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Marine Ecology
•
Species – a group of similar
organisms whose members
interbreed and produce viable
offspring.
•
Population – members of the
same species that live together in
the same area at the same time.
•
Community – all the populations of
different species that live and
interact together within an area at
the same time.
•
Ecosystem – a community
together with its physical (abiotic)
environment.
How Populations Work in a Community
• Population growth
– More individuals
– Birth rates > death rates
– Decrease in resources
• Food, nutrients, space
• Until the available
resources can no
longer support more
growth
– Lag phase
• Period of relatively slow
growth
– Post-lag phase…
• Linear, Exponential, or
logistic growth
• Renewable resources:
replenished by natural processes at a
rate comparable or faster than its rate of
consumption.
–
solar radiation, oxygen, tides, food, water,
and winds
• Non renewable:
–
used at a rate greater than the
environment's capacity to replenish
them
• Linear growth
– Constant numerical
increase; constant slope
– Doubling occurs relatively
slowly
• Exponential growth
– Growing numerical
increase; “J” curve
– Doubling occurs rapidly
– Occurs with no limits to
growth
– e.g fig. 10.2b
(dinoflagellates…much like
these bacteria)
Exponential growth until?
• Environmental resistance
– Limiting factors
• Supply restricts the growth of
a population (e.g. food)
• Logistic growth
– Converts a “J” curve to an
“S” curve (fig. 10.4)
– Sets carrying capacity
• Population size sustained by
available resources
…as resources decrease, competition
increases
Organisms interact within a community
• competition, predation,
symbiosis
• Competition
– organisms compete for
same resources
• Intraspecific (within same
species)
• Interspecific (between
species)
– Superior competitor wins
• Outcompeting to the point
of eliminating the other =
competitive exclusion
Sharing to avoid exclusion
• Resource partitioning
– Specializing in part of
the resources
• slightly different food
• different spaces
• different times
– Dividing the resources
– Lends to smaller
populations of a single
species
• Giving up some of the
resources is limiting
Symbiosis (living together)
• Mutualism
– Both organisms benefit
• “Cleaner” shrimp & fish
(facultative)
• Zooxanthellae & Cnidaria
(obligate)
• Commensalism
– One organism benefits w/o
affecting the other
• E.g. whale barnacles
(shelter & food)
• Parasitism
– One organism benefits at
the expense of the other
• E.g. intestinal worms
(Nematodes in fin whale gut)
• Ectoparasitic isopods
Marine communities
• Lifestyles
– Benthic (bottoms)
– Pelagic (open-water)
• Plankton: drifting in the
currents
– Phytoplankton
» autotrophic
– Zooplankton
» Heterotrophic
– Nekton: free swimming
• Environment/structure
– Transitional: land & sea
– Depth
– Topography
Fig. 10.12
Flow of energy w/in ecosystem
•
How energy passes through the
ecosystem
– one way flow (Fig. 10.13)
•
Producers
– autotrophs (self nourishment) that
use simple inorganic molecules to
make complex organic molecules
(photosynthesize)
•
Consumers
– heterotrophs (different
nourishment) that eat producers to
gain energy, cannot gain energy
just from simple inorganics
•
Decomposers
– heterotrophs that break down
dead material to make energy
•
At each level some heat is given
off or lost
– energy that is unavailable to the
next level
Most food webs are
complex… this
Antarctic example is
considered simple:
Trophic levels
• Steps of energy
transfer
• Each level relies on
the level(s) below
Energy efficiency
• 10% E (ave) passes
to next level
– Only a small amount
goes toward actual
growth
• Sustains fewer
organisms
• 10 times more
biomass is required to
sustain the level
above
Fig 10.16
Primary productivity
• Amount of carbon
converted (fixed) from
CO2 to usable organics
– Gross primary production
– Net primary production
• Leftover after respiration
gC/m2/day
gC/m2/year
• Can also measure O2
production via
photosynthesis
• Productivity
depends on:
–
–
–
–
Light
Location
Depth
Abundance of
organics
– Etc…
Carbon cycle
• CO2 is highly
soluble
– 50 times >
atmosphere
• Converted by
photosynthesis
• Broken down by
respiration
– Consumers,
decomposers, &
producers
Homework (due 4/30/08)
• Review pgs. 231-240
• Describe the human impact of burning
fossil fuels & increasing the amount of
CO2 in the atmosphere
• What does this do to global temperatures?
• How does this impact our oceans?
• How does this impact the marine trophic
levels?
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