Transcript Marine Ecology-- 2009 final Lecture 1May 30

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 predict these patterns?
– Can we find underlying mechanisms that
produce the patterns?
Natural History
• Ecologists understand nature by:
– Asking questions
– Discovering connections
– And developing a detailed understanding of
natural phenomena
• Natural History forms the basis of ecology
Natural World is Dynamic
• Constant tension between change and
equilibrium
– Removal of organisms by death
– Replacement by birth
• Disturbance
• Renewal and Replenishment
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
Individual
• Autecology
– relationship between individual organisms
and their environment
• Ecophysiology
• Evolutionary ecology - study of adaptation
Population ecology
• A group of same species inhabiting a particular area
• Study of
– Species properties (birth rate, death rate)
– Interactions with environment
that determine population size (& structure)
Community
• Species that occur together in space and time
(Begon et al. 1990)
• An association of interacting populations,
usually defined by the nature of their interactions
(Ricklefs 1990)
Community Structure
• Species composition
• Relative abundance
• Size
• Trophic relationships
• Species diversity
What controls structure?
Patterns and Processes
• Distribution, Abundance and Diversity
• Competition
• Predation/grazing
• Supply side ecology – settlement / recruitment
• Habitat modification
Ecosystems Ecology
• An ecosystem is a biotic community and the
abiotic environment, and is the functional
system that transfers and circulates energy
and matter.
• Ecosystems ecology is concerned with interactions
between organisms and their environments, and
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 whole community of
floating organisms (plankton) . Nothing comparable on
land, and a fundamental difference.
•All other marine organisms are bathed in seawater
which contain this planktonic community.
•Led to the evolution of filter feeding organisms
•Dispersal stage for many organisms which produce
larvae which can and so 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 (must rely
on energy that drops down on them from the productive
zone above).
Terrestrial vs Marine Environments
Physical and Chemical Differences
3. Gravity – because bouyancy is provided by the seawater,
organisms do not have to invest as much energy in skeletal
material (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
Exceptions?
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.
Terrestrial vs Marine Environments
Biological Differences
Land
Sea
a. Large plants dominate the system
(long lived)
a. Microscopic plants dominate
(few exceptions) (short lived)
b. Dominant herbivores – large
(insects to elephants)
b. Dominant herbivores – small
(mostly microscopic; copepods)
c. Plant Community matrix
-mostly indigestible
-small portion of individual plant
removed at any one time by
herbivore (deer taking leaves off a
shrub = partial predation)
c. Plant is consumed in its entirety
Differences in Primary Producers
Terrestrial vs Marine Environments
Biological Differences
Land
Sea
a. Large plants dominate the system
(long lived)
a. Microscopic plants dominate
(few exceptions) (short lived)
b. Dominant herbivores – large
(insects to elephants)
b. Dominant herbivores – small
(mostly microscopic; copepods)
c. Plant Community matrix
-mostly indigestible
-small portion of individual plant
removed at any one time by
herbivore (deer taking leaves off a
shrub = partial predation)
c. Plant is consumed in its entirety
Differences in herbivore size
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
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
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,
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 predator sizes
– And, the largest
marine predators and
their prey are larger
by 1-2 orders of
magnitude than
continental predators
and their prey
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
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,
transfer of energy less efficient
(from 1st to 2nd trophic level)
f. Production lower, transfer of
energy more trophic level)
Time scale of study
• Ecological:
– Question is how organisms function now
– How do contemporary processes act to maintain
observed community structure?
• Evolutionary
– Question is the history of how a community
came to its present state over evolutionary time
– How do species evolve in response to selection
due to community processes?
Temporal and Spatial Scale
Matters
Ecological vs. Evolutionary
questions
• Ecological studies much more readily done
• Evolutionary studies rely less on direct
experiment and more on comparative,
observational, & theoretical methods
• Evolutionary questions imply ecological
questions
• Ecological questions do not necessarily
imply evolutionary questions
Important Abiotic and Biotic Influences
on the Distribution of Marine Organisms
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 nicheis usually a smaller
hypervolume, whose smaller size is due to the
negative effects of biotic interactions.
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
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 nonnative species and destruction and alteration
of critical habitats
Shifting Baselines