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Light Limitation (light + limitation)
Selected AbstractsEffects of Interspecific Interactions between Microcystis aeruginosa and Chlorella pyrenoidosa on Their Growth and PhysiologyINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2007Min Zhang Abstract Interactions between Microcystis aeruginosa and Chlorella pyrenoidosa were analyzed by flow cytometry and by phytoplankton pulse-amplitude-modulated fluorimetry (Phyto-PAM) in joint cultures as well as in cultures separated by dialysis membranes. Results showed that the growth of C. pyrenoidosa was greater than that of M. aeruginosa, and that the growth of M.aeruginosa but not the growth of C. pyrenoidosa was significantly inhibited by the interactions between M. aeruginosa and C. pyrenoidosa. Culture filtrates of these two algae showed no apparent effects on the growth of the competing species. For M. aeruginosa, decreases in esterase activity, chlorophyll a fluorescence, and maximum quantum yield were observed in joint cultures, indicating that the metabolic activity and photosynthetic capacity of M.aeruginosa were suppressed. Light limitation from the shading effect of C. pyrenoidosa may be the main reason for such inhibition. For C. pyrenoidosa, esterase activity was suppressed in membrane-separated and joint cultures, suggesting that C.pyrenoidosa was probably affected by allelopathic substances secreted by M.aeruginosa. However, no significant difference was observed in the chlorophyll a fluorescence and maximum quantum yield of C. pyrenoidosa in the two cultures. In addition, interspecific interactions induced a reduction in size in both M. aeruginosa and C.pyrenoidosa, which may contribute to the development of C. pyrenoidosa dominance in the present study. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Variability of the photosynthetic antenna of a Pelodictyon clathratiforme population from a freshwater holomictic pondFEMS MICROBIOLOGY ECOLOGY, Issue 1 2001Frederic B. Gich Abstract A population of the green sulfur bacterium Pelodictyon clathratiforme was monitored during the stratification period of Coromina Lake, a freshwater, holomictic pond of the Banyoles lacustrine area (Girona, NE Spain). The chromatographic analysis of this population revealed the presence of a wide variety of both bacteriochlorophyll (BChl) d and BChl c homologues. Isolation of chlorosomes from cultured Pelodictyon cells and their further analysis by steady-state fluorescence indicated that, although both pigment were present in chlorosomes, only BChl c gave rise to an emission signal, suggesting a fast energy transfer from BChl d to BChl c. Likewise, chlorosomes isolated from natural samples were significantly larger (60,70 nm in width and 115,120 nm in length) than those isolated from cells grown in laboratory under optimal light conditions (48±6.8 nm and 100±15.8 nm in width and length, respectively). The potential role of heterogeneous BChl c - and BChl d -containing chlorosomes and the differences in chlorosome size measured are discussed in terms of the severe light limitation (available light intensity <0.1 ,mol photons m,2 s,1 at the bacterial plate) under which the population subsisted during the study period. [source] Allelopathic effect of the aquatic macrophyte, Stratiotes aloides, on natural phytoplanktonFRESHWATER BIOLOGY, Issue 3 2006GABI MULDERIJ Summary 1. A survey of different Dutch Stratiotes stands showed that the density of phytoplankton (except cyanobacteria) was always higher outside S. aloides than between the rosettes of S. aloides. Analyses of water samples revealed that nutrient limitation was unlikely to have caused the lower phytoplankton biomass in the vicinity of S. aloides. 2. An in situ incubation experiment in the Danube Delta, Romania, indicated allelopathic activity against phytoplankton in S. aloides stands. The growth rate of natural phytoplankton populations exposed to water from S. aloides stands was significantly lower than that of populations that had not been in contact with S. aloides exudates. 3. A laboratory microcosm experiment showed a significantly lower phytoplankton biomass in treatments with S. aloides exudates. Nutrient concentrations and the light intensity were high enough that the lower phytoplankton biomass could not be explained by nutrient or light limitation. [source] The long-term effect of artificial destratification on phytoplankton species composition in a subtropical reservoirFRESHWATER BIOLOGY, Issue 6 2005JASON P. ANTENUCCI Summary 1. The response of phytoplankton to the installation of an artificial destratification system in North Pine Dam, Brisbane (Australia) was investigated over an 18 year period (1984,2002); 11 years before and 7 years after installation. 2. An overall increase in phytoplankton abundance was revealed for some groups (in particular, diatoms, cyanobacteria and chlorophytes), but not for others (chlorophytes). Changes in the abundance of chlorophyte functional groups was attributed to eutrophication. 3. A strong spatial gradient in phytoplankton abundance and chlorophyll a was observed, with low abundance in the downstream regions affected by the destratification system which was likely because of light limitation induced by vertical mixing. The upstream region acted as a surrogate for the unaltered state of the reservoir, particularly as an indicator of eutrophication without direct influence from the destratification system. Despite the continuous trend in eutrophication of the reservoir, there has been a definite decrease in the rate of eutrophication (approximately 30%) since the installation of the destratification system at the downstream locations. 4. Correlations of the dominant cyanobacteria Cylindrospermopsis raciborskii with other genera changed after destratification, indicating that prior to destratification the dominance of Cylindrospermopsis was because of its ability to compete for phosphorus, whereas after destratification its dominance was because of its ability to compete for light. [source] Top-down control of phytoplankton: the role of time scale, lake depth and trophic stateFRESHWATER BIOLOGY, Issue 12 2002JÜrgen Benndorf SUMMARY 1.,One of the most controversial issues in biomanipulation research relates to the conditions required for top-down control to cascade down from piscivorous fish to phytoplankton. Numerous experiments have demonstrated that Phytoplankton biomass Top-Down Control (PTDC) occurs under the following conditions: (i) in short-term experiments, (ii) shallow lakes with macrophytes, and (iii) deep lakes of slightly eutrophic or mesotrophic state. Other experiments indicate that PTDC is unlikely in (iv) eutrophic or hypertrophic deep lakes unless severe light limitation occurs, and (v) all lakes characterised by extreme nutrient limitation (oligo to ultraoligotrophic lakes). 2.,Key factors responsible for PTDC under conditions (i) to (iii) are time scales preventing the development of slow-growing inedible phytoplankton (i), shallow depth allowing macrophytes to become dominant primary producers (ii), and biomanipulation-induced reduction of phosphorus (P) availability for phytoplankton (iii). 3.,Under conditions (iv) and (v), biomanipulation-induced reduction of P-availability might also occur but is insufficient to alter the epilimnetic P-content enough to initiate effective bottom-up control (P-limitation) of phytoplankton. In these cases, P-loading is much too high (iv) or P-content in the lake much too low (v) to initiate or enhance P-limitation of phytoplankton by a biomanipulation-induced reduction of P-availability. However, PTDC may exceptionally result under condition (iv) if high mixing depth and/or light attenuation cause severe light limitation of phytoplankton. 4.,Recognition of the five different conditions reconciles previous seemingly contradictory results from biomanipulation experiments and provides a sound basis for successful application of biomanipulation as a tool for water management. [source] Trends of Superoxide Dismutase and Soluble Protein of Aquatic Plants in Lakes of Different Trophic Levels in the Middle and Lower Reaches of the Yangtze River, ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2009Ai-Ping Wu Abstract A limnological study was carried out to determine the responses of superoxide dismutase (SOD) activities and soluble protein (SP) contents of 11 common aquatic plants to eutrophication stress. Field investigation in 12 lakes in the middle and lower reaches of the Yangtze River was carried out from March to September 2004. Our results indicated that non-submersed (emergent and floating-leafed) plants and submersed plants showed different responses to eutrophication stress. Both SOD activities of the non-submersed and submersed plants were negatively correlated with their SP contents (P < 0.000 1). SP contents of non-submersed plants were significantly correlated with all nitrogen variables in the water (P < 0.05), whereas SP contents of submersed plants were only significantly correlated with carbon variables as well as ammonium and Secchi depth (SD) in water (P < 0.05). Only SOD activities of submersed plants were decreased with decline of SD in water (P < 0.001). Our results indicate that the decline of SOD activities of submersed plants were mainly caused by light limitation, this showed a coincidence with the decline of macrophytes in eutrophic lakes, which might imply that the antioxidant system of the submersed plants were impaired under eutrophication stress. [source] HOST PARASITE INTERACTIONS BETWEEN FRESHWATER PHYTOPLANKTON AND CHYTRID FUNGI (CHYTRIDIOMYCOTA),JOURNAL OF PHYCOLOGY, Issue 3 2004Bas W. Ibelings Some chytrids are host-specific parasiticfungithat may have a considerable impact on phytoplankton dynamics. The phylum Chytridiomycota contains one class, the Chytridiomycetes, and is composed of five different orders. Molecular studies now firmly place the Chytridiomycota within the fungal kingdom. Chytrids are characterized by having zoospores, a motile stage in their life cycle. Zoospores are attracted to the host cell by specific signals. No single physical,chemical factor has been found that fully explains the dynamics of chytrid epidemics in the field. Fungal periodicity was primarily related to host cell density. The absence of aggregated distributions of chytrids on their hosts suggested that their hosts did not vary in their susceptibility to infection. A parasite can only become epidemic when it grows faster than the host. Therefore, it has been suggested that epidemics in phytoplankton populations arise when growth conditions for the host are unfavorable. No support for such a generalization was found, however. Growth of the parasitic fungus Rhizophydium planktonicum Canter emend, parasitic on the diatom Asterionella formosa Hassal, was reduced under stringent nutrient limitation,because production and infectivity of zoospores were affected negatively. A moderate phosphorous or light limitation favored epidemic development, however. Chytrid infections have been shown to affect competition between their algal hosts and in this way altered phytoplankton succession. There is potential for coevolution between Asterionella and the chytrid Zygorhizidium planktonicum Canter based on clear reciprocal fitness costs, absence of overall infective parasite strains, and possibly a genetic basis for host susceptibility and parasite infectivity. [source] 160 Copepodology for the Phycologist with Apologies to G. E. HutchensonJOURNAL OF PHYCOLOGY, Issue 2003P. A. Tester Heterocapsa triquetra is one of the most common bloom forming dinoflagellates found in estuaries and near shore regions around the world. In order to bloom, H. triquetra optimizes a suite of factors including low grazing pressure, increased nutrient inputs, alternative nutrient sources, and favorable salinity and hydrodynamic conditions, as well as the negative factors of temperature-limited growth, short day lengths, and periods of transient light limitation. The prevailing environmental conditions associated its wintertime blooms are largely the result of atmospheric forcing. Low-pressure systems moved through coastal area at frequent intervals and are accompanied by low air temperatures and rainfall. Runoff following the rainfall events supplies nutrients critical for bloom initiation and development. Heterocapsa triquetra blooms can reach chl a levels >100 mg L,1 and cell densities between 1 to 6×106 L,1. As the blooms develop, nutrient inputs from the river became insufficient to meet growth demand and H. triquetra feeds mixotrophically, reducing competition from co-occurring phytoplankton. Cloud cover associated with the low-pressure systems light limit H. triquetra growth as do low temperatures. More importantly though, low temperatures limit micro and macrozooplankton populations to such an extent that grazing losses are minimal. [source] Disturbance frequency and functional identity mediate ecosystem processes in prairie streamsOIKOS, Issue 6 2009Katie N. Bertrand A major consequence of climate change will be the alteration of precipitation patterns and concomitant changes in the flood frequencies in streams. Species losses or introductions will accompany these changes, which necessitates understanding the interactions between altered disturbance regimes and consumer functional identity to predict dynamics of streams. We used experimental mesocosms and field enclosures to test the interactive effects of flood frequency and two fishes from distinct consumer groups (benthic grazers and water-column minnows) on recovery of stream ecosystem properties (algal form and biomass, invertebrate densities, metabolism and nutrient uptake rates). Our results generally suggest that periphyton communities under nutrient limitation are likely to recover more quickly when grazing and water-column minnows are present and these effects can diminish or reverse with time since the disturbance. We hypothesized that increased periphyton production and biomass was the result of increased nutrient turnover, but decreased light limitation and indirect effects on other trophic levels are alternative explanations. Recovery of stream ecosystem properties after a natural flood differed from mesocosms (e.g. lower algal biomass and no long algal filaments present) and species manipulations did not explain recovery of ecosystem properties; rather, ecosystem processes varied along a downstream gradient of increasing temperature and nutrient concentrations. Different results between field enclosures and experimental mesocosms are attributable to a number of factors including differences in algal and invertebrate communities in the natural stream and relatively short enclosure lengths (mean area=35.8 m2) compared with recirculating water in the experimental mesocosms. These differences may provide insight into conditions necessary to elicit a strong interaction between consumers and ecosystem properties. [source] Kinetic modeling of light limitation and sulfur deprivation effects in the induction of hydrogen production with Chlamydomonas reinhardtii: Part I. Model development and parameter identificationBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Swanny Fouchard Abstract Chlamydomonas reinhardtii is a green microalga capable of turning its metabolism towards H2 production under specific conditions. However this H2 production, narrowly linked to the photosynthetic process, results from complex metabolic reactions highly dependent on the environmental conditions of the cells. A kinetic model has been developed to relate culture evolution from standard photosynthetic growth to H2 producing cells. It represents transition in sulfur-deprived conditions, known to lead to H2 production in Chlamydomonas reinhardtii, and the two main processes then induced which are an over-accumulation of intracellular starch and a progressive reduction of PSII activity for anoxia achievement. Because these phenomena are directly linked to the photosynthetic growth, two kinetic models were associated, the first (one) introducing light dependency (Haldane type model associated to a radiative light transfer model), the second (one) making growth a function of available sulfur amount under extracellular and intracellular forms (Droop formulation). The model parameters identification was realized from experimental data obtained with especially designed experiments and a sensitivity analysis of the model to its parameters was also conducted. Model behavior was finally studied showing interdependency between light transfer conditions, photosynthetic growth, sulfate uptake, photosynthetic activity and O2 release, during transition from oxygenic growth to anoxic H2 production conditions. Biotechnol. Bioeng. 2009;102: 232,245. © 2008 Wiley Periodicals, Inc. [source] | ||||||||||