Download Marine Ecology

Figure 10.22
Subtidal Zone
• The part of the continental shelf that is
always covered by water
– from the low tide mark to the shelf break (150m
or 490 ft)
Subtidal Zone
• Temperature varies from place to place due
to its shallowness
• Bottom still affected by waves, tides and
currents
• Very productive areas – nutrients & light
Subtidal Zone
• Soft Bottom Communites
– Seagrass Beds
• Hard Bottom Communites
– Kelp Forests
Seagrass Beds
• Develop in sheltered shallow water
• Most species prefer warm waters
– Turtle Grass
• Some are found in colder areas
– Eelgrass (Zostera marina) our local species
Figure 13.17
Ecological Targets
Hard Clams
Seagrass Meadows
Seagrass Beds
• Slow down currents
• Increase the depositing of sediments
• Have roots - can absorb nutrients from the
sediment
Seagrass Beds
• Important nursery for juvenile animals
– Bay scallop on Long Island
Figure 13.16
Generalized food web in a seagrass community
Hard-Bottom Subtidal
Communities
• Less common than soft-bottom
• Submerged extension of rocky intertidal,
hard parts of organisms (oyster shells,
calcareous algae)
• Sometimes called “reefs” – not coral
Kelp
• Kelp = large brown seaweed
• Large holdfast to hold onto the rocky
bottom
• Long stipes
• Fronds… 20-30m (65-100ft)
• Go through two stages in their life cycle
Laminaria
Laminaria
Alaria (edible)
Geographic Kelp Distribution
Kelp Communities
• Arranged in distinct layers
• Giant kelp forms in deeper waters
– reduced wave action
– Forms a canopy
Figure 13.23
Kelp:
Baja, CA
Figure 13.25
Kelp Communities
• Many organisms
• Sea Urchins = most important grazers or
herbivores
Fig. nft
Sea Urchins
• What leads to population explosions?
– Absence of their predators
– Overfishing, less seals & sea lions, killer
whales eat sea otters, more urchins
Figure 13.26