Introduction to Marine Ecology
• Physical limiting factors
– light, temperature, salinity, nutrients, gases
– variation within the ocean: depth and
geography
• Marine habitats: where to make a living
• Marine feeding types: how to make a
living
Ecology
• The study of the relationships among
physical and biological aspects of the
environment.
– how organisms adapt to and alter their
environment
– factors that control distribution and
abundance of organisms
– How do organisms meet their needs?
• Physiological tolerances, food, mates, …
Ecological communities
and ecosystems
• Ecological community: Interacting organisms
living in a specific habitat
– Marine examples: coral reef, mangrove, estuary,
intertidal…
• Community ecology studies the distribution
and abundance of species in a community, and
their interactions
– E.g. patterns of species richness and productivity;
processes such as predator-prey interactions and
succession
• Ecosystem ecology studies how the biotic and
abiotic components of an ecosystem interact
Limiting factors
• Some aspect of the environment that
limits an organism’s distribution.
• Physical limiting factors
– temperature, salinity, nutrients, light...
• Biological limiting factors
– competition, predation, herbivory
– E.g. how climate, nutrients, etc. influence species and
their interactions - and how the biota influence the
physical and biogeochemical aspects of the system
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Limiting factors
Physical factors: light penetration
Coastal
ocean
Light penetrates
deeper in clear, open
ocean than it does in
turbid, coastal water
Open
ocean
Physical factors:
light and light penetration
• Photic zone: depth to which light
penetrates
Photosynthesis
6 CO2 + 6 H2O
sunlight
glucose
– Defines zone of photosynthesis and
primary productivity (base of the food web).
• Aphotic zone is below photic zone.
Most of the ocean is dark.
• Dysphotic zone is very low light; too
little for photosynthesis
C6H12O6 + 6 02
Respiration
C6H12O6 + 6O2
6 CO2 + 6 H2O + Energy
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Light limitation
Example: Whale-fall communities
-2891 m deep
-Monterey
Canyon
• Confines most
productivity to
upper 100-200 m
• Organisms below this have to be creative
in how they obtain food
– Feed on detritus
– Chemosynthesis at black smokers
-Worms and
sea cucumbers
• New species of worm that feeds
exclusively on whale carcasses
• Roots that extend into bone
• Massive egg sacs, and dozens of
microscopic males (larval, with
“copious” sperm) living in the
female
• Why??
http://w w w .mbari.org/new s/new s_releases/2004/w halefall.html
Limiting factors: temperature
• Temperature affects metabolic rate: the rate at
which reactions proceed in an organism
• Metabolic rate doubles for every 10°C increase in
body temperature
• Most marine organisms are ectothermic
Limiting factors: temperature
Endotherms can tolerate a broader range of
external temperature than ectotherms.
But endotherms require more energy (food)
than ectotherms.
– same body temperature as the surrounding water.
– clams, shrimp, most fish...
• Some marine organisms are endothermic – constant and usually higher body temperature than the
surrounding water.
– marine mammals, birds, some tuna and sharks.
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Temperature
affects activity
• Barnacle cirri beat
faster at higher
temperature
• Faster beat = more
efficient feeding
Limiting factors: salinity
• Normal marine salinity is 35‰
• Too high or too low is damaging
– Low diversity in estuaries (low salinity)
– Low diversity in areas of high evaporation (high
salinity)
• Maintaining salt balance is critical organisms do this by:
Temperatures
in the ocean
Extremophiles beyond
this range
- submarine hot springs
- in polar ice: antifreeze
glycoproteins in blood
Diffusion
• Passive equalizing of concentrations
• Substance (or temperature) diffuses from high to
low concentration, equalizing them
• Examples: diffusion of gases into ocean, into cells;
diffusion of nutrients into (and wastes out of)
phytoplankton
– Diffusion – passive movement from areas of high
concentration to low concentration
– Osmosis – diffusion of water through a membrane
– Active transport – active removal of substances
from an area of low concentration to high
concentration
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Limiting factor Pressure
Osmosis
Type of diffusion that
equalizes water
concentration
• High pressure in deep:
makes life impossible?
• No! Most organisms do not
perceive this
Water (but not salts) flows
thru cell membranes into
region of higher salt
concentration
– No gases in body (gases are
compressible)
Can create osmotic stress if
cell is moved into region of
contrasting salinity
• Fishes with gas bladders are
adjusted for this pressure
– Die (explode) if brought rapidly
to surface
– Can adjust to move up and
down gradually on their own
Salt water is dehydrating;
it removes water from
within the cell.
Limiting factors:
dissolved nutrients
• Required for the production of organic
matter
• Required for photosynthesis - the base of
the food web
NO3-
– Phosphates PO4-
surface
Low in the
photic zone,
High in
upwelling
areas
• Limiting nutrients:
– Nitrates
Global nitrates
200 m
Slides/
global
nitrate
“fertilizers”
1,000 m
– Sometimes, Fe (iron), Si (silicon)
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Global
phosphates
Fig/ nutrient/energy cycling
surface
Low in the
photic zone,
High in
upwelling
areas
200 m
Slides/
global
phospho
rus
1,000 m
Ocean has a tremendous
variety of physical habitats!
Fig/ typical ocean
profiles
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Marine habitats:
Where to make a living
• Pelagic zone: living in the water
– neritic zone: nearshore, over the continental
shelf
– oceanic zone: beyond the continental shelf
• Benthic zone: living on the bottom
– littoral - between high and low tide “intertidal”
– sublittoral - out to edge of continental shelf
– bathyal - continental slope
– abyssal - abyssal plain
– hadal - deep sea trenches
Plankton
Marine lifestyles
• Planktonic: drift almost passively; cannot
counteract a current.
– phytoplankton (plants)
– zooplankton (animals)
• Nektonic: active swimmers:
– fish
– reptiles
– mammals
– birds
• Need ways to
stay in photic
zone
– Small mass =
slow settling
– High friction =
more drag
• Benthic: Live on the bottom
– Epifaunal
– Infaunal
• An organism can change modes through its
lifetime, e.g. larvae or juvenile vs adult
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Benthic Habitats
infaunal, epifaunal
Infauna
Animals that burrow into soft substrates
(sand and mud)
• Challenges include:
– Displacing sediment
(digging/burrowing)
– Constructing
structurally sound
burrows
– Protecting tissues from
abrasion
• Benefits include:
– Protection from
predators, wave
energy, desiccation
What’s the best way to swim?
• Minimize drag
• Be fast
– Accelerate
– Cruising
• Be maneuverable
How to swim fast?
• Speed of a fish is dependent upon:
– body length (long = fast)
– beat frequency (more beats/sec = faster)
– the aspect ratio of the caudal fin (high = fast)
• Aspect ratio is the ratio of the square of the
caudal fin height to caudal fin area:
AR = (Caudal Fin Height)2/Caudal Fin Area
Faster
Slower
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Marine habitats:
how to make a living
Note “specialists”
vs “generalists”
• Primary producers: Autotrophs (make
own food)
Phytoplankton - floating
photosynthetic algae
Marine habitats:
how to make a living
• Primary producers: autotrophs
Benthic macroalgae
Sea grass
Marine habitats:
how to make a living
• Primary producers: autotrophs
• Suspension (filter) feeders: filter
water for food:
– pelagic suspension feeders: zooplankton
– benthic suspension feeders:many
mollusks, sponges, baleen whales
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Whale shark
(http://en.w ikipedia.org/w iki/Image:
W hale_shark_Georgia_aquarium.jpg
Jellyfish
Yellow
tube
sponge
http://cas.bellarmine.edu/tietjen
/images/phylum_porifera.htm
Slide/ sponge - colonial
Copepod
Marine habitats:
how to make a living
• Primary producers: autotrophs
• Suspension feeders: filter water for food
• Benthic grazers: scrape the bottom for
algae: sea urchins, snails, nudibranchs,
manatees
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Marine habitats:
how to make a living
Sea urchin
Nudibranch
Gastropod (snail)
• Primary producers: autotrophs
• Suspension feeders: filter water for food
• Benthic grazers: scrape the bottom for
algae
• Benthic deposit feeders: eat sediment:
many worms, crabs, some sea urchins,
some fish
Manatee
Heart urchin
Marine habitats:
how to make a living
• Primary producers: autotrophs
• Suspension feeders: filter water for food
• Benthic grazers: scrape the bottom for
algae
• Benthic deposit feeders: eat sediment
• Predators: eat other animals: sharks,
many fish, dolphins, octopus, killer
whales, barnacles, corals
Primary, secondary, tertiary....
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Shark
Coral polyps
Barnacle
Frogfish (camouflaged)
Orca
http://w w w .s hiftingbaselines.org/
blog/archives/2005_11.html
Tuna
http://e n.wik ipe dia.o rg/wik i/Im a ge :Mo nta stre a _ca ve rno sa .jpg
Octopus
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