Lake (limnic) ecosystems
 Origins and classifications
 Lakes as open systems
 Light and temperature
 Lake chemistry
 Primary productivity
 Secondary productivity
 Lake evolution
 Perturbations
Lake classification:
geological origin
Lakes result from impoundment of water by:
• tectonic downwarping (e.g. Lake Victoria)
• tectonic faulting (e.g. Dead Sea)
• volcanic eruption (e.g. Crater Lake)
• landslide dams
• ice dams
• biotic dams (e.g. Beaver lake)
• glacial erosion (e.g. Lake Peyto)
• glacial deposition (e.g. Moraine Lake)
• river channel abandonment (e.g. Hatzic Lake)
• deflation
Lake classification: morphology
• Lake morphology (size, surface area
and depth) largely determined by
origin.
• Substrate (rocky, sandy, muddy,
organic) initially determined by
geological origin; thereafter by
inputs.
Lake classification:
hydro-regime
• Open lakes have outflow
streams.
• Closed lakes are found in
endorheic basins in arid
areas; e.g Lake Eyre
(Australia): shallow lake
forms in La Niña years (e.g.
2000), usually persists for 1
year. Never overflows - lake
sits at 15m below sea level.
Lakes as open systems
Kamloops Lake: inflow, water level and
residence time variations
Thermal stratification of lakes:
the physical properties of water
Thermal stratification of
temperate lakes
Variations in epilimnion depth on
windy and calm days
Seasonal temperature profile
Lake
mixing
types
Lake mixing types
Turbidity,
illumination,
and the
euphotic
zone (--)
Kamloops Lake turbidity profile
Thompson R. inflow
equilibrium level
Kamloops
Lake:
euphotic
zone and
epilimnion
Biomass
(= lake
primary
productivity)
in relation to
P availability
Lake classification: trophic status
What is the trophic status of
Kamloops Lake?
Total P: 4 - 10 µg l-1
Total N: 150 -250 µg l-1
Total inorganic solids: 60 mg l-1
TN: TP = 25 -35
Mean primary productivity = 88 mgC m-2 d-1
Kamloops Lake: relative abundance
of phytoplankton groups
Kamloops Lake: primary productivity
euphotic
zone (May)
euphotic
zone (Aug.)
Energy sources
Small
temperate
lake fodwebs
are detritusbased
(e.g. Marion
Lake).
Predictions
for Kamloops
Lake?
Lake environment and community structure
(North American boreal lakes)
Environmental
factor
Fish assemblage
BASS
MUDMINNOW
PIKE
Area
pH
Conductivity
Depth
Isolation
large -------------------- small
high -------------------- low
high -------------------- low
shallow -- deep -shallow
low
-------------------- high
Lake evolution
1. All lakes are temporary features of the Erth’s
landscape - eventually they fill with organic and
inorganic sediments to become bogs or ‘playas’.
2. The pathway of lake evolution prior to infilling is
a matter of debate. The classical European
literature (1920’s -50’s) suggests that lakes
progress from oligotrophic to eutrophic status.
Pollution by agricultural fertilizers, etc. accelerates
this process.
Lake infilling: Cedar Creek,
Minnesota
Engstrom et al. (2000) Nature 408: 161
Lake evolution:
Glacier Bay foreland, AK.
Stream and lake evolution:
Glacier Bay foreland, AK.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Source: Milner et al., 2007, Bioscience, 57, 237-24
Perturbations of lake
environments
1. GEOLOGICAL
local events such as landslides;
regional events such as tephra deposition
2. CLIMATIC
changes in regional climate (precip. or evap.)
3. ANTHROPOGENIC
agricultural/industrial/urban pollution
4. BIOTIC
invasion by exotic species (often anthropogenic)
Perturbation: tephra deposition
into Opal Lake, Yoho NP
Hickman & Reasoner (1994) J. Paleolimnology 11, 173-
Perturbations
of coastal
lakes on
Vancouver
Island
Reconstructing
perturbations
in lake
environments
using diatoms
as a proxy for
lake chemistry
I: calibration
based on 53
lakes in
Ontario
II. Case study of anthropogenic
pollution of Little Round Lake, Ontario.
~1970
~1850
Stream (lotic) ecosystems
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Controls on stream ecosystems
Discharge regimes and biotic activity
Segment/reach analysis
Stream foodwebs
The river continuum concept
Nutrient cycling
Patch stability and dynamics
Stream communities
Physical
habitat
Biotic
community
• Physical structure
• Flow dynamics
• Community organization
• Community dynamics
Available species pool
Stream classification
Stream classification
Poff and Ward (1989)
Can. J.Fish. & Aquat. Sci. 46, 1805.
Discharge regimes
Poff and Ward (1989)
Can. J.Fish. & Aquat. Sci. 46, 1805.
Stream
segment
(reach)
classification
and analysis
Stream foodwebs
nutrient
sources
allochthonous
autochthonous
functional
feeding
groups
POM = particulate organic matter (C =coarse; F= fine)
DOM = dissolved organic matter
River continuum concept
• Continuous physical gradient from headwaters to
mouth.
• Consistent biotic patterns of loading, storage and
utilization of organic matter.
• Stream communities conform to the mean (most
probable) state of the physical system.
• Biotic communities are graded downstream to
accommodate leakage of organic matter from
upstream.
Vannote et al. (1980) Can. J.Fish. & Aquat. Sci. 37, 130.
RCC parameters
River
continuum
concept in
application
Vannote et al. (1980)
Can. J.Fish. & Aquat. Sci. 37, 130.
Headwater
streams are
heterotrophic
(P/R ratio <<1);
downstream
reaches are
balanced (P/R
ratio ~1)
Alpinearctic
streams:
dominantly
autotrophic
RCC:
boreal
streams
RCC:
deciduous
forest
streams
Stream nutrient cycling dynamics
Stream hierarchy and patch
(pool/riffle and microhabitat)
dynamics: complex habitats produce
stable communities
Pool-riffle
sequences and
patchy lotic
habitats
Blackwater rivers: terrestrial
inputs are not always beneficial
Kaieteur Falls, Guyana
Marine subsidies in riverine and
riparian environments
Salmon streams:
 dead salmon add considerable quantities of marinederived N (22-73% of total N) to their natal streams.
bears and other scavengers drag salmon carcasses
into riparian habitats; as a result (in AK-PNW):
 15-30% of the N in riparian plant foliage is derived
from marine sources; the amount declines with
distance from the stream;
 Sitka spruce grows 3x as fast adjacent to salmon
streams but western hemlock shows no response;
 annual variations in tree growth are significantly
correlated with salmon escapements in riparian
forests of the Pacific Northwest.
Notes derived from:
http://www.fish.washington.edu/people/naiman/Salmon_Bear/