Unit 14 Animals of the Benthic Environment

1. Unit 14Animals of the Benthic Environment

2. 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…Why?

3. Benthic biomass closely matches surface productivity Surface productivity Benthic biomass

4. Shoreline habitats • The type of shoreline depends on the waves, currents, and topography. • Rockyshores occur along steep shorelines exposed to wave and storm action • Sandyshores occur along shallow shorelines where waves and currents deposit sediments.

5. 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

7. Spray Zone • Supratidalzone • Organisms • Avoid drying out • Many animals have shells • Few species of marine algae

8. Intertidal Zone Organisms • High tide zone • Animals have shells to avoid drying out • Marine algae—rock weeds with thick cell walls

9. Intertidal Zone Organisms • Middle tide zone • More types of marine algae • Soft-bodied animals

10. Intertidal Zone Organisms • Low tide zone • Abundant algae • Many animals hidden by sea weed and sea grass • Crabs abundant in all intertidal zones

11. Movement of epifauna • Sessile– attached to the sea floor (e.g. kelp, barnacles) • Motile– move over the sea floor (e.g. crabs, snails)

12. Sea anemone • A vicious predator cleverly disguised as a harmless flower but armed with stinging cells

13. Sediment-covered shores • Most organisms burrow into the sediment (infauna) • Sediment-covered shores include: • Beaches • Salt marshes • Mud flats

14. Intertidal zonation and organisms

15. Modes of feeding

16. Bivalve Mollusks • Soft body, hard hingedshell • Example: clams and mussels • Greatest number in low tide regions • How a clam burrows

17. Gastropod mollusks • Gastropods are mollusks that form the spiral-shaped sea shells we find on beaches • They move with a single foot • Are found in the ocean, freshwater, and on land (slugs and snails)

18. Shallow offshore ocean floor • Extends from the spring low-tide shoreline to the edge of the continental shelf • Mostly sediment-coveredbut contains rocky exposures • Includes: • Kelp forests • Coral reefs

19. Kelp forests • Kelp forests are found on rocky bottoms and provide habitat for many organisms • Gant brown bladder kelp Macrocystishas a strong holdfast and gas-filled floats • Macrocystis can grow up to 0.6 meter (2 feet) per day

20. Kelp Distribution

21. 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 symbioticphotosynthetic zooxanthellae algae

22. Conditions for coral reef development • Coral reefs need: • Warm water: 18-30°C (64-86°F) • Strong sunlight (for symbiotic algae) • Strong wave/current action • Lack of turbidity (clear seawater) • Normal salinity (not too fresh or salty) • Hard substrate for attachment

23. Coral reef distribution and diversity

24. Coral reef zonation

25. 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 • Mixotrophs – derive part of nutrition from algae

26. 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--25% of all marine species found on reefs • Important tourist locales • Fisheries • Reefs protect shorelines

27. Humans and Coral Reefs Fishing, tourist collecting, and sedimentinflux due to shore development harm coral reefs. Sewage discharge and agricultural fertilizers increase nutrientsin reef waters.

28. Crown of Thorns Phenomenon Sea star eats coral polyps Outbreaks (greatly increased numbers) decimatse reef

29. Stages of coral reef development

30. Coral bleaching • Coral bleaching occurs when symbiotic zoothanthellae algae is removed or expelled • Associated with high water temperatures

31. 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

32. Food sources for deep-sea organisms

33. 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

34. Alvin approaches a hydrothermal vent biocommunity

35. Locations of deep-sea biocommunities

36. Deep-sea vent biocommunity food source: Chemosynthesis • Deep-sea vent biocommunities rely on bacteria and archaeon that chemosynthesize

37. Other deep-sea biocommunities • Low-temperature seep biocommunities are associated with: • Hypersaline seeps • Hydrocarbon seeps • Subduction zone seeps