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 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.

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Figure 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.

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Kelp Communities Many organisms Sea Urchins = most important grazers or herbivores

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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.

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