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Competition within the marine microalgae over the polar dark period in the Greenland Sea of high Arctic
Zhang Qing, Rolf Gradinger, Zhou Qingsong
2003(2): 233-242.
Keywords: Competition, marine microalgae, dark, the Greenland Sea, Arctic
With the onset of winter, polar marine microalgae would have faced total darkness for a period of up to 6 months. A natural autumn community of Arctic sea ice microalgae was collected for dark survival experiments from the Greenland Sea during the ARKTIS-XI/2 Expedition of RV Polarstern in October 1995. After a dark period of 161 days, species dominance in the algal assemblage have changed from initially pennate diatoms to small phytoflagellates (< 20 μm). Over the entire dark period, the mean algal growth rate was -0.01 d-1. Nearly all diatom species had negative growth rates, while phytoflagellate abundance increased. Resting spore formation during the dark period was observed in less than 4.5% of all cells and only for dinoflagellates and the diatom Chaetoceros spp. We assume that facultative heterotrophy and energy storage are the main processes enabling survival during the dark Arctic winter. After an increase in light intensity, microalgal cells reacted with fast growth within days. Phytoflagellates had the highest growth rate, followed by Nitzschia frigida. Further investigations and experiments should focus on the mechanisms of dark survival (mixotrophy and energy storage) of polar marine microalgae.
Differential gene expression in the body wall of the sea cucumber (Apostichopus japonicus) under strong lighting and dark conditions
ZHANG Libin, FENG Qiming, SUN Lina, FANG Yan, XU Dongxue, ZHANG Tao, YANG Hongsheng
2018, 37(5): 54-66. doi: 10.1007/s13131-017-1101-4
Keywords: sea cucumber, Apostichopus japonicus, gene expression, dark, light, body wall
Sea cucumber, Apostichopus japonicus is very sensitive to light changes. It is important to study the influence of light on the molecular response of A. japonicus. In this study, RNA-seq provided a general overview of the gene expression profiles of the body walls of A. japonicus exposed to strong light ("light"), normal light ("control") and fully dark ("dark") environment. In the comparisons of "control" vs. "dark", "control" vs. "light" and "dark" vs. "light", 1 161, 113 and 1 705 differentially expressed genes (DEGs) were identified following the criteria of|log2 ratio| ≥ 1 and FDR ≤ 0.001, respectively. Gene ontology analysis showed that "cellular process" and "binding" enriched the most DEGs in the category of "biological process" and "molecular function", while "cell" and "cell part" enriched the most DEGs in the category of "cellular component". And the DEGs were mapped to 214, 41 and 229 pathways in the Kyoto Encyclopedia of Genes and Genomes database, and 51, 2 and 57 pathways were significantly enriched, respectively. Light-specific DEGs identified in this study will be important targets for further investigation to establish the biochemical mechanisms involved in the adaption of this sea cucumber to changes in the level of environmental light.
Dark respiration in the light and in darkness of three marine macroalgal species grown under ambient and elevated CO2 concentrations
ZOU Dinghui, GAO Kunshan, XIA Jianrong
2011(1): 106-112. doi: 10.1007/s13131-011-0096-5
Keywords: marine macroalgae, respiration, CO2, carbon balance
Dark respiration (non-photorespiratory mitochondrial respiration), which occurs both in the light and in darkness, is vital for growth and survival of algae and plays a critical role in modulating the carbon balance of them. In the present study, we have investigated dark respiration in the light (RL) and in darkness (RD) in three marine macroalgal species, Hizikia fusiformis (phaeophyta), Gracilaria lemaneiformis (Rhodophyta) and Ulva lactuca (Chlorophyta), cultured at 20 ℃ using aeration with two CO2 conditions:current ambient (CO2 concentration about 380 μl/L) and elevated CO2 (approximately 720 μl/L) air. RL was estimated by using the Kok method, whereas RD was determined as the rate of O2 influx at zero light. The results showed that both RL and RD were unchanged for the elevated CO2-grown algae relative to ambient CO2 concentration for all the algal species tested. However, RL was significantly lower than RD across all the algal species and growth CO2 treatments, demonstrating that daytime respiration was partly depressed by the light. The percentage of inhibition of respiration by light was similar between ambient and elevated CO2-grown algae. The ratio of respiration to photosynthesis, which tended to decrease when estimated using RL instead of RD, was not altered for the elevated relative to ambient CO2 concentration. The results suggest that RL, rather than RD, is a more accurate estimate of nonphotorespiratory carbon loss in marine macroalgae during the daytime. It would not be anticipated that elevated atmospheric CO2 would exert a substantial influence on respiratory flux either in the light or in darkness in these particular marine macroalgal species.
Comparison of pigment composition and melanin content among white, light-green, dark-green, and purple morphs of sea cucumber, Apostichopus japonicus
XING Lili, SUN Lina, LIU Shilin, LI Xiaoni, MIAO Ting, ZHANG Libin, YANG Hongsheng
2017, 36(12): 45-51. doi: 10.1007/s13131-017-1056-5
Keywords: Apostichopus japonicas, pigment composition, color morphs, melanin, pigment content
Sea cucumber, Apostichopus japonicus (Selenka), is a commercially important marine species in China. Among the differently colored varieties sold in China, white and purple sea cucumbers have the greatest appeal to consumers. Identification of the pigments that may contribute to the formation of different color morphs of sea cucumbers will provide a scientific basis for improving the cultivability of desirable color morphs. In this study, sea cucumbers were divided into four categories according to their body color: white, light green, dark green, and purple. The pigment composition and contents in the four groups were analyzed by high performance liquid chromatography (HPLC). The results show that the pigment contents differed significantly among the white, light-green, dark-green, and purple sea cucumbers, and there were fewer types of pigments in white sea cucumber than in the other color morphs. The only pigments detected in white sea cucumbers were guanine and pteroic acid. Guanine and pteroic acid are structural colors, and they were also detected in light-green, dark-green, and purple sea cucumbers. Every pigment detected, except for pteroic acid, was present at a higher concentration in purple morphs than in the other color morphs. The biological color pigments melanin, astaxanthin, β-carotene, and lutein were detected in light-green, dark-green, and purple sea cucumbers. While progesterone and lycopene, which are also biological color pigments, were not detected in any of the color morphs. Melanin was the major pigment contributing to body color, and its concentration increased with deepening color of the sea cucumber body. Transmission electron microscopy analyses revealed that white sea cucumbers had the fewest epidermal melanocytes in the body wall, and their melanocytes contained fewer melanosomes as well as non-pigmented pre-melanosomes. Sea cucumbers with deeper body colors contained more melanin granules. In the body wall of dark-green and purple sea cucumbers, melanin granules were secreted out of the cell. The results of this study provide evidence for the main factors responsible for differences in coloration among white, light-green, dark-green, and purple sea cucumbers, and also provide the foundation for further research on the formation of body color in sea cucumber, A. japonicus.
The study of fluorescence characteristics and biochemical composition of a marine diatom Thalassiosira pseudonana 3H in light and dark cycles Ⅰ. The effects of nutrients
Zhu Mingyuan, Yang Xiaolong, J. J. Cullen
1992(4): 593-602.
The effects of nutrients on the fluorescence characteristics and biochemical composition of marine diatom Thalassiosira pseudonana 3H in light and dark cycles were investigated with continuous culture. The results show that with the increase of nutrient deficiency, the ratio of enhanced fluorescence to fluorescence (Fd/F), cellular chloropyll-a and protein content of the algae decline, but the fluorescence yield (F/Chl), DCMU enhanced fluorescence yield (Fd/Chl), cellular carbohydrate content, carbohydrate/Chl, protein/Chl, carbohydrate/protein increase. The changing amplitude of each parameter is different at different nutrition status, sampling time and different light intensity.
The study of fluorescence characteristics and biochemical composition of a marine diatom Thalassiosira pseudonana 3H in light and dark cycles-Ⅱ. The effects of light
Yang Xiaolong, Zhu Mingyuan, J. J. Cullen
1993(3): 457-464.
The effects of light on the fluorescence characteristics and biochemical composition of a marine diatom Tha-lassiosira pseudonana in light and dark cycles were investigated with semi-continuous culture.The results indicate that, with the increase of growing light intensity, DCMU enhanced fluorescence yield (Fd/Chl), enhanced fluorescence ratio (Fd/F), cellular carbohydrate content.carbohydrate/chlorophyll a and carbohydrate/protein ratio increased, but the fluorescence yield and cellular chlorophyll a content decreased; The protein content declined with the increase of light intensity in the range of 10-100 μmol/(m2·s) and increased at higher than 100 μmol/(m2·s).Sampling time during the day had great effect on the relationships between growing light intensity and cellular chlorophyll a, carbohydrate content, carbohydrate/chlorophyll a and carbohydrate/protein ratio.
Locomotor activity rhythm in the Japanese eel Anguilla japonica elvers
DOU Shuozeng, TSUKAMOTO Katsumi
2007(5): 76-89.
Keywords: activity rhythm, Japanese eel, light-dark cycle, temperature, zeitgeber
Under artificial LD cycles (6, 12, 18 L), the elvers of Japanese eel, Anguilla japonica, showed a 24 h cycle of locomotor activity rhythm being most active at light transitions:the eels' activity rose to a primary peak after lights-off, followed by a quiescent period during which they buried into the shelters or lying motionlessly on sand for most of the time, and then reached a secondary peak before lights-on.Elvers could resynchronize their activity rhythm with a new photo cycle within 4 d.Moreover, their activity level at dark phase significantly increased as the light period was prolonged:higher activity levels during shorter dark period.However, the elvers did not display clearly the existence of a circadian rhythm under constant light or dark conditions.The timing of daily activity rhythm evidenced in the Japanese eels may occur through the action of the LD cycles with a weak participation of an endogenous circadian system.In all the LD cycles, over 99% of the activity occurred in the dark phase, indicating that the eels were always nocturnally active no matter what time of day it might be.Under 12 L conditions, the eels' activity level and the time outside sand were significantly elevated both at light and dark phases as temperature increased from 10~15 to 20~25℃.The activity rhythm pattern (i.e., two peaks occurring around light transitions) did not apparently change among temperatures.However, in contrast with the primary activity peaks immediately after lights-off at 20 and 25℃, the timing of the primary peaks at 10 and 15℃ showed a latency of a few hours following lights-off, indicating the inhibiting effect of low temperature on the eels' activity.
Circadian rhythms in the growth and reproduction of the brown alga Undaria pinnatifida and gametogenesis under different photoperiods
ZHANG Zhihuai, PANG Shaojun
2007(4): 104-111.
Keywords: Undaria pinnatifida, circadian rhythm, egg release, gametogenesis
Circadian growth rhythm of the juvenile sporophyte of the brown alga Undaria pinnatifida was measured with the computer-aided image analysis system in constant florescent white light under constant temperature (10℃). The growth rhythm persisted for 4 d in constant light with a free-running period of 25.6 h. Egg release from filamentous gametophytes pre-cultured in the light-dark regime was evaluated for six consecutive days at fixed time intervals in constant white light and 12 h light per day. Egg release rhythm persisted for 3 d in both regimes, indicating the endogenous nature. Temporal scale of egg release and gametogenesis in 18, 16, 12 and 8 h light per day were evaluated respectively using vegetatively propagated filamentous gametophytes. Egg release occurred 2 h after the onset of dark phase and peaked at midnight. Evaluation of the rates of oogonium formation, egg release or fertilization revealed no significant differences in four light-dark regimes, indicating the great plasticity of sexual reproduction. No photoperiodic effect in gametogenesis in terms of oogonium formation and egg release was found, but fertilization in short days was significantly higher than in long days. Results of this investigation further confirmed the general occurrence of circadian rhythms in intertidal seaweed species.
A novel oil spill detection method from synthetic aperture radar imageries via a bidimensional empirical mode decomposition
YANG Yonghu, LI Ying, ZHU Xueyuan
2017, 36(7): 86-94. doi: 10.1007/s13131-017-1086-z
Keywords: bidimensional empirical mode decomposition, synthetic aperture radar image, detection of oil spill, hilbert spectral analysis
Oil spills pose a major threat to ocean ecosystems and their health. Synthetic aperture radar (SAR) sensors can detect oil spills on the sea surface. These oil spills appear as dark spots in SAR images. However, dark formations can be caused by a number of phenomena. It is aimed to distinguishing oil spills or look-alike objects. A novel method based on a bidimensional empirical mode decomposition is proposed. The selected dark formations are first decomposed into several bidimensional intrinsic mode functions and the residue. Subsequently, 64 dimension feature sets are calculated using the Hilbert spectral analysis and five new features are extracted with a relief algorithm. Mahalanobis distances are then used for classification. Three data sets containing oil spills or look-alikes are used to test the accuracy rate of the method. The accuracy rate is more than 90%. The experimental results demonstrate that the novel method can detect oil spills validly and accurately.
Optical remote sensing image characteristics of large amplitude convex mode-2 internal solitary waves: an experimental study
Zhixin Li, Meng Zhang, Keda Liang, Jing Wang
2023, 42(6): 16-23. doi: 10.1007/s13131-022-2145-7  Published:2023-06-25
Keywords: mode-2 internal solitary waves, optical remote sensing, characteristic parameter, wave characteristic
A series of experiments are designed to propose a new method to study the characteristics of convex mode-2 internal solitary waves (ISWs) in optical remote sensing images using a laboratory-based optical remote sensing simulation platform. The corresponding wave parameters of large-amplitude convex mode-2 ISWs under smooth surfaces are investigated along with the optical remote sensing characteristic parameters. The mode-2 ISWs in the experimentally obtained optical remote sensing image are produced by their overall modulation effect on the water surface, and the extreme points of the gray value of the profile curve of bright-dark stripes appear at the same location as the real optical remote sensing image. The present data extend to a larger range than previous studies, and for the characteristics of large amplitude convex mode-2 ISWs, the experimental results show a second-order dependence of wavelength on amplitude. There is a close relationship between optical remote sensing characteristic parameters and wave parameters of mode-2 ISWs, in which there is a positive linear relationship between the bright-dark spacing and wavelength and a nonlinear relationship with the amplitude, especially when the amplitude is very large, there is a significant increase in bright-dark spacing.
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