zooplankton grazing mechanisms and impacts on phytoplankton amanda lee murby field limnology...
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Zooplankton GrazingZooplankton Grazing
Mechanisms and Impacts on Phytoplankton
Amanda Lee MurbyField Limnology
PBIO/ZOOL 719/819FALL 2005
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Grazing: Grazing: Terrestrial
Consumption of a portion of a plant’s tissue is most often referred to as Grazing.
Herbivores eat whole plants or parts of plants. Functioning as a Predator = Consumption of entire plant. Functioning as a Parasite = Consumption of tissue, but without
killing plant.
Terrestrial grazing usually applies to grasses and other herbaceous vegetation.
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Predator!Predator!
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Grazing: Grazing: Aquatic (Plankton)
Grazing refers to the predator- prey interactions in water where algae and bacteria are the prey organisms.
Filtering is an example of grazing in the aquatic world; removal of algae or the portion of water volume that is (ideally) cleaned of particles.
Aquatic grazing usually applies to algae, bacteria, and other plankton.
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Which are the zooplankton Which are the zooplankton grazers?grazers?
Cladocerans
Copepods
Rotifers
Example:Example: Red Red CalanoidsCalanoids
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Cladoceran TypesCladoceran Types
Daphnia ambigua Bosmina longirostris
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Calanoids Cyclopoids
Predominantly Herbivores
Predominantly Predators
Copepod TypesCopepod Types
Feeding appendages
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Keratella
Rotifer TypesRotifer Types
Kellicottia
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Grazing MechanismsGrazing Mechanisms
Filter Feeders
Nonselective (except for size of food)
Size of prey relatively small
Example: Cladocerans and some Rotifers
Raptorial
Selective (medium-sized particles)
Select on basis of chemical qualities (taste)
Example: Copepods
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Zooplankton do not eat all Zooplankton do not eat all phytoplankton with the phytoplankton with the
same efficiency…same efficiency…
Many algae can avoid being eaten or digested.
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Grazers : Grazers : Filter Feeders
Edible particle sizes for filter feeding zooplankton is determined by the mesh width of the filtering apparatus.
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Edible Particle SizesEdible Particle Sizes
Lower boundary limits: Particles must fit between setules and third
pair of legs.
-Range from 0.16 to 4.2 m (for Cladocera)
Majority of Daphnia species have an average mesh width of 1.0 m.
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Edible Particle SizesEdible Particle Sizes
Upper boundary limits: Particles determined by the opening of the
mandibles and/or the opening of the carapace gape.
-Range from 20 to 50 m (for Cladocera) Particles that exceed the upper size limit can
be broken if fragile or are protected from Cladocera…
Copepods generally eat these larger particles.
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Refer to your handout for the Refer to your handout for the next clip: next clip:
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Strategies of Phenotypic Low Strategies of Phenotypic Low Food Adaptations in Food Adaptations in
Daphnia: Filter screens, Daphnia: Filter screens, mesh sizes, and appendage mesh sizes, and appendage
beat rates (ABR)beat rates (ABR)
W. Lampert & H. BrendelbergerW. Lampert & H. Brendelberger(1996)(1996)
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Predictions of gain in filtering rate of Predictions of gain in filtering rate of differently sized differently sized DaphniaDaphnia without without
increasing energy costs for pumping increasing energy costs for pumping (ABR)(ABR)
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Projected filter area Appendage beat Projected filter area Appendage beat raterate
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Body lengths in correlation with the Body lengths in correlation with the projected filter areas and with mesh widths.projected filter areas and with mesh widths.
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Community grazing ratesCommunity grazing rates
The abundance of herbivorous zooplankton correlated with the community grazing rates.
(Lampert 1988)
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Grazing Rate: EquationGrazing Rate: Equation
y = Gw
Grazing rates (y) are estimated from the filtering rate of the total zooplankton community (G) and the coefficient of selectivity (w) for the specific algae that is being considered.
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Coefficient of SelectivityCoefficient of Selectivity
Phytoplankton can avoid mortality.
wi = yi/ yopt.
The Selection Coefficient expresses lower mortality, compared to optimally eaten species.
* Not a fixed Characteristic for a particular species.
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Clear Water PhaseClear Water Phase
“Describes the very regular occurrence of a minimum density of phytoplankton in the
middle of the growth period (North temperate latitudes usually in May-June). Most
frequently in meso- and eutrophic lakes”.(Lampert and Sommers 1997)
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Grazing is directly involved with Grazing is directly involved with the Clear Water Phasethe Clear Water Phase
During the clear water phase (usually Spring), a large amount of herbivorous zooplankton will occur.
Zooplankton grazing is a major cause of phytoplankton mortality.
(Lampert and Sommers 1997)
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SummarySummary
Zooplankton grazing applies to the consumption of algae, bacteria, and other planktonic species.
Types: Cladocerans, Copepods, and Rotifers Grazing mechanisms: Filter-feeder v. Raptorial Mesh widths and Edible Particles: upper & lower Filtrations rates correlate with body size More food is collected at low particle concentrations (and is
more efficient) by increasing maximum filtering rate by enlarging its filter screens than by increasing ABR.
Community grazing rates and the coefficient of selectivity
Clear Water Phase and impacts on Phytoplankton mortality
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ReferencesReferences
Lampert, Sommers. Limnoecology: The Ecology of Lakes and Streams. Oxford University Press. 1997
Ricklefs, R.E. The Economy of Nature (fifth Ed.) WH Freeman and Company New York. 2001
Lampert, Brendelberger. “Strategies of Phenotypic Low Food Adaptation in Daphnia: Filter screens, mesh sizes, and appendage beat rates”. Limnology. Oceanography – 41(2), (1996): 216-223.
Lampert, Winfried. “The Relationship between Zooplankton Biomass and Grazing : A Review”. Limnology (Berlin) – 19(1), (1988): 11-20.
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Questions?Questions?