Transcript Lecture 5 Powerpoint

EVPP 550
Waterscape Ecology and
Management
Professor
R. Christian
Jones
Fall 2007
Adaptation to Flowing Water
• Life Cycles are often adaptive
– Many aquatic insects are aerial as adults to
facilitate dispersal and crossbreeding
– Some species concentrate their growth
phases in periods of favorable conditions
(moderate temp, plenty of water and food)
and revert to dormant stages (eggs, pupae)
during other stages
Adaptation to Flowing Water
• Feeding mechanisms:
– Scrapers: radula in snails,
mayfly nymphs use bristles
– Filtering mechanisms:
• Fringes of hairs on
mouthparts and legs
• Caddisfly Nets
• Blackfly
Adaptation to Flowing Water
• Anchoring
– Flattening of bodies to stay in boundary layer
– Suckers, hooks, silky secretions
– Ballast
Adaptation to Flowing Water
• Modes of existence (habits)
– Skaters (water striders)
– Divers (water boatmen and diving beetles)
– Swimmers (streamlined mayfly nymphs)
– Clingers (net-spinning caddisflies, blackflies)
– Sprawlers (some mayflies and dragonflies)
– Climbers (damselflies, mayflies, chironomids)
– Burrowers (chironomids, oligochaetes,
bivalves)
Comparative Energy
Flow in Streams
• Bear Brook
– Wooded second order stream in
New England
– Dominated by allochthonous
inputs from forest canopy directly
and from upstream
Comparative
Energy Flow in
Streams
• New Hope Creek, NC
– Third order stream with more open canopy,
but still allochthonous material is more
important
Comparative Energy
Flow in Streams
• Thames River
– Larger stream with more varied sources of
primary production
Comparative Energy
Flow in Streams
• Silver Spring
– Large underground source of clear water
– Almost all production is autochthonous
Stream
Energy Flow
• Importance of
insects to
stream food
web is shown
by experiments
that
substantially
removed
insects from
the stream
food web
Stream Energy Flow
• Importance of autochthonous production in
small to medium streams?
• Minshall (1978) argues that it has been
underestimated
Stream Energy Flow
• Streams in some areas have little or no
canopy, eg prairie, desert, urban, farm
Example:
Deep Creek,
Idaho
Small stream
(1-6 m wide,
10-60 cm
deep)
In Great Basin
Stream Energy Flow
• In streams with
deciduous canopy,
during periods with
no leaves, light
reaching stream is
substantial
• Periphyton
production tends to
be highest in spring
and fall when
consumers are
most active
Stream Energy Flow
• Even in streams with relatively closed
canopy and apparent low algal density,
periphyton may be important
– High rates of production may occur under low
light (shade-adapted)
– High rates of production may be masked by
high rates of production (grazing rate ≈
production)
– Periphyton are a high quality food source and
important food supplement
Large Rivers
• In large rivers,
interactions between
main river channel and
floodplain become
increasingly important
• Length>2000 km,
Order>7
Large Rivers
• Channel is deep and turbid
• Substrate is fine and in
constant motion
• Upstream food supplies are of
poor quality, best compounds
have already been utilized
• Many backwaters and side
channels with slower flow
• Flood plain inundation is
relatively predictable so aquatic
communities can adapt to this
as a resource
Large Rivers
• Many large rivers
show a single
strong annual
discharge peak
which inudates
the floodplain
• “Flood-pulse”
concept
Large Rivers
• Flood pulse concept
emphasizes lateral or
latitudinal gradients whereas
RCC emphasizes longitudinal
processes
Large Rivers
• Single large pulse
inundates the entire flood
plain
• Land-water interface
(littoral) is pushed to the
edge of the floodplain
• As year proceeds, the
moving littoral (ATTZ)
slowly edges back toward
the channel margin
• ATTZ-aquatic-terrestrial
transition zone
Large Rivers
• The flood plain has
high productivity due
to:
– High nutrient
concentration
– Shallow water depth
– Low current velocity
& resulting increase
in transparency
– Lots of edges
Large Rivers
• Habitats within the
floodplain:
– Backwaters
– Lakes
– Wetlands
Large Rivers – Exchanges of
Materials
• River brings
– Plant nutrients (N&P),
organic particulates,
inorganic particles
from upstream
– N&P  fuel high
production
– Particulates  build
up flood plain, carry P
• Flood plain contributes
– Fresher CPOM, FPOM,
DOM than upstream
sources
– Nursery ground for
many invertebrate prey
organisms
– Many larger predator
animals enter flood plain
to feed
Large Rivers - Biota
• Plants
– Respond to water levels
– Amazon plants grow fastest at rising water levels
– At this time water and nutrient levels are high and
no low DO stress that occurs later
– Seed production coincides with peak O2 levels
Large Rivers Biota
• Animals enter the flood
plain to feed
• On rising tide much of
food consists of pollen,
fruits, seeds, terrestrial
insects dropping from the
canopy
• Spawning occurs near the
beginning of the rising
water
• Larvae and juveniles feed
in the flood plain, adults
move back into the main
channels
Large Rivers - Animals
• Timing of flood
waters affects
usefulness to
differing groups
of biota in
temperate areas
Origins of Lakes
•
•
•
•
•
•
Glacial
Tectonic
Volcanic
Solution
Fluviatile
Impoundments
Origins of Lakes
• Glacial phenomena
are responsible for
the greatest
number natural
lakes esp the
immense number of
small lake basins
Origins of Lakes
• Glacial action in
currently restricted to
Antarctic, Greenland
and high mountains,
but during the
Pleistocene
glaciation, vast ice
sheets covered
much of the Northern
hemisphere
Origins of Lakes
• Definitions:
– Drift: accumulation of material directly or indirectly resulting
from glacial action
– Moraine: drift deposited directly by glacier either at its end
(terminal) or underneath (ground)
– Outwash: drift washed away from a glacier and deposited
Origins of Lakes
• Glacial Rock Basins
– Lakes formed by direct
glacial scour of rocky
basins
– Includes small lakes
such as cirques formed
at the head of glacial
valleys
– Also includes larger
fjord lakes like Loch
Ness and Lake
Windermere
Origin of Lakes
• Moraine or
outwash
dams
– Back up
water into
an existing
valley
– Finger
Lakes, NY
Origin of Lakes
• Drift Basins
– Irregularities in the
ground moraine such
as ice blocks left
behind which then
melt
– Kettle lakes
– Northern Wisconsin,
Walden Pond
– Vast number in flat
glaciated areas
Origin of Lakes
• Tectonic Activity
(crustal instability
and movement)
– Graben = faulttrough = rift lake
– Formed between
two faults
Origin of Lakes
• Some are
symmetrical
such as
Lake Tahoe
• Some are
assymetrical
such as
Lake
Tanganyika
Origin of Lakes
• The World’s oldest and deepest lake –
Lake Baikal is a graben complex