Marine Biology: May 16, 2007

Kelp Forests

I.Introduction

II.What are seaweeds and kelp?

  1. Classification
  2. Generally considered to be in “Kingdom Protista”…
  3. Major groups of algae [Various figures in Ch. 6]
  4. Phylum Chlorophyta: green algae
  5. Why found only in the intertidal and very shallow subtidal?
  6. Examples: Ulva (sea lettuce) and Codium (dead man’s fingers)
  7. Phylum Rhodophyta: red algae
  8. What makes them red? Adaptive value?
  9. Example: Corallina
  10. Phylum Phaeophyta: brown algae (including kelp, the large brown algae)
  11. What makes them brown? Adaptive value?
  12. Example: Fucus (rockweed) and Macrocystis pyrifera (giant kelp)
  13. Parts of a kelp “thallus” and their significance [Fig. 6.1].

**Be able to create/label a diagram and know the key functions of these parts!

  1. Holdfast
  2. Stipe
  3. Pneumatocyst
  4. Blade (or “frond”)
  1. Life cycle of Macrocystis pyrifera [Fig. 13.24]
  2. Sporophyte generation
  3. Appearance
  4. Spore production (within sporophylls)
  5. What do the spores become?
  6. Gametophyte generation
  7. Appearance
  8. Gamete production
  9. Fertilization
  10. What does the zygote (fertilized egg) become?
  11. Distribution of kelp (West coast of North America) [Fig. 13.25]
  12. Egregia (feather boa)
  13. Laminaria
  14. Pterygophora
  15. *Macrocystis pyrifera (giant kelp)
  16. *Nereocystis (bull kelp)
  17. *Pelagophycus (elk kelp): deep forests, huge fronds (10 meters long!)

*Indicates those that form the kelp forests.

III.Where are kelp forests found and what conditions do they need to thrive?

  1. Locations
  2. Requirements of kelp
  3. Cold water (<62ºC)
  4. Nutrients
  5. Upwelling as related to cold water and nutrients (see figures in PowerPoint)
  6. Light
  7. Why important?
  8. What happens to light during heavy upwelling and why?
  9. Rocky substrate
  10. Effects of storms
  11. Reduction of storms
  12. Kelp rafts and dispersal
  13. El Niño
  14. Effects on upwelling, and thus on temperature and nutrients
  15. Net effects on kelp forests (different in different locations…)

IV.Key inhabitants of kelp forests

  1. What does the kelp forest provide?
  2. Holdfast dwellers
  3. What types of organisms are within the holdfast?
  4. Invertebrates
  5. What types of invertebrates are found in kelp forests?
  6. Some invertebrates of special note…:
  7. Bryozoans that grow on the fronds
  8. Potential impact on kelp?
  9. Kelp crabs
  10. A variety of snails (niche partitioning)
  11. Abalone
  12. Sea urchins
  13. Fish
  14. Giant kelpfish
  15. Kelp bass
  16. Rockfish (many species that partition their niches…
  17. Other vertebrates
  18. Harbor seals
  19. Sea otters

V.Orcas, sea otters, sea urchins and kelp in the Aleutian islands [Fig. 13.26]

  1. Understand the role of these different organisms in maintaining vs. reducing the kelp forests!
  2. What role did humans play in this scenario?

VI.Other aspects of human impact on kelp forests

  1. Sewage/storm drain run-off (mixed effects)
  2. Moderate nutrient addition may actually promote kelp growth
  3. Associated sediments make water cloudy and block light
  4. Can promote growth of young urchins
  5. But if chlorinated, can prevent fertilization of sea urchins
  6. Fishing and collection of invertebrates (examples)
  7. California sheephead
  8. Decrease in size of dominant males indicates overfishing
  9. California spiny lobster
  10. Decrease in size indicates overfishing
  11. Abalones very difficult to find

Study questions

  1. The three major groups of algae
  2. Name the three major groups of algae.
  3. In what major way do the groups differ?
  4. Which group is only found at shallow depths (intertidal, very shallow subtidal), and what keeps this group from surviving at deeper depths?
  1. Sketch a kelp thallus, labeling all key parts. Then describe the key function(s) of each of the parts.
  1. Sketch the life cycle of Macrocystis pyrifera, being sure to indicate all major steps and stages.
  1. Be able to answer the following questions about the Macrocystis pyrifera life cycle. Note that your life cycle diagram should show these aspects of the life cycle.
  2. Which life stage produces spores? Is this life stage large and conspicuous or nearly microscopic? Which specific structures produce the spores?
  3. Are spores are haploid or diploid? What does this mean?
  4. What do spores become?
  5. What is a gametophyte? Is this life stage haploid or diploid? Is this life stage large and conspicuous or nearly microscopic? What does the gametophyte produce?
  6. Once fertilization occurs (should show fertilization on your diagram), a zygote is formed. What does the zygote become? Is this life stage haploid or diploid?
  1. Describe and discuss the conditions required for a kelp forest to thrive as well as conditions/factors that can cause the decline of a kelp forest.
  1. What does the kelp forest provide for other organisms?
  1. Is the holdfast community relatively diverse in terms of animal phyla? Describe some characteristics that holdfast dwellers possess.
  1. Overall, how does invertebrate diversity in the kelp forest compare to invertebrate diversity in the intertidal?
  1. What are bryozoans (brief description) and what is their potential impact on the kelp?
  1. What adaptations make the giant kelpfish well-adapted to the kelp forest habitat?
  1. Between 1987 and 1997, kelp forests in the Aleutian Islands have declined drastically. Discuss the hypothesis presented in the course and book that presumes to explain this decline. Be as specific as possible, making sure you describe the relationships among all the organisms involved (including baleenwhale populations [not just orcas] and humans as well as the organisms in Fig. 13.26).
  1. How do sewage and storm drain runoff affect kelp forests? Discuss both potentially positive and potentially negative impacts on kelp forests.
  1. What key type of evidence suggests that several species in kelp forests, including spiny lobsters and California sheephead, have been overfished?

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