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CH 15 Animals of the Benthic Environment

• Benthic communities include a variety of Communities on Rocky Shores habitats. • Epifauna • Corals need specific environmental conditions. – Attached to substrate (e.g., marine algae) • Hydrothermal vents support diverse – Move over seafloor (e.g., crabs, snails) communities that rely on chemosynthesis. • Moderate diversity of species • Benthic biomass matches surface chlorophyll – Greatest animal diversity at tropical latitudes distribution. – Greatest algae diversity at mid‐latitudes • Benthic organisms live mainly on continental shelves. • Their distribution is affected by surface ocean currents.

Intertidal Zonation Distribution of Benthic Organisms • Rocky shore: • Spray zone – above spring tide zone • Intertidal zone – High tide zone – Middle tide zone – Low tide zone

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Spray / Supratidal Zone • Organisms: Sandy Beach Organisms and Adaptations – Avoid drying out – Many animals have shells • Burrowing animals – Few species of marine algae • No stable, fixed Intertidal Zone surface • High tide zone – Animals have shells to • Burrowing provides avoid drying out more stable – Marine algae—rock weeds with thick cell walls environment • Bivalve mollusks • Middle tide zone – Less risk of – Soft body, hard shell – More types of marine algae temperature extremes – Soft‐bodied animals – Example: clams and and drying out • Low tide zone mussels – Abundant algae – Greatest number in low – Many animals hidden by tide regions sea weed and sea grass – Crabs abundant in all • Annelid worms intertidal zones

• Crustaceans – Segmented body, hard exoskeleton, paired jointed limbs – Example: crabs, lobsters • Echinoderms – Spiny skin – Five tapered legs – Example: starfish and heart urchin • Meiofauna – Small, feed on bacteria

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Mud Flats Kelp • Eelgrass and turtle grass Distribution common • Bivalves and other mollusks • Fiddler crabs

Shallow Offshore Ocean Floor Communities • Rocky bottoms (subtidal) • Kelp and kelp forests – Attaches to rocky bottoms – Can grow up to 0.6 meters (2 feet) per day – Productive ecosystems – Provides shelter for other organisms

Coral Reef Rocky Bottom Shallow Offshore Ocean Floor Communities Distribution • Lobsters • Reefs – shallow – Large, spiny antennae water communities – Live in water deeper than 20 restricted to meters tropics (65 feet) • Polyps – – Scavengers individual corals – Also feed on live animals

Conditions for Coral Reef Development • Oysters • Warm (but not hot) seawater – Sessile bivalve mollusks • Sunlight (for symbiotic algae) – Thick shell • Strong waves or currents – Start life as plankton • Clear seawater • Normal salinity • Hard substrate

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Symbiosis of Coral • Coral reefs made of algae, and Algae mollusks, foraminifers as well as corals Coral Reef Zonation • Hermatypic coral – mutualistic relationship with algae – Algae provide food – Corals provide nutrients • Mixotrophs –derive part of nutrition from algae

Deep Ocean Food Sources and Species Importance of Coral Reefs in Diversity Coral Reefs Decline

• Largest structures • 30% healthy today, 41% healthy created by living in 2000 organisms • One third of corals –high risk of – Great Barrier Reef, extinction Australia, more than • Humans –greatest threat 2000 km (1250 miles) long • Other threats • Great diversity of species – Hurricanes • No primary productivity • Important tourist locales – Global warming • Only 1 –3% of euphotic food • Fisheries • Coral bleaching – Floods present • Reefs protect shorelines – Tsunami • Special adaptations for detecting food • Species diversity equivalent to rain forest

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Deep‐Sea Hydrothermal Vent Locations of Hydrothermal Vent Biocommunities Communities • Discovery – Alvin in 1977 • Galapagos Rift in Pacific Ocean • Water temperature 8–12°C (46–54°F) • Chimney vents, hot acidic water – Black smokers

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