Download Lecture Notes for ecological_structure

1. Longitudinal Patterns in ecological organization of Rivers
•Patterns in species richness
•Patterns in species composition
•Patterns in functional organization
•Patterns in habitats and environmental template
2. Processes and Mechanisms…
Species area curves for Stream Fish in
356 Catchments: Lower Peninsula, Michigan
6
5.5
ln Fish = 1.42 + .23 * ln Area; R2 = .31
5
4.5
ln No. of Species
4
3.5
3
2.5
2
1.5
1
.5
3
4
5
6
7
8
9
Catchment Area (ln km2)
ln No. of Species
Species Diversity of Stream Fish Assemblages
in 18 Major River Basins: Lower Peninsula, Michigan
ln Fish = 1.25+ .36 * lnArea; R2= .83
4.75
4.5
4.25
4
3.75
3.5
3.25
3
5.5
6
6.5
7
7.5
8
8.5
Basin Area (ln km2)
9
9.5
10
(Sepkowski and Rex 1974)
Bivalve [Unionidae] spp in Atlantic coastal rivers
Longitudinal Zonation in species composition
Observations
•Carpenter (1928)
•Huet (1949-1962)
•Illies et al. (1955,1963)
•Statzner (1986)
Theories
Huet’s fish-zones of Western Europe (1949-1962)
Huet’s “slope rule” for western European streams
Illies (1955) Major River Zones
Crenon
Rhithron
Potamon
Source areas: glacial meltwaters, springs, wetlands, lakes.
small very cold, low to moderate slopes, fauna variable
Mean monthly temp rises to 20 C; high oxygen concentrations
flow is turbulent; erosional, gravel-cobble substrate predominate
Fauna is cold stenothermal. No true plankton.
Mean monthly temp above 20 C; oxygen deficits may occur.
Flow is slower, tends towards laminar.
Sand and finer substrates are dominant.
Fauna is eurythermal and most species well-adapted to lentic settings.
Plankton develops.
Illies and Botosaneanu (1963)
Latitude:
high
middle
low
Illies (1955)
What causes Longitudinal variation in biological communities?
Variables associated with longitudinal patterning
•changes in biological community
•temperature
•substrate
•hydraulics (slopes, velocities, power dissipation)
Processes associated with longitudinal structure
•changing landscape controls on carbon production [light, nutrs, alloch source]
•demographic equilibria
•changing temperatures
•patterns in hydraulic stress and disturbance
•increasing habitat diversity with hydrologic scale
•population interactions (predation, competition, and disease)
•{changes in water quality}
The River Continuum Concept
[RCC]
Vanote et al 1980
Key ideas in the RCC
Hydraulic gradients organize carbon sources for the food web
Hydraluic gradients organize temperature variability
Community composition equilibrates to carbon sources
Species diversity reflects temperature variability
emphasis on continua [gradients] rather than zones
background concepts
Sources and fate of organic carbon
two general categories for sources
allochthonous from “outside”
soil water, leaves, woody debris, blown in insects,etc.
autochthonous from “self”
aquatic primary producers:vascular plants, algae, autotrophic bacteria
•terrestrial versus aquatic origin
•here versus there
RCC background concepts
Veg
Edge/area
allocthonous
[terrestrial
leaves, wood, DOC]
autochthonous
[algae+ macrophytes]
Veloc
Nutrients
DETRITAL
POOL
Ldecomposers
Bacteria & fungi
L1
L0
L2
grazers
shredders
collector-gathers
filter-feeders
invert
predators
Light
invertivorous fish
/birds
L3
L4
piscivorous fish
L5
piscivorous birds
/mammals
NR411
River Food Web
BASICS
trophic role:
decomposer
food web position:
trophic category:
functional feeding designation:
Common Name
Principal Taxa
??
bacteria
x
??
fungi
x
macro Algae
Chlorophyceae and others
diatoms
Bacillariophyceae
mosses
Bryophytes
aquatic plants
Macrophytes
sow Bugs
Isopoda
scuds
Amphipoda
snails
Gastropoda
clams
Bivalvia
mayflies
Ephmeroptera
stoneflies
Plecoptera
dragonflies
Odonata
damselflies
Odonata
bugs
Hemiptera
alder and dobson flies
Megaloptera
caddisflies
Trichoptera
2-winged flies [e.g. midges,
Diptera blackflies]
butterflies
Lepidoptera
crayfish
Decapoda
boney fishes
teleost fishes
birds
various spp [kingfishers, mergansers, herons]
mammals
otter, mink, beaver, people
producer
primary
consumer
primary
herbivore detritivore/omnivore
grazer
shredder
filter-feeder collector
secondary tertiary
invertivore piscivore
predator
predator
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Relative importance of autochthonous and allochthonous inputs often a matter of
physical opportunity
e.g. lakes versus small woodland stream
auto>allo
allo>auto
CPOM
allo?auto
DOC
sometimes a matter of human intervention-e.g.: organic pollution
Death, Detritus and Decomposition
allochthonous inputs are already usually dead or soon dead -> detrital carbon
autochthonous carbon eventually dies
-> detrital carbon
because HOH is a solvent, the chemical nature of detritus rapidly diverges from that of living carbon
role of the biota
bacteria & fungi colonize detrital surface and enzymatically extract labile compounds
larger macro-invertebrate shredders (caddisflies, craneflies, some stoneflies, amphipods etc.) mechanically
breakup larger pieces (CPOM) while feeding on attached decomposers and in some cases on the CPOM
itself…
really feeding on the microbial community on the CPOM; like peanut butter on a cracker
Carbon form
Lipids
Carbohydrates
Deciduous leaf
Deciduous wood
bacteria
fungi
Aq. macrophytes
8
2-6
10-35
1-42
4-5
22
1-2
5-30
8-60
20-70
Cellulose/
structural polysaccharides
29
36-50
4-32
2-15
14-61
Protein
9
insig
50-60
14-52
8-35
Decomposition in an aquatic environment
Decomposition
Autolysis + leaching + mechanical breakdown + biochemical mineralization by respiration
generally involves a serial reduction in both size and quality
CPOM->FPOM->VFPOM<->DOM -> INORG C
mediated by biology
bacteria,fungi,shredders, fp detritivore
% remaining
Decomposition rates
time
masst = massinit * e -Kt
Example plant
White oak (Quercus alba)
Dogwood (Cornus amomum)
K (days -1)
.005 or less
.010-.015
T50
4.6 months
1.5-2.5 months
T90
>15 months
8 months
Cattail (Typha latifolia)
Najas (N.flexilis)
Pondweed (Potomogeton spp.)
.01
.022
~.1
2.5 months
1+ month
1 week
8 months
< 4 months
< 1 month
•differential decomposition rates
•Allochthonous: willow>alder>dogwood>maple>aspen>oak>pine&spruce
•Autochthonous: algae> submersed aquatic macrophytes> emergent/terrestrial macrophytes
• life cycle timing of shredders often cued to cued to leaf fall in temperate NA
2 sources: allochthonous and authochthonous
2 pathways: detrital and herbivorous
allocthonous
[terrestrial
leaves, wood, DOC]
autochthonous
[algae+ macrophytes]
DETRITAL
POOL
Ldecomposers
Bacteria & fungi
L1
L0
L2
P/R = Ecosystem Photosynthesis /Respiration
grazers
shredders
collector-gathers
filter-feeders
invert
predators
invertivorous fish
/birds
L3
P/R ~ autoch /(autoch + alloch)
P/R ~ total carbon produced/ total carbon respired
L4
piscivorous fish
L5
piscivorous birds
/mammals
P/R>1
autotrophic
Photosynthesis
Org
Carbon
Respiration
P/R<1
Org
Carbon
heterotrophic
Respiration
Photosynthesis
Photosynthesis
Heterotrophic
(dystrophic)
P/R<1
Org
Carbon
Allocthonous
inputs
Respiration
Advective
transport
“downstream”
The River Continuum Concept
[RCC]
Vanote et al 1980
Caveats…
Number of taxa
Species- Area Relationships
Observed: log-normal distribution
Number of individuals
Darlington 1952
Preston 1962
MacArthur and Wilson 1967
Sample size
Log S = .263 J/m + 3.17
S …# of spp
J …# of individuals in sample
m …# of individuals in rarest spp
if randomly dispersed
J~ area sampled
S = c AREA Z
Z=
theoretical = .26
insular fauna= .23-.35
non-insular = .12-20
Immigration rate
larger
Equilibrium Theory
smaller
[Island Biogeography 1967]
Number of species
harsher
milder
Extirpation rate
Immigration rate
Extirpation rate
MacArthur and Wilson’s
Number of species
Demographic equilibrium
applied to river networks
upstream
Number of species
Harsher-less storage
Milder-more storage-
Extirpation rate
Immigration rate
Extirpation rate
Immigration rate
Downstream-larger upstream species pool
Dowbstream equilib.
Upstream equilib.
Number of species
Temperature
its’ effect on biology
is profound
Zonation and temperature
Some thermal changes
are more important than other
SHORTWAVE RAD.
BLACKBODY
CONVECTION
LONGWAVE RAD.
EVAPORATION
Ground water
ADVECTION
CONDUCTION
Tributaries
ADVECTION
Proximate mechanism:heat Budget
Water temp = heat units/volume * 1/specific heat
Heat Balance Equation:
dheat/dt = S
Radiation (short-wave)
Radiation (long-wave)
Back Radiation
Convection
Conduction
Evaporation
Advection
f(SA,sunlight)
f(SA,air temp)
f(SA, water temp)
f(SA,temp diff,wind)
f(Perim,soil temp)
f(SA,humidity,wind)
f(source temps)
Proximate mechanism:heat Budget
dheat = Radiation (short-wave)
Radiation (long-wave)
Back Radiation
Convection
Conduction
Evaporation
Advection
f(SA,sunlight)
f(SA,air temp)
f(SA, water temp)
f(SA,air-water temp diff, wind)
f(Perim,soil-water temp diff)
f(SA,water temp, humidity,wind)
f( confluing source temps)
when dheat = 0, temperature equilibrium (constant)
Temp equil = T0 e-kt
Proximate mechanism:heat Budget
Longitudinal effects:
Runoff routing
Velocity?
Volume (Q) ?
Te
GW routing
Ultimate mechanism:landscape
dheat/dt = S
Key modifying factors
Radiation (short-wave)
Radiation (long-wave)
Back Radiation
Convection
Conduction
Evaporation
Advection
f(SA,sunlight)
f(SA,air temp,riparian structure)
f(SA, water temp)
f(SA,air-water temp diff, wind)
f(Perim,soil-water temp diff)
f(SA, temp, humidity diff,wind)
f( confluing source temps &vol)
riparian shade,climate
riparian shade,climate
water temperature
channel shape,climate
channel shape,climate
wind, riparian conditions
Stratification effects
f(lentic volume,SA,strat)
lakes,wetlands,reservoirs
hydro-geology,landuse
heat content proportional to volume
heat flux proportional to surface area
July mean Co
30
25
20
15
10
5
0
0
2000
4000
6000
8000
10000
Watershed Area km2
12000
14000
16000
Proximate mechanism:heat Budget
Diel effects:
Te_day
Te_night
Velocity?
Volume (Q) ?
2899
2738
2577
2416
2255
2094
1933
1772
1611
1450
1289
1128
967
806
645
484
323
1
2917
2755
2593
2431
2269
2107
1945
1783
1621
1459
1297
1135
973
811
649
487
325
163
-2
162
1
18
16
14
12
10
8
Upper Cedar
April, 2003
6
4
2
0
16
14
12
10
8
Lower Cedar
April, 2003
6
4
2
0
20
July mean Co
Daily flux Co
18
16
14
12
10
8
6
4
2
0
0
2000
4000
6000
8000
10000
12000
14000
16000
0
2000
4000
6000
8000
10000
12000
14000
16000
30
25
20
15
10
5
0
Watershed Area km2
20
Daily flux Co
18
16
14
12
10
8
6
4
2
0
0
2000
4000
6000
8000
10000
12000
14000
16000
Longitudinal Gradients in depth, velocity, substrate, shear stress,
Catastrophic
disturbance
Velocity
Position
and
movement
shear
Habitat utilization
substrate
Diffusion,
Reaeration
&
metabolism
A Lotka-Volterra 3 species simulation
dx/dt = rX - (kxX - ayxY - azxZ) 1/kx
dy/dt = rY - (kyY - axyX - azyZ) 1/ky
dz/dt = rZ - (kzZ - ayzY - axzX) 1/kz
axx ayx azx
.5 .75 .5
axy ayy azy
.3
1
.7
axz ayz azz
.1 .1
1
xr .01 kx
yr .007 ky
zr .05 kz
600 red
1000 blue
500 green
Disturbance frequency = 0
Disturbance frequency = 2
Disturbance frequency = 4
Disturbance frequency = 0
Disturbance frequency = 7
Disturbance frequency = 13
Disturbance frequency = 0
Disturbance frequency = 20
Disturbance frequency = 100
Number of species
Total population size
Intermediate Disturbance Hypothesis
Log Frequency of Disturbance
Geomorphic effects on Biology
Nutrient gradients and the regional
structure of stream communities
C.H.Riseng, M.J Wiley and R.J. Stevenson2
80,000.0
60,000.0
40,000.0
30,000.0
20,000.0
Benthic Biomass (mg m
-2
)
10000.0
6,000.0
4,000.0
3,000.0
2,000.0
1000.0
600.0
400.0
300.0
200.0
100.0
60.0
40.0
30.0
20.0
10.0
6.0
4.0
3.0
2.0
1.0
0.0
2
3
4
5 6 7 8
0.1
2
3
4
5 6 7 8
(Critical SS for d84 / gRS) bankfull
1.0
2
3
What kinds of Disturbances
might potentially shape stream insect communities?
High Flow events
(Floods)
Low flow events
(Droughts)
Pathogen outbreaks (Disease)
Catastrophic
disturbance
Velocity
Position
and
movement
shear
Habitat utilization
substrate
Diffusion,
Reaeration
&
metabolism
Because the rate of molecular diffusion is faster in air than in water all organisms
that take dissolved oxygen from the water to support their metabolism
face a fundamental physical constraint related to diffusion rate:
Fick’s Law
again provides a basic description of this diffusive process
diff rate = K (saturation - concentration)
diff rate = kA/L (pO2 inside - pO2 outside)
k=rate constant characteristic of the type of tissue oxygen must diffuse across (gill, cell
wall. etc.)
A= exchange surface area where diffusion can occur
L= diffusion distance (how far molecules must travel)
(pO2 inside - pO2 outside)= gradient in partial pressure of oxygen
(pO2 inside - pO2 outside)  gradient in oxygen concentration
effectively depends on the external oxygen concentration since internal
oxygen levels almost always low
for a simple imaginary organism
resp
rate
time
time 1
begins with resp rate set by kA/L and the external O2 concentration
but rate of resp decreases with time
occurs because of O2 depletion immediately around exchange surface
resp
rate
average diffusion
distance
time 2
time
average diffusion
distance
Intrinsic problem with diffusion in water
due to relatively low diffusion coeff in water
time 3
solution: ventilate  replace water at exchange surface
average diffusion
distance
Stenacron
As the environmental O2
concentration declines, the
concentration gradient in
Fick’s eq, also declines...
regulators must compensate
by ventilating more rapidly
in order to decrease the
diffusion distance and offset
the gradient decline.
Many aquatic animals actively ventilate exchange surfaces
ventilation periodically replaces spent water
 controlling deterioration of diffusion distance
animals which manipulate diffusion distance or other parameters of Fick’s law
are called respiratory regulators
animals ventilate by different methods
e.g. mayflies, fish, dragonflies
Not all aquatic animals invest energy and tissue in diffusion regulation
organisms which let their respiration rate vary with ambient O2 levels are called
respiratory [ metabolic] conformers
conformers
respiration
rate
regulators
oxygen concentration
Concentration-velocity tradeoffs
For conformers
current velocity
can act as a
substitute for O2
concentration in
terms of regulating
respiration rates.
For regulators
reduced velocity
requires more
work and therefore
energy
Heterotroph oxygen requirements
Even regulators have a concentration below which they can not further compensate by ventilation,
below that critical concentration metabolic rate declines with declining oxygen. For regulators, this
critical concentration represents a concentration threshold below which an organisms energy supply
rapidly declines.
When respiration rates are only sufficient meet current maintenance costs, there is no excess eenergy
to invest in foraging, growth or reproduction. The concentration of oxygen which provides only this
level of respiration is known as the incipient lethal level, since an organism/population (although it
may live for some time) cannot achieve reproductive below this level.
At some low concentration (the acute lethal level) respiration rate is so far below immediate
maintenance needs that rapid death follows.
Respiration
rate
maintenance rate
critical concentration
incipient lethal level
acute lethal level
Oxygen concentration ---->
}
scope for
activity
Sublethal affects of low oxygen
When [O2] lies between the
critical concentration and the
incipient lethal level,
an organisms ability to do
physiological work is
diminished.
reduced oxygen can have
important sublethal affects
on feeding, growth,
locomotion and even
survival
Lethal Limits
Acute lethal levels of oxygen vary considerably between organisms
•Concentrations below 1-2 ppm are lethal to a wide array of aquatic organisms.
•Concentrations below 4 ppm are lethal to many, a common regulatory water quality standard.
•Some organisms can survive <1 ppm (are especially tolerant) and dominate low oxygen environments.
Acute lethal [O2] ppm
•Velocity - [O2] tradeoffs can be important here too, especially for conformers.
1
2
3
4
5
current velocity cm sec-1
6
What determines Oxygen concentrations?
ATMOSPHERE
Henry's law
for gases dissolved in water
[c]=solubility * partial pressure
[c] is the equilibrium saturation conc
= the concentration the system reaches if left alone
note it is independent of starting concentration
Henry's law
ATMOSPHERE
[c]=solubility * partial pressure

[c] is an important benchmark

if water conc > henry's saturation value then atm is a sink

if O2 is less than saturation concentration: atmosphere is a source

Henry's law applies to all gases in the atmosphere

Different partial pressures and different solubility lead to different
concentrations in aqueous solution.
Partial pressure%
CO2
0.03
02
20.99
N2
78.0 ppm
solubility at 0 C
solubility at 10 C
solubility at 20 C
solubility at 30 C
3350 ppm
2320 ppm
1690 ppm
1260 ppm
69.5 ppm
53.7 ppm
43.3 ppm
35.9 ppm
28.8 ppm
22.6 ppm
18.6 ppm
15.9 ppm
saturation at 0C
saturation at 10C
saturation at 20C
saturation at 30C
1.005 ppm
0.70 ppm
0.51 ppm
0.38 ppm
14.5 ppm
11.1 ppm
8.9 ppm
7.2 ppm
22.4 ppm
17.5 ppm
14.2 ppm
11.9 ppm
ATMOSPHERE
How long does it take
Oxygen to reach saturation?
Fick’s Law
provides a basic description of the rate at which diffusive processes occur.
diffusion rate = K ([Saturation] - [O2 ] )
k = rate constant, sometimes called the diffusivity
Bulk reaeration rate
k = f[molecular diffusivity and eddy diffusion (turbulence)]
ATMOSPHERE
Fick’s Law implies that Oxygen concentration approach equilibrium asymptotically
When [saturation-DO] is large, rates of exchange with the atm are high
When [saturation-DO] is small, rates of exchange are small
The direction of oxygen exchange depends on Henry’s law
•if over-saturated (supersaturated) water will lose oxygen to atmosphere
•if under-saturated, water will gain oxygen from the atmosphere
diffusion rate = K ([Saturation] - [O2 ] )
Saturation
diffusion 0
rate
time
Output 2
Using a Mass Balance Approach
Boxes = mass storage
arrows = rates of flux
Mass
Input 1
Output 1
Input 2
then
Dmass in storage per unit time = Sinputs - Soutputs
For the example diagram above
d/dt Mass=[ (Input 1 + Input 2) - (Output 1 + Output 2)]
ATM
Mass balance for O2
diffusive aeration
photosynthesis
O2
respiration
DO2 = Photosynthesis - Respiration  diffusion
d/dt O2=[ P - R  k([saturation]-[O2])]
ATM
Streeter-Phelps Model
diffusive aeration
O2
Respiration due organic pollution
Carbon and nitrogen
(ss +diss)
DO2 = Respiration  diffusion
d/dt O2=[R  k([saturation]-[O2])]
predicts an temporary oxygen sag downstream form sewage plant effluents
Diffusion is a constant process, but biological activity is
not. Photosynthesis varies in a regular diel fashion
following the availability of light. The O2 mass balance
100% Saturation
equation can be thought of as having two distinct forms:
during the day
DAY
NIGHT
DAY
supersaturated
100% Saturation
DDO=P-R± k[saturation-DO] but
during the night DDO=R± k[saturation-DO] since P=0
The shape of this diel oxygen curve is determined
by the relative magnitude of the component rates
[diffusion, photosynthesis and respiration]. When
diffusion rates are high due a high reaeration
coefficient (k) and biological rates are relatively
low, almost no diel sag is detectable-- diffusion
swamps the P-R term in the mass balance.
diffusion
+++++++++++++++++++++----------------------------------++
P-R
++++++++++------------------------------------++++++++
DAY
DAY
supersaturated
100% Saturation
100% Saturation
diffusion
-+++++++++++++++++-------------------------------
P-R
+++++++++++------------------------------------++++++++++
DAY
When biological rates are high (e.g., nutrientrich systems like agricultural streams) or
diffusion rates are relatively slow (e.g. stagnant
ponds), biological processes can swamp
diffusion rates and lead to widely fluctuating
diel curves
NIGHT
NIGHT
DAY
supersaturated
100% Saturation
100% Saturation
diffusion
---++++++++++++++++++--------------------------------------
P-R
+++++++++-------------------------------++++++++
Catastrophic
disturbance
Velocity
Position
and
movement
shear
Habitat utilization
substrate
Diffusion,
Reaeration
&
metabolism
Mapping approaches to Longitudinal Structure
Where
Homogeneous longitudinal units
[ geomorphic/ecologic]
data
Landscape (GIS) data
Registered field data
Model projections
Scale
Valley segments
Reaches
Basins
Current examples:
MRI-VSEC (IL,WI verions);
TNC Macrohabitat Classifications
USGS Aquatic GAP program
Geomorphic Valley Segment Classifications [Hupp]
Geomorphic Reach Classifications [Rosgen]
What is Ecological Unit Mapping?
“Identifying the basic [structural] units of nature” (Rowe 1991)
Geomorphic
character
Biological
character
Integrated
Ecological
Character
of a River Segment
Hydrologic
character
Chemical
character
Raisin River
mainstem units
Central role of GIS
Michigan Rivers Inventory
VSEC units MAP
10 km
270 main river segments
and
400 tributary units
[mri-vsec v1.1]
Grazers:
Animals that feed on living algae or
macrophyte tissue. Some are free roaming,
others are central-lace foragers making
short excursions out from some central tube
or burrow.Specialization by growth form
common but not by plant species.
Food types: algae, vascular plant tissue (rare)
examples: many mayflies, many midges, many cased caddisflies, some stoneflies
Shredders:
Animals that feed on large allochthonous
organic carbon fragments (e.g.leaves) which
have been colonized by bacterial and fungal
communities. Some shedders have
commensal gut flora to assist in the
digestion of cellulose. A few have specialized
enzymes to assist in the same task..
Food types: coarse particulate carbon (CPOM), and associated microflora
examples: Cranefly larvae (Tipula), Giant stoneflies (Pteronarcys), many cased caddisflies, scuds
Filter Feeders:
Animals that feed by filtering suspended
Organic material from the water column.
Filtering mechanisms can be
anatomical [e.g. blackflies]
or more elaborate constructions
involving silk capture nets
[e.g. some Caddisflies and midges]
Food types: animal, algae, detritus
examples: blackflies, net-spinning caddisflies, burrowing mayflies
Collector-gatherers:
Omnivorous animals that feed by moving
around the substrate in search
of fine particulate organic matter (FPOM)
which is either ingested on the spot, or
retrieved and accumulated at some central
tube or burrow. Often includes embedded
algae and even small animals.
Food types: algae, detritus
examples: some mayflies, many midges and worms (tubificids), scuds
Predators:
Animals that feed on other animals. An
invertivore feeds principally on
invertebrates.
Food types: animal tissue
examples: dragonflies, many stoneflies, water scorpions and other bugs, most smaller fishes