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

Figure 13-6

Surface productivity

Figure 15-1Benthic biomass

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 organismsGant brown bladder kelp Macrocystis has a strong holdfast and gas-filled floatsMacrocystis 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 antAre related to jellyfishFeed with stinging tentaclesLive attached to the sea floor in large coloniesConstruct hard calcium carbonate structures for protectionContain 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 expelledAssociated with high water temperatures

Figure 15B

The deep-ocean floor

Characteristics of the deep ocean:Absence of sunlightTemperatures around freezingAverage salinityHigh dissolved oxygenExtremely high pressureSlow 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