Essentials of Oceanography Eleventh Edition

Transcription

1 Chapter Chapter 1 15 Clickers Lecture Essentials of Oceanography Eleventh Edition Animals of the Benthic Environment Alan P. Trujillo Harold V. Thurman

2 Chapter Overview Benthic communities include a variety of habitats. Corals need specific environmental conditions. Hydrothermal vents support diverse communities that rely on chemosynthesis.

3 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.

4 Distribution of Benthic Organisms Benthic biomass matches surface chlorophyll distribution.

5 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

6 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

7 Spray Zone Supratidal zone Organisms Avoid drying out Many animals have shells Few species of marine algae

8 High Tide Zone Animals have shells to avoid drying out. Marine algae rock weeds with thick cell walls Rock weeds colonize first Sessile animals establish later

9 Middle Tide Zone More types of marine algae Soft-bodied animals Barnacles and mussels

10 Middle Tide Zone Carnivorous snails and starfish Sea anemones Stinging nematocysts on tentacles poison prey

11 Middle Tide Mussel Bed and Sea Star

12 Middle Tide Zone Hermit crabs Sea urchins

13 Low Tide Zone Abundant algae and surf grass Many animals hidden by seaweed and sea grass

14 Low Tide Zone Various shore crabs Scavengers

15 Physical Environment of Sediment-Covered Shores Sediment size related to wave and current strength Course boulder beaches Sand beaches Salt marshes Mud flats

16 Intertidal Zonation and Common Organisms

17 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

18 Sandy Beach Organisms and Adaptations Bivalve mollusks Soft body, hard shell Example: clams and mussels Greatest number in low tide regions Annelid worms

19 Sandy Beach Organisms and Adaptations Crustaceans Segmented body, hard exoskeleton, paired jointed limbs Sand crabs common

20 Sandy Beach Organisms and Adaptations Echinoderms Spiny skin Five tapered legs Example: starfish and heart urchin

21 Sandy Beach Organisms and Adaptations Meiofauna Small, feed on bacteria Polychaetes, mollusks, arthropods, nematodes

22 Mud Flats Eelgrass and turtle grass common Bivalves and other mollusks Fiddler crabs

23 Shallow Offshore Ocean Floor Communities Subtidal zone rocky bottom Kelp Attaches to rocky bottoms with strong holdfast Stipes and blades supported by pneumatocysts

24 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

25 Kelp Distribution

26 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

27 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

28 Coral Reefs Reefs shallow water communities restricted to tropics Polyps individual corals

29 Coral Reef Distribution

30 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

31 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

32 Coral Reefs Other reef animals with symbiotic relationships Mixotrophs derive part of nutrition from algae Include coral, foraminifers, sponges, and mollusks

33 Coral Reef Zonation

34 Coral Reef Zonation Many fish species inhabit shallow water near reef Reef lagoon habitat for other animals

35 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

36 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

37 Crown of Thorns Phenomenon Sea star eats coral polyps Outbreaks (greatly increased numbers) decimate reef

38 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

39 Bleached Corals

40 Coral Bleaching Some causes High surface water temperatures Elevated UV levels Decrease in sunlight-blocking atmospheric particles Pollution Salinity changes Disease

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

42 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

43 Deep-Ocean Floor Communities Less known about than shallower water communities Expensive to explore the deep Limited oxygen Robotic technology for exploration

44 Deep Ocean Physical Environment Bathal, abyssal, hadal zones Light absent below 1000 meters (3300 feet) Temperature usually between 1.8 C (28.8 F) and 3 C (37 F)

45 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

46 Deep Ocean Food Sources and Species Diversity No primary productivity Only 1 3% of euphotic food present Special adaptations for detecting food Species diversity equivalent to rain forest

47 Deep-Sea Hydrothermal Vent Biocommunities Discovery Alvin in 1977 Galapagos Rift in Pacific Ocean Water temperature 8 12 C (46 54 F) Chimney vents, hot acidic water

48 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

49 Locations of Hydrothermal Vent Communities

50 Hydrothermal Vent Species Giant tubeworms Giant clams Giant mussels Crabs Microbial mats Life supported by chemosynthesis

51 Hydrothermal Vent Species

52 Hydrothermal Vent Species

53 Chemosynthesis Microscopic archaea thrive on hydrogen sulfide from vents Manufacture sugar, carbon dioxide, and dissolved oxygen Base of hydrothermal vent food chain

54 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

55 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

56 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

57 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

58 Low-Temperature Seep Biocommunities Chemosynthetically support life Hypersaline seeps High salinity Florida Escarpment seeping water from limestone fractures

59 Low-Temperature Seep Biocommunities Gulf of Mexico seep from limestone escarpment fractures Sulfide rich waters support diverse biocommunitiy

60 Low-Temperature Seep Biocommunities Hydrocarbon seeps Oil and gas seeps Hydrogen sulfide and/or methane Hydrocarbon seep biocommunities

61 Low-Temperature Seep Biocommunities Subduction zone seeps Juan de Fuca plate Folded sedimentary rocks Methane

62 Beneath the Sea Floor A new frontier Deep biosphere Exists within sea floor Microbes live in pore fluids Might represent much of Earth s total biomass

63 End of CHAPTER 15 Animals of the Benthic Environment