Shigehisa Yamasaki

Effects of temperature, light intensity, salinity and source of nitrogen on the growth, total lipid and fatty acid composition of Ulva pertusa Kjellman (Chlorophyta)

Growth, total lipid content and fatty acid composition of Ulva pertusa Kjellman were studied in a 4 × 2 factorial laboratory experiment at two levels (low and high) of temperature (15 and 25 °C), subsaturating light intensities (16-32 and 48-64 μE m −2 s −1 ), salinity (20 and 35‰) and two sources of nitrogen (nitrate and ammonia). Specific growth rate (SGR) was highest at low temperature (15 °C), high light intensity (48-64 μE m −2 s −1 ) and high salinity (35‰). Interaction between temperature, light intensity and nitrogen source was the highest source of variation in SGR at the beginning of culture, while salinity and salinity-light intensity interactions were the most limiting factors during the later part of culture

Fatty acid composition of Ulva pertusa Kjellman (Chlorophyta) and Gracilaria incurvata Okamura (Rhodophyta) in Japanese coastal waters

Crude lipid content and total fatty acid composition of 2 macrophytes, Ulva pertusa Kjellman (Chlorophyta) and Gracilaria incurvata Okamura (Rhodophyta) were monitored using material from the wild from March to July 1992. Ulva pertusa contained high levels of C16 (16: 4 n - 3) and C18 (18: 1, 18: 2 n-6, 18: 3 n - 3 and 18: 4 n - 3) unsaturated fatty acids (36 - 54% of total fatty acids), while the only unsaturated fatty acid occurring at high levels in G. incurvata was arachidonic acid (20: 4, 26 -46% of total fatty acids). Both seaweeds contained high levels of palmitic acid (16: 0, 19-33%). Temperature and daylength were not regarded as completely distinct environmental factors because of their highly significant correlation during the period of study (r 2 = 0.91, p < 0.003)

Effect of salinity on the growth and fatty acid composition of Ulva pertusa Kjellman (Chlorophyta)

Changes in the specific growth rate and fatty acid composition of Ulva pertusa were observed at various salinities (20, 25, 3O, 35 and 40‰), in a completely randomized laboratory experiment. Specific growth rates were highest at 30 and 35‰. Moisture content did not significantly vary between salinity treatments. Crude lipid contents of thalli at salinities above 30‰ were 30-70% higher than at lower salinities (e.g., at 30‰, crude lipid was 1.47% of fresh weight or 5.59% of dry weight; at 25‰, crude lipid was 0.42% of fresh weight, or 1.93% of dry weight). High salinity increased the overall levels of the n-3 major polyunsaturated fatty acids (16:4n-3, 18:3n-3 and 18:4n-3), whereas, low salinity increased the levels of the fatty acids, 16:0, 18:1, 20:3 and the essential fatty acid 20:5

Continuous culture of the rotifer Brachionus plicatilis fed recycled algal diets

A culture system for the rotifer Brachionus plicatilis was designed to maintain higher food conversion rates and stable population densities. Two 2001 plastic tanks were employed in the culture experiments, tank A for ‘feedback’ culture and tank B for a control culture. The experiments were carried out for 70 days at 24 °C, light intensity, 1500 lux, and a photoperiod of L:D 15:9. B. plicatilis were fed once a day on bakers yeast and Chlorella.Food conversion rates in tanks A and B were 24.7% and 10.1%, respectively. Population density of B. plicatilis in tank A was consistently stable at 100–150 ind. ml−1 throughout the culture period. Density in tank B, however, showed large fluctuations after 40 or 50 days and by the end of the experiment, declined to zero.

Culture of Tetraselmis tetrathele and its utilization in the hatchery production of different penaeid shrimps in Asia

The prasinophyte Tetraselmis tetrathele is an important live feed organism for shrimp/prawn hatchery operations because of its high nutritional value and ease of culture. It can replace Brachionus plicatilis and Artemia nauplii as live diet during the protozoeal and mysis feeding stage. This study tried to determine the different optimum culture conditions for T. tetrathele, and to evaluate its application in the hatchery production of different penaeid species. Tetraselmis tetrathele was cultured at combinations of six levels of salinities (10–60 g kg−1), nine levels of pH (3–10.5), and two temperatures (25°C and 30°C) in a three factorial combination experiment. Effects of varying concentrations of different organic and inorganic media including the use of vitamins and trace metals were also assessed. The dietary value of T. tetrathele was evaluated by feeding it to different shrimp larvae from protozoea-1 (PZ-1) until postlarva-1 (PL-1).

CO2 concentration change in Nannochloropsis sp. culture medium

Abstract CO 2 concentration in a marine phytoplankton, Nannochloropsis sp., culture medium was observed to consider whether or not CO 2 defficiency for growth occurs in the culture medium of a mass culture. In the first experiment, the Nannochloropsis sp. culture was continued for 4–5 days and the CO 2 concentration was observed three times a day, namely, the initial, middle and end of the light period. While, in the second experiment, the CO 2 concentration was observed every 2–3 hr for 24 hr on the second day after inoculation. In the first experiment, the total CO 2 concentration decreased gradually throughout the culture period, repeating its decrease and increase in the light and dark periods, respectively. At the end of the light period of the third day after inoculation, the CO 2 concentration decreased to concentrations which could not be determined. In the second experiment, the CO 2 concentration decreased in the light period, and increased in the dark period. The increment in the dark period was faster at heavier aeration. It was considered that some kind of carbon source should be supplied to obtain high density of Nannochloropsis sp. ealier under strong light intensity.

Effect of feeding on the respiration rate of the rotifer Brachionus plicatilis

The effect of feeding on the respiration rate of Brachionus plicatilis was studied. Oxygen consumption was determined under two feeding regimes, duplicate feeding and constant feeding. Oxygen consumption rate increased during feeding. The oxygen consumption profile is discussed in relation to the following processes:

Influence of Light Intensity on the Fatty Acid Composition of Ulva pertusa Kjellman (Chlorophyta)

Changes in the fatty acid (FA) composition of the green seaweed, Ulva pertusa, in response to irradiance (15, 30, 45, 90, 135 and 195 μE m −2 s −1 ), and to the natural photoperiod were investigated. The levels of the following FAs increased with increasing light intensity, suggesting a role as storage products: 15:0, palmitic (16:0), linolenic (18:2n-6), arachidonic (20:4) and 22:4. The level of 16:0, a major FA, increased (from 25% to 29% of total FAs) up to 90 μE m −2 s −1 , beyond which, levels slightly decreased. Levels of 14:1 and the major FA, hexadecatetraenoic (16:4n-3), were inversely related to light intensity, suggesting a role as components of photosynthetic membranes. Levels of 16:4n-3 at the lowest light intensity (21% of total FAs, 15 μE m −2 s −1 ) were nearly twice that observed at the highest light intensity (11% of total FAs, 195 μE m −2 s −1 )

Improvement of a rotifer ecosystem culture to promote recycling marine microalga, Nannochloropsis sp

Abstract An ecosystem culture with a consumer-producer relationship based on the cycle of substances in the natural ecosystem was constructed in order to study the feasibility of economical cultivation of the marine microalga Nannochloropsis sp. in rotifer waste water. To promote algal growth, the following points were investigated to determine: (1) whether micronutrients necessary for Nannochloropsis culture are generated by rotifers, (2) the favorable and optimal ranges of nutrient concentrations in aged rotifer culture water involved in the optimal growth of Nannochloropsis sp., and (3) the suitability of some economical organic fertilizers in rotifer waste water at earlier stages. In new rotifer waste water, the growth of Nannochloropsis was equal to that in enriched sea water with Enriched Sea Water Provasoli (ESP) nutrients. Micronutrients could be recycled rapidly through feeding and excretion of rotifers. Using aged rotifer waste water, the maximum cellular density was obtained in a waste water with nitrogen and phosphorus concentrations of 364 and 179 μg at. 1 −1 , respectively. This growth was 23% higher than that obtained in enriched sea water with ESP nutrients (control). On the other hand, the organic fertilizers used in this experiment (chicken manure extract and decomposed shark meat) were found to be suitable for enhancing growth of Nannochloropsis sp. in rotifer waste water at earlier stages. The use of chicken manure with an additional inorganic nitrogen source to rotifer waste water resulted in a 50% increase in cellular density of Nannochloropsis sp. compared with that obtained in the control. However, addition of decomposed shark meat to rotifer waste water led only to a 20% increase.

Functions of a stream unit on the growth of phytoplankton, zooplankton and fish fry in a new culture tank system

Abstract The functions of a stream unit in a new culture tank system, which was composed of the stream unit and a conventional tank, were evaluated by cultivation of phytoplankton (freshwater Chlorella sp.), Zooplankton ( Moina micrura ) and fish fry ( Puntius gonionotus ). Ratios of the growth rates of phytoplankton and zooplankton in the new tank system, to the control tank were 1·2:1 and 1·1:1 on average, respectively, and ratios of total weight of fish growth were 1·1:1. On the basis of the results and several water quality parameters (DO, PO 4 P content and pH), the follwing functions were considered: 1. (1) Enhancement of the growth of algae, water weeds, and bacteria; (a) production of food materials for zooplankton and fish, (b) oxygen supply, (c) pH increase, (d) absorption of nutrients, (e) acceleration of decomposition of biodeposits. 2. (2) Accumulation of biodeposits.