Selection of Suitable Species of Chlorella , Nannochloris , and Nannochloropsis in High- and Low-Temperature Seasons for Mass Culture of the Rotifer Brachionus plicatilis
- DOI : 10.5657/FAS.2011.0323
- Author: Bae Jean Hee, Hur Sung Bum
- Organization: Bae Jean Hee; Hur Sung Bum
- Publish: Fisheries and aquatic sciences Volume 14, Issue4, p323~332, 31 Dec 2011
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ABSTRACT
To find seasonally optimal microalgae for mass culture of the rotifer
Brachionus plicatilis , the growth rates of 12 microalgal spe-cies (two marineChlorella spp., five marineNannochloris spp., two marineNannochloropsis spp., one estuarineNannochloropsis sp., and two estuarineChlorella spp.) were compared at 25℃ at 15 psu and 30 psu. Among these, six species showing high growth rates were chosen and examined again at high (30℃ and 32℃) and low (10℃) temperatures. Their amino and fatty acids and the dietary value of the rotifers that fed on each microalgal species were examined.Nannochloris sp. (KMMCC-119) andChlorella vulgaris (KMMCC-120) showed the highest growth rates at temperatures over 30℃ and at 10℃, respectively. The growth rate ofNannochloris was higher than those ofChlorella andNannochloropsis at high temperatures, but lower than those of the latter at low temperatures. The growth rate of rotifers fed onNannochloropsis was highest and that of those fed onChlorella was lowest. Levels of eicosapentaenoic acid and docosahexaenoic acid were highest inNannochloropsis and lowest inNannochloris . However, total amino acid content was highest inNannochloris and lowest inChlorella . In conclusion,Nannochloropsis sp. (KMMCC-33) was the best microalgal species for the mass culture of the rotifer. However, during high- or low-temperature seasons in whichNannochloropsis does not grow well,Nannochloris spp. (KMMCC-119, 395) andC. vulgaris (KMMCC-120) would adequately replaceNannochloropsis sp. (KMMCC-33).
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KEYWORD
Brachionus plicatilis , Chlorella , Nannochloris , Nannochloropsis , Rotifer
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The rotifer
Brachionus plicatilis is prevalently used as an early larval food for the seed production of seawater fish, as it is small, with low motility, and is suitable for high-density culture. Since the rotifer was first used as feed forPagrus ma-jor in Japan (Fukusho, 1989), microalgae and yeast have been widely used as feed in the mass production of the rotifer.Examples of commonly used microalgae and yeast include the microalgae
Nannochloropsis (Fukusho, 1989; Kosto-poulou and Vadstein, 2007; Ferreira et al., 2009),Chlorella (Maruyama et al., 1997; Cabrera et al., 2005; Zhou et al., 2009), andNannochloris (Witt et al., 1981; Cabrera and Hur, 2001, Cho et al., 2007), and the yeasts bread yeastSaccharomyces cerevisiae (Gilberto and Mazzola, 1981; Sarma et al., 2002; Wang et al., 2009) and marine yeastCandida utilis (Kim et al., 2005).Yeasts are more economical than microalgae, but contain insufficient amounts of unsaturated fatty acids, which are es-sential for the growth of rotifers (Watanabe et al., 1980; Kim et al., 2009). In an attempt to supplement the shortcomings of yeast, ω-yeast was developed using bread yeast infused with squid oil. However, this had lower nutritional value than microalgae and caused water pollution (Hirayama and Funa-moto, 1983). Thus, in spite of the high costs incurred on the mass culture of rotifers, live microalgae are still preferred by hatcheries (Hur, 1991; Borowitzka, 1997).
Chlorella ,Nannochloris , andNannochloropsis have been well-known to be easily mass-cultured and to have high con-tents of protein or unsaturated fatty acids (Chini Zittelli et al., 1999; Hu and Gao, 2003; Cho et al., 2007). However, they are also at high risk of sudden mortality at temperatures over 30℃, and their low growth rates in water temperatures under 10℃ are problematic (Fukusho et al., 1985; Hur, 1991).Therefore, this study aimed to identify a new species among
Chlorella ,Nannochloris , andNannochloropsis that would be specifically suitable for mass culture as rotifer feed during sea-sons of high and low temperature.The microalgae used in this study, from the Korea Marine Microalgae Culture Center (KMMCC), included nine ma-rine species and three estuarine species. These consisted of four kinds of
Chlorella , five kinds ofNannochloris , and three kinds ofNannochloropsis (Table 1). Their growth rates were observed and compared to each other.Microalgae in the log phase stage were inoculated in 100 mL of f/2 culture medium (Guillard and Ryther, 1962) in a 250-mL Ehrenmeyer flask at a density of 100 × 104 cells/mL. Microalgae were cultured in standing water at 25℃ and 15 and 30 psu, with continuous light of 100 ㎛ol m-2 s-1, three times during 7 days. The salinity was adjusted by the mixture
of filtered seawater and distilled water.
To measure growth rate, cells were counted by hemacy-tometer regularly, four times a day. The specific growth rate (SGR) was calculated according to Guillard (1973) [SGR = 3.322 × log(N1/N0)/t, where t is culture days after inocula-tion, and N0 and N1 are cell density after inoculation or t days, respectively].
> Growth of six kinds of microalgae at high and low temperature
Six kinds of microalgae that showed high growth rates in the aforementioned experiment were cultured at high tempera-tures of 30℃ and 32℃ and a low temperature of 10℃ at 15 psu with 100 ㎛ol m-2 s-1 of continuous lighting, namely,
Nan-nochloropsis sp. (KMMCC-33),Nannochloropsis oceanica (KMMCC-13),Nannochloris oculata (KMMCC-16),Nanno-chloris sp. (KMMCC-119),Nannochloris sp. (KMMCC-395), andChlorella vulgaris (KMMCC-120). Their SGR was exam-ined using the previously described method for 10 days.> The adequacy of the six microalgae as rotifer feed
The rotifer
Brachionus plicatilis (R-4, L-type), provided by the Culture Collection of Useful Marine Plankton (CCUMP) at Pukyung National University in Korea, was used in this study. The amount of microalgae fed daily to an individual rotifer was in accordance with algal cell volume as follows. For the smallest cells,N. oculata ,Nannochloris sp. (KMMCC-119), andNannochloris sp. (KMMCC-395), 30 × 104 cells were provided as feed. ForN. oceanica andNannochloropsis sp. (KMMCC-33), 22 × 104 cells were fed. For the largest cells,C. vulgaris (KMMCC-120), 15 × 104 cells were supplied. The ro-tifer was inoculated at 10 individuals/mL in 100 mL of a 250-mL Ehrenmeyer flask and cultured in standing water at 26℃ and 15 psu under continuous lighting of 60 ㎛ol m-2 s-1. Cul-ture was conducted in triplicate during 5 days. One milliliter of each culture group was arbitrarily drawn and placed in Lu-gol's solution and the number of rotifers in 1 mL was counted under a stereoscopic microscope three times a day. The SGR of the rotifers was calculated by the method described above.> Analysis of the nutritional content of the microal-gae and rotifers
The amino and fatty acids of the six selected microalgae and the rotifers fed on three selected microalgae, which in-duced high growth rates in rotifers, were analyzed. They were cultured by the method described above. At the end of the log phase of growth, they were harvested and kept at -80℃ until analysis.
For the analysis of amino acids, 20 mg of sample infused with 15 mL of 6 N HCl was heated, sealed, and hydrolyzed at 110℃ for 24 h. The sample was then filtered and dried to remove HCl. Then 25 mL of the sample was set by sodium dilution buffer (pH 2.2) and a portion of the sample was ana-lyzed by the ninhydrin method using S433 (Sykam, Fursten-feldbruck, Germany). Conditions of the analysis were as fol-lows: column size, 4 mm × 150 mm; absorbance level, 570 nm and 440 nm; reagent flow rate, 0.25 mL/min; buffer flow rate, 0.45 mL/min; reactor temperature, 120℃; reactor size, 15 m; and analysis time, 65 min.
For the analysis of fatty acids, 20 mg of sample in a 15-mL flask was added to 2 mL of 10% BF3-methanol. Nitrogen was added to the sample and heated at 85℃ for an hour and a half to draw methyl ester (Morrison and Smith, 1964; Budge, 1999). Cooled to 30-40℃, the sample was combined with wa-ter and hexane to draw fatty acids separately. The extracted fatty acids were analyzed with a HP GC 6890 Plus installed with a HP autosampler (Agilent Technologies, Santa Clara, CA, USA). The GLC used in this analysis was the DB-225 (20 m × 0.1 mm, i.d., 0.1 ㎛ film thickness; J&W Scientific, Agilent Technologies, Santa Clara, CA, USA). Conditions of the analysis were as follows: column temperature levels, 60-195℃ (25℃/min); temperature conditions, 195-205℃ (3℃/min), 205-230℃ (8℃ min); injector, 250℃; detector, 250℃; and carrier gas used, He (60 cm/s). Fatty acids were identified by comparison with known standards.
The results of this study were analyzed by one-way ANO-VA, and Duncan's multiple range test (Duncan, 1955) was ap-plied for the significance level (
P < 0.05). The SPSS version 17 (SPSS Inc., Chicago, IL, USA) program was used for all statistical analyses.After 7 days culture of the nine marine microalgae at 30 psu and 15 psu, results (Fig. 1) indicated that
N. oculata andNan-nochloris . sp. (KMMCC-395) in 30 psu showed the highest growth rates of 0.9734 and 0.9640, respectively (highest cell densities, 11,229 × 104 cells/mL and 10,733 × 104 cells/mL, respectively). The growth rates ofC. salina andC. vulgaris at 0.7912 and 0.7812 were not significantly different from each other. The growth rates ofN. oceanica andNannochloropsis . sp. at 0.7866 and 0.7842 were as low as those ofChlorella , whileNannochloris showed a significantly higher growth rate than those ofChlorella andNannochloropsis (P < 0.05). The growth rate ofNannochloris sp. (KMMCC-58) was signifi-cantly lower than those of the other four kinds ofNannochlo-ris (P < 0.05).At 15 psu, the growths of
N. oculata and the three kinds ofNannochloris (KMMCC-117, 119, and 395) were highest, inthe range of 0.9393 and 0.9504 (highest cell density, 9,718 × 104 cells/mL to 10,145 × 104 cells/mL). Conversely,
Nanno-chloris sp. (KMMCC-58) showed a significantly lower growth rate than other strains, similar to that ofChlorella .N. oceanica andNannochloropsis sp., the two kinds ofNannochloropsis , showed significantly lower growth rates compared to the four kinds ofNannochloris , but significantly higher growth rates thanChlorella (P < 0.05). The growth rates ofChlorella andNannochloropsis tended to be higher at 15 psu than at 30 psu. However, the four kinds ofNannochloris , except forNan-nochloris sp. (KMMCC-58), showed slightly higher growth rates at 30 psu.> Growth of estuarine microalgae
At 30 and 15 psu, the growth rates of
C. vulgaris (KMMCC-120) were 0.8495 and 0.8601 (6,166 × 104 cells/mL and 6,491 × 104 cells/mL), respectively, indicating the sig-nificantly highest rate (
P < 0.05) (Fig. 2). The growth rates ofChlorella sp. (KMMCC-137) andNannochloropsis sp. (KMMCC-327) were in the range of 0.7781-0.8204, which were lower than that ofC. vulgaris (KMMCC-120). The growth rate ofChlorella sp. (KMMCC-137) was significantly higher at 30 psu than at 15 psu. As a result,Chlorella sp. (KMMCC-137) was distinguished as a marine microalga. The growth rates of the other two kinds ofChlorella indicated no significant difference according to salinity (P < 0.05).In contrast to the estuarine
C. vulgaris (KMMCC-120), which showed a higher growth rate than marineChlorella (KMMCC-79 and 95),Chlorella sp. (KMMCC-137) andNan-nochloropsis sp. (KMMCC-327) showed similar growth rates to those of marine microalgae.The growth and nutritional content of the marine microal-gae
N. oceanica ,Nannochloropsis sp. (KMMCC-33),N. ocu-lata ,Nannochloris sp. (KMMCC-119), andNannochloris sp. (KMMCC-395) and the estuarineC. vulgaris (KMMCC-120) were studied.Growth rates under the same culture conditions, 15 psu, 25℃, and 100 ㎛ol m-2 s-1, are shown in Fig. 3. Among the six kinds of microalgae, the growth rate of
Nannochloris sp. (KMMCC-119) was highest at 0.8753 (highest cell density, 6,987 × 104 cells/mL). The growth rates of the two kinds ofNannochloropsis were significantly higher than that ofChlo-rella and lower than that ofNannochloris (P < 0.05). In addi-tion, the growth rate of estuarineC. vulgaris (KMMCC-120), 0.7807 (highest cell density, 4,416 × 104 cells/mL), was the lowest compared to those of marine microalgae (P < 0.05).Nannochloris sp. (KMMCC-395) contained the highest percentage amino acid content at 72.97% andC. vulgaris (KMMCC-120) the lowest at 45.72% (Table 2). The amino acid contents ofN. oceanica andNannochloris sp. (KMMCC-119) were lower than that ofNannochloris sp. (KMMCC-395) andhigher than that of
C. vulgaris . Among nonessential amino acids, glutamine and leucine contents were high. Essential amino acids were highest inNannochloris sp. (KMMCC-395) at 32.51%.Nannochloropsis ,Nannochloris , andChlorella indicated high contents of fatty acids at ratios of 14:0, 15:1, 16:0, and 16:1 (Table 3). The contents of polyunsaturated fatty acid, PUFA, inNannochloropsis sp. (KMMCC-33) andNannochlo-ris sp. (KMMCC-119) were highest at 40.68% and 39.63%, respectively. The content of eicosapentaenoic acid (EPA,20:5n-3) in
Nannochloropsis sp., 34.88%, was high com-pared to that inNannochloris sp. (KMMCC-119), which was the lowest at 0.35%. The contents of docosahexaenoic acid (DHA, 22:6n-3) inNannochloropsis sp. (KMMCC-33) andNannochloris sp. (KMMCC-119) were as low as 0.29% and 0.02%, respectively. The content of EPA+DHA inNannochlo-ropsis sp. (KMMCC-33), 35.17%, was the highest and inNan-nochloris sp. (KMMCC-119), 0.37%, the lowest.> Growth of Nannochloropsis, Nannochloris, and Chlorella in high and low water temperatures
The growth rates of six kinds of
Nanno-chloropsis ,Nannochloris , andChlorella at high (30℃ and 32℃) and low (10℃) temperatures are shown in Fig. 4. At 30℃,Nannochloris sp. (KMMCC-119) andN. oculata showed the highest cell den-sity within 9-10 days of culture at 7,950 × 104 cells/mL and 7,951 × 104 cells/mL, respectively. The growth rate ofN. oce-anica was 2,991 × 104 cells/mL up to the sixth day of culture, but thereafter, the growth rate rapidly decreased. At 32℃,Nannochloris spp. (KMMCC-119 and 395) showed the high-est cell density among the microalgae at 6,475 × 104 cells/mL and 5,932 × 104 cells/mL, respectively. In comparison to the other microalgae, however,N. oceanica showed a much lower cell density, as it did at 30℃.The growth rates of
N. oculata andNannochloris sp. (KMMCC-119) at 30℃ were significantly the highest: 0.6313 and 0.6281, respectively. Conversely,N. oceanica showed the lowest growth rate: 0.3483 (P < 0.05). At 32℃, growth rates significantly differed according to the individual strain. The growth rate ofNannochloris sp. (KMMCC-119), 0.6017, was the highest and that ofN. oceanica , 0.1521, was the lowest. In high water temperatures of 30℃ and 32℃,Nannochloris had a significantly higher growth rate thanChlorella andNan-nochloropsis (P < 0.05).At 10℃, the growth rate of
C. vulgaris (KMMCC-120) was significantly the highest at 0.5052 (highest cell density, 3,316 × 104 cells/mL) (P < 0.05). Growth rates of the other marine microalgae were low, in the range of 0.0109-0.3303 (highest cell density, 107-986 × 104 cells/mL). The growth rate ofN. oculata in particular was significantly the lowest at 0.0109 (highest cell density, 107 × 104 cells/mL).The growth rates of rotifers fed on the six kinds of microal-gae are shown in Fig. 5. In 5 days of culture, the growth rates of rotifers fed on
Nannochloropsis sp. (KMMCC-33) andN. oceanica were significantly higher than those of the other ex-perimental groups at 0.6806 (highest density, 301 individu-als/mL) and 0.6605 (highest density, 272 individual/mL), re-spectively (P < 0.05).Nannochloris sp. (KMMCC-395) andC. vulgaris (KMMCC-120) showed the lowest growth rates at 0.5332 and 0.5376 (P < 0.05), respectively.Nannochlo-ris spp. (KMMCC-16 and 119) indicated lower growth rates thanNannochloropsis sp. (KMMCC-33) andN. oceanica , but higher growth rates thanC. vulgaris (KMMCC-120) andNan-nochloris sp. (KMMCC-395) (P < 0.05).Nannochloris sp. (KMMCC-119), with a high growth rate at high temperature,C. vulgaris (KMMCC-120), with a high growth rate at low temperature, andNannochlorop-sis sp. (KMMCC-33), as a nutritious feed for rotifers, were cultured in three separate groups. The amino acid contents of these groups were analyzed (Table 4). The kinds of amino acids in the three experimental groups were similar to each other. The content of total amino acids in rotifers fed onC. vulgaris (KMMCC-120) was the highest at 57.15%, and onNannochloropsis sp. (KMMCC-33) was the lowest at 50.54%. Rotifers showed relatively high contents of leucine and lysine among essential amino acids and of glutamine and aspartate among nonessential amino acids.For the contents of fatty acids in rotifers fed on the afore-mentioned three kinds of microalgae (Table 5), those fed on
C. vulgaris (KMMCC-120) contained 41.62% of C18:2n9 compared to 11.0% and 24.60% inNannochloropsis sp. (KMMCC-33) andNannochloris sp. (KMMCC-119), respec-tively. The contents of C16:0 in all three experimental groups were similar, in the range of 12.63-15.94%. The total content of PUFA in rotifers fed onC. vulgaris (KMMCC-120) was the highest at 63.51%. The content of EPA was highest in theNannochloropsis sp. (KMMCC-33) group at 15.27%, and the content of DHA in rotifers fed onC. vulgaris (KMMCC-120) was the highest at 9.39%.The growth of rotifers depends on the kind of microalgae used as feed (Hirayama et al., 1979; Cho et al., 2007). Various kinds of microalgae as feed for rotifers have been reported, with
Nannochloropsis ,Nannochloris , andChlorella , which are highly nutritious and suitable for high density culture, be-ing the most widely used in mass culture.One of the obstacles to the mass culture of rotifers comes from difficulties in the outdoor mass culture of microalgae during certain seasons. In summer, sudden cell mortality of-ten occurs, and in the winter, the cell growth rates tend to be very low. Thus, further developing microalgae that are highly adaptive to conditions in the two aforementioned seasons is
essential (Watanabe et al., 1978; James and Abu-Rezeq, 1988; Hur, 1991).
This study aimed to identify microalgae among
Nannochlo-ropsis ,Nannochloris , andChlorella , which are specifically adaptive to high- and low-temperature seasons in Korea. The optimal salinity for the culture of rotifers was 15 psu (Miracle and Serra, 1989; Kim et al., 2005). Since marine microalgae are also euryhaline, their growth rates were compared at sa-linities of 15 and 30 psu.Nine kinds of marine microalgae showed similar growth rates to each other at 15 and 30 psu. Their growth, howev-er, exhibited slight differences according to microalgal type
and salinity. Three estuarine microalgae also showed similar growth rates at 15 and 30 psu. Based on these results, the 12 kinds of microalgae studied in this research can be inferred to be suitable as feed for rotifers because they were euryhaline.
The growth rates of the six kinds of microalgae cultured at 30℃ and 32℃ for the high-temperature experiments were highest for
Nannochloris and lowest forNannochloropsis . The growth rate ofChlorella was much lower than that ofNannochloris , but higher than that ofNannochloropsis . In terms of the highest cell density at 30℃ and 32℃,Nannochlo-ris showed a 25% decrease in growth rate, whileChlorella andNannochloropsis exhibited 40% and 35% decreases in their growth rates, respectively. These results highlight the fact that the two aforementioned microalgae are more prone thanNan-nochloris to mortality at temperature levels over 30℃.Among the three kinds of
Nannochloris , the growth rates ofNannochloris sp. (KMMCC-119) collected at Deukryang Bay and importedN. oculata (UTEX, 1998) were the highest at 30℃. The growth rate ofNannochloris sp. (KMMCC-395) collected at Puan was significantly lower (P < 0.05). At 32℃, however, the growth rate ofNannochloris sp. (KMMCC-119) was the highest and that ofN. oculata was the lowest.Nan-nochloris sp. (KMMCC-395) showed similar growth at both 32℃ and 30℃. Such growth traits can be explained byNan-nochloris sp. (KMMCC-395) being adaptive to higher tem-peratures, as it originated from salt ponds in Puan.At 10℃, for the low-temperature experiment,
N. oculata andNannochloris sp. (KMMCC-119), which were highly vital at high temperature, exhibited the lowest growth rate. However, the growth ofC. vulgaris (KMMCC-120), which was isolated from brackish water, was significantly higher than those of the other microalgae, which were from marine water (P < 0.05). Thus, it is considered suitable for mass cul-ture in low-temperature seasons.At high temperature,
N. oculata was found to have a higher growth rate thanChlorella ellipsoidea orNannochloropsis sa-lina (James et al., 1989; Hur, 1991).Phaeodactylum tricornu-tum , which belongs to the Bacillariophyceae, shows a higher growth rate thanC. ellipsoidea at low temperature. However, it is also reported to be inadequate as a rotifer feed because its dietary value is lower than that ofC. ellipsoidea (Hur, 1991; Cho et al., 2007).The essential amino acid contents of most microalgae are in-fluenced by factors including the intensity of lighting (Thomp-son et al., 1990; Brown et al., 1997), temperature (James et al., 1989; Thompson et al., 1992), pH (Guckert and Cooksey, 1990), culture medium (Wikfors et al., 1984), and harvesting times (Brown et al., 1997; Pernet et al., 2003). In this study, the fatty acid contents of the two kinds of
Nannochloropsis , 16:0 and 16:1, were high, which is consistent with reports by Hodgson et al. (1991) and Volkman et al. (1993). Whyte and Nagata (1990) reported that the main components of fatty ac-ids in the marineChlorella saccharophila were 16:0, 16:1n7, and 18:1n9. However, estuarineC. vulgaris (KMMCC-120) differed from marineC. saccharophila in its main component of fatty acids 17:1 and 20:0.With regard to EPA and DHA, Volkman et al. (1993) re-ported that
Nannochloropsis sp. cultured at 20℃ contained no DHA and 16.1-28.2% EPA. The result of the present study, on microalgae cultured at 25℃, slightly differs from that of Volk-man et al. (1993). Conversely, the report of James et al. (1989) onNannochloropsis cultured at 25℃ containing 0.4% of DHA is similar to the result of the present study.The fatty acid contents of rotifers fed on
Nannochloropsis sp. (KMMCC-33),Nannochloris sp. (KMMCC-119), andC. vulgaris (KMMCC-120) were 16:0, 16:1, and 18:2, respec-tively, which were similar to the contents of fatty acids in the aforementioned microalgae. The growth rate of rotifers fed onNannochloropsis sp. (KMMCC-33), which had the high-est EPA content, was high and its content of EPA was also high. Thus, the nutritional content of a feed can be concluded to directly affect the rotifer (Scott and Middleton, 1979; Ben-Amotz et al., 1987; Frolov et al., 1991).Nannochloris spp. (KMMCC-119 and 395), isolated from Korean coastal waters, showed higher growth rates at 30℃ and 32℃ than the foreign speciesN. oculata (UTEX, 1998). EstuarineC. vulgaris (KMMCC-120) showed a high growth rate at 10℃, at which temperature most microalgae hardly sur-vived. However, their effectiveness as rotifer feed was lower than that ofNannochloropsis because of their low EPA and DHA contents.In conclusion,
Nannochloropsis sp. (KMMCC-33) is the best choice for the mass culture of rotifers.Nannochlo-ris spp. (KMMCC-119 and 395) and estuarineC. vulgaris (KMMCC-120) seem the most adequate species to replaceNannochloropsis sp. (KMMCC-33) during high- and low- temperature seasons, respectively.-
[Table 1.] List of microalgal species used in the study
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[Fig. 1.] Specific growth rate of nine marine microalgal species at 30 psu (A) and 15 psu (B) 25℃ and 100 ㎛ol m-2 s-1 (KMMCC Korea Marine Microalgae Culture Center; KMMCC-79 Chlorella salina; KMMCC-95 C. vulgaris; KMMCC-58 Nannochloris sp.; KMMCC-16 N. oculta; KMMCC-117 Nannochloris sp.; KMMCC-119 Nannochloris sp.; KMMCC-395 Nannochloris sp.; KMMCC-33 Nannochloropsis sp.; KMMCC-13 N. oceanica). Different letters on the bar mean significantly difference (P < 0.05).
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[Fig. 2.] Specific growth rate of three estuarine microalgal species at 30 psu (black bar) and 15 psu (white bar) 25°C and 100 ㎛ol m-2 s-1 (KMMCC Korea Marine Microalgae Culture Center; KMMCC-120 Chlorella vulgaris; KMMCC-137 Chlorella sp.; KMMCC-327 Nannochloropsis sp.). Different letters on the bar mean significantly difference (P < 0.05).
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[Fig. 3.] Specific growth rate of six microalgal species at 15 psu 25℃ 100 ㎛ol m-2 s-1 (KMMCC Korea Marine Microalgae Culture Center; KMMCC-33 Nannochloropsis sp.; KMMCC-13 N. oceanic; KMMCC-16 Nannochoris oculata; KMMCC-119 Nannochoris sp.; KMMCC-395 Nannochoris sp.; KMMCC-120 Chlorella vulgaris). Different letters on the bar mean significantly difference (P < 0.05).
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[Table 2.] Amino acid composition (%) of six microalgal species
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[Table 3.] Fatty acid composition (%) of six microalgal species
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[Fig. 4.] Cell density of six microalgal species at 30℃ (A) 32℃ (B) and 10℃ (C) and specific growth rate (D) under 15 psu and 100 ㎛ol m-2 s-1 (KMMCC Korea Marine Microalgae Culture Center; KMMCC-33 Nannochloropsis sp.; KMMCC-13 N. oceanic; KMMCC-16 Nannochoris oculata; KMMCC-119 Nannochoris sp.; KMMCC-395 Nannochoris sp.; KMMCC-120 Chlorella vulgaris). Different letters on the bar in each temperature mean significantly difference (P < 0.05).
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[Fig. 5.] Specific growth rate of Brachionus plicatilis fed different microalgal species (KMMCC Korea Marine Microalgae Culture Center; KMMCC-33 Nannochloropsis sp.; KMMCC-13 N. oceanic; KMMCC-16 Nannochoris oculata; KMMCC-119 Nannochoris sp.; KMMCC-395 Nannochoris sp.; KMMCC-120 Chlorella vulgaris). Different letters on the bar mean significantly difference (P < 0.05).
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[Table 4.] Amino acid composition (%) of Brachionus plicatilis fed different microalgal species
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[Table 5.] Fatty acid composition (%) of Brachionus plicatilis fed different microalgal species