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Subtidal Communities Hard Bottom Kelp Forests

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Figure 10.22

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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)

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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

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Subtidal Zone Hard Bottom Communities Kelp Forests Other: Soft Bottom Communities Seagrass Beds (addressed later)

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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

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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

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Laminaria Alaria (edible)

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Geographic Kelp Distribution

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

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Kelp Communities Several species of kelp-community fishes sheltering near giant kelp, Macrocystis. Galina Barskaya/ShutterStock, Inc.

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Fig. 13.23

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Figure 13.23 Kelp: Baja, CA

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Figure 13.25

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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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Fig. nft

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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

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Figure 13.26

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Kelp Communities Trophic relationships of some dominant members of a southern California kelp community.

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Kelp Communities Trophic relationships of the common members of a New England kelp community.

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Fig. 13.20

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