RESUMEN
We investigated how elevated CO2 affects the responses of Gracilariopsis lemaneiformis and Ulva lactuca to NH4+ enrichments. All algae were incubated under four nutritional conditions (zero addition, 100, 500, and 2500⯵M NH4+), and two CO2 levels (390â¯ppm and 1000â¯ppm). The growth, photosynthesis, and soluble protein contents of both species increased under the eutrophication condition (100⯵M NH4+). However, the growth and carotenoid contents of the two species declined when NH4+ concentration increased. Under the super eutrophication condition (2500⯵M NH4+), all indexes measured in G. lemaneiformis were suppressed, while the growth and photosynthesis in U. lactuca changed indistinctively, both compared with the control. Moreover, under the super eutrophication condition, elevated CO2 reduced the suppression in the growth of G. lemaneiformis, but decreased the growth of U. lactuca. Nonetheless, G. lemaneiformis displayed much lower growth rates than U. lactuca under the super eutrophication and elevated CO2 condition.
Asunto(s)
Compuestos de Amonio/toxicidad , Dióxido de Carbono/toxicidad , Fotosíntesis/efectos de los fármacos , Rhodophyta/crecimiento & desarrollo , Ulva/crecimiento & desarrollo , Contaminantes Químicos del Agua/toxicidad , Compuestos de Amonio/metabolismo , Antioxidantes/metabolismo , Dióxido de Carbono/metabolismo , Eutrofización , Modelos Teóricos , Rhodophyta/metabolismo , Agua de Mar/química , Ulva/metabolismoRESUMEN
The terrestrial cyanobacterium Nostoc flagelliforme, inhabiting arid areas, withstands prolonged periods of dehydration. How dehydration and occasional wetting affect inorganic C acquisition in this organism is not well known. As inorganic C acquisition in cyanobacteria often involves carbonic anhydrases (CA), we studied the effect of cycles of hydration and dehydration on the extracellular and intracellular CA activities, at the pH values presumably associated with dew or rain wetting. The external CA of N. flagelliforme (or of the microorganismal consortium of which N. flagelliforme is the main component) is activated by hydration, especially at low pH, and it may facilitate inorganic C acquisition when N. flagelliforme colonies are wetted by dew. Internal CA is present in dry colonies and is rapidly inactivated upon rehydration, therefore an anaplerotic role for this enzyme is proposed.