• ALGAE
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• v.18 no.3
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• pp.217-223
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• 2003

Seasonal growth and maturation process of Caulerpa okamurae were investigated in natural populations and in culture. Monthly sampling was carried out by SCUBA diving at Baekunpo, Busan, southeastern coast of Korea from November 1999 to October 2001. Growth of erect branches depended mainly on the water temperature in the natural habitat. Maximum length of erect branches was 14.0 $\pm$ 1.4 cm in June 2001 when the water temperature was 19.7$^{\circ}C$ and minimum was 2.8$\pm$0.2 cm in April when the water temperature was 14.7$^{\circ}C$. Fresh weight of erect branches was 3.9 $\pm$ 0.5 g in June 2001 and 0.2 $\pm$ 0.04 g in September 2000. Biomass of the population was maximum of 922.5 g dw${\cdot}m^{-2}$ in July and minimum of 125.6 g dw${\cdot}m^{-2}$ in April. Gametangial network was observed on the ramuli when the water temperature was over 19$^{\circ}C$ in August 2000 and June 2001. In the culture regime of 4 temperatures (15, 20, 25 and 30$^{\circ}C$) and 3 irradiances (20, 50 and 80 $\mu$mol${\cdot}m^{-2}{\cdot}s^{-1}$) combination, the maturation of excised erect branches was mainly affected by temperature. Maturation was induced under all irradiance conditions at 20 and 25$^{\circ}C$; under 80 $\mu$mol${\cdot}m^{-2}{\cdot}s^{-1}$ at 15$^{\circ}C$; and under 20 $\mu$mol${\cdot}m^{-2}{\cdot}s^{-1}$ at 30$^{\circ}C$. The highest rate of maturation was 64% under 20 $\mu$mol${\cdot}m^{-2}{\cdot}s^{-1}$ at 25$^{\circ}C$. These results suggested that developmental initiations of C. okamurae occurred at higher than 13$^{\circ}C$ and maturation took about 270 degree-days.

• ALGAE
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• v.31 no.1
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• pp.61-72
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• 2016

Arctic microalgae thrive and support primary production in extremely cold environment. Three Arctic green microalgal strains collected from freshwater near Dasan Station in Ny-Alesund, Svalbard, Arctic, were analyzed to evaluate the optimal growth conditions and contents of fatty acids. The optimal growth temperature for KNF0022, KNF0024, and KNF0032 was between 4 and 8℃. Among the three microalgal strains, KNF0032 showed the maximal cell number of 1.6 × 107 cells mL^-1 at 4℃. The contents of fatty acids in microalgae biomass of KNF0022, KNF0024, and KNF0032 cultured for 75 days were 37.34, 73.25, and 144.35 mg g^-1 dry cell weight, respectively. The common fatty acid methyl esters (FAMEs) analyzed from Arctic green microalgae consisted of palmitic acid methyl ester (C16:0), 5,8,11-heptadecatrienoic acid methyl ester (C17:3), oleic acid methyl ester (C18:1), linoleic acid methyl ester (C18:2), and α-linolenic acid methyl ester (C18:3). KNF0022 had high levels of heptadecanoic acid methyl ester (26.58%) and heptadecatrienoic acid methyl ester (22.17% of the total FAMEs). In KNF0024 and KNF0032, more than 72.09% of the total FAMEs consisted of mono- and polyunsaturated fatty acids. Oleic acid methyl ester from KNF0032 was detected at a high level of 20.13% of the FAMEs. Arctic freshwater microalgae are able to increase the levels of polyunsaturated fatty acids under a wide range of growth temperatures and can also be used to produce valuable industrial materials.

• ALGAE
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• v.18 no.4
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• pp.281-288
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• 2003

To study the environmental features causing a bloom of the novel dinoflagellate Heterocapsa circularisquama (Dinophyceae), hydrographic and chemical aspects were measured in the Uranouchi Bay, Kochi Prefecture, Japan, from January to December, 1997. The cell density of H. circularisquama increased rapidly in early October, and dropped sharply in mid-October. Growth rate of H, circularisquama during bloom period appeared 1.50 division day$^{-1}$ under high water temperature (25$^{\circ}C$) and salinity (32 psu) conditions. Althought the result from hydrographic aspect indicated good condition for their growth, dissolved inorganic phosphorus (DIP) concentration in surface layer before bloom formation was less than 0.70uM, which is lower than their half saturation constant(Ks). Dissolved inorganic nitrogen(DIN): DIP ratio was > 30, indicating potential P-limitation. However, before bloom formation period of H. circularisquama, DIP concentrations were high in bottom layer (> 4.0 uM). Some studies reported that H. circularisquama had the ability to migrate vertically and to utilize dissolved organic phosphorus (DOP). Thus, DIP in bottom layer might have been utilized by H. circularisquama for their growth.DOP might have weakly affected their growth because of low reactive DOP concentrations owing to low DOP concentration (ca. 0.39 uM). Thus, if nutrient condition of bottom layer in Uranuchi Bay is not improved, the outbreaks of H. circularisquama red tides may became an annual feature.

• ALGAE
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• v.31 no.3
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• pp.257-266
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• 2016

Nitrogen is one of the most critical nutrients affecting cell growth and biochemical composition of microalgae, ultimately determining the lipid or carbohydrate productivity for biofuels. In order to investigate the effect of nitrogen sources on the cell growth and biochemical composition of the marine microalga Tetraselmis sp., nine different N sources, including NaNO₃, KNO₃, NH₄NO₃, NH₄HCO₃, NH₄Cl, CH₃COONH₄, urea, glycine, and yeast extract were compared at the given concentration of 8.82 mM. Higher biomass concentration was achieved under organic nitrogen sources, such as yeast extract (2.23 g L⁻¹) and glycine (1.62 g L⁻¹), compared to nitrate- (1.45 g L⁻¹) or ammonium-N (0.98 g L⁻¹). All ammonium sources showed an inhibition of cell growth, but accumulated higher lipids, showing a maximum content of 28.3% in ammonium bicarbonate. When Tetraselmis sp. was cultivated using yeast extract, the highest lipid productivity of 36.0 mg L⁻¹ d⁻¹ was achieved, followed by glycine 21.5 mg L⁻¹ d⁻¹ and nitrate 19.9 mg L⁻¹ d⁻¹. Ammonium bicarbonate resulted in the lowest lipid productivity of 14.4 mg L⁻¹ d⁻¹. The major fatty acids in Tetraselmis sp. were palmitic, oleic, linoleic and linolenic acids, regardless of the nutritional compositions, indicating the suitability of this species for biodiesel production.

• ALGAE
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• v.31 no.3
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• pp.243-256
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• 2016

Concerns about how ocean acidification will impact marine organisms have steadily increased in recent years, but there is a lack of knowledge on the responses of macroalgae. Here, we adopt an outdoor continuous-flowing mesocosm system designed for ocean acidification experiment that allows high CO₂ conditions to vary with natural fluctuations in the environment. Following the establishment of the mesocosm, five species of macroalgae that are common along the coast of Korea (namely Ulva pertusa, Codium fragile, Sargassum thunbergii, S. horneri, and Prionitis cornea) were exposed to three different CO₂ concentrations: ambient (×1) and elevated CO₂ (2× and 4× ambient), over two-week period, and their ecophysiological traits were measured. Results indicated that both photosynthesis and growth exhibited species-specific responses to the different CO₂ concentrations. Most notably, photosynthesis and growth increased in S. thunbergii when exposed to elevated CO₂ conditions but decreased in P. cornea. The preference for different inorganic carbon species (CO₂ and HCO₃⁻), which were estimated by gross photosynthesis in the presence and absence of the external carbonic anhydrase (eCA) inhibitor acetazolamide, were also found to vary among species and CO₂ treatments. Specifically, the two Sargassum species exhibited decreased eCA inhibition of photosynthesis with increased growth when exposed to high CO₂ conditions. In contrast, growth of U. pertusa and C. fragile were not notably affected by increased CO₂. Together, these results suggest that the five species of macroalgae may respond differently to changes in ocean acidity, with species-specific responses based on their differentiated photosynthetic acclimation. Understanding these physiological changes might allow us to better predict future changes in macroalgal communities in a more acidic ocean.

• ALGAE
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• v.29 no.2
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• pp.153-163
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• 2014

Mesodinium rubrum is a cosmopolitan ciliate that often causes red tides. Predation by heterotrophic protists is a critical factor that affects the population dynamics of red tide species. However, there have been few studies on protistan predators feeding on M. rubrum. To investigate heterotrophic protists grazing on M. rubrum, we tested whether the heterotrophic dinoflagellates Gyrodiniellum shiwhaense, Gyrodinium dominans, Gyrodinium spirale, Luciella masanensis, Oblea rotunda, Oxyrrhis marina, Pfiesteria piscicida, Polykrikos kofoidii, Protoperidinium bipes, and Stoeckeria algicida, and the ciliate Strombidium sp. preyed on M. rubrum. G. dominans, L. masanensis, O. rotunda, P. kofoidii, and Strombidium sp. preyed on M. rubrum. However, only G. dominans had a positive growth feeding on M. rubrum. The growth and ingestion rates of G. dominans on M. rubrum increased rapidly with increasing mean prey concentration < $321ngCmL^{-1}$, but became saturated or slowly at higher concentrations. The maximum growth rate of G. dominans on M. rubrum was $0.48d^{-1}$, while the maximum ingestion rate was 0.55 ng C $predator^{-1}d^{-1}$. The grazing coefficients by G. dominans on populations of M. rubrum were up to $0.236h^{-1}$. Thus, G. dominans may sometimes have a considerable grazing impact on populations of M. rubrum.

• Environmental Engineering Research
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• v.20 no.1
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• pp.25-32
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• 2015

The growth of the algae strains Neochloris oleabundans, Botryococcus Braunii and Dunaliella sp. under mixotrophic conditions in the presence of different concentrations of crude glycerol was evaluated with the objective of increasing the biomass growth and algal oil content. A high biomass concentration was characteristic of these strains when grown on crude glycerol compared to autotrophic growth, and 5 g/L glycerol yielded the highest biomass concentration for these strains. Mixotrophic conditions improved both the growth of the microalgae and the accumulation of triacylglycerols (TAGs). The maximum amount of TAGs in the algal strains was obtained in the 5 g/L glycerol growth medium. The fatty acid profiles of the oil for the cultures met the necessary requirements and are promising resources for biofuel production.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.4
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• pp.597-603
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• 1999

Even though the development of livestock industry in Asia and Australasia has brought the economic growth and thus elevated the living standard in these areas, it has also brought the pollution caused by the increasing amount of animal wastes. Among them, Japan probably is the first country that suffered from the animal waste pollution as early as in 1970s. Nowadays, the animal waste pollution has been a common problem for almost every countries in this region. To solve it, different measures and regulations have been implemented in many countries. In this paper, different methods for animal waste disposal are discussed, including: manure-bed animal housing, composting, anaerobic treatment, odor control, utilization of biogas, aerobic treatment, three-step process, N and P removal, land application, cultivation of algae, anaerobic treatment of dead animals. It is hoped that an animal industry without pollution can be achieved in the future.

• ALGAE
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• v.25 no.3
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• pp.115-120
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• 2010

The natural growth of a population of Gomphosphaeria aponina Kutzing (Chroococcales, Cyanoprocaryota) was studied in a cemented freshwater tank in Allahabad, India. This population appeared to be a polymorphic species. Different species of the genus Gomphosphaeria have been segregated based on morphological features of colonies, cells and mucilage. However, these features are not well defined for different species. Our observations revealed many feature variations and, interestingly, certain features that have been described for different Gomphosphaeria species were seen in a single population. In this study, records of such variable morphological features were possible due to the availability of numerous specimens and continuous observations for more than two years. Further, this study revealed two points: (i) more detailed morphological studies are required both from nature as well as in culture to identify critical differences among the species, and (ii) molecular characterization of taxa appears to be necessary for final species settlement.

• ALGAE
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• v.20 no.4
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• pp.295-298
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• 2005

The growth of subaerial microalgae on historic buildings or various cultural properties causes discoloration and physico-chemical deterioration of the surfaces. We collected a subaerial chlorophyte, Chlorella sp., from the stone Standing Buddha statue at Jungwon Miruksazi, which is a national treasure of Korea, and found dormant, thickwalled spores with regular pentagonal ornamentation along with the vegetative Chlorella cells. The morphology of Chlorella resting spores was compared to that of the other green algal resting cells. The ornamented spores and smooth-walled vegetative cells revived in 2 weeks in a liquid freshwater medium and started reproduction by autospores. To our knowledge, the ability of Chlorella to form ornamented dormant spores in drought condition was not previously recorded. The ornamentation of spores would supplement taxonomic characteristics of this genus.