Influence of temperature and salinity on carbon and nitrogen content in Dunaliella viridis teodoresco under nitrogen sufficiency

Cell carbon and nitrogen in D. viridis are strongly dependent on the culturing conditions. Both elements increase with increasing salinity. At 31°C cell carbon is maximum and cell nitrogen minimum. This temperature was described previously (Jiménez, C., Niell, F. X. & Fernandez, J. A. (1990). Hydrobiologia, 197, 165-72) as the optimal one for achieving the maximum oxygen evolution. These results point out a possible competence for the reducing power during carbon and nitrogen assimilation processes, and under conditions of high photosynthesis (carbon assimilation) there is a partial inhibition of nitrate reduction, making C:N ratio maximum under conditions of maximum net photosynthesis.The study of cell glycerol, nitrate, structural proteins and free amino acids indicates that all of these solutes accumulate in the cells as a result of the high salinity adaptation.     

The performance and distribution of species along soil salinity gradients of mangrove swamps in southeastern Nigeria

Based on periodic soil salinity measurements direct gradient analysis procedures were used to relate the performance and distribution of mangrove swamp species to salinity gradients. Variations in soil salinity were due to distance from the coast, tidal incursions and freshwater inputs. All overstorey species showed statistically significant negative correlations with salinity while most groundlayer species were positively correlated with the same factor. Based on ecological group classification, no species was found to occur on the highest values of soil salinity. There were overlapping range of occurrences and ecological optima for most species along the gradients.     

Chemical mobility and bioavailabity of sediment-bound heavy metals influenced by salinity

The transfer of metals from contaminated sediments to algal cell walls (Scenedesmus quadricauda) and organisms from various trophic levels (euryhaline osmoconform hydroid Cordylophora caspia and algae Brachiomonas submarina) was studied with a multichamber device. The system consists of a central chamber which contained the mud suspension and six external chambers containing the different biological indicators. The solids in the central and external chambers are separated by 0.45 m-diameter membranes which allow diffusion of the mobilized, dissolved metal compounds. Experiments were performed with dredged sediments at various salinities (0.5, 1.0, 1.5, and 2.0 percent, respectively) and the kinetic of re-adsorption was obtained by taking samples after different time intervals. High enrichment of Cd was found in the living alga Brachiomonas submarina, but on the other side only a weak influence of salinity on re-adsorption could be observed. Model experiments with ionic Cd showed a clear dependency on Cd-sorption on the algae, Cd-concentration in solution, and salinity. These results indicate that the transfer of metals mainly depends on the specific surface properties of the substrates and on the specific chemical form of the dissolved mobilized metal.     

Impact of salinity stress on soil-borne fungi of sugarbeet

The sugarbeet cultivar Kaumera was found to be highly susceptible to infection by the root-rot pathogens Rhizoctonia solani and Sclerotium rolfsii in the absence of salinity stress. Under this environmental condition, R. solani was more efficient than S. rolfsii in producing cell wall-degrading enzymes in infected hypocotyls. Xylanase and galactanase were most effective. The rate of cell wall degradation by R. solani was nearly 2.5 times that of S. rolfsii when cells walls of healthy hypocotyls were used as sole carbon substrate for the in vitro produced crude enzymes.Under salinity stress the pathogenicity and the performance of cell wall-degrading enzymes of R. solani and S. rolfsii varied profoundly. Pathogenicity studies showed that R. solani appeared to be more tolerant than S. rolfsii of the salinity stresses applied, and relatively more virulent to cv Kaumera. The activities of cell wall enzymes of R. solani decreased and those of S. rolfsii increased with increased salt concentration when cell wall material was used as a sole carbon source. The metabolic products produced under salinity stress by R. solani and R. solani in the cell wall amended culture media shifted the initial pH towards neutrality or slight alkalinity for R. solani and to high acidity for S. rolfsii.When model substrates were used, xyland and galactan were the most responsive substrates for degradation by the cell wall enzymes of the two fungi studied. The rate of degradation was higher for S. rolfsii than for R. solani. The excessive acidity in salt stressed S. rolfsii culture media suggested reduced activities of the enzymes involved in cell wall degradation in vivo. This may explain the decreased virulence potentialities.     

Protein synthesis in halophytes: The influence of potassium,sodium and magnesium in vitro

The amino acid (³⁵S-methionine) incorporating activity of an in vitro wheat germ translation system was found to be maximal in 80 to 125 mol m^–3 K with 2 to 4 mol m^–3 Mg both as the acetate. Substitution of Na for K, or chloride for acetate at concentrations above 80 mol m^–3 inhibited incorporation. When the K acetate concentration was raised to 200 mol m^–3, no incorporation of radioactive methionine occurred.Translation by polysomes extracted from leaf tissue of S. maritima, supplemented with postribosomal supernatant from wheat germ, showed activity which was optimal in the presence of 225 mol m^–3 K acetate and 8 mol m^–3 Mg acetate. However, the translation system was not directly comparable with the wheat germ system, as studies with an initiation inhibitor, aurintricarboxylic acid, suggested that the S. maritima system was essentially elongation-dependent, while initiation occurred in the wheat germ system.Elongation-dependent polysomal preparations were extracted from leaves of the glycophytes Pisum sativum, Triticum aestivum, Oryza sativa and Hordeum vulgare, and from the halophytes Atriplex isatidea and Inula crithmoides. Translation by polysomes from the salt-tolerant plants was optimal at higher K and Mg concentrations, than by polysomes from the glycophytes. Furthermore, NaCl was better able partially to substitute for the role of K in polysomal preparations from halophytes than glycophytes.     

The photosynthesis of Dunaliella parva Lerche as a function of temperature,light and salinity

The photosynthetic behaviour of Dunaliella parva Lerche from the athalassic lagoon of Fuente de Piedra (Málaga, Southern Spain) was studied experimentally at three NaCl concentrations (1, 2 and 3 M), five temperatures (15, 23, 31, 38 and 42°C) and nine different irradiances between 82 and 891 mol m^–2 s^–1. Results are analyzed to define the best growing conditions for the algae. D. parva shows the highest photosynthetic rates at a NaCl molarity of 2 M, under a moderate light intensity (600 mol m^–2 s^–1) at 31°C. Above this light intensity a clear photoinhibition of the photosynthesis was found at 2 M and 3 M of NaCl. D. parva is a halotolerant and a thermoresistant species as evidenced by its net photosynthesis rate and positive values of oxygen evolution at 42°C.Two methods for modelling photosynthesis vs. irradiance curves are discussed. The first is a single model, based on third-order polynomial equations, and the second is double model, based on hyperbolical Michaelis-Menten type functions and negative exponential to define photoinhibition.     

Seasonal and areal features of the lagoonal environment in Lake Nakanoumi,a shallow coastal lagoon in Japan

Lake Nakanoumi is a shallow coastal lagoon connected with the Japan Sea by a narrow channel. Over the past decade, land reclamation resulted in a 33% reduction of the lagoon's surface area. The remaining water basin of Lake Nakanoumi is scheduled to be artificially freshened to supply irrigation water for the newly reclaimed lands. This paper deals with the seasonal and areal features of the lagoonal environment prior to the beginning of the artificial desalinization.     

The effect of salinity on lipid composition and on activity of Ca2+- and Mg2+-stimulated ATPases in salt-sensitive and salt-tolerant Plantago species

Lipid composition of the roots and the shoot of the salt-sensitive Plantago media L., the salt-tolerant P. maritima L. and the less salt-tolerant P. coronopus L. was followed under saline conditions. In the roots of P. media the level of phospho-, galacto- and sulpholipids decreased strongly with increased NaCl concentration, indicating decreased control of permeability of the root cell membranes. In the roots of the two salt-tolerant species the level of most lipid classes was maintained or even raised up to 75 mM NaCl, and a decrease was noted only at higher NaCl concentrations. In P. maritima, a species from relatively nutrient-rich habitats, decreased lipid levels in the roots and shoot were observed with increasing salinity in combination with a low nutrient availability. The Ca²⁺- and Mg²⁺-stimulated ATPase activities of the microsomal fraction of the roots of P. maritima was decreased at a salinity level in excess of 150 mM, while in P. coronopus they were decreased at all NaCl levels tested. The obtained results are discussed as part of the adaptation of the species to salinity.     

The seasonal cycle of the phytoplankton in the coastal waters of Ghana

Seasonal changes in the phytoplankton at four depths off Tema, Ghana were investigated between September 1973 and November 1974. The physico-chemical factors show that there are two marine seasons, the season of major upwelling (July–October), characterized by low water temperatures (< 25°C), high salinity (> 35) and high nutrient levels, and a non-upwelling period (November–June) when water temperatures are higher and salinity and nutrients are lower. The latter marine season is broken by a small, unpredictable upwelling (December-January). Phytoplankton cell counts are high (> 1000 × 103 cells/1) during the major upwelling period and can be very low (< 2 × 10³ cells/1) during the non-upwelling period. Dinoflagellates form the main components of the phytoplankton population during the nonupwelling period and diatoms form the dominant components at other times. There is a close relationship between the physicochemical factors and the phytoplankton population especially during the major upwelling period. For example there is a good correspondence between the peaks in phytoplankton numbers and low levels of nutrients such as silicate, nitrate and phosphate with the reverse taking place at other times.