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 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 Alaria (edible)

Geographic Kelp Distribution

Kelp Communities Arranged in distinct layers Giant kelp forms in deeper waters –reduced wave action –Forms a canopy

Figure 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