Microalgae culture media and glass ware

Microalgae culture with desired species of flagellates or diatoms is the basis of any finfish or shell fish larval rearing and culture system. Natural sea water is a complex culture medium containing more elements and organic compounds, and which supports mixture of all phytoplankton and zooplankton. But in the laboratory culture, monospecies culture of micro algae is being maintained to support different culture requirements. Natural sea water with added nutrients is recommended, because direct sea water may not provide the optimum nutritional requirement of specific algae. So enrichment of natural sea water is necessary with the addition of macro nutrients, micro nutrients, trace elements and vitamins. Each micro alga needs the specific culture media, with basic nutrients like nitrogen, phosphorous, vitamins and trace metals for better growth and multiplication

Stock culture maintenance and mass culture of micro algae

Marine micro algae are found in marine systems living both in water as well as in sediment have an important role in ecological pyramid of the marine ecosystem. These are the base of the trophic web and provide energy for all successive trophic level in the marine eco system. These are single celled, chlorophyll bearing organisms uses solar energy and nutrients from water to convert it into organic matter. Out of 8 Lakhs species of different genera of algae available from marine ecosystem very few have been tapped for their use as availability of biomedical compounds and also as feed in different finfish, shellfish and molluscan hatchery. Their role is also very much vital and critical in a successful mariculture hatchery management. An alga serves as a feed for other zooplanktons and also added to the larval rearing tanks to improve quality of water as green water technology. Among microalgae, flagellate and diatom species are cultured in hatcheries in suitably treated seawater enriched with nutrients such as nitrates, phosphates, essential trace elements and vitamins. To support growth of high densities of larvae and juveniles reared in the hatchery high density of micro algal culture is essential. Considering the importance of marine algal culture, different indoor laboratories and outdoor mass culture systems being carried out in various hatcheries in world like Japan, Taiwan, China, Philippines, Indonesia as well as India

Selection of candidate species for cage culture in India

In recent years, cage culture has emerged as one of the most viable method of sea farming. This aquaculture farming system offers the farmer a chance to utilize existing water resources, which is not used for other purposes. At present, situations like increase in consumption of fish, decline in wild stock and poor return from other culture systems paved strong interest for the fish production through cage culture among the fish farmers. Selection of fish species is playing major role in cage culture operation. Therefore, while selecting the species the biological as well as economical criteria should be taken into consideration, which includes available source of fish seed either from wild or hatcheries, seasonal abundance of the fish seeds in wild, acceptance to artificial feeds, consumer acceptance to the fish, economic value of the fish in local and international market, regional preference, compatibility of the species to culture in various system, resistance to disease and stress, ability to breed and produce the seed in confined environments. By considering the above criteria, a variety of commercially important marine fish species are highly found suitable for cage farming. The important candidate species from different parts of the world includes cobia (Rachycentron canadum), seabass (Lates calcarifer), snappers (Lutjanus sp.), pompanos (Trachinotus sp.) and groupers (Epinephelus sp.), etc. Commercial level seed production technology for majority of these fishes has been developed in many of the South East Asian countries. In India, the seed production of cobia, silver pompano, seabass and orange spotted grouper has been achieved successfully by different fisheries research institutions

High Thermal Conductivity Coatings via LENS™ for Thermal Management Applications

Surface modification has been used to improve wear resistance, corrosion resistance and thermal barrier properties of metals. However, no significant attempts have been made to improve thermal conductivity by surface modification. In this work, we have examined the feasibility of enhancing thermal conductivity (TC) of stainless steel by depositing brass using Laser Engineered Net Shaping (LENS). The coating increased the TC of the substrate by 65% at 100 C°. Significantly low thermal contact resistance was observed between the coating and the substrate due to minimal dilution and defect free sound interface. Our results indicate that laser processing can be used on low coefficient of thermal expansion metal matrix composites to create feature based coatings to enhance their heat transfer capability.Mechanical Engineerin

Engineering aspects of cage design, mooring and net design for open sea cage farming in India

Cage is an aquaculture production structure comprising of a rigid floating frame, flexible net materials and mooring system (synthetic mooring rope, buoy and anchor) with a round or square shape floating net pen to hold and culture large number of fishes and other aquatic resources which can be installed in reservoir, river, lake or sea. The design and operating variables in engineering aspects of an open sea cage is of great concern in mariculture operations as they are installed in exposed sites in the off shore areas. The design of the cage and its accessories is specially made in agreement to the individual farmer’s requirements. A well engineered cage design will provide the opportunity to reduce the cost of the cages. HDPE material is found to be suitable to make cage frame for open sea cages. The HDPE float frames installed in open unprotected water can withstand wave conditions. Round cage (volume depends on diameter) with floatation system made of butt-welded HDPE pipes, designed for the culture of fishes such as milkfish, mullet, cobia or pompano, sea bass and lobsters, and this very well used in many countries

Capture based aquaculture - Alternate method for sustainable fish production

Global aquaculture has grown considerably and contributing significant quantities to the world’s supply of fish for human consumption and it has shown to be an attractive option for enhancing the fish production in the world. It is the fastest growing, animal based food production sector with 73.8 million tonnes of production in 2014. Food and Agriculture Organization of the United Nations (FAO) define aquaculture as it is the farming of aquatic organisms including fish, molluscs, crustaceans and aquatic plants. Farming implies some sort of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc. It is a diverse sector, which employs different strategies for fish production. There are two major strategies are followed in the sector including hatchery based aquaculture (HBA) and capture based aquaculture (CBA). The HBA allows the commercial and viable production for number of organisms through the management of their entire life cycles

Marine microalgae culture techniques for finfish and shellfish larval rearing

Aquaculture system is based on microalgae and their animal consumers. The uptake of microalgae biomass by filter-feeders is very promising from the energetic standpoint. Microalgae are the biological starting point for energy flow through most aquatic ecosystems, and are the basis of the food chain in all most all aquaculture operations. Microalgae are used for rearing larvae and juveniles of many species of commercially important molluscs, crustaceans and fish (marine and freshwater) either directly as a source of feed or indirectly through zooplankton (rotifers, copepod or Artemia). In addition, the microalgae are directly introduced in the larval tanks (green water techniques) during marine finfish larval rearing, where they are believed to play a role in stabilizing the water quality, provide nutrition to the larvae and enable microbial control. Thus the management of microalgae population and their culture is considered to be an integral part of hatchery operations

Effects of Hot Isostatic Pressing on the Properties of Laser-Powder Bed Fusion Fabricated Water Atomized 25Cr7Ni Stainless Steel

25Cr7Ni stainless steel (super duplex stainless steels) exhibits a duplex microstructure of ferrite and austenite, resulting in an excellent combination of high strength and corrosion resistance. However, Laser-Powder Bed Fusion fabrication of a water-atomized 25Cr7Ni stainless steel of novel chemical composition resulted in a purely ferritic microstructure and over 5% porosity. The current study investigated the effects of two hot isostatic pressing parameters on the physical, mechanical, and corrosion properties as well as microstructures of water-atomized 25Cr7Ni stainless steel of novel composition fabricated by L-PBF for the first time in the literature. The corrosion behaviour was studied using linear sweep voltammetry in a 3.5% NaCl solution. The Hot Isostatic Pressing-treated sample achieved over 98% densification with a corresponding reduction in porosity to less than 0.1% and about 3 similar to 4% in annihilation of dislocation density. A duplex microstructure of ferrite 60% and austenite 40%was observed in the X-Ray Diffraction and etched metallography of the HIP-treated samples from a purely ferritic microstructure prior to the HIP treatment. With the evolution of austenite phase, the HIP-treated samples recorded a decrease in Ultimate Tensile Strength, yield strength, and hardness in comparison with as-printed samples. The variation in the morphology of the evolved austenite grains in the HIP-treated samples was observed to have a significant effect on the elongation. With a reduction in porosity and the evolution of the austenite phase, the HIP-treated samples showed a higher corrosion resistance in comparison with the as-printed samples

Characteristics of CVD Grown Diamond Films on Langasite Substrates

Surface acoustic wave (SAW) devices consist of a piezoelectric substrate with interdigitated (IDT) electrodes. These devices can be used to fabricate wireless and passive sensors that can be mounted in remote and/or inaccessible places. If encapsulated with CVD diamond, the SAW devices can be made to operate under extremely hostile conditions. The piezoelectric layer (AlN, ZnO etc.) deposited on the diamond or an inverse system can increase the frequency of the SAW device. Most piezoelectric materials (such as quartz) show phase transition temperatures below diamond deposition temperature (650º-1100ºC), preventing their use as a substrate for diamond growth. Langasite La3Ga5SiO14 (LGS) is recently fabricated piezoelectric material that can withstand high temperatures without being deteriorated. LGS does not have phase transitions up to its melting point of 1470°C.Here we report the deposition of diamond films by microwave plasma CVD in methane-hydrogen gas mixtures on polished and rough surfaces of the LGS substrates seeded with nanodiamonds. No buffer layer between the substrate and the coating had been used. The effect of substrate pretreatment (PT) was also investigated on the growth behaviour of diamond films on LGS. The resulting films are characterised by Raman spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS). The effect of substrate roughness on the growth behaviour was found to favour bigger grain sizes on the unpolished substrates. Whereas, the effect of substrate pretreatment (PT) was found to produce unique microstructural features with better polycrystalline diamond (PCD) quality than on the substrates without PT. Raman signals confirm the deposition of PCD in all the cases but the X-ray results interestingly show new phase formation of hcp and rhombohedral diamond lattice structures under CVD growth environment

Photo bioreactor-based microalgae culture for mariculture applications

Microalgae are considered as a valuable organic resource with a potential application in finfish, shellfish and molluscan culture. Being, rich source of essential fatty acids (EPA and DHA), the microalgae have very important role even in human nutrition. Microalgae culture forms an inevitable component in aquaculture venture especially seed production of either finfishes or shell fishes. Cultivated microalgae have long been integral to the hatchery production of many farmed finfish, shellfish and other commercially important aquaculture species. Molluscs like oysters, mussels and clams filter them from the sea water in all stages of life. Rotifers and brine shrimps also ingest algae, and are then themselves used as food for larval fish and prawns. The shrimp hatcheries use micro algae as food for the early larvae and later for the water quality maintenance. In many hatchery systems algae are added to the water containing larvae to improve the ‘quality’ of water as green water systems. The production of live algae is very critical in the successful hatchery management. In the natural environment, the larvae feed on any minute plant components which are readily available to them. But in a hatchery, the feed which are acceptable to the larvae for their growth and further development have to be identified and isolated. In the early critical stages of the rearing larvae of fin fishes and shellfishes, the phyto-flagellates (species of Isochrysis, Pavlova, Dicrateria, Chromulina and Tetraselmis) and other nanoplankters (species of Chlorella and Synechocystis) form the basic food. But in the post larval stages of crustaceans and spat or juvenile stages of bivalves, the diatoms (species of Chaetoceros, Skeletonema and Thalassiosira) form the primary food. Hence the culture of micro algae is an essential prerequisite for the rearing operations of economically important cultivable organisms in a hatchery system