Subtidal Communities

1. Subtidal Communities Hard Bottom Kelp Forests

2. Figure 10.22

4. 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)

5. 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

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

7. 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

8. 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

10. Laminaria Laminaria Alaria (edible)

11. Geographic Kelp Distribution

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

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

15. Fig. 13.23

20. Figure 13.23 Kelp: Baja, CA

21. Figure 13.25

22. 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.

23. Fnft

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

26. Fig. nft

27. Sea Urchins • What leads to population explosions? • Absence of their predators • Overfishing, less seals & sea lions, killer whales eat sea otters, more urchins

31. Figure 13.26

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

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

34. Fig. 13.20

35. Pictoral Food Web Example