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Effects of residual chlorine on the mortality, grazing and respiration of Labidocera euchaeta (Copepoda)
MA Zengling, LIN Hongping, GU Xiaolian, XU Zhaoli
2011(2): 96-102. doi: 10.1007/s13131-011-0109-4
Keywords: copepod, grazing, Labidocera euchaeta, residual chlorine, respiration, zooplankton
In this study, the authors investigated the effects of residual chlorine on mortality, grazing and respiration of Labidocera euchaeta in laboratory. The grazing rate was evaluated by subtraction method of food concentration and respiration rate was measured using oxygen electrode. It was found that the lethal effect of residual chlorine on L. euchaeta increased with enhanced concentration and prolonged duration. The medium lethal concentration (LC50) of chlorine for L. euchaeta in 24 h was about 0.58 mg/L and the safe concentration was about 0.21 mg/L. However, the grazing and respiration of L. euchaeta decreased by 32.6% and 18.9% when exposed to 0.2 mg/L residual chlorine for 4 h. It indicated that the physiological activities of zooplankton could be suppressed by the residual chlorine less than the safety concentration. Therefore, both survival and physiological activities of the organisms living in the thermal (nuclear) power plant discharging waters should be considered when carrying out the ecological risks assessment.
Grazing and performance of the copepod Pseudodiaptomus poplesia on a Chinese strain of Aureococcus anophagefferens
HE Xuejia, HAN Didi, HAN Liuyu, LU Songhui
2018, 37(4): 69-76. doi: 10.1007/s13131-018-1168-6
Keywords: A. anophagefferens, copepod, grazing, growth, development, reproduction
Brown tides have recurred in estuary areas globally, but trophic interactions between the causative species Aureococcus anophagefferens and planktonic copepods remain poorly understood. In this study, we investigated performance (ingestion, growth, development and reproduction) of the planktonic copepod, Pseudodiaptomus poplesia, offered either mono-algal or mixed-algal diets containing a Chinese strain of A. anophagefferens. A typical Michaelis-Menten pattern existed between ingestion rate and food level when copepod fed on the mono-algal diet of this species. Nauplii exhibited the highest maximum ingestion rate (Imax) than copepodids and adult females. In addition, Imax value was higher in nauplii feeding on A. anophagefferens than on Skeletonema costatum. When fed mixtures of A. anophagefferens and S. costatum, P. poplesia selected against A. anophagefferens cells, but less strongly at the naupliar stage. Nauplii did not undergo metamorphosis and died at late naupliar stages feeding on A. anophagefferens alone, similar to those under starvation. Furthermore, the presence of A. anophagefferens greatly reduced the reproduction rate of females in mixtures but did not influence the growth rate of copepodids. These results suggest that P. poplesia nauplii may exert grazing pressure on A. anophagefferens population during a brown tide, which, however, may not be persistent because of copepod population decline.
Impacts of solar UV radiation on grazing, lipids oxidation and survival of Acartia pacifica Steuer (Copepod)
MA Zengling, LI Wei, GAO Kunshan
2012(5): 126-134. doi: 10.1007/s13131-012-0230-2
Keywords: Acartia pacifica, copepod, grazing, malonaldehyde (MDA), mortality, UVR
UV radiation is known to affect aquatic primary producers and their grazers. However, little has been documented on its effects on zooplankton grazing. In this study, the authors investigated the effects of photosynthetically active radiation (PAR, 400-700 nm), ultraviolet-A (UV-A, 320-400 nm) and ultraviolet-B (UV-B, 280-320 nm) radiation on grazing, mortality and lipids oxidation of the copepod Acartia pacifica collected from the Xiamen Bay. After 30 min of the exposures, the copepod was fed in darkness with the diatom Phaeodactylum tricornutum at two cell concentrations (2.5×104 and 2.5×105 cells/ml). At the low cell concentration, the individuals pre-exposed to PAR (218.0 W/m2)+UV-A (48.2 W/m2) or PAR+UV-A+UV-B (2.1 W/m2) showed suppressed clearance and grazing activities compared with those receiving PAR alone, by 22.7% and 17.1% for clearance and by 22.6% and 5.5% for grazing rates, respectively. However, the suppression on clearance and grazing became indistinctive at the high food concentration. Exposures to UV-A and UV-B led to increased lipid oxidation and higher mortality, furthermore, the mortality linearly increased with enhanced oxidation of lipid.
Grazing impact of microzooplankton on phytoplankton in the Xiamen Bay using pigment-specific dilution technique
HUANG Bangqin, LIU Yuan, XIANG Weiguo, TIAN Haojie, LIU Hongbin, CAO Zhenrui, HONG Huasheng
2008(5): 147-162.
Keywords: microzooplankton, growth rate, grazing mortality, photosynthetic pigments, Xiamen Bay, dilution method
Phytoplankton group-specific growth and microzooplankton grazing were determined seasonally using the dilution technique with high-performance liquid chromatography (HPLC) in the Xiamen Bay, a subtropical bay in southeast China, between May 2003 and February 2004. The results showed that growth rates of phytoplankton ranged from 0.71 to 2.2 d-1 with the highest value occurred in the inner bay in May. Microzooplankton grazing rates ranged from 0.5 to 3.1 d-1 with the highest value occurred in the inner bay in August. Microzooplankton grazing impact ranged from 39% to 95% on total phytoplankton Chl a biomass, and 65% to 181% on primary production. The growth and grazing rates of each phytoplankton group varied, the highest growth rate (up to 3.3 d-1) was recorded for diatoms in August, while the maximum grazing rate (up to 2.1 d-1) was recorded for chlorophytes in February in the inner bay. Among main phytoplankton groups, grazing pressure of microzooplankton ranged from 10% to 83% on Chl a biomass, and from 14% to 151% on primary production. The highest grazing pressure on biomass was observed for cryptophytes (83%) in August, while the maximum grazing pressure on primary production was observed for cyanobacteria (up to 151%) in December in the inner bay. Net growth rates of larger phytoplanktons (diatoms and dinoflagellates) were higher than those of smaller groups (prasinophytes, chlorophytes and cyanobacteria). Relative preference index showed that microzooplankton grazed preferentially on prasinophytes and avoided to harvest diatoms in cold seasons (December and February).
Phytoplankton growth and microzooplankton grazing in the central and northern South China Sea in the spring intermonsoon season of 2017
Dawei Chen, Congcong Guo, Linhui Yu, Yuanzhen Lu, Jun Sun
2020, 39(6): 84-95. doi: 10.1007/s13131-020-1593-1  Published:2020-06-25
Keywords: dilution technique, phytoplankton growth, microzooplankton grazing, South China Sea, spring intermonsoon season
Phytoplankton growth rates and mortality rates were experimentally examined at 21 stations during the 2017 spring intermonsoon (April to early May) in the northern and central South China Sea (SCS) using the dilution technique, with emphasis on a comparison between the northern and central SCS areas which had different environmental factors. There had been higher temperature but lower nutrients and chlorophyll a concentrations in the central SCS than those in the northern SCS. The mean rates of phytoplankton growth (μ0) and microzooplankton grazing (m) were (0.88±0.33) d–1 and (0.55±0.22) d–1 in the central SCS, and both higher than those in the northern SCS with the values of μ0 ((0.81±0.16) d–1) and m ((0.30±0.09) d–1), respectively. Phytoplankton growth and microzooplankton grazing rates were significantly coupled in both areas. The microzooplankton grazing impact (m/μ0) on phytoplankton was also higher in the central SCS (0.63±0.12) than that in the northern SCS (0.37±0.06). The microzooplankton abundance was significantly correlated with temperature in the surface. Temperature might more effectively promote the microzooplankton grazing rate than phytoplankton growth rate, which might contribute to higher m and m/μ0 in the central SCS. Compared with temperature, nutrients mainly affected the growth rate of phytoplankton. In the nutrient enrichment treatment, the phytoplankton growth rate (μn) was higher than μ0 in the central SCS, suggesting phytoplankton growth in the central SCS was nutrient limited. The ratio of μ0/μn was significantly correlated with nutrients concentrations in the both areas, indicating the limitation of nutrients was related to the concentrations of background nutrients in the study stations.
Studies on growth rate and grazing mortality rate by microzooplankton of size-fractionated phytoplankton in spring and summer in the Jiaozhou Bay, China
ZHANG Liyong, SUN Jun, LIU Dongyan, YU Zishan
2005(2): 85-101.
Keywords: microzooplankton, phytoplankton, selective grazing, carbon to chlorophyll-a ratio, grazing pressure, Jiaozhou Bay
Dilution experiments were performed to examine the growth rate and grazing mortality rate of size-fractionated phytoplankton at three typical stations, inside and outside the bay, in the spring and summer of 2003 in the Jiaozhou Bay, China. In spring, the phytoplankton community structure was similar among the three stations, and was mainly composed of nanophytoplankton, such as, Skeletonema costatum and Cylindrotheca closterium. The structure became significantly different for the three stations in summer, when the dominant species at Stas A, B and C were Chaetoceros curvisetus, Pseudo-nitzschia delicatissima, C. affinis, C. debilis, Coscinodiscus oculus-iridis and Paralia sulcata respectively. Tintinnopsis beroidea and T. tsingtaoensis were the dominant species in spring, whereas the microzooplankton was apparently dominated by Strombidium sp. in summer. Pico-and nanophytoplankton had a relatively greater growth rate than microzooplankton both in spring and summer. The growth rate and grazing mortality rate were 0.18~0.44 and 0.12~1.47 d-1 for the total phytoplankton and 0.20~0.55 and 0.21~0.37 d-1 for nanophytoplankton in spring respectively. In summer,the growth rate and grazing mortality rate were 0.38~0.71 and 0.27~0.60 d-1 for the total phytoplankton and 0.11~1.18 and 0.41~0.72d-1 for nano-and microphytoplankton respectively. The carbon flux consumed by microzooplankton per day was 7.68~39.81 mg/m3 in spring and 12.03~138.22 mg/m3 in summer respectively. Microzooplankton ingested 17.56%~92.19% of the phytoplankton standing stocks and 31.77%~467.88% of the potential primary productivity in spring; in contrast, they ingested 34.60%~83.04% of the phytoplankton standing stocks and 71.28%~98.80% of the potential primary productivity in summer. Pico-and nanophytoplankton appeared to have relatively greater rates of growth and grazing mortality than microphytoplankton during the experimental period. The grazing rate of microzooplankton in summer was a little bit greater than that in spring because of the relatively higher incubation temperature and different dominant microzooplankton species. Microzooplankton preferred ingesting nanophytoplankton to microphytoplankton in spring, while they preferred ingesting picophytoplankton to nanophytoplankton and microphytoplankton in summer. Compared with the results of dilution experiments performed in various waters worldwide, the results are in the middle range.
A statistical distribution of quad-pol X-band sea clutter time series acquired at a grazing angle
WANG Yunhua, LI Qun, ZHANG Yanmin
2018, 37(3): 94-102. doi: 10.1007/s13131-018-1202-8
Keywords: sea clutter, quad-pol coherent X-band radar, statistical distribution function
Although the complex Wishart distribution has been widely used to analyze the statistic properties of quad-pol SAR spatial data, the applicability of this complex distribution to the time series of sea clutter is rarely discussed. The measured data of the quad-pol X-band marine radar demonstrate that the time series of the sea echoes are also satisfied the circular Gaussian distributions if the low intensity signals, which are mainly dominated by a radar noise, in the shadow regions of the large-scale waves are removed. On the basis of this fact, the probability density functions (PDFs) of the intensity as well as the phase, the real and the imaginary parts of the sea echoes obtained by the marine radar have been derived, and the theoretical models are all expressed in closed forms. In order to validate the theoretical results, the PDFs are compared with the experimental data collected by the McMaster IPIX radar. And the comparisons show that the PDF models are in good agreement with the experimental data.
Sea-surface acoustic backscattering measurement at 6–25 kHz in the Yellow Sea
Lehua Qi, Guangming Kan, Baohua Liu, Yanliang Pei, Zhiguo Yang, Shengqi Yu
2020, 39(3): 113-122. doi: 10.1007/s13131-020-1539-7  Published:2020-03-25
Keywords: sea-surface acoustic scattering, moderate frequency, scattering model, bistatic backscattering, frequency dependence
Sea-surface acoustic backscattering measurements at moderate to high frequencies were performed in the shallow water of the south Yellow Sea, using omnidirectional spherical sources and omnidirectional hydrophones. Sea-surface backscattering data for frequencies in the 6–25 kHz range and wind speeds of (3.0±0.5) and (4.5±1.0) m/s were obtained from two adjacent experimental sites, respectively. Computation of sea-surface backscattering strength using bistatic transducer is described. Finally, we calculated sea-surface backscattering strengths at grazing angles in the range of 16°–85°. We find that the measured backscattering strengths agree reasonably well with those predicted by using second order small-roughness perturbation approximation method with “PM” roughness spectrum for all frequencies at grazing angles ranged from 40° to 80°. The backscattering strengths varied slightly at grazing angles of 16°–40°, and were much stronger than roughness scattering. It is speculated that scattering from bubbles dominates the backscattering strengths at high wind speeds and small grazing angles. At the same frequencies and moderate to high grazing angles, the results show that the backscattering strengths at a wind speed of (4.5±1.0) m/s were approximately 5 dB higher than those at a wind speed of (3.0±0.5) m/s. However, the discrepancies of backscattering strength at low grazing angles were more than 10 dB. Furthermore the backscattering strengths exhibited no significant frequency dependence at 3 m/s wind speed. At a wind speed of 4.5 m/s, the scattering strengths increased at low grazing angles but decreased at high grazing angles with increasing grazing angle.
THE BOTTOM REFLECTION OF CONTINENTAL SHELF
JIANG SHENGLI, SHANG ERCHANG
1985(3): 359-373.
This paper analyses the seabed reflection coefficient of the "geoacoustic model" of continental terrace in shallow water, which includes two kinds of parametres:the "type parameters" and the "structure parameters".
For small grazing angle, the "structure parameters" become nonsensitive in a certain band of sound frequency and the reflection coefficient is determined by the "type parameters".However, the former are sensitive for "low sound speed" sea floors.
For large grazing angle, the "structure parameters" affect sound reflection character greatly.
Acoustic backscattering measurement from sandy seafloor at 6–24 kHz in the South Yellow Sea
KAN Guangming, LIU Baohua, YANG Zhiguo, YU Shengqi, QI Lehua, YU Kaiben, PEI Yanliang
2019, 38(5): 99-108. doi: 10.1007/s13131-019-1388-4
Keywords: acoustic backscattering strength, sandy bottom, South Yellow Sea, gazing angle dependence, frequency dependence
The acoustic bottom backscattering strength was measured at the frequency range of 6-24 kHz on a typical sandy bottom in the South Yellow Sea by using omnidirectional sources and omnidirectional receiving hydrophones. In the experiment, by avoiding disturbances due to scattering off the sea surface and satisfying the far-field condition, we obtained values of acoustic bottom backscattering strength ranging from -41.1 to -24.4 dB within a grazing angle range of 18°-80°. In the effective range of grazing angles, the acoustic scattering strength generally increases with an increase in the grazing angles, but trends of the variation were distinct in different ranges of frequency, which reflect different scattering mechanisms. The frequency dependence of bottom backscattering strength is generally characterized by a positive correlation in the entire frequency range of 6-24 kHz at the grazing angles of 20°, 40° and 60° with the linear regression slopes of 0.222 9 dB/kHz, 0.513 0 dB/kHzand 0.174 6 dB/kHz, respectively. At the largest grazing angle of 80°, the acoustic backscattering strength exhibits no evident frequency dependence.
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