Transcript Marine Ecology-- 2011 final Lecture 1

Ecology
• Study of the relations of organisms to one
another and to their surroundings
• We seek to understand the order of the natural
world
– Can we identify patterns and connections
between organisms and their physical
/chemical environment?
– Can we find underlying mechanisms that
produce the patterns?
– Can we predict these patterns?
Natural History
• Natural History forms the basis of ecology
---it is essential to understand the biology of
the organisms you are studying
Levels of Complexity
Solar system
Planet earth
Ecosystems
Communities
Populations
Organisms
Cells
Molecules
Atoms
Sub-atomic particles
Ecological Questions
• “Ecology starts with a question”
• Proximate Questions
– Questions about mechanisms or functions
underlying current patterns
• Ultimate Questions
– Questions about selective pressures over
evolutionary time
Ecological vs. Evolutionary
questions
• Ecological studies are much more readily
done, and experiments are common
• Evolutionary studies rely less on direct
experiment and more on comparative,
observational, & theoretical methods
Individual
• Autecology
– relationship between individual organisms
and their environment
• Ecophysiology
• Evolutionary ecology - study of adaptation
Population ecology
• A population is formed by multiple individuals of the
same species inhabiting the same area at the same time.
• Population ecology is the study of:
– Species properties (birth rate, death rate)
– Interactions with the environment
that determine population size (& structure)
Community
• A community is an assemblage of multiple
species that occur together in space and time
or
• An association of interacting populations,
usually defined by the nature of their interactions
Community Structure
• Species composition
• Relative abundance
• Size spectrum
• Trophic relationships
• Species diversity
What controls structure?
Processes
• Competition
• Predation/grazing
• Supply side ecology – settlement / recruitment
• Habitat modification
Ecosystems Ecology
• An ecosystem is a biotic community together
with the abiotic environment, and is the
functional system that transfers and
circulates energy and matter.
• Ecosystems ecology is concerned with the
fluxes of energy between different elements
of food webs, and of materials such as
nutrients (e.g., Nitrogen and Phosphorus)
Ecosystems Are Energy
Transformers
J.M. Teal (1962)
Terrestrial vs Marine Environments
Physical and Chemical Differences
1. Seawater is much denser than air (= organisms float in
it readily)
Result: Aquatic ecosystems evolved a whole community of
floating organisms (plankton) . Nothing really comparable
on land, and a fundamental difference.
•All other marine organisms are bathed in seawater
which contain this planktonic community.
•Has led to the evolution of filter feeding organisms, and
•Dispersal stages for many organisms which produce
larvae that become part of the plankton
Terrestrial vs Marine Environments
Physical and Chemical Differences
2. Seawater strongly absorbs light (most of the light is
gone below 100m).
•
Most of the world’s oceans are without light which
prevents primary production in these areas (animals
must therefore rely on energy that drops down to them
from the productive zone above).
Terrestrial vs Marine Environments
Physical and Chemical Differences
3. Gravity – because buoyancy is provided by seawater,
organisms do not need to invest as much energy in skeletal
material (e.g., bone, cellulose)
Movements on land are energetically more costly – so
terrestrial forms require greater concentrations of energy.
Land forms
-carbohydrates
-long lived
-slow growing
-rich in stored energy
Sea forms
- proteins
- short lived
- rapid growth
- do not store energy
Terrestrial vs Marine Environments
Physical and Chemical Differences
4. O2 can be limiting in marine environments
Has consequences for the distribution and
abundance of many marine organisms because
areas can be so low in oxygen that they cannot
support life.
Terrestrial vs Marine Environments
Biological Differences
Land
a. Large plants dominate the
system (long lived)
Sea
a. Microscopic plants dominate
(most are short lived)
b. Dominant herbivores – large
(insects to elephants)
b. Dominant herbivores – small
(mostly microscopic, like
copepods)
c. Plant matrix is mostly
indigestible
-small portions of individual
plants consumed (deer taking
leaves off shrubs = partial
predation)
c. Plant is entirely consumed
(predation)
Differences in Primary Producers
Exceptions?
Terrestrial vs Marine Environments
Biological Differences
Land
a. Large plants dominate the
system (long lived)
Sea
a. Microscopic plants dominate
(with few exceptions, short lived)
b. Dominant herbivores – large b. Dominant herbivores – small
(insects to elephants)
(mostly microscopic, like
copepods)
c. Plant Community matrix is
mostly indigestible
-small portion of individual
plant removed (deer taking
leaves off shrubs = partial
predation)
c. Plant is consumed in its
entirety (predation)
Differences in herbivore size
Terrestrial vs Marine Environments
Biological Differences
Land
Sea
d. On land, fauna is short
d. In sea, fauna is long lived
lived compared to plants
(commonly named by
dominant plant; maple
forest, tall grass prairie)
compared to plants
(commonly named for
dominant animal; oyster
reefs and coral reefs)
e. Large animals are often
herbivores (lower trophic
level)
e. Large animals are often
carnivores (higher trophic
level)
f. Generally, production
higher, transfer of energy less
efficient (from 1st to 2nd level)
f. Production lower, transfer
of energy more efficient
(from 1st to 2nd level)
Differences in ages
Terrestrial fauna
short lived in
comparison to
plants (deciduous
forests), marine
fauna are longlived when
compared to plants
(coral reefs)
Terrestrial vs Marine Environments
Biological Differences
Land
Sea
d. On land, fauna is short
lived compared to plants
(commonly named by
dominant plant; maple
forest, tall grass prairie)
d. In sea, fauna is long lived
e. Large animals are often
herbivores (lower trophic
level)
e. Large animals are often
carnivores (higher trophic
level)
f. Generally, production
higher, transfer of energy less
efficient (from 1st to 2nd level)
f. Production lower, transfer
of energy more efficient
(from 1st to 2nd level)
compared to plants
(commonly named for
dominant animal; oyster
bank/ coral reef
Differences in predator sizes
– The largest marine
predators and
their prey are
larger by 1-2
orders of
magnitude than
terrestrial
predators and
prey
Terrestrial vs Marine Environments
Biological Differences
Land
Sea
d. On land, fauna is short lived
d. In sea, fauna is long lived
compared to plants (commonly
named by dominant plant;
maple forest, tall grass
prairie)
compared to plants (commonly
named for dominant animal;
oyster bank/ coral reef)
e. Large animals are often
herbivores (lower trophic level)
e. Large animals are often
carnivores (higher trophic
level)
f. Generally, production higher,
but transfer of energy less
efficient (from 1st to 2nd trophic
level); only 4 trophic levels
f. Production lower, but
transfer of energy more
efficient, (thus, more trophic
levels are possible; often 5)
Temporal and Spatial Scale
Matters
Important Abiotic and Biotic Influences
on the Distribution of Marine Organisms
Salinity
Salts can cause organisms to lose water through
osmosis. If this happens major disruptions in
ionic concentrations of body fluids occur,
resulting in severe stress or death.
Thus, organisms that can’t regulate their internal
salt content are restricted to waters where salt
concentrations allow them to survive.
Salinity varies with environment
•
•
•
•
Open ocean
Shallow coastal seas
Estuaries
Semi-enclosed seas
(Baltic Sea)
• Hypersaline Seas
(Red Sea)
•
•
•
•
32-38 (mean 35) psu
27-30 psu
0-30 psu
<25 psu
• >40 psu
Temperature in the Ocean
• Temperature is one of the most important
abiotic physical properties in the ocean
• Temperature controls the rate at which
chemical reactions and biological processes
occur
• As such, temperature can control the
distribution and abundance of marine
organisms and the function of marine
ecosystems
Temperature controls faunal
distribution patterns
• Sea surface temperature varies greatly with latitude
–
–
–
–
Tropical (25oC)
Subtropical (15oC)
Temperate (5oC northern limit-2oC southern limit)
Polar <2oC
Temperature varies with depth
• Thermocline is a A
layer of water in
which the
temperature
decreases rapidly
with depth.
Light in the Ocean
• Light is essential for many aspects of life in the
ocean
• Light supplies the energy used by autotrophs to
convert inorganic matter into organic matter
• Light availability decreases with increasing
depth
• Animal depend on light to move around, detect
prey, predators and the timing of reproduction
Light penetration varies with depth
and location
• The depth to which different
colors of light penetrate ocean
waters. Water absorbs warm
colors like reds and oranges
(long wavelength light) and
scatters the cooler colors (short
wavelength light).
Dissolved Gases in the Ocean
• Dissolved oxygen is added to the ocean via mixing
with the atmosphere and photosynthesis
• Dissolved oxygen is lost from the ocean via
respiration by organisms
• Dissolved oxygen is controlled by temperature and
nutrient inputs
– Increased nutrient inputs in terrestrial runoff
can create hypoxia areas at the base of many
watersheds which cause dramatic changes in
marine communities
Origins of hypoxia
Waves and Tides
• Waves transfer significant amounts of energy
from the wind to the ocean
• The frequency and intensity of waves and the
materials they carry (wave shock) can play an
important role in determining the composition
of marine communities by
– abrasion
– crushing
– pressure drag
Sediment Type
• As a rule, muddy sediments support
more infaunal organisms than do sandy
sediments
• More filter feeders occur in sand and
more deposit feeders occur in mud
Nutrients
• Nitrogen and phosphorus are most
important, but other important nutrients
for plants and animals include silicon and
iron.
Dispersal
• Planktonic larvae
• Rafting
• Movement by Humans
Biological Interactions
• Factors such as competition, predation,
parasitism and mutualism
Habitat Selection
• Some organisms do not occupy all of their
potential range, even though they are
capable of dispersing into unoccupied areas
• Therefore, individuals can choose not to live
in certain areas, and the distribution of a
species may be limited by the behavior of
individuals in selecting where they live
Niches

The fundamental nicheis a multidimensional
hyperspace, defined by a species’ tolerance to
all environmental variables. (Problem: how to
measure all environmental variables? Answer::
restrict attention to the few that matter most)

The realized niche is usually a smaller
hypervolume, whose smaller size is due to the
negative effects of biotic interactions .
Important New Discoveries in
Marine Ecology over the Last
three Decades
• Deep-sea hydrothermal vents and other
habitats that rely on geochemical energy
rather than photosynthesis
• Biodiversity of every marine habitat that is
much greater than previously understood, as
primarily revealed by molecular studies
Important New Discoveries in
Marine Ecology over the Last
three Decades (2)
• Phytoplankton smaller than 2 micrometers,
and mostly unknown, account for up to half
of the oceans’ primary production
• Using field experiments, ecologists found
that complex, indirect effects among species
(known as trophic cascades) can affect food
webs profoundly and structure entire
communities over large areas
Important Progress in Marine
Ecology over the Last three
Decades (3)
• Humans have affected marine ecosystems
world-wide and fundamentally via
fisheries, aquaculture, addition of
nutrients and chemical pollutants,
introduction of non-native species and
destruction and alteration of critical
habitats
Shifting Baselines
• http://www.shiftingbaselines.org/slideshow/
index.html
• http://dotearth.blogs.nytimes.com/2011/04/1
4/climate-communication-and-the-nerdloop/
Eocene Epoch
Paleozoic Era
History of Soft-Sediment Communities
500 million
years ago
History of Soft-Sediment Communities
350 million
years ago
History of Soft-Sediment Communities
190 million
years ago
Modern Skeleton-Breaking Predators,
Which Structure Benthic Communities…
Bony Fish
Sharks and Rays
Crustaceans
…Diversified in the Mesozoic (25065 mybp)
History of Soft-Sediment Communities
History of Soft-Sediment Communities
40 million
years ago
Onshore-Offshore Theory
• Evolutionary novelties arise primarily in
nearshore, heterogeneous environments.
• Nearshore faunas expand offshore, species-byspecies, progressively displacing elements of
the previous fauna further offshore.
• This is why the deep sea is the repository of
living fossils and archaic, retrograde, primeval,
Paleozoic-type communities.
Some General Terms to Know
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Copepods
Polychaetes
Tunicates (Ascidians)
Diatoms
Foraminiferans
Sponges
Benthos
Plankton
Decomposer
Standing crop
Species richness
Sessile and sedentary
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Filter feeders (Suspension feeders)
Deposit feeders
Grazers
Carnivores
Primary production
Autotroph
Heterotroph
Trophic levels
Food chains, food webs
Detritus
Pelagic zone
Intertidal zone
Subtidal zone