Download Subtidal Communities

Subtidal Communities
Hard Bottom
Kelp Forests
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
• Hard Bottom Communities
– Kelp Forests
– Other: Soft Bottom Communities
Seagrass Beds (addressed later)
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
Kelp Communities
Several species of kelp-community
fishes sheltering near giant kelp, Macrocystis.
© Galina Barskaya/ShutterStock, Inc.
Fig. 13.23
Figure 13.23
Kelp:
Baja, CA
Figure 13.25
Kelp Communities
• Below the effects of waves and tides, kelp
communities dominate in temperate areas.
General structure of a West Coast kelp forest, with a complex
understory of plants beneath the dominant Macrocystis or Nereocystis.
Fnft
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
Kelp Communities
Trophic relationships of some dominant members of a southern California
kelp community.
Kelp Communities
Trophic relationships of the common
members of a New England kelp community.
Fig. 13.20
Pictoral Food Web Example
PRIMARY PRODUCERS
PRIMARY CONSUMERS 2ND LEVEL CONSUMERS 3RD LEVEL CONSUMERS
KELP
SEA URCHINS
SEA OTTERS
MICROSCOPIC ALGAES
SMALL FISH
LARGE FISH
KILLER WHALES