Major ocean basins
Patterns of Global Diversity
Terrestrial vs. Marine
Taxon
Marine
Terrestrial
Phyla
31
14
Classes
85
28
• At the level of phylum
and class, diversity is
highest in the oceans
• However, there is much
disagreement at the
species level
Number of Species Described: Marine = 250,000
Terrestrial = 1.5 million
Number of Species Estimated: Marine = 400,000 – 10 million
Terrestrial = 4 – 50 million
Plankton – can include gametes/eggs
Phytoplankton:
photosynthetic unicellular algae
and bacteria
Zooplankton:
heterotrophic animals
Nekton
Organisms that actively swim
Benthos
Organisms that live on, buried in or associated with the bottom
Seaweeds and Plants
Invertebrates
Vertebrates
Divisions of the Oceans
Epipelagic (0-200m)
Mesopelagic (200-1000m)
Bathypelagic (1000-4000)
Abyssalpelagic (4000-6000m)
Hadalpelagic (6000+m)
3 Main Layers
Thermocline
• The thermocline is the zone
of rapid temperature decline
• This is persistent in tropical
water, seasonal in temperate
water and absent in polar
water
• The rapid change in
temperature produces a
rapid change in density –
called the pycnocline
Upwelling
Major Upwelling Regions
Coastal Upwelling
•
Surface water is replaced
by cold, nutrient-rich
water from depth
Equatorial Upwelling•
•
Currents parallel to the
equator are deflected to
the right and left
In this area of divergence,
cold water is upwelled
from depth
The Epipelagic
Epipelagic (0-200m)
Mesopelagic (200-1000m)
Bathypelagic (1000-4000)
Abyssalpelagic (4000-6000m)
Hadalpelagic (6000+m)
Phytoplankton and Primary Productivity
Ocean
Food Web
Importance of Phytoplankton
• Phytoplankton are the
major primary producers
in the oceans
• Responsible for all
primary production in
pelagic waters and most
in coastal waters
• They are the foundation
of oceanic food webs
• Simple food web on
chalkboard
Primary Production
•
•
•
Phytoplankton are efficient
producers
Can take up dissolved nutrients
quickly
Can reproduce rapidly – up to 6
generations/day
So, what factors control primary production in the ocean?
Light
Nutrients
Grazers
Light
Productivity varies with depth
Above
compensation
depth
Below
compensation
depth
Light
Compensation depth can vary in
response to phytoplankton
blooms
Compensation depth can vary geographically and
seasonally
• Day length
• Angle of incidence
- Area
- Reflection
Light and
Nutrients
• Tropical seas:
Never light limited
Thermal stratification
occurs year-round
• Temperate seas:
Light limited & no
thermal stratification in
Fall and Winter
Spring bloom with light
and stratification
• Polar seas:
Never nutrient limited
Blooms in summer
Global patterns of primary production
Grazers
Euphausids (krill)
Copepods
• Crustaceans:
Large, dominant
grazers of larger
phytoplankton
• Protozoans:
Newly appreciated
small grazers of very
small phytoplankton
(nano and pico)
• Grazers:
Critical link between
sun’s energy and
epipelagic food webs
Predators and their prey
The epipelagic is featureless
• Lateral line: allows fish to sense
vibrations in the water
• Light: there is plenty of it so many
predators and prey have well
developed eyes
• Echolocation: used by some cetaceans
to locate prey
Predator/Prey Interactions
Hiding in the blue water
Transparency: many zooplankton have some degree of transparency =
camouflaged as water
Predator/Prey Interactions
Hiding in the blue water
Countershading: dorsal
Bars: break up outline in
surface dark, ventral surface
dappled light
white or silver
Predator/Prey Interactions
Hiding in the blue water
Coloration: silvery sides reflect light to blend in
Predator/Prey Interactions
Avoiding Capture
Schooling: may reduce an individual’s probability of capture during
encounter with predator
The Arctic
Ocean
Physical Characteristics
• Constant ice, snow, cold
temperatures
• Drastic seasonal change
in photoperiod
• High river inputs =
stratification
• Thick pack ice with low
seasonal variation
• Surrounded by land
• Only 2 outlets
Physical Characteristics
Polynyas
• Occur where swift
currents prevent
freezing of surface
water
• Vary in size &
permanence
• Can be important overwintering place for
marine mammals/birds
• Also in south
Arctic Communities
Birds
Most are migratory:
• Summer in Arctic
when relatively warm
and lots to eat
• Winter elsewhere
Arctic Communities
Mammals
The Southern Ocean
Physical Characteristics
Antarctic vs. Arctic
•
•
•
•
•
Open to all other oceans
No river inputs
Pack ice is seasonal
Nutrients are high year-round
Shelf is narrow and drops
steeply
• Less drastic seasonal change
in photoperiod
Southern
Ocean
Food Web
• No seasonal
depletion of nutrients
so productivity is
VERY HIGH in spring
and summer
• Krill feed on plankton
and are critically
important to animals
at higher tropic levels
– everything either
eats krill or eats
things that eat krill
Antarctic Communities
Invertebrates: Krill
Trapped plankton
Antarctic Communities
Birds
• As in the Arctic, most are
migratory to take advantage
of seasonal food
• Most eat fish, krill and squid
Antarctic Communities
Birds: Penguins
Antarctic Communities
Marine Mammals
Aphotic Pelagic Communities
Physical
Characteristics
• Largest habitat
on earth
• Made up of
several zones
• Abiotic
environment is
very stable
• Always dark,
always cold
Physical
Characteristics
Light
• Mesopelagic = “Twilight
Zone” from 200-1000m
• Dim light but no
photosynthesis
• No primary production
• No light in lower zones
– except
bioluminescence
• Tremendous change in
pressure with depth (201000+ atm)
• Deep sea organisms are
adapted to life at high
pressure
Physical
Characteristics
Food
Animals of the Deep Sea
Zooplankton
• No Phytoplankton!
Fishes
• Most are small
• Many have photophores
Vertical migration
• Daytime from 300-500m, at sunset rises to the surface
• Depth related to light intensity – deeper during full moons,
moves up and down as clouds pass over the moon
• Composed of fishes, shrimps, copepods, jellies, squids
Adaptations
Coloration
• In shallower parts of the
mesopelagic transparency is
common
• With depth fishes tend to be
black, zooplankton typically
orange, red or purple
• Red light is absorbed, so red
appears the same as black
Adaptations
Specialized Eyes
• In mesopelagic many have
large, sensitive eyes
• Special eye lenses that can
discriminate between natural
light and bioluminescence,
thereby seeing through
counter-illumination
camouflage
Adaptations
Coloration
• In mesopelagic camouflage
strategies are similar to
epipelagic
• In lower zones there is no
need for counterillumination – most are gray,
black or red
• Bioluminescence
– mesopelagic for counterillumination, deeper for
attracting mates/prey
Adaptations
Bioluminescence
• Almost all marine
bioluminescence is blue to
green –
• These wavelengths transmit
the furtherest
• Most organisms lack visual
pigments to absorb other
wavelengths
Adaptations
Bioluminescence
Decoy/Surprise
Counter Illumination
Lures
Adaptations
Bioluminescence – “Night Vision”
• Malacosteid family of fishes
(aka Loosejaws) produce and
are able to see red light
• Wavelengths are almost
infrared (barely visible to
humans)
• The light allows them to see
their prey without alerting the
prey (or other predators)
Deep Sea Benthic Communities
• Mud Communities
• Chemosynthetic-based
– Hydrothermal vents
– Whale carcasses
Deep Sea Environment
• Low and stable temperature
2-5oC (<1oC variation)
• High and stable oxygen
(thermohaline circulation
and low respiration)
• At mean depth 4000m
pressure is 400 atm = 3
tons/in2
Deep Sea Environment
• No light = no
photosynthesis
• Chemosynthesis at vents
• Sparse food
• Inputs from small detritus,
fecal pellets, marine
snow, carcasses of fishes
and whales
• Deep sea floor is mostly
mud, basaltic outcrops at
mid-ocean ridges
Deep Sea Mud Communities
• Organisms are small and at
low densities due to limited
food
• Most have fragile structure
due to slow currents and little
calcification
• Very high species diversity
Hydrothermal Vents
• Discovered in 1976
• Most organisms were unknown to science
• Water is heated by magma deep in
sediments and spewed out at seafloor.
• Found at both rift and subduction zones
Hydrothermal Vents
Physical Characteristics
• Water is extremely acidic –
some snails cannot form
CaCO3 shells
• Pressure is extreme
• Temperature ranges from
2 – 400oC
• No sunlight so organisms
rely on chemosynthesis for
energy
• Water contains many
compounds, including
hydrogen sulfide
Hydrothermal Vents
Animal Community
Hydrothermal Vents
• Vents are ephemeral
• Change with plate tectonics
• Whale carcasses may act
as stepping stones between
vent communities
Whale Carcasses
• Severe depletion of whale
populations may have profound
impacts on deep sea
communities
• Difficult to evaluate due to lack of
historical and contemporary
information
Coral Distribution
The majority of reef building corals occur
between 300 north and 300 south latitudes.
Coral Distribution
• Temperature – nearly all
found within 20o isotherm
• Depth - do not develop in
water deeper than 50-70m
• Light – needed by symbiotic
algae for photosynthesis
• Salinity – intolerant of low
salinity
• Sedimentation – high levels
smother corals
• Emergence – can withstand
short time in the air, long
exposure is lethal
Physical Characteristics
Stable year-round climate
• Few environmental changes
throughout the year:
• Weak seasonal changes in
sunlight
• Consistently warm water
• Low surface nutrients
Physical Characteristics
Limits on productivity
• Year-round sunlight and
heat warms surface
water
• Warmer water is less
dense and so floats on
top of the colder water
• Persistent thermal
stratification prevents
nutrient rich bottom
water from mixing with
warm surface water
• Nutrient limitation means
few phytoplankton
Physical Characteristics
Tropical Seas = Marine Deserts
Coral Reefs are the exception!
Reefs = 1500-5000gC/m2/yr
Open ocean = 18-50gC/m2/yr
Nutrition
• Corals are carnivores
that feed on plankton
• Open ocean is low in
plankton - only
enough to satisfy 510% of the food
requirements
• So, how do corals get
enough food?
Nutrition
• Zooxanthellae are 1o
producers
• Mostly microscopic and live
in tissue of other organisms
• Corals provide nutrients in
the form of waste products
so the zoox can thrive in
otherwise nutrient poor
water
• Zooxanthellae provide the
corals with food in the form
of sugars produced during
photosynthesis
• Coral reefs support the most
diverse fish communities in
the world
• What factors are important
in maintaining this diversity?
Habitat, Competition
• Reefs encompass an
enormous diversity of
structural habitats – both
biotic (i.e. corals, algae etc)
and abiotic (i.e. caves,
crevices, sand)
• Habitats also vary with
depth and wave exposure
World Wide Kelp Distribution
Factors Affecting Distribution
• Substrate – kelps need
hard surfaces on which the
holdfast can attach
• Light – needed for
photosynthesis, kelps are
found deeper where the
water is clearer
• Temperature – kelps need
cool water
• Nutrients – warm water and
low nutrients restrict them
from the tropics
• Grazing – grazing pressure
can create barren areas
Kelp Forest Zonation
Holdfast
Kelp Forest Zonation
Midwater
Kelp Forest Zonation
Canopy
Importance of Kelp Forest
• Three-dimensional structure
provides habitat for a diverse
set of organisms
• Provides nursery habitat for
juvenile rockfish
• Harvested as food for
abalone farms and for algin
(used in ice cream,
toothpaste and cosmetics)
Estuaries, Salt Marshes
and Mangroves
Estuary: Physical Characteristics
Salinity
• Tides – high tide drives
salt water further up an
estuary, low tide
reduces salinity (2 high
tides per day, typically)
Physical Characteristics
Substrate
• Most have soft, muddy
substrates
• Both fresh and salt water
inputs carry particles which
settle to the bottom
Temperature
• Smaller volume and larger
surface area result in
greater variation in water
temperature
• Freshwater inputs are more
variable with season
Physical Characteristics
Wave Action
• Reduced wave action due to
small fetch and shallow
depth
• Currents are caused by
tides and river flow
Oxygen
• There is usually plenty of
oxygen in the water
• Can vary with temperature
and salinity
• Substrate is anoxic below
the first few cm
Salt Marshes
• Communities of emergent
herbs, grasses and low
shrubs rooted in soils
alternately inundated and
drained by tidal action
• Border temperate and
subpolar estuaries,
protected shores and bays
• Dominant intertidal feature
on Atlantic coast, minor on
Pacific coast
Physical Characteristics
• Salinity – fluctuates with
inputs and tides, can be
more extreme than estuaries
• Temperature – also show
extreme variation, below 0C
in winter, above 30C in
summer
• Substrate – typically mud
with high salt content, soil is
often anoxic
Mangrove Forests
Distribution
Estimated in 1974 that 60-70% of the world’s tropical
and subtropical coastlines are lined with mangroves
Physical Characteristics
Water Movement
• Can only establish
themselves in areas with
little wave action, so water
motion is minimal
• Slow water means particles
settle out and accumulate
on the bottom
• Substrate is usually mud
• Prop roots further slow
water and increase deposits
of particles – can increase
coast by up to 200m/yr
Physical Characteristics
Tides
• Mangroves are only found in
shallow water and intertidal
areas
• Salt tolerance enables them
to out-compete other
vascular plants
• Tides move salt water
further inland, extending
their range
• Tidal flux moves nutrients
into forests
• Water movement prevents
soil salinity from reaching
lethal levels
Importance
• Nursery ground for many
fish and invertebrate species
• Stabilize sediment and thus
prevent coastal erosion
• Sediment trapping reduces
the amount that might
otherwise smother reefs