EVPP 550Waterscape Ecology and

Management

Professor R. Christian

JonesFall 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 = fault-

trough = 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