 and LG morphs were inversely proportional to ammonium concentrations, and those higher than 15 µM were lethal. Growth responses of colour morphs of H. musciformis showed intraspecific variations, and they could be used as bioindicators of nitrogen pollution in marine environment by their low tolerance to ammonium.
Highlights
The genus Hypnea (Gigartinales, Rhodophyta) includes 50 species distributed in warm waters (Masuda et al 1997), much of them with economic importance in several countries (Critchley & Ohno 1998)
In ASP 12-NTA medium, growth rates of the four morphs were lower than those observed in VSES medium, and the highest growth rates of the BR-1 and dark-green morph (DG) morphs were observed in low nitrate concentration (125 mM)
Ammonium inhibited the growth of BR-1, BR-2 and light-green morph (LG) morphs, and concentrations higher than 15 mM were lethal to LG and BR-2 morphs
Summary
The genus Hypnea (Gigartinales, Rhodophyta) includes 50 species distributed in warm waters (Masuda et al 1997), much of them with economic importance in several countries (Critchley & Ohno 1998). A brown plant with only one green branch was collected, and a phycoerythrin-deficient morph (light-green phenotype) was originated from this green branch In laboratory, these specimens were isolated, and cultured in different environmental conditions as irradiance levels, photoperiod, temperature and salinity in order to evaluate if the thallus colour could be an acclimatation to environmental variations. These specimens were isolated, and cultured in different environmental conditions as irradiance levels, photoperiod, temperature and salinity in order to evaluate if the thallus colour could be an acclimatation to environmental variations The colour of these H. musciformis morphs is a stable characteristic, and is not a result of photoacclimation processes (Yokoya et al 2003, Martins et al 2008).
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