Assessment of Nitrate Removal Capacity of Two Selected Eukaryotic Green Microalgae

Eutrophication is a leading problem in water bodies all around the world in which nitrate is one of the major contributors. The present study was conducted to study the effects of various concentrations of nitrate on two eukaryotic green microalgae, Chlamydomonas sp. MACC-216 and Chlorella sp. MACC-360. For this purpose, both microalgae were grown in a modified tris-acetate-phosphate medium (TAP-M) with three different concentrations of sodium nitrate, i.e., 5 mM (TAP-M5), 10 mM (TAP-M10) and 15 mM (TAP-M15), for 6 days and it was observed that both microalgae were able to remove nitrate completely from the TAP-M5 medium. Total amount of pigments decreased with the increasing concentration of nitrate, whereas protein and carbohydrate contents remained unaffected. High nitrate concentration (15 mM) led to an increase in lipids in Chlamydomonas sp. MACC-216, but not in Chlorella sp. MACC-360. Furthermore, Chlamydomonas sp. MACC-216 and Chlorella sp. MACC-360 were cultivated for 6 days in synthetic wastewater (SWW) with varying concentrations of nitrate where both microalgae grew well and showed an adequate nitrate removal capacity.

Luxury Uptake and Removal of Phosphorus from Water Column by Representative Aquatic Plants and Its Implication for Wetland Management

Aquatic plants with their high relative growth rates efficiently absorb nutrients from their surrounding media, thereby providing a simple and inexpensive solution for nutrient-polluted aquifers. The present study determined the P accumulation efficiencies of four different aquatic plants namely, Eleocharis plantaginea, Eichhornia crassipes, Pistia stratiotes, and Hydrilla verticillata from the 6043 ha Kabar Wetland (86°05′ E to 86°09′ E, 25°30′ N to 25°32′ N). The aim of the study was to select the most efficient P accumulator. Water, sediment, and plant samples from Kabar were monthly analyzed for P content for 13 months from July 2009 to July 2010. Pistia stratiotes L. accumulated the highest amount of tissue P (1.06±0.22 mg/g dw). The maximum capacity of luxury uptake of P under greenhouse conditions as exhibited by Pistia was further tested. Pistia individuals tolerated up to 50 mg/L phosphate medium and accumulated 6.12±0.95 mg/g dw P after 35 days under greenhouse conditions. Up to 91% phosphate was removed from the surrounding medium within 60 days at 50 mg/L supply. Tissue P levels increased with increasing phosphate levels in the surrounding media but variation with incubation period was statistically insignificant. Our studies present Pistia as more efficient than other common wetland species like Eichhornia, Phragmites, Typha, and so forth when grown in the sub-tropics and confirm its ability to ameliorate P-polluted subtropical wetlands.

Comparison of media used to evaluateRhizobium leguminosarumbivarviciaefor phosphate-solubilizing ability

Rhizobium leguminosarum is well known for its ability to fix nitrogen (N). In addition, its capacity to solubilize phosphate (Ph) has been receiving attention in recent years. Our ultimate objective was to select a R. leguminosarum bv. viciae isolate with superior Ph-solubilizing ability. The first step was to identify a culture medium that is sensitive and effective in identifying the ability of R. leguminosarum bv. viciae isolates to solubilize Ph. Thirty isolates were evaluated for Ph solubilization in broth and on solid formulations of three media: yeast mannitol extract (YEM), National Botanical Research Institute phosphate nutrient medium (MNBRI), and Pikovskaya phosphate medium (PVK). All media contained 5 g/L CaHPO4as the only phosphorus (P) source. All 30 isolates increased the Ph concentration in liquid cultures, but the amount of Ph released into solution by individual isolates varied from one medium to another. In contrast, only a subset of the 30 isolates solubilized Ph on the solid cultures. Furthermore, some of the isolates that were able to solubilize Ph were only able to do so on a single medium. Regression analysis revealed no relationship between the Ph concentration in the liquid media and the zones of clearing on the solid media (p > 0.05). Although the pH of all of the liquid media dropped after 12 days of growth of the isolates, a relationship between Ph concentration and pH existed only for the MNBRI medium (r2= 0.485, p < 0.001). Increasing the amount of N in the MNBRI medium from 0.1 g/L of (NH4)2SO4to 0.5 g/L of (NH4)2SO4did not affect the amount of Ph in solution, but it profoundly reduced the survival of the R. leguminosarum by approximately 50-fold. Consequently, the surviving bacteria were either more efficient at solubilizing Ph in the high N media or organic acids released from the lysis of the dead cells solubilized the CaHPO4source.