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1

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Artificial mixing prevents nuisance blooms of the cyanobacterium Microcystis in Lake Nieuwe Meer, the Netherlands (1996)

VISSER, PETRA ; IBELINGS, BAS ; VAN DER VEER, BART ; [et al.]

Oxford BSL : Blackwell Science Ltd

Freshwater biology 36 (1996), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Artificial mixing in the hypertrophic Lake Nieuwe Meer was successful in preventing blooms of the cyanobacterium Microcystis. During the 2 years of artificial, deep mixing the number of colonies of Microcystis per litre and also per m2 was lower than in the two preceding control years. Hardly any nuisance scums of Microcystis occurred in the lake.2. The phytoplankton shifted from a cyanobacteria-dominated community in summer to a mixed community of flagellates, green algae and diatoms. Reduced sedimentation losses in the mixed lake, probably in combination with a lower pH, favoured non-buoyant algae, while the entrainment of cyanobacteria in the turbulent flow nullified their advantage of buoyancy.3. The chlorophyll concentrations were much lower in the mixed lake, but the euphotic depth did not show clear differences between the years. The chlorophyll content integrated through depth (m–2) increased in the artificially mixed lake.4. The deep lake normally stratified in summer, but artificial mixing of the lake in 1993 resulted in a homogeneous temperature and oxygen distribution with depth. In spring 1994, the mixing was applied intermittently with a reduction of 75% of the energy costs, while the mixing was still sufficient to prevent stratification.5. Determination of the buoyancy state of the colonies on a sunny and calm day showed that the buoyancy loss was low close to the bubble plumes, and high at some distance from these plumes. This suggests that Microcystis could escape the mixing at some distance from the plumes, and could synthesize more carbohydrates during its stay in the upper illuminated layer of the lake than the deep mixed colonies close to the bubble plumes. Determination of the buoyancy state appeared to be a good and simple method to investigate the extent of entrainment of colonies in the turbulent flow.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.1996.00093.x

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2

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Benthic–pelagic coupling in the population dynamics of the harmful cyanobacterium Microcystis (2005)

VERSPAGEN, JOLANDA M. H. ; SNELDER, EVELINE O. F. M. ; VISSER, PETRA M. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Freshwater biology 50 (2005), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. In eutrophic lakes, large amounts of the cyanobacterium Microcystis may overwinter in the sediment and re-inoculate the water column in spring.2. We monitored changes in pelagic and benthic populations of Microcystis in Lake Volkerak, The Netherlands. In addition, sedimentation rates and the rate of recruitment from the sediment were measured using traps. These data were used to model the coupling between the benthic and pelagic populations and to calculate the contribution of overwintering benthic and pelagic populations to the magnitude of the pelagic summer bloom.3. Changes in the benthic Microcystis population showed a time lag of 3–14 weeks compared with the pelagic population. This time lag increased with lake depth. The largest amount of benthic Microcystis was found in the deepest parts of the lake. These observations suggest horizontal transport of sedimented Microcystis from shallow to deep parts of the lake.4. Recruitment from and sedimentation to the sediment occurred throughout the year, with highest recruitment and sedimentation rates during summer. Model simulations indicate that the absence of benthic recruitment would reduce the summer bloom by 50%.5. In spring, the total pelagic population was three to six times smaller than the total benthic population. Yet, model simulations predict that the absence of this small overwintering pelagic population would reduce the summer bloom by more than 64%.6. Reduction of the overwintering pelagic populations, for instance by flushing, may be a useful management strategy to suppress or at least delay summer blooms of Microcystis.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.2005.01368.x

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3

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Microprofiles of photosynthesis and oxygen concentration in Microcystis sp. scums (1991)

Ibelings, Bas W. ; Mur, Luuc R.

Oxford, UK : Blackwell Publishing Ltd

FEMS microbiology ecology 9 (1991), S. 0

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ISSN: 1574-6941

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Oxygen microelectrodes were used to monitor oxygen concentration and rates of gross photosynthetic activity in Microcystis sp. scums which were formed and incubated under laboratory conditions. The depth of the photic layer, rate of photosynthesis, oxygen concentration and the location of the transition to anoxia in the scum depended on irradiance levels and colony size. Gross photosynthetic activity never extended below 2.5 mm depth in the scum. At high irradiance levels oxygen concentration in the upper 1.5 mm of the scum decreased and the oxygen concentration peak shifted to greater depth. Oxygen concentrations in scums composed of small colonies (〈 55 μm) were higher than concentrations in large colonies scums (〉300 μm) but small colonies showed stronger indications of photoinhibition. In a natural scum small colonies are presumably shielded from inhibitory intensities by larger colonies which will dominate the upper layers. Accumulation of low-light adapted, smaller colonies in deeper layers likely yielded a second peak in photosynthetic activity. In order to systematically discuss scums and scum formation a distinction is made in three different scum types.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1574-6941.1991.tb01753.x

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4

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Microprofiles of photosynthesis and oxygen concentration in Microcystis sp. scums (1992)

Ibelings, Bas W. ; Mur, Luuc R.

Oxford, UK : Blackwell Publishing Ltd

FEMS microbiology letters 86 (1992), S. 0

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ISSN: 1574-6968

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Abstract Oxygen microelectrodes were used to monitor oxygen concentration and rates of gross photosynthetic activity in Microcystis sp. scums which were formed and incubated under laboratory conditions. The depth of the photic layer, rate of photosynthesis, oxygen concentration and the location of the transition to anoxia in the scum depended on irradiance levels and colony size. Gross photosynthetic activity never extended below 2.5 mm depth in the scum. At high irradiance levels oxygen concentration in the upper 1.5 mm of the scum decreased and the oxygen concentration peak shifted to greater depth. Oxygen concentrations in scums composed of small colonies (〈55 μm) were higher than concentrations in large colonies scums (〉 300 μm) but small colonies showed stronger indications of photoinhibition. In a natural scum small colonies are presumably shielded from inhibitory intensities by larger colonies which will dominate the upper layers. Accumulation of low-light adapted, smaller colonies in deeper layers likely yielded a second peak in photosynthetic activity. In order to systematically discuss scums and scum formation a distinction is made in three different scum types.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1574-6968.1992.tb04810.x

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5

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Adaptive divergence in pigment composition promotes phytoplankton biodiversity (2004)

Stomp, Maayke ; de Jongh, Floris ; Veraart, Annelies J. ; [et al.]

[s.l.] : Macmillian Magazines Ltd.

Nature 432 (2004), S. 104-107

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] The dazzling diversity of the phytoplankton has puzzled biologists for decades. The puzzle has been enlarged rather than solved by the progressive discovery of new phototrophic microorganisms in the oceans, including picocyanobacteria, pico-eukaryotes, and bacteriochlorophyll-based and ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/nature03044

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6

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The effect of dynamic light regimes on Chlorella (1992)

Kroon, Bernd M. A. ; Latasa, Mikel ; Ibelings, Bas W. ; [et al.]

Springer

Hydrobiologia 238 (1992), S. 71-78

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ISSN: 1573-5117

Keywords: dynamic light regime ; chlorophyll a ; chlorophyll b ; optical ; in vivo absorption ; cross sections

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The patterns of diurnal variations in pigmentation and optical cross-section were compared for two cyclostat cultures of Chlorella pyrenoidosa, where the dynamics of the photoperiod differed. Populations were light-limited, nutrient rich and growing on an 8:16 light-dark (LD) cycle. One light regime was an 8 h sine function of the light period (sinusoidal culture), while the second had an 1 h sine function super-imposed on the 8 hour sine function (oscillating sinusoidal culture). Hourly samples were taken throughout a 12 h period including the light period. Determinations were made of chlorophyll (Chl) a and b abundance, in vivo absorption spectra, cell number and volume and used to derive both cell-specific (σcell) and optical chlorophyll specific (σchl) cross sections, as well as the absorption efficiency, Q, of the cells. The results indicate that C. pyrenoidosa is capable of adapting to dynamics in light intensity within an 8 h photoperiod. The sinusoidal culture showed a constant decrease in the Chl a/b ratio of 28% while the total Chl content per cell increased slightly and σchl and Q remained constant, suggesting coordinated changes in reaction centers and light harvesting complexes. Over the oscillating photoperiod, however, the second culture displayed a diurnal variation in Chl a/b ratio, a 20% increase in σchl and an apparent oscillation in Q. These observations suggest that an oscillating photoperiod promoted the capability of Chl molecules to collect light and that the fractional area of all Chl molecules exposed to the photon flux is inversely related to the photon flux.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00048775

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7

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Monitoring of algae in Dutch rivers: does it meet its goals? (1998)

Ibelings, Bas ; Admiraal, Wim ; Bijkerk, Ronald ; [et al.]

Springer

Journal of applied phycology 10 (1998), S. 171-181

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ISSN: 1573-5176

Keywords: Cyanobacteria ; diatoms ; eutrophication/kwd〉 ; green algae ; monitoring ; phytoplankton ; rivers ; water management ; The Netherlands

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Observations on phytoplankton in the lower reaches of the rivers Rhine and Meuse were carried out in the framework of the national monitoring programme of the main water systems in The Netherlands. Seasonal changes in density and species composition were analysed to detect the major variables and to discuss whether this monitoring meets its goals. Phytoplankton reached peak densities of 140 and 65 µg L-1 Chl a in the Rhine and Meuse, respectively. Overall density was correlated with seasonal variation in water discharge rather than with nutrient concentrations, that are high in both rivers. The position of sampling sites in relation to the downstream development of the plankton was very important, especially in the regulated Meuse. Despite hydrographic and chemical differences between the two rivers, many species, predominantly diatoms and green algae, were shared. The occurrence of the diatom Skeletonema subsalsum in the Rhine and the green algae Neodesmus danubialis, Micractinium pusillum and Pseudotetrastrum punctatum in the Meuse (1992, but not 1996) was interpreted as a feature related, respectively, to the high salinity of the Rhine and specific riverine conditions of the Meuse. In general the potamoplankton was characterised as an opportunistic assemblage exploiting the high nutrient contents and disturbed hydrography of both rivers. Nevertheless, the phytoplankton contributed to the characterisation of the present river communities, ones that differ rather strongly in historic records. Although year to year variation in phytoplankton density is mainly related to variation in water discharge, phytoplankton biomass did increase as a result of eutrophication over a period of decades. The widespread nature of many of today's potamoplankton species in the two rivers render these organisms less useful for indicating short-term changes in water quality. However the importance of phytoplankton in trophic relationships merits its inclusion in the monitoring of riverine ecosystems.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008049000764

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