Peculiarities of summer phytoplankton spatial distribution in Onega Bay of the White Sea under local hydrophysical conditions

The species composition and phytoplankton biomass, concentrations of chlorophyll “a” (Chl) and nutrients in the surface water layer, and accompanying hydrophysical conditions were studied in Onega Bay of the White Sea in June 2015. The temperature and salinity of surface water layer and the water column stability varied greatly in the bay. The nutrients' concentrations exceeded the limiting threshold necessary for the phytoplankton development. The phytoplankton abundance was relatively low, averaged as 13.46 ± 9.00 mg C/m³ (total phytoplankton biomass), 0.78 ± 0.43 mg/m³ (concentration of chlorophyll “a”), and 0.18 ± 0.27 mg C/m³ (picophytoplankton biomass). The highest phytoplankton biomass has been registered along the frontal zones. Three phytoplankton communities that differed significantly in their structure have been found.     

Community structure and competition between plankton algae of the White Sea using different nitrogen substrates

Phytoplankton was studied in the Kandalaksha Bay, White Sea, and exposed in situ for 18 days with the addition of 180 micromol of nitrogen in the form of nitrate, urea, ammonium, and glycine. Species composition, abundance, and biomass of algae were estimated every three days. After the enrichment, the abundance of phytoplankton increased, and its structure changed. On the 18th day of the experiment, the biomass of phytoplankton communities assimilating different nitrogen substrates was subequal. Because all the environmental factors except nitrogen substrates were identical and the level of grazing was insignificant, the similarity of the dynamics of phytoplankton assimilating organic and nitrogen demonstrates that the algae compete for organic nitrogen. Competitive parameters of algae were related to the form of nitrogen source. For instance, the competitive ability of Cylindrotheca closterium was the highest in communities that assimilated organic nitrogen, while the competitive ability of Licmophora oedipus was the highest in communities that assimilated nitrate. The competitive ability of species also depended on the type of organic substrate. For example, in L. oedipus the ability to compete for urea was higher than the ability to compete for glycine. On the contrary, in small pennate diatoms and in Nitzschia sp. the ability to compete for glycine was higher.     

空气 NH3增高和不同氮源供应下大叶相思叶片光合参数的变化

生长在空气 NH3增高下 45 d的 NOˉ3- N大叶相思植株 ,其光饱和光合速率较对照的植株高 ;而生长在空气 NH3增高下的 NH 4- N和 NH4 NO3- N的大叶相思 ,当光强在 70 0 μmol·m- 2 ·s- 1左右时 Pn 达到最大值 ,较对照植株的要高。而当光强 >70 0 μmol·m- 2·s- 1时 ,Pn 降低 ,且较生长在对照条件下的低。表明在空气 NH3增高下生长的 NH 4- N和 NH4 NO3- N植株 ,其净光合速率 Pn会受到强光抑制。空气 NH3增高并不明显改变光呼吸 ( Rd)和无光呼吸下的 CO2 补充点 (Γ* )。无论生长在何种氮源下的大叶相思 ,其最大Ru BP饱和羧化速率 ( Vcmax)和最大电子传递速率 ( Jmax)均较生长在对照植株的高 ( P<0 .0 5 ) ,其叶氮含量亦较高 ( P<0 .0 5 ) ,其碳氮比较对照的低。在空气 NH3增高下 ,无论何种氮源生长的大叶相思 ,其 PR和 PB明显高于对照的植株 ,表明大叶相思能从空气 NH3中摄取和同化氮 ,增加氮积累和有利于 Rubisco和电子传递组分的合成 ,增高光合速率。空气 NH3增高可能有利于 Rubisco和电子传递组分的合成 ,在较低光强下能增高光合速率。空气 NH3增高可能有利于退化生态系统的生态恢复过程中的氮积累和先锋植物的早期生长。     

Fluorescence depolarization studies of melanosomal membranes from different sources

In the present paper we report a comparative study of physical properties and biochemical composition of isolated melanosomal membranes extracted from bovine eyes and from an equine spleen melanoma. Some biophysical characteristics of such membranes were obtained by steady-state and time resolved fluorescence spectroscopy using DPH as fluorescent probe. By these methods we have measured both static fluorescence polarization and fluorescence lifetimes and from the experimental data we have calculated the rotational correlation times by Perrin's equation. Since dynamic and static parameters, such as fluidity and molecular order, can be determined by these methods, the results are discussed on the basis of the recent theories of the role of the biochemical composition in the molecular structure and properties of membranes.     

Response of Anabaena species to different nitrogen sources

Nitrogenase activity, ammonia excretion and glutamine synthetase (GS) activity were examined in five strains of Anabaena (A. anomala ARM 314, A. fertilissima ARM 742, A. variabilis ARM 310, A. oryzae ARM 313 and A. oryzae ARM 570) in the presence of 2.5 mM NO3-N (KNO3), 2.5 mM NH-4-N [(NH4)2SO4] and diatomic nitrogen (N2). Ammonium-N was more inhibitory to nitrogenase activity as compared to NO3-N in all the strains. Maximum GS activity was exhibited in NO3-N medium, irrespective of the cyanobacterial strains studied. Uninduced release of ammonia was observed in all the species, with A. oryzae ARM 313 and Anabaena variabilis ARM 310 exhibiting maximum excretion of 0.25-0.31 and 0.27-1.23 mu moles NH4 mg Chl(-1) respectively on the 15th day of incubation. The glutamine synthetase activity of A. oryzae ARM 313 was relatively very high as compared to Anabaena variabilis ARM 310. There was no nitrate reductase activity in any of the Anabaena sp. grown on NH3-N or N2-N on the 15th day of incubation.     

Changes in bacterioplankton composition under different phytoplankton regimens

The results of empirical studies have revealed links between phytoplankton and bacterioplankton, such as the frequent correlation between chlorophyll a and bulk bacterial abundance and production. Nevertheless, little is known about possible links at the level of specific taxonomic groups. To investigate this issue, seawater microcosm experiments were performed in the northwestern Mediterranean Sea. Turbulence was used as a noninvasive means to induce phytoplankton blooms dominated by different algae. Microcosms exposed to turbulence became dominated by diatoms, while small phytoflagellates gained importance under still conditions. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments showed that changes in phytoplankton community composition were followed by shifts in bacterioplankton community composition, both as changes in the presence or absence of distinct bacterial phylotypes and as differences in the relative abundance of ubiquitous phylotypes. Sequencing of DGGE bands showed that four Roseobacter phylotypes were present in all microcosms. The microcosms with a higher proportion of phytoflagellates were characterized by four phylotypes of the Bacteroidetes phylum: two affiliated with the family Cryomorphaceae and two with the family Flavobacteriaceae. Two other Flavobacteriaceae phylotypes were characteristic of the diatom-dominated microcosms, together with one Alphaproteobacteria phylotype (Roseobacter) and one Gammaproteobacteria phylotype (Methylophaga). Phylogenetic analyses of published Bacteroidetes 16S rRNA gene sequences confirmed that members of the Flavobacteriaceae are remarkably responsive to phytoplankton blooms, indicating these bacteria could be particularly important in the processing of organic matter during such events. Our data suggest that quantitative and qualitative differences in phytoplankton species composition may lead to pronounced differences in bacterioplankton species composition.     

Fluorescence parameters of marine plankton algae at the assimilation of organic nitrogen

fluorescence parameters of marine plankton algae Pseudo-nitzschis delicatissima, Thalassiosira weissflogii, and Tetraselmis viridis were estimated after the addition of organic (urea and glycine) and inorganic (nitrate and ammonia) nitrogen to nitrogen-limited cultures acclimated to limited and saturated irradiance. The photochemical efficiency of photosystem 2, the maximum relative electron transport, and the light saturation index increased in the algae assimilating organic nitrogen. The dynamics of parameters depended species specifically on the nitrogen source and irradiance. The ecological role of organic nitrogen in the seasonal dynamics and vertical distribution of phytoplankton is discussed.     

Cryobiological parameters of multipotent stromal cells obtained from different sources

Stem cells are important for regenerative medicine mainly due to their multilineage differentiation capacity. However, the cells rapidly loose this capability during culturing. Cryopreservation preserves the differentiation potential of the cells, until they are needed. In this study, specific cell properties of multipotent stromal cells (MSCs), from the common marmoset monkey Callithrix jacchus MSCs derived from amnion (Am) and bone marrow (Bm) were studied in order to predict optimal cooling rates for cryopreservation. Cell volume behaviour in anisotonic media, hydraulic membrane permeability at supra as well as subzero temperatures, and time point of intracellular ice formation (IIF) were investigated by Coulter Counter and cryomicroscopy. Cryopreservation outcome was studied using the predicted and experimentally determined cooling rate followed by 24 h re-cultivation. Little differences in osmotically inactive volume were found between amnion (0.27 × V_o) and bone marrow (0.28 × V_o) derived MSCs. The activation energy for water transport at suprazero temperature was found to be similar for both cell types; 4.4 ± 0.2 and 5.0 ± 0.15 kcal mol⁻¹ for amnion and bone marrow derived MSCs, respectively. At subzero temperatures in the absence of dimethyl sulfoxide (Me₂SO), the activation energy for water transport increased to 24.8 ± 3 kcal mol⁻¹ and 27.4 ± 0.9 kcal mol⁻¹ for Am and BmMSCs respectively. In the presence of Me₂SO, activation energies were found to be 11.6 ± 0.3 kcal mol⁻¹ and 19.5 ± 0.5 kcal mol⁻¹ respectively. Furthermore, Me₂SO was found to decrease the incidence of intracellular ice formation. The predicted optimal cooling rates of 11.6 ± 0.9 °C/min (AmMSCs) and 16.3 ± 0.5 °C/min (BmMSCs) resulted in similar post-thaw viability values compared to the experimentally determined optimal cooling profiles of 7.5 °C/min to −30 °C, followed by 3 °C/min to −80 °C.     

Isolate-specific conidiation in Trichoderma in response to different nitrogen sources

A characteristic feature of Trichoderma is the production of concentric rings of conidia in response to alternating light/dark conditions and a single ring of conidia in response to a single burst of light. In this study, conidiation was investigated in four biocontrol isolates (T. hamatum, T. atroviride, T. asperellum, T. virens) and one isolate from the mushroom pathogen species, T. pleuroticola. All five isolates produced concentric conidial rings under alternating light/dark conditions on potato-dextrose agar (PDA), however, in response to a 15min burst of blue light, only T. asperellum and T. virens produced a clearly defined conidial ring. Both T. pleuroticola and T. hamatum photoconidiated in a disk-like fashion and T.?atroviride produced a broken ring with a partially filled in appearance. In the presence of primary nitrogen, T. asperellum and T. pleuroticola conidiated in a disk, whereas, when grown in the presence of secondary nitrogen, a ring of conidia was produced. Primary nitrogen promoted photoconidiation and competency to conidiate in response to light appeared dependent on the nitrogen catabolite repression state of the cell. Mycelial injury was also investigated in the same five isolates of Trichoderma on PDA and under different nitrogen statuses. For the first time, we report that conidiation in response to injury is differentially regulated in different isolates/species of Trichoderma.     

Growth and nitrogen metabolism of Catasetum fimbriatum (orchidaceae) grown with different nitrogen sources

Catasetum fimbriatum is an epiphytic orchid from South America that has been used for 15 years as a model plant for metabolic and developmental studies in our laboratory. In this work, C. fimbriatum plants were aseptically grown with 6 mol m(-3) of either glutamine or inorganic nitrogen forms (NO(3)(-):NH(4)(+) ratios). The highest biomass accumulation was found in plants supplied with glutamine; no significant difference was observed in plants incubated in the presence of inorganic nitrogen sources. Nitrogen assimilation was limited in the presence NO(3)(-) as a sole nitrogen source. C. fimbriatum did not accumulate NO(3)(-) and very low rates of in vivo nitrate reductase activity were observed. Most nitrate reductase activity (70%) was detected in the 2 cm apical roots. Nitrate-treated plants exhibited relatively lower amounts of free amino-N, chlorophyll and free NH(4)(+) contents and higher soluble sugar contents than the NH(4)(+)-treated plants. While shoot glutamine synthetase activity was only slightly affected by nitrogen sources, root glutamine synthetase activity was not modified by any nitrogen form. Glutamate dehydrogenase-NADH activity in shoot tissues was not influenced by any nitrogen source. However, the glutamate dehydrogenase-NADH activity in roots was enhanced when NH(4)(+) tissue contents was augmented by increasing NH(4)(+) in the medium and by the presence of glutamine. Our results strongly suggest that organic nitrogen and NH(4)(+) are probably the most important nitrogen sources to C. fimbriatum plants.     

不同无机氮源对东海原甲藻生长的影响

在实验室条件下,研究了不同浓度、不同形态的氮(NaNO₃、NH₄Cl和NaNO₂)对东海原甲藻(Prorocentrum donghaiense)生长的影响。结果表明:在NH₄Cl浓度为5.20μmol·L^-1(N/P为8)时藻的比生长率最高,而N/P为32和100时,藻的生长明显受到抑制。在NaNO₃为氮源时,最适N/P为12(氮浓度为7.80μmol·L^-1)。而NaNO₂作氮源,N/P为16(10.40μmol·L^-1)时藻的比生长率最高,N/P为32和100时藻的生长也明显受到抑制。研究显示,东海原甲藻对无机氮NH₄Cl和NaNO₃和NaNO₂都可以利用,最适生长的N/P比范围在8～20之间,相对高的N/P(32、100)不利于东海原甲藻的生长。     

Effect of different nitrogen and carbon sources on the proteolytic activity

Two-three fold increases in the levels of proteolytic activities in one strain of Bacillus licheniformis (R1-8) were obtained when changes in the nature of the nitrogen source (food and fodder yeast instead of soybean meal) and in the amount of invert sugars in the culture medium were performed.     

Effects of different nitrogen sources on lignocellulose degradation and APPL production

Naphthalene utilizing bacteria were isolated from several sites above and below the discharge from a coking plant. The distribution of the bacteria was influenced by the effluent. Of these isolates, 11·4% obtained from the effluent discharge site, contained plasmids. No conjugal transfer of naphthalene utilizing ability was observed in over 1000 matings. Curing and transformation experiments demonstrated that one plasmid pNB33 (101 kb) was concerned with naphthalene catabolism.     

Root responses to nitrogen pulse frequency under different nitrogen amounts

Responses of morphology and biomass allocation of roots to frequency of nitrogen (N) pulse potentially influence the fitness of plants, but such responses may be determined by root size. We grew 12 plant species of three functional groups (grasses, forbs, and legumes) under two N pulse frequencies (high vs. low supply frequency) and two N amounts (high vs. low supply amount). Compared to low-amount N supply, high-amount N supply stimulated biomass accumulation and root growth by either increasing the thickness and length of roots or decreasing the root mass fraction. Compared to low-frequency N supply, high-frequency N supply improved biomass accumulation and root growth in forbs or grasses, but not in legumes. Furthermore, the magnitude of the response to N frequency was significantly negatively correlated with root size at the species scale, but this was only true when the N amount was high. We conclude that root responses to N frequency are related to plant functional types, and non-legume species is more sensitive to N frequency than legume species. Our results also suggest that root size is a determinant of root responses to N frequency when N supply amount is high.     

Contrasting nitrogen uptake by diatom and Phaeocystis-dominated phytoplankton assemblages in the North Sea

This paper documents ambient concentrations of nutrients in the Belgian coastal waters of the North Sea during the spring of 1996 and 1997. The paper elaborates the differences of uptake rates of oxidised nitrogen (NO₃⁻) and reduced nitrogen (NH₄ and urea) by Phaeocystis and diatoms. The nitrogen concentrations were dominated by NO₃⁻ with a maximum concentration of 30 μM (January 1997) and 40 μM (March 1996). In 1996, Phaeocystis dominated the spring biomass with a maximum of 521 μg C l⁻¹, while maximum diatom biomass was 174 μg C l⁻¹. In 1997, the maximum Phaeocystis spring biomass was 1600 μg C l⁻¹ and diatom maximum biomass was below 100 μg C l⁻¹. A maximum bacteria biomass of about 55 μg C l⁻¹ was observed in mid-May 1996. The maximum nitrogen uptake rates were recorded during spring and were dominated by NO₃⁻ (0.005 h⁻¹ in 1996 and 0.032 h⁻¹ in 1997). Maximum specific NH₄ uptake rates were between 0.005 h⁻¹ in May 1996 and 0.006 h⁻¹ in April 1997. The NO₃⁻ uptake rates displayed exponential decrease versus increasing ambient reduced nitrogen concentrations (ammonium and urea), whereas the reduced nitrogen uptake increased but never compensated the decreased nitrate uptake. The NH₄ uptake kinetics of diatoms displayed lower v_max compared to Phaeocystis. Consequently, Phaeocystis showed ability to increase their NH₄ uptake capacity when more NH₄ became available while diatoms failed to do so, after ammonium had exceeded their saturation concentration (>1 μM). Although reduced nitrogen has a negative effect on the uptake of NO₃⁻, Phaeocystis have more advantage than diatoms on the uptake of ammonium. This might be contributing to the biomass domination shown by Phaeocystis over extended periods in spring.     

Inorganic phytoplankton nutrients in the Wadden Sea areas off Schleswig-Holstein. I. Dissolved inorganic nitrogen

In the summer months of 1984, 1986, 1987 und 1988, several stations off the west coast of Schleswig-Holstein were investigated with regard to the situation of dissolved inorganic nitrogen. An increase in nutrients was observed during the last few years related to a decrease in salinity. This is possibly due to an increased freshwater outflow caused by higher rainfall during recent summers.     

Retrospective analysis of environmental impact on growth parameters in White Sea mussel Mytilus edulis

The environmental impact on growth was retrospectively analyzed in two White Sea populations of mussel Mytilus edulis by measuring the growth rings on their shell surface. The analysis involving the nonlinearity test and recurrent von Bertalanffy growth equation demonstrated the best environmental conditions for mussel growth in the regions of the Kast’yan Island and Malaya Pir’-guba in 1999 and 2001, respectively; while the worst conditions were observed in 1998 for both populations.