Cyanophyte blooms: The role of cell buoyancy1

Humphries, Stella E.; Lyne, Vincent

doi:10.4319/lo.1988.33.1.0079

Cited by 99 publications

(56 citation statements)

References 41 publications

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“…In fact, this is the natural behaviour for colony-forming cyanobacteria such as Microcystis. They are well adapted to conditions of varying mixing intensity, rapidly floating up into the illuminated surface mixed layer during-even briefperiods of quiescence (sometimes described as 'tracking the surface mixed layer', Humphries and Lyne 1988). Smaller colonies or filaments need several hours or days to rise from deep layers to the euphotic zone and will receive only a small light dose when mixing intermittently takes them to greater depth.…”

Section: Mixing Regimesmentioning

confidence: 99%

Artificial mixing to control cyanobacterial blooms: a review

et al. 2015

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Artificial mixing has been used as a measure to prevent the growth of cyanobacteria in eutrophic lakes and reservoirs for many years. In this paper, we give an overview of studies that report on the results of this remedy. Generally, artificial mixing causes an increase in the oxygen content of the water, an increase in the temperature in the deep layers but a decrease in the upper layers, while the standing crop of phytoplankton (i.e. the chlorophyll content per m 2 ) often increases partly due to an increase in nutrients entrained from the hypolimnion or resuspended from the sediments. A change in composition from cyanobacterial dominance to green algae and diatoms can be observed if the imposed mixing is strong enough to keep the cyanobacteria entrained in the turbulent flow, the mixing is deep enough to limit light availability and the mixing devices are well distributed horizontally over the lake. Both models and experimental studies show that if phytoplankton is entrained in the turbulent flow and redistributed vertically over the entire depth, green algae and diatoms win the competition over (colonial) cyanobacteria due to a higher growth rate and reduced sedimentation losses. The advantage of buoyant cyanobacteria to float up to the illuminated upper layers is eradicated in a wellmixed system.

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Section: Mixing Regimesmentioning

confidence: 99%

Artificial mixing to control cyanobacterial blooms: a review

et al. 2015

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“…In order to keep the buoyant Microcystis in suspension, the artificial mixing velocity should exceed the flotation velocity of the cyanobacterium . The mixing velocity needs to be rather high as the maximal vertical velocity of Microcystis can be as high as 2 .6 m h-1 (Visser, 1995) ; 8 .3 m h-1 (Humphries & Lyne, 1988) or 10 .8 m h -1 (Reynolds et al ., 1987) . This variety of velocities mainly results from differences in the radius of the colonies .…”

Section: Introductionmentioning

confidence: 99%

Diurnal buoyancy changes of Microcystis in an artificially mixed storage reservoir

Visser

Ketelaars²,

Breemen³

et al. 1996

Hydrobiologia

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General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Key words : buoyancy, artificial mixing, aeration, Microcystis, cyanobacteria Abstract In a storage reservoir, which is artificially mixed in order to reduce algal and especially cyanobacterial growth, the cyanobacterium Microcystis is still present . The aim of the research was to investigate why Microcystis was able to grow in the artificially mixed reservoir . From the results it could be concluded that the large shallow area in the reservoir allows this growth . The loss of buoyancy during the day was much higher in this shallow part than in the deep part. Assuming that the loss of buoyancy was the result of a higher carbohydrate content, a higher growth rate in the shallow part may be expected . A higher received light dose by the phytoplankton in the shallow mixed part of the reservoir than in the deep mixed part explains the difference in buoyancy loss . A significant correlation between the received light dose (calculated for homogeneously mixed phytoplankton) and the buoyancy loss was found . Apparently, the Microcystis colonies were entrained in the turbulent flow in both the shallow and the deep part of the reservoir. With a little higher stability on one sampling day, due to the late start of the artificial mixing, the loss of buoyancy at the deep site was higher than on the other days and almost comparable to the loss at the shallow site . Although the vertical biomass distribution and the temperature profiles showed homogeneous mixing, the colonies in the upper layers apparently received a higher light dose than those deeper in the water column . Determination of the buoyancy state of cyanobacteria appeared to be a valuable method to investigate the light history and hence their entrainment in the turbulent flow in the water column .

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“…In a deep turbid lake, therefore, diffusivities are always likely to be high enough to cause strong mean upward buoyant velocity. We expect an organism such as Microcystis, which is most often observed to be positively buoyant (Humphries and Lyne 1988), to be better able to exist in such turbid conditions than 0. agardhii. This expectation is simply because Microcystis colonies float faster than 0. agardhii and so are better able to maintain themselves in the euphotic zone without depleting their carbohydrate ballast.…”

Section: Nonlinear Solutions With D@usionmentioning

confidence: 99%

Chaotic solutions for irradiance‐regulated buoyant motion of cyanobacteria

Sanderson¹,

Webster²,

Humphries³

1992

Limnology & Oceanography

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A very simple model for the irradiance-regulated buoyant motion of the cyanobacterium Oscillatoria agardhii is described. Removing the dimensions from this model enables us to find three independent parameters (a, b, c) that control the character of the motion. Small changes in the three parameters can cause large changes in the average irradiance incident upon a colony. The motion can be either periodic or chaotic depending on the values of these parameters. Motion with periods of 2 d is possible, in which case there can be subpopulations that move synchronously but 1 d out-of-phase with one another. The model is intrinsically nonlinear in any conceivable natural setting, but an analytic family of solutions exists for nighttime and an analytic family of approximate solutions for daytime can be found for velocity as a function of depth. The numerical solutions can be interpreted by switching between these analytic families of solutions. Vertical turbulent diffusivity causes a mean buoyant velocity that acts to oppose the downward diffusive flux. This turbulence results in the organism seeing less light, although its average depth is hardly changed because it is mixed deeper during the day and rises more at night.

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Cyanophyte blooms: The role of cell buoyancy1

Cited by 99 publications

References 41 publications

Artificial mixing to control cyanobacterial blooms: a review

Artificial mixing to control cyanobacterial blooms: a review

Diurnal buoyancy changes of Microcystis in an artificially mixed storage reservoir

Chaotic solutions for irradiance‐regulated buoyant motion of cyanobacteria

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