S. Jeyanthi

Effect of different dosages of zinc on the growth and biomass in five marine microalgae

Marine environment often restrain toxic heavy metals that may enter into the food web via uptake by microalgae and eventually cause severe poisoning problems at higher tropic levels. The effects of Zinc cations upon growth of five native microalgal species, Chlorella marina, Isochrysis galbana, Tetraselmis sp., Nannochloropsis sp., and Dunaliella salina were evaluated. Growth inhibition of the microalgal cells were determined by exposing them to different concentrations of aqueous solutions of zinc metal for 15 days. A major reduction in cell density was observed in all the five cultures in the concentration of 50 ppm. Among the five micro algal species tested, Tetraselmis sp. alone showed growth up to 250 ppm concentration of zinc metal till the final day (15th day) of experiment. Key words: Zinc, microalgae, heavy metal, Chlorella marina, Tetraselmis sp.

Isolation and Culture of Microalgae

Marine microalgae or phytoplankton are the floating microscopic unicellular plants of the seawater which are generally free living, pelagic with the size range of 2–20 μm. The important components of microalgae are the diatoms, dinoflagellates, green algae, blue-green algae, and coccolithophores. Most microalgae have got immense value as they are rich sources of essential fatty acids, pigments, amino acids, and vitamins. They play a critical role in the coastal aquaculture of fish, molluscs, shrimps, and oysters, especially to meet the nutritional requirement of the larvae as well as for bioencapsulation. It is an established fact that the success of any hatchery operation mainly depends on the availability of the basic food, the phytoplankton. The maintenance and supply of the required species at appropriate time form a major problem being encountered by the algal culturists. The procedure for the phytoplankton culture involves aspects such as the isolation of the required species, preparation of the suitable culture media, and maintenance of the culture in the laboratory scale, as well as large scale under controlled conditions of light, temperature, and aeration, and their constant supply to the aqua farmers in different phases of growth. A culture may be defined as an artificial environment in which the microalgae grow. The culture of phytoplankton is an important aspect of planktonology, and the mass culture of phytoplankton is achieved under laboratory-controlled conditions and under field/outdoor conditions. Under laboratory conditions, sterilized or thoroughly cleaned containers are filled with filtered/sterilized seawater (28–34‰) and enriched with the addition of fertilizers, i.e., Guillard and Ryther’s F medium, Walne’s medium, or TMRL medium. The culture containers are inoculated with pure strains of the desired phytoplankton previously cultured in the laboratory. They are provided with heavy aeration and light using aerators and fluorescent bulbs respectively in a controlled laboratory with temperature of 25 ± 2 °C. The exponential growth phase is generally observed in 36 h to 3 days after inoculation. Cell density of 1.5–4.5 million cells per ml could be recorded. As a sufficient quantity of phytoplankton inoculums usually is present in the coarsely filtered seawater when the nutrients are added, a phytoplankton bloom develops in a course of few days under substantial sunlight. However, it happens sometimes that diatom bloom is inhibited by lack of sunlight or due to the nature of seawater in the tank. In such cases, the addition of new seawater and/or addition of ferric chloride in small amounts may stimulate instant resumption of the diatom in culture.

Preliminary study on the dye removal efficacy of immobilized marine and freshwater microalgal beads from textile wastewater

Discharge of textile wastewater containing toxic dyes can adversely affect aquatic organisms and human health. The objective of the study was to investigate the potential of immobilized marine microalgae ( Chlorella marina, Isochrysis galbana, Tetraselmis sp . Dunaliella salina and Nannochloropsis sp.) and freshwater microalga ( Chlorella sp.) in removing dye from textile wastewater (TW). The present study incorporated the use of 2% sodium alginate matrixes for decoloration. Among the algal species tested, the highest colour removal was noticed in Isochrysis galbana (55%) followed by freshwater Chlorella sp. (43%). The present method is easy to use, cost effective and devoid of technical problems. Keywords: Marine microalga, immobilization, textile wastewater, Chlorella marina, Isochrysis galbana, Dunaliella salina, biosorption, bioremediation. African Journal of Biotechnology , Vol 13(22) 2288-2294

Isolation, Culture, and Application of Marine Microalga Dunaliella salina (Volvocales, Chlorophyceae) as an Aqua Feed Additive

Microalgae are microscopic unicellular organisms capable to convert solar energy to chemical energy via photosynthesis. They contain numerous bioactive compounds that can be harnessed for commercial use. The potential of microalgal photosynthesis for the production of valuable compounds or for energetic use is widely recognized due to their more efficient utilization of sunlight energy as compared with higher plants. Microalgae can be used to produce a wide range of metabolites such as proteins, lipids, carbohydrates, carotenoids, or vitamins for health, food and feed additives, cosmetics, and energy production (Adams et al. 2009). However, microalgal biotechnology only really began to develop in the middle of the last century. Nowadays, there are numerous commercial applications of microalgae such as microalgae can be used to enhance the nutritional value of food and animal feed owing to their chemical composition; they play a crucial role in aquaculture. Moreover, they are cultivated as a source of highly valuable molecules. For example, polyunsaturated fatty acid oils are added to infant formulas and nutritional supplements, and pigments are important as aqua feed additive.

An Intensive Culture Techniques of Marine Copepod Oithona rigida (Dioithona rigida) Giesbrecht

Copepods are the main prey for fish and other crustacean larvae in the marine environment compared to other preys (Stottrup 2000; Ostergaard et al. 2005; Sampey et al. 2007). Their dietic value to fish larvae is known to be greater than the rotifer, Brachionus spp. and brine shrimp Artemia spp., they are the main live prey presently used in aquaculture hatcheries widely (Stottrup 2000; Lee 2003). Using rotifers and Artemia during the early fish larval rearing periods of life history not always enhances finest larval growth since these live prey usually have an inadequate fatty acid report and, in some instances, inappropriate size (Kahan et al. 1982; Sargent et al. 1999; Holt 2003; Faulk and Holt 2005). Thus, alternative food sources that do not have these inadequacies and promote larval growth are required. Copepods, copepodites, and naupliar stages are good nominees (Holt 2003), and studies on their mass production have been developed to investigate their efficiency on novel diets in aquaculture (Drillet et al. 2006). The small cyclopoid copepod genus Oithona is one of the most prevalent and copious in temperate, tropical, and polar oceans (Gallienne and Robins 2001; Hopcroft et al. 2005; Castellani et al. 2007); Oithona sp. can be used as feed transition between Rotifera and Artemia, or as a substitution of Artemia, recently. The calcium content of Oithona sp. is higher than that of Artemia (Castellani et al. 2008). The content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is also higher than that of Artemia and Rotifera. The high content of EPA/DHA will be helpful for growth improvement and survival rate and to reduce the occurrence of abnormality on shrimp and fish larvae. Oithona sp. contains immunostimulant; attractant and some significant digestive enzyme given the importance of Oithona sp. as a substitute for Artemia in the aquaculture, and also the sustainable availability of Oithona sp., were significant (Diana and Suminto 2015). Furthermore, owing to limitations of mouth gape, newly hatched larvae of some warmwater marine fish species have complexity ingesting Rotifera and Artemia nauplii but are able to feed upon copepod nauplii (Stottrup 2003). Optimizing copepod diets to meet their inclination can result in growth, egg production, and successful egg hatching (Milione and Zeng 2008; Rahman and Meyer 2009; Rahman and Verdegem 2010). Based on the commercial availability and production, the aquaculture industry is dominated by rotifers and Artemia, even though without enrichment of Artemia nauplii and rotifers did not fulfill the HUFA level required by the fish larvae (Raju 2012). The fast growth and higher survival of larvae were noticed when the fish larvae are fed with copepod alone or in combinations with other live feeds (Stottrup 2000, 2003; Payne et al. 2001; Ananthi et al. 2011; Santhanam and Perumal 2012a; Jayaraj 2012; Kathiresan 2013; Nandakumar 2015; Ananth 2015; Dinesh Kumar 2015). For the successful rearing of larvae, nutrition-rich, small-sized feed should be used. Copepods can work on it and considered as a promising live feed for larval stages of shrimp and fish (Santhanam 2002). Temperature, pH, and salinity are the main key factors that ruled the growth and reproductive potential of copepod in aquaculture systems followed by food and food concentration (Sun et al. 2008; Rhyne et al. 2009; Santhanam and Perumal 2012a; Santhanam et al. 2013; Nandakumar et al. 2015). Temperature plays a main role throughout the life cycle when the food factor is satisfactory. When pH is low in water, the skeptical damage was found in crustacean (Whiteley 2011), and growth and reproductive success were also affected (Whiteley 2011; Engstrom-Ost et al. 2014). Most of the marine invertebrates including copepods are weak during early developmental and reproductive stages (Kurihara 2008). Previous studies also suggested that the when the pH decreases, egg production, egg-hatching success, and nauplius survival also decreased (Mayor et al. 2007; Kurihara 2008). Only few reports are available on the culture of Oithona rigida with reference to environmental condition (Santhanam and Perumal 2012b; Vasudevan et al. 2013). Kahan (1979) optimized the copepod diet with vegetable juice as remedy for algal feed shortages. Though their diet depends on microalgae, we may have reinstated the algal diet with some other edible waste materials (Kahan 1979). The culture materials with various shapes will be given to troubleshoot the various physical barriers such as stable humidity, swimming activity behaviors, etc.; the type of vessels and their shape have been used since the copepod culturing mechanism begins (De Lepiney and Lionelle 1962; Santhanam et al. 2015). Light is also a complex external and ecological factor which includes spectrum of colors, intensity, and periodicity. It is considered to be a critical abiotic factor, influencing biological functions of any organism. With the above merits and demerits, the present study has been focused on optimization, and culturing O. rigida with a series of experiments was conducted to know the effect of temperature, salinity, pH, diets, and diet concentration on the survival, nauplii production rate, population density, development time, generation time, alternate diets, shape of the culture vessels, nature of the culture vessels, different light intensities, and different photo periods which have been analyzed under controlled and sophisticated laboratory condition. The main intention of this study is to develop the intensive culturing technology for copepod O. rigida to achieve greater population density of species.