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Animals of the Benthic Environment

Chapter 1 Clickers

Essentials of Oceanography Eleventh Edition

Alan P. Trujillo Harold V. Thurman

Chapter 15 Lecture

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Chapter Overview

Benthic communities include a variety of habitats.

Corals need specific environmental conditions.

Hydrothermal vents support diverse communities that rely on chemosynthesis.

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Distribution of Benthic Organisms

More than 98% of 250,000 known marine species live in or on ocean floor

Benthic organisms live mainly on continental shelves.

Their distribution is affected by surface ocean currents.

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Distribution of Benthic Organisms

Benthic biomass matches surface chlorophyll distribution.

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Communities on Rocky Shores

Epifauna Attached to substrate (e.g., marine algae) Move over sea floor (e.g., crabs, snails)

Moderate diversity of species Greatest animal diversity at tropical latitudes Greatest algae diversity at mid-latitudes

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Intertidal Zonation

Spray zone above spring tide zone

Intertidal zone High tide zone

relatively dry Middle tide zone

covered by all high tides/exposed by all low tides

Low tide zone usually wet

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Spray Zone

Supratidal zone Organisms

Avoid drying out Many animals have

shells Few species of

marine algae

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High Tide Zone

Animals have shells to avoid drying out.

Marine algaerock weeds with thick cell walls

Rock weeds colonize first

Sessile animals establish later

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Middle Tide Zone

More types of marine algae

Soft-bodied animals Barnacles and

mussels

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Middle Tide Zone Carnivorous snails

and starfish Sea anemones

Stinging nematocysts on tentacles poison prey

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Middle Tide Mussel Bed and Sea Star

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Middle Tide Zone

Hermit crabs Sea urchins

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Low Tide Zone

Abundant algae and surf grass

Many animals hidden by seaweed and sea grass

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Low Tide Zone

Various shore crabs Scavengers

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Physical Environment of Sediment-Covered Shores Sediment size related to wave and current

strength Course boulder beaches Sand beaches Salt marshes Mud flats

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Intertidal Zonation and Common Organisms

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Sandy Beach Organisms and Adaptations

Infauna burrowing animals No stable, fixed surface Burrowing provides more stable

environment Less risk of temperature extremes and

drying out

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Sandy Beach Organisms and Adaptations

Bivalve mollusks Soft body, hard shell Example: clams and

mussels Greatest number in

low tide regions Annelid worms

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Sandy Beach Organisms and Adaptations

Crustaceans Segmented body, hard

exoskeleton, paired jointed limbs

Sand crabs common

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Sandy Beach Organisms and Adaptations

Echinoderms Spiny skin Five tapered legs Example: starfish

and heart urchin

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Meiofauna Small, feed on bacteria Polychaetes, mollusks,

arthropods, nematodes

Sandy Beach Organisms and Adaptations

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Mud Flats

Eelgrass and turtle grass common

Bivalves and other mollusks

Fiddler crabs

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Shallow Offshore Ocean Floor Communities

Subtidal zone rocky bottom

Kelp Attaches to rocky

bottoms with strong holdfast

Stipes and blades supported by pneumatocysts

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Shallow Offshore Ocean Floor Communities

Kelp forests beds of giant brown bladder kelp and bull kelp Fast growing Highly productive

ecosystems Shelter for variety of

organisms

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Kelp Distribution

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Rocky Bottom Shallow Offshore Ocean Floor Communities Lobsters

Large, spiny antennae Live in water deeper

than 20 meters (65 feet)

Scavengers Also feed on live

animals

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Rocky Bottom Shallow Offshore Ocean Floor Communities Oysters

Sessile bivalve mollusks

Thick shell Food for sea stars,

fish, crabs, and snails Oyster beds empty

shells with living generation on top

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Coral Reefs

Reefs shallow water communities restricted to tropics

Polyps individual corals

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Coral Reef Distribution

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Conditions for Coral Reef Development

Warm seawater Sunlight for zooxanthellae symbiotic

photosynthetic microscopic algae in coral tissues

Strong waves or currents Clear seawater Normal salinity Hard substrate

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Symbiosis of Coral and Algae

Coral reefs made of algae, mollusks, foraminifers as well as corals

Hermatypic coral mutualistic relationship with algae Algae provide food Corals provide nutrients

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Coral Reefs

Other reef animals with symbiotic relationships

Mixotrophs derive part of nutrition from algae Include coral,

foraminifers, sponges, and mollusks

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Coral Reef Zonation

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Coral Reef Zonation

Many fish species inhabit shallow water near reef

Reef lagoon habitat for other animals

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Importance of Coral Reefs

Largest structures created by living organisms Great Barrier Reef, Australia, more than

2000 km (1250 miles) long Great diversity of species Important tourist locales Fisheries Reefs protect shorelines

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Coral Reefs and Nutrient Levels

Fishing, tourist collecting, and sediment influx due to shore development harm coral reefs.

Sewage discharge and agricultural fertilizers increase nutrients in reef waters. Hermatypic corals thrive at low nutrient levels Phytoplankton overwhelm at high nutrient levels Bioerosion of coral reef by algae-eating organisms

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Crown of Thorns Phenomenon

Sea star eats coral polyps

Outbreaks (greatly increased numbers) decimate reef

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Coral Bleaching and Other Diseases

Coral bleaching loss of color in corals Symbiotic zooxanthallae die, leave, or

become toxic Bleached coral lacks nourishment from algae

Linked to climate changes

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Bleached Corals

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Coral Bleaching

Some causes High surface water temperatures Elevated UV levels Decrease in sunlight-blocking atmospheric

particles Pollution Salinity changes Disease

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Other Diseases

Causes still under investigation Bacteria, viruses, fungi Human population stressors Increased nutrients and turbidity Environmental stress

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Coral Reefs in Decline

30% healthy today, 41% healthy in 2000 One third of corals high risk of extinction Humans greatest threat Other threats

Hurricanes Global warming Floods Tsunami

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Deep-Ocean Floor Communities

Less known about than shallower water communities Expensive to explore the deep Limited oxygen Robotic technology for exploration

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Deep Ocean Physical Environment

Bathal, abyssal, hadal zones Light absent below 1000 meters

(3300 feet) Temperature usually between 1.8C

(28.8F) and 3C (37F)

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Deep Ocean Physical Environment

High oxygen High pressure Abyssal storms

Affect bottom currents Created by warm and cold core eddies of

surface currents Can last weeks

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Deep Ocean Food Sources and Species Diversity

No primary productivity

Only 13% of euphotic food present

Special adaptations for detecting food

Species diversity equivalent to rain forest

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Deep-Sea Hydrothermal Vent Biocommunities

Discovery Alvin in 1977 Galapagos Rift in Pacific Ocean Water temperature

812C (4654F) Chimney vents, hot acidic water

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Deep-Sea Hydrothermal Vent Communities

Hydrothermal vent biocommunities Organisms previously

unknown to science Unusually large for

depth in ocean Black smokers

underwater chimney vents emit sulfides

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Locations of Hydrothermal Vent Communities

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Hydrothermal Vent Species

Giant tubeworms Giant clams Giant mussels Crabs Microbial mats Life supported by

chemosynthesis

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Hydrothermal Vent Species

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Hydrothermal Vent Species

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Chemosynthesis

Microscopic archaea thrive on hydrogen sulfide from vents

Manufacture sugar, carbon dioxide, and dissolved oxygen Base of hydrothermal

vent food chain

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Hydrothermal Vent Communities

Vents active for years or decades Animal species similar at widely separated vents Larvae drift from site to site Dead whale hypothesis

Large carcasses may be stepping stone for larvae

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Hydrothermal Vent Communities

First Atlantic vents with biocommunities discovered in 1985

First Indian Ocean vent found in 2000

Vents differ in chemical and geological characteristics

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Life Span of Hydrothermal Vents

Vents controlled by sporadic volcanic activity Vent may be active for only years to decades Organisms die when vent is inactive Increased volcanic activity can kill organisms

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Hydrothermal Vents and the Origins of Life

Life on Earth may have originated at hydrothermal vents. Uniform conditions Presence of archaea bacteria Microbes with genes identical to those found

in humans

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Low-Temperature Seep Biocommunities

Chemosynthetically support life

Hypersaline seeps High salinity Florida Escarpment

seeping water from limestone fractures

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Low-Temperature Seep Biocommunities

Gulf of Mexico seep from limestone escarpment fractures

Sulfide rich waters support diverse biocommunitiy

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Low-Temperature Seep Biocommunities Hydrocarbon seeps

Oil and gas seeps Hydrogen sulfide

and/or methane Hydrocarbon seep

biocommunities

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Low-Temperature Seep Biocommunities

Subduction zone seeps Juan de Fuca plate Folded sedimentary

rocks Methane

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Beneath the Sea Floor

A new frontier Deep biosphere

Exists within sea floor Microbes live in pore fluids Might represent much of Earths total

biomass

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End of CHAPTER 15 Animals of the Benthic Environment

Slide Number 1Chapter OverviewDistribution of Benthic OrganismsDistribution of Benthic OrganismsCommunities on Rocky ShoresIntertidal ZonationSpray Zone High Tide ZoneMiddle Tide ZoneMiddle Tide ZoneMiddle Tide Mussel Bed and Sea StarMiddle Tide ZoneLow Tide Zone Low Tide ZonePhysical Environment of Sediment-Covered ShoresIntertidal Zonation and Common OrganismsSandy Beach Organisms and AdaptationsSandy Beach Organisms and AdaptationsSandy Beach Organisms and AdaptationsSandy Beach Organisms and AdaptationsSandy Beach Organisms and AdaptationsMud FlatsShallow Offshore Ocean Floor CommunitiesShallow Offshore Ocean Floor CommunitiesKelp DistributionRocky Bottom Shallow Offshore Ocean Floor CommunitiesRocky Bottom Shallow Offshore Ocean Floor CommunitiesCoral ReefsCoral Reef DistributionConditions for Coral Reef DevelopmentSymbiosis of Coral and AlgaeCoral Reefs Coral Reef ZonationCoral Reef ZonationImportance of Coral ReefsCoral Reefs and Nutrient LevelsCrown of Thorns PhenomenonCoral Bleaching and Other DiseasesBleached CoralsCoral Bleaching Other DiseasesCoral Reefs in DeclineDeep-Ocean Floor CommunitiesDeep Ocean Physical EnvironmentDeep Ocean Physical EnvironmentDeep Ocean Food Sources and Species DiversityDeep-Sea Hydrothermal Vent BiocommunitiesDeep-Sea Hydrothermal Vent CommunitiesLocations of Hydrothermal Vent CommunitiesHydrothermal Vent SpeciesHydrothermal Vent SpeciesHydrothermal Vent SpeciesChemosynthesis Hydrothermal Vent CommunitiesHydrothermal Vent CommunitiesLife Span of Hydrothermal VentsHydrothermal Vents and the Origins of LifeLow-Temperature Seep BiocommunitiesLow-Temperature Seep BiocommunitiesLow-Temperature Seep BiocommunitiesLow-Temperature Seep BiocommunitiesBeneath the Sea FloorEnd of CHAPTER 15Animals of the Benthic Environment