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 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

Essentials of Oceanography 7th Edition End of Chapter 15 Essentials of Oceanography 7th Edition