Download Aquatic Ecosystems - Oregon State University

Aquatic Ecosystems
Organic Inputs
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Allochthonous organic matter
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Organic matter that is derived from outside the
system (in lakes, this is usually leaves, needles,
wood, and twigs from terrestrial vegetation)
Autochthonous organic matter
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Organic matter derived within the system (in lakes,
this is usually algae, mosses, and aquatic vascular
macrophytes)
Trophic Properties
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Autotrophic - production within the system
exceeds respiration
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This is often expressed as the ratio of production to
respiration (P/R)
In autotrophic systems, P/R > 1
Heterotrophic - respiration within the system
exceeds production
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In heterotrophic systems, P/R < 1
Major Habitats of Lentic Ecosystems
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Planktonic - free-floating
Phytoplankton - free-floating algae
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Zooplankton - free-floating animals with limited
powers of locomotion
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Tychoplankton - Suspended benthic organisms
(not true plankton)
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Metaphyton - Phytoplankton existing within the
macrophyte communities of littoral zones
Nekton
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Nekton - free-swimming
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Some organisms (such as larvae of fish) can
shift between planktonic to nektonic
existence within their life cycle
Pleuston
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Pleuston - organisms adapted to the habitat of
the air-water interface
Neuston - the microscopic component of the
pleuston
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Epineuston or epipleuston are those forms that exist
on top of the water's surface
Hyponeuston or hypopleuston are those forms that
exist under the water's surface but still are
associated with the air-water interface
Benthos
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Benthos - organisms that live on the
bottom of a lake, stream, or river
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Benthic is the adjective that is used to
describe organisms that live on the
bottom
Benthos
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The film of algae, bacteria, fungi, and
microscopic invertebrates that exist on
substrates is known as periphyton
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Periphyton literally refers to organisms living "on
plants" but is most often used in the more general
sense
The term Aufwuchs is sometimes used
synonymously with periphyton
Aufwuchs is a term derived from the German for
"growth upon”
Biofilm is most common recent term
Benthic Communities
Epilithic - living on rock substrates
! Epipelic - living on fine organic sediments
("mud")
! Epiphytic - living on plants
! Epizooic - living on animals
! Epipsammic - living on sand grains
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Littoral Zone
Epilittoral - above the high water level and
uninfluenced by spray
! Supralittoral - above the high water level
and subject to spray
! Eulittoral - the shoreline region between
the highest and lowest seasonal water
levels
! Eulittoral plus infralittoral = littoral zone
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Littoral Zone
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Infralittoral
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Upper infralittoral - zone where emergent rooted
macrophytes exist
Middle infralittoral - zone where floating-leaved
macrophytes exist
Lower infralittoral - zone where rooted or adnate
macrophytes exist
Littoriprofundal - zone where only
photosynthetic algae and bacteria exist (often
associated with the metalimnion)
Profundal - zone where sediments are free of
vegetation
Measure of Production
and Abundance
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Production - weight of new organic matter
formed over a period of time plus any loss
due to respiration, excretion, secretion,
injury, death, and grazing
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Productivity - the rate of production
Quantity
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Standing crop - weight of organic matter that
can be sampled or harvested at one time from a
given area (not necessarily the whole plant)
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Biomass - the weight of all living matter in a unit
area at a given time (must include the whole
plant)
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Yield - Standing crop expressed as a rate
Abundance
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Estimation of abundance of organisms
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Enumeration
Volume
Weight
• Dry weight - dried in oven at 55ºC for at least 24 hours
• Ash-free dry weight - weight of ash (determined by weighing
the residue after burning sample in furnace at 550ºC for at
least 4 hours) is subtracted from the dry weight to determine
ash-free dry weight
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Cellular constituents - carbon (40-60% for most
plants), nitrogen, phosphorus
Productivity
P/B Ratios
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Production to biomass ratio (P/B)
High P/B ratio for smaller organisms
! P/B generally decreases with increasing size
! P/B decreases with increasing trophic level
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