Search results for "algae"
showing 10 items of 403 documents
Non-hydrolysable macromolecular constituents from outer walls of Chlorella fusca and Nanochlorum eucaryotum
1992
Abstract Many green microalgae possess a thin trilaminar outer wall (TLS) with a very high resistance to chemical degradation. TLS are known to play an important protective role in living cells. They are also selectively preserved during fossilization and thus provide a major contribution to the fossil organic matter of a number of sedimentary rocks. However, little information is available on TLS chemical structure. Examination of the TLS of Chlorella fusca (a lacustrine Chlorophycea) and of Nanochlorum eucaryotum (a recently discovered marine Chlorophycea) indicated that (i) they exhibit morphological features commonly observed in other green microalgae, (ii) their non-hydrolysable macrom…
Inorganic Polyphosphate in Eukaryotes: Enzymes, Metabolism and Function
1999
Inorganic polyphosphates (polyP) are linear polymers of orthophosphate (Pi) residues linked by high-energy phosphoanhydride bonds. These polymers are widely distributed in nature, from archaebacteria, eubacteria, fungi, algae, and protozoa to higher plants and animals (for reviews, see Kulaev 1979; Wood and Clark 1988; Kornberg 1994, 1995). PolyP molecules are stable in neutral aqueous solutions, but are hydrolyzed by heat-treatment, and under acidic or alkaline conditions. The chain length of polyP may range from 3 to more than 1000 Pi residues; it can be analyzed on urea/polyacrylamide gels (Clark and Wood 1987; Lorenz et al. 1994a). In contrast to the linear polymer, branched inorganic p…
The Interaction of State Transitions and Chlororespiration in the Xanthophycean Alga Pleurochloris Meiringensis
1990
Wavelength dependent State I-State II-transitions have been shown to exist in chlorophytes and red algae. Little is known about the regulation of energy distribution between the photosystems of chlorophyll c-containing plants. Previously it was shown that in the xanthophycean alga Pleurochloris meiringensis two states of energy distribution could be established [l]: In state “D” light is preferentially transferred to PS II, whereas in state “L” PS I is favoured. These state regulations strictly depend on the intensity and not on the wavelength of prei1lumination. In this paper we give new evidence that chlororespiration is involved in the mechanism of state “L”-state “D”-transitions.
A STUDY ON THE POSSIBLE EFFECT OF TWO CRAYFISH SPECIES ON EPILITHIC ALGAE IN A MOUNTAIN STREAM FROM CENTRAL SPAIN
2006
The effects on epilithic algae of increasing densities of two crayfish species, Austropotamobius italicus and Pacifastacus leniusculus, the latter recently introduced in Spain, have been monitored using riverine enclosures, within a large experimental study on crayfish-macrobenthos interactions in a mountain stream. A 3-month test was carried out for each species using crayfish densities comprising between 0-5 individuals/m2 kept in 1-m2 enclosures. Epilithon was sampled periodically within the enclosures and chlorophyll a, b and c were measured by spectrophotometry. Neither statistically significant positive nor negative effects were observed on algal abundance (Chl concentrations) during …
Responses of macroalgal community to environmental changes
2009
Species of Cystoseira (Ochrophyta, Fucales) seem to be sensitive to a variety of environmental changes, as a consequence of which, they are now used in ecological status assessment. On the contrary, invasive species tend to be more resilient to disturbances than Cystoseira species, and thus environmental changes to allow them to out-compete these species. All these evidences lead to consider Cystoseira species, as well as invasive species, as biological indicators of environmental changes. Therefore, the effects of environmental changes can be measured through: (1) the assessment of the current state of the popu- lations of Cystoseira species and of invasive species, (2) the comparison of i…
Simulated eutrophication and browning alters zooplankton nutritional quality and determines juvenile fish growth and survival
2018
Source at https://doi.org/10.1002/ece3.3832. The first few months of life is the most vulnerable period for fish and their optimal hatching time with zooplankton prey is favored by natural selection. Traditionally, however, prey abundance (i.e., zooplankton density) has been considered important, whereas prey nutritional composition has been largely neglected in natural settings. High‐quality zooplankton, rich in both essential amino acids (EAAs) and fatty acids (FAs), are required as starting prey to initiate development and fast juvenile growth. Prey quality is dependent on environmental conditions, and, for example, eutrophication and browning are two major factors defining primary produ…
Consistency of Targeted Metatranscriptomics and Morphological Characterization of Phytoplankton Communities
2020
The composition of phytoplankton community is the basis for environmental monitoring and assessment of the ecological status of aquatic ecosystems. Community composition studies of phytoplankton have been based on time-consuming and expertise-demanding light microscopy analyses. Molecular methods have the potential to replace microscopy, but the high copy number variation of ribosomal genes and the lack of universal primers for simultaneous amplification of prokaryotic and eukaryotic genes complicate data interpretation. In this study, we used our previously developed directional primer-independent high-throughput sequencing (HTS) approach to analyze 16S and 18S rRNA community structures. C…
Population dynamics of Cyclotella ocellata (Bacillariophyceae): endogenous and exogenous factors
1999
Population dynamics of Cyclotella ocellata PANTOCSEK were examined from 1991 to 1993 in an oligo-mesotrophic, gravel-pit lake near Madrid (Spain). Monthly and daily sampling was carried out to track seasonal- and auxosporulation dynamics, respectively. This species was the most abundant planktonic diatom in the lake. The population increased steadily in spring until the seasonal peak (3.8.10 6 ind/ L in April) and then abundance declined slowly through late winter. Time series techniques showed that the seasonal dynamics were driven by exogenous factors: there was a relationship between Cyclotella abundance and the chemical environment, both TP (synchronic) and SRSi (with delay). Auxosporul…
Population Dynamic of Algae and Bacteria in an Oxidation Channel
2003
A study on algae and bacteria population changes, as a function of time, was carried out in a pilot scale oxidation channel bioreactor using a carrousel system. Total Coliforms, Pseudomonas aeruginosa, and Streptococcus faecalis, the most common bacteria found in sewage, Scenedesmus obliquus and Chlorella vulgaris were the microalgae considered in this work. Physicochemical parameters such as COD, BOD, Chlorophyll a, nitrogen, and phosphorous compounds were studied and determined during the experiments. It was demonstrated that the level of wastewater contamination could be predicted based on the bacterial and algae composition. The relationships between the algae and bacteria population, a…
Innovative extraction and separation technologies to improve the recovery of microalgae nutrients and bioactive compounds with potential beneficial e…
2023
Las microalgas son ricas en una gran variedad de compuestos bioactivos, que incluyen proteínas, polifenoles, polisacáridos, pigmentos, minerales, vitaminas, etc., que pueden utilizarse o separarse directamente para obtener componentes de mayor valor. La extracción y la separación son pasos clave en la obtención y posterior procesamiento de los productos relacionados con las microalgas, representando las tecnologías innovadoras de procesado una estrategia innovadora y eficiente para mejorar la calidad de estos productos. Actualmente, las microalgas y sus compuestos (nutrientes, compuestos bioactivos, etc.) se utilizan como alimento y también con finalidades desde el punto de vista de salud, …