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Selected AbstractsFeeding efficiency of white bream at different inorganic turbidities and light climatesJOURNAL OF FISH BIOLOGY, Issue 2 2007Z. Pekcan-Hekim Experiments were conducted to test the effects of turbidity (10,50 NTU) and light (0,2 ,E m,2 s,1) on the feeding efficiency of white bream Abramis björkna preying on Chaoborus flavicans. Increased turbidity and low light levels did not have a significant impact on the feeding of white bream. In total darkness feeding was impeded indicating that white bream depends on vision for feeding. The dominance of white bream in temperate eutrophic lakes could be attributed to their success of feeding in turbid and low light environments. [source] NITROGEN ENRICHMENT OF PORPHYRA PERFORATA THROUGH HIGH DOSE PULSE FERTILIZATIONJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Zertuche-González, J. A1., Chanes-Miranda L2., Carmona, R3., Kraemer G4., Chopin T.5 & Yarish, C3 1Universidad Autonoma de Baja California, Instituto de Investigaciones Oceanologicas, PO Box #453, C.P. 22830, Ensenada, Baja California, Mexico. 2CBTIS-41, Km 115 Carretera Transpeninsular, Ensenada, BC Mexico. 3University of Connecticut, Department of Ecology and Evolutionary Biology, 1 University Place, Stamford, CT, 06901-2315, USA. 4State University of New York, Purchase College, Div. of Nat. Sciences, Purchase, NY, 10577, USA. 5University of New Brunswick, Centre for Coastal Studies and Aquaculture and Centre for Environmental and Molecular Algal Research, P.O. Box 5050, Saint John, New Brunswick, E2L 4L5, Canada Porphyra perforata is a highly preferred seaweed used as fodder in abalone culturing due to its relatively high nutritional value. High growth rates of abalone, particularly in the early stages, are suspected to be due the high protein-aminoacid and low water content of the Porphyra. Also, high NO3 content may be important to improve the bacterial flora in the animals, which in turn may favor more efficient digestion. Changes in the composition of Porphyra, however, can occur rapidly due to environmental conditions decreasing the nutritional value of the plant. Short term N pulse fertilization were performed on P. perforata in order to evaluate the feasibility to increase its nutritional value. Enrichment was performed under low light conditions (<5 ,E m -2 s -1) to inhibit growth and promote higher N enrichment per unit of biomass. Tissue N in the form of NO3, NH4 and total organic N were measured, after 3,6,12 and 24 hrs, in tissue exposed to 500 ,M of N. Results indicated a rapid N tissue enrichment particularly in the form of NO3. Nitrate accumulation occurs continuously, up to 24 hrs. Total organic N is maximum after 12 hrs and tends to decrease after that. Fertilization with NH4 promotes NO3 accumulation. These results suggest the feasibility to improve the nutritional value of P. perforata by short-term pulse fertilization. The capacity of this species to uptake NH4 under low light conditions (similar to those use in abalone culturing) makes it also ideal for integrated aquaculture. [source] PRELIMINARY ANALYSIS OF QUANTITATIVE GENETICS AND PHENOTYPIC PLASTICITY IN AULACOSEIRA SUBARCTICA (BACILLAR-IOPHYTA)JOURNAL OF PHYCOLOGY, Issue 2000S. M. Edgar Several clones of Aulacoseira subarctica were isolated from Yellowstone, Lewis, and East Rosebud Lakes (Montana, Wyoming). Two to four clones from each lake were grown in batch cultures under three light intensities, 2, 11.4 and 115 ,E m,2 s,1. Clones were conditioned to their light environment for a three-week period. Inoculants from the conditioned clones taken during log phase of growth, were grown until in log phase, then samples were collected. Five randomly chosen valves for 2 replicates of each clone were examined using a scanning electron microscope and captured on film at a magnification of 20,000x. Each image was digitized and quantitative morphometric characters were measured. A preliminary quantitative genetic analysis was performed on selected characters within each light environment. Plasticity of characters within clones across the three light regimes were also examined. The amount of variability found within characters in A. subarctica will be discussed in terms of environmental, genetic, and microenvironmental sources. [source] The Effect of Decreasing Temperature up to Chilling Values on the in vivo F685/F735 Chlorophyll Fluorescence Ratio in Phaseolus vulgaris and Pisum sativum: The Role of the Photosystem I Contribution to the 735 nm Fluorescence Band ,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2000Giovanni Agati ABSTRACT The effect of leaf temperature (T), between 23 and 4°C, on the chlorophyll (Chl) fluorescence spectral shape was investigated under moderate (200 ,E m,2 s,1) and low (30,35 ,E m,2 s,1) light intensities in Phaseolus vulgaris and Pisum sativum. With decreasing temperature, an increase in the fluorescence yield at both 685 and 735 nm was observed. A marked change occurred at the longer emission band resulting in a decrease in the Chl fluorescence ratio, F685/F735, with reducing T. Our fluorescence analysis suggests that this effect is due to a temperature-induced state 1,state 2 transition that decreases and increases photosystem II (PSII) and photosystem I (PSI) fluorescence, respectively. Time-resolved fluorescence lifetime measurements support this interpretation. At a critical temperature (about 6°C) and low light intensity a sudden decrease in fluorescence intensity was observed, with a larger effect at 685 than at 735 nm. This is probably linked to a modification of the thylakoid membranes, induced by chilling temperatures, which can alter the spillover from PSII to PSI. The contribution of photosystem I to the long-wavelength Chl fluorescence band (735 nm) at room temperature was estimated by both time-resolved fluorescence lifetime and fluorescence yield measurements at 685 and 735 nm. We found that PSI contributes to the 735 nm fluorescence for about 40, 10 and 35% at the minimal (F0), maximal (Fm) and steady-state (Fs) levels, respectively. Therefore, PSI must be taken into account in the analysis of Chl fluorescence parameters that include the 735 nm band and to interpret the changes in the Chl fluorescence ratio that can be induced by different agents. [source] The Effect of Irradiance on Carboxylating/Decarboxylating Enzymes and Fumarase Activities in Mesembryanthemum crystallinum L. Exposed to Salinity StressPLANT BIOLOGY, Issue 1 2001Z. Miszalski Abstract: In Mesembryanthemum crystallinum plants, treated for 9 days with 0.4 M NaCl at low light intensities (80 - 90 or 95 - 100 ,E m -2 s -1; , = 400 - 700 nm), no day/night malate level differences (,malate) were detected. At high light (385 - 400 ,E m -2 s -1) strong stimulation of PEPC activity, accompanied by a ,malate of 11.3 mM, demonstrated the presence of CAM metabolism. This indicates that, to evolve day/night differences in malate concentration, high light is required. Salt treatment at low light induces and increases the activity of NAD- and NADP-malic enzymes by as much as 3.7- and 3.9-fold, while at high light these values reach 6.4- and 17.7-fold, respectively. The induction of activity of both malic enzymes and PEPC (phospoenolpyruvate carboxylase) take place before ,malate is detectable. An increase in SOD (superoxide dismutase) was observed in plants cultivated at high light in both control and salt-treated plants. However, in salt-treated plants this effect was more pronounced. Carboxylating and decarboxylating enzymes seem to be induced by a combination of different signals, i.e., salt and light intensity. Plants performing CAM, after the decrease of activity of both the decarboxylating enzymes at the beginning of the light period, showed an increase in these enzymes in darkness when the malate pool reaches higher levels. In CAM plants the activity of fumarase (Krebs cycle) is much lower than that in C3 plants. The role of mitochondria in CAM plants is discussed. [source] Mixotrophy in the Phototrophic Harmful Alga Cochlodinium polykrikoides (Dinophycean): Prey Species, the Effects of Prey Concentration, and Grazing ImpactTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 5 2004HAE JIN JEONG ABSTRACT We first reported here that the harmful alga Cochlodinium polykrikoides, which had been previously known as an autotrophic dinoflagellate, was a mixotrophic species. We investigated the kinds of prey species and the effects of the prey concentration on the growth and ingestion rates of C. polykrikoides when feeding on an unidentified cryptophyte species (Equivalent Spherical Diameter, ESD = 5.6 ,m). We also calculated grazing coefficients by combining field data on abundances of C. polykrikoides and co occurring cryptophytes with laboratory data on ingestion rates obtained in the present study. Cocholdinium polykrikoides fed on prey cells by engulfing the prey through the sulcus. Among the phytoplankton prey offered, C. polykrikoides ingested small phytoplankton species that had ESD's , 11 ,m (e.g. the prymnesiophyte Isochrysis galbana, an unidentified cryptophyte, the cryptophyte Rhodomonas salina, the raphidophyte Heterosigma akashiwo, and the dinoflagellate Amphidinium carterae). It did not feed on larger phytoplankton species that had ESD's , 12 ,m (e.g. the dinoflagellates Heterocapsa triquetra, Prorocentrum minimum, Scrippsiella sp., Alexandrium tamarense. Prorocentrum micans, Gymnodinium catenatum, Akashiwo sanguinea, and Lingulodinium polyedrum). Specific growth rates of C. polykrikoides on a cryptophyte increased with increasing mean prey concentration, with saturation at a mean prey concentration of approximately 270 ng C ml,1 (i.e. 15,900 cells ml,1)- The maximum specific growth rate (mixotrophic growth) of C. polykrikoides on a cryptophyte was 0.324 d,', under a 14:10 h light-dark cycle of 50 ,E m,2 s,1, while its growth rate (phototrophic growth) under the same light conditions without added prey was 0.166 d,. Maximum ingestion and clearance rates of C. polykrikoides on a cryptophyte were 0.16 ng C grazer,1d 1 (9.4 cells grazer 1d,1) and 0.33 ,1 grazer 1h,1, respectively. Calculated grazing coefficients by C. polykri koides on cryptophytes were 0.001,0.745 h,1 (i.e. 0.1,53% of cryptophyte populations were removed by a C. polykrikoides population in 1 h). The results of the present study suggest that C. polykrikoides sometimes has a considerable grazing impact on populations of cryptophytes. [source] | ||||||||||