Digital library

Studies were made on the yield and physical properties of agar from Gelidiella aceiosa, Gracilaria arcuata and G. edulis and algin and mannitol from Padim boergesenii, Chnoospom implexa, Sargassum duplkatum, Turbimria conoides and T, ormta growing in eight islands of Lakshadweep. The yield of agar ranged from 16.9 to 43.1 % and gel strength from 42 to 278 gm/cm* in G. acerosa, G. arcuala and G. edulis. Algin varied from 4.4 to 27.3%and mannitol from 1.4 to 9.5% in the brown algae studied. The agar and algin yielding seaweeds can be exploited from Lakshadweep Islands as an additional resource of raw material to the Indian seaweed industries.

The present work is focused on the biosynthesis of the Silver (Ag) Nanoparticles using an aqueous extract of the green seaweed Halimeda gracilis. The visible colour change indicated the biosynthesis of Silver Nanoparticles and the specific peak produced within the UV-Vis spectrum confirmed the biosynthesis of Silver Nanoparticles. The possible functional groups were identified with Fourier Infrared Spectroscopy. The morphological characterization of biosynthesized Silver Nanoparticles was done by Scanning Electron Microscopy and Dynamic light scattering measurements and Zeta potential. The average size distribution of Ag-Nanoparticles were 295.9 (d.nm) and fairly stable with a zeta potential value of-28.6 mV. The size of biosynthesized Ag-Nanoparticles was also measured with X-ray diffraction assay. Due to agglomeration, the size difference of biosynthesized Ag-Nanoparticles in case of SEM and EDX occurred. The biosynthesized Ag-Nanoparticles were assayed for their antibacterial activity against some human pathogens and for their potential on seed germination of Abelmoschus esculentus and Raphanus sativus var. longipinnatus. The antibacterial activity of biosynthesized Ag Nanoparticles was the highest against Proteus mirabilis (2.33±0.2 cm), followed by Klebsiella pneumoniae, (1±0.0 cm). The effect of biosynthesized Ag-Nanoparticles on the seed germination of Raphanus sativus var. longipinnatus was excellent as the germination rate was 100 percent for Ag-Nanoparticles treated seeds, which was better than normal seaweed extract and seaweed liquid fertilizer treated seeds. The seed germination was also good for Abelmoschus esculentus with the treatment of seaweed mediated Ag-Nanoparticles as germination rate was 60 percent. This work proved that seaweed synthesized Ag-Nanoparticles are Phyto-friendly in nature and in future nano-bio fertilizer may be used as the growth promoter and eco-friendly Nano-bio-fertilizer.

The world is faced with the vast challenge of meeting ever-increasing food demands placed on the agriculture sector due to a rapidly growing population. In fact, the world population has been increasing by an estimated 78 million each year, about the size of the population of Germany. Challenges around food security – ensuring there is enough food to meet demand – will be exacerbated when the population surpasses 9 billion by 2050 and 10 billion by the turn of the century. 

Global food production must be 70 percent greater than today’s level to close the deficit between supply and demand, commonly referred to as the productivity gap.  And, it must be done without using substantially more land. With current grain stocks at historically low levels and food demand increasing at rates higher than production, the challenge is not decades into the future, but is here today.

Airborne hyperspectral and thermal infrared imagery collected over the Florida Current provide a view of the disintegration of a Sargassum drift line in 5 m s−1 winds. The drift line consists mostly of rafts 20–80 m2 in size, though aggregations larger than 1000 m2 also occur. Rafts tend to be elongated, curved in the upwind direction, and 0.1–0.5 °C warmer than the surrounding ocean surface. Long weed ‘trails’ extending upwind from the rafts are evidence of plants dropping out and being left behind more rapidly drifting rafts. The raft line may be a remnant of an earlier Sargassum frontal band, which is detectible as an upwind thermal front and areas of submerged weed. Issues are identified that require future field measurements.Research highlights► A Sargassum drift line disintegrates under a wind speed of 5 m s−1. ► Weed left behind more rapidly drifting rafts form long upwind ‘trails’. ► Wave drag may be creating a distinct raft-and-trail morphology. ► Remnant frontal accumulations of only submerged Sargassum occur upwind.