Chapter 15
Animals of the Benthic
Environment
Essentials of Oceanography
7th Edition
Benthic organisms
Benthic organisms are those that live in or
on the ocean floor
More than 98% of known marine species
are benthic
The vast majority of benthic species live
within the shallow continental shelf
Benthic biomass closely matches
surface productivity
Surface productivity
Figure 13-6
Benthic biomass Figure 15-1
Rocky shores
Most organisms live on the surface (epifauna)
Zonation of rocky shores:
Spray zone (rarely covered by water)
High tide zone
Middle tide zone
Low tide zone (rarely exposed)
Upper zones have mostly shelled organisms
Lower zones have many soft-bodied organisms
and algae
Rocky shores: Intertidal
zonation and organisms
Figure 15-2a
Sea anemone
A vicious
predator
cleverly
disguised as
a harmless
flower but
armed with
stinging
cells
Figure 15-4
Sediment-covered shores
Most organisms burrow into the sediment
(infauna)
Sediment-covered shores include:
Beaches
Salt marshes
Mud flats
Sediment-covered shores: Intertidal
zonation and organisms
Figure 15-8
Sediment-covered shores: Modes
of feeding
Figure 15-9
How a clam burrows
Figure 15-10
Shallow offshore ocean floor
Extends from the spring low-tide shoreline
to the edge of the continental shelf
Mostly sediment-covered but contains
rocky exposures
Includes:
Kelp forests
Coral reefs
Kelp forests
Kelp forests are found on
rocky bottoms and provide
habitat for many organisms
Gant brown bladder kelp
Macrocystis has a strong
holdfast and gas-filled floats
Macrocystis can grow up to
0.6 meter (2 feet) per day
Figure 15-15a
Coral reefs
Coral reefs are hard, wave-resistant structures
composed of individual coral animals (polyps)
Individual coral polyps:
Are about the size of an ant
Are related to jellyfish
Feed with stinging tentacles
Live attached to the sea floor in large colonies
Construct hard calcium carbonate structures for
protection
Contain symbiotic photosynthetic zooxanthellae algae
Coral reefs: Environmental
conditions
Coral reefs need:
Warm water: 18-30°C (64-86°F)
Strong sunlight (for symbiotic algae)
Strong wave/current action
Lack of turbidity
Salt water
Hard substrate for attachment
Coral reefs found in shallow, tropical waters
Coral reef distribution and
diversity
Figure 15-18
Coral reef zonation
Figure 15-19
Stages of coral reef development
Figure 2-30
Coral bleaching
Coral bleaching
occurs when
symbiotic
zoothanthellae
algae is
removed or
expelled
Associated with
high water
temperatures
Figure 15B
The deep-ocean floor
Characteristics of the deep ocean:
Absence of sunlight
Temperatures around freezing
Average salinity
High dissolved oxygen
Extremely high pressure
Slow bottom currents (except abyssal storms)
Low food supply
Food sources for deep-sea
organisms
Figure 15-22
Deep-sea hydrothermal vent
biocommunities
Found in deep water near black smokers along the
mid-ocean ridge
Do not rely on food from sunlit surface waters
Organisms include:
Tube worms
Clams
Mussels
Crabs
Microbial mats
Alvin approaches a hydrothermal
vent biocommunity
Figure 15-23
Locations of deep-sea
biocommunities
Figure 15-24
Deep-sea vent biocommunity
food source: Chemosynthesis
Deep-sea vent biocommunities rely on
bacteria and archaeon that chemosynthesize
Figure 15-25
Other deep-sea biocommunities
Low-temperature seep biocommunities are
associated with:
Hypersaline seeps
Hydrocarbon seeps
Subduction zone seeps
End of Chapter 15
Essentials of Oceanography
7th Edition