Kelp Forests I. Factors Affecting Kelp Forests A. vanaqua.org Intensity and frequency of winter storms Presence/Absence of urchin predators (sea otters/lobsters) Abundance and behavior of herbivores Winter storms can rip kelps from their holdfasts After severe storms, portions of sea floor may be stripped of kelp 1. 2. 3. • • • • Urchins deprived of preferred foods (mature kelp or drift algae) may increase mobility and eat newly recruited kelps Grazing may prevent kelps from re-growing • Leads to establishment of more resistant coralline algae • Leads to urchin barrens
Kelp forests Kelp forests are found on rocky bottoms and provide habitat for many organisms Gant brown bladder kelp Macrocystis has a strong holdfast and gas-filled floats Macrocystis can grow up to 0.6 meter (2 feet) per day Figure 15-15a
Kelp Forests I. Kelp Forest Ecology B. Sea otters/Lobsters important top-down regulators of community structure • • • • Prey on important grazers like urchins (Pac/Atl) and abalones (Pac) Urchins, abalones, other herbivores graze on attached seaweeds, drift kelp Urchin populations can have a major impact on community composition Fig. 16-11
Kelp Forests I. Dominated by brown algae Found in shallow open coastal settings where water temperature usually <20 oC Bottom depth typically <20 m • • • • Light readily available Highly productive, diverse ecosystems • • Productivity related to fast kelp growth rates
Phaeophyta • Brown/yellow pigment – Fucoxanthin, some phycobilin, some carotenoids (& chl) • Diverse morphologies – Simple, small individual to large & complex (i.e. lengths up to 100m) • kelp forest communities • Some exhibit rapid growth – 1 to 2 feet a day – Important source of algin • Thickener, stabilizer, emulsifier in many products
Seaweeds And Land Plants Are Diverse and Effective Primary Producers (a) The thallus (body) of a typical multi-cellular alga. These organisms can grow at a rate of 50 centimeters (20 inches) per day and reach a length of 40 meters (132 feet). (b) Macrocystis. This fastgrowing, alga is one of the common kelp forest species of western North America.
Shallow offshore ocean floor Extends from the spring low-tide shoreline to the edge of the continental shelf Mostly sediment-covered but contains rocky exposures Includes: Kelp forests Coral reefs
Keystone Predator (or Keystone Consumer –) • Species essential to maintenance of ecosystem structure/diversity • Example (there are many): CA sea otter – kelp forest community
DIVISIONS OF ALGAE Green algae: May be unicellular or multicellular. Have cellulose cell walls, contain chlorophyll a and b, and store starch like plants. Most are microscopic. Live close to water surface. Believed to be the ancestors of terrestrial plants. Brown Algae or Kelp: Macroscopic (up to 50 m long). Most are found in coastal waters, at intermediate depths. Rapid growth. Can be harvested regularly. Red Algae: Live at greater ocean depths than other algae. Red pigments allow them to absorb blue light that penetrates deepest into ocean. Agar is extracted from many red algae. Some produce lethal toxins.