KELP FOREST

 

KELPS - BROWN SEAWEEDS OF THE GROUP LAMINARIALES

 

habitat: hard substratum, exposed marine, cold water less than 20, but even less than 16 degrees, nutrient rich water

 

biology: morphology variable, often rapid growth, 30 cm per day in California

 

LIFE CYCLE: involves sexual and asexual spread, supply of gametes a problem for spread, also supply of spores by currents

KELP FORESTS - IMPORTANT FACTORS

(1) Physical - Nutrients, currents, temperature, storms

(2) Recruitment of kelp, larvae of invertebrates

(3) Plant - plant interactions such as shading

(4) Grazing by urchins, predation on urchins

 

Kelp Succession in Alaska

 

(1) Initiated by disturbance, predation

(2) Get mixture of kelps, including giant Nereocystis leutkeana

(3) Nereocystis is an annual so it dies off

(4) Laminaria establishes dense growths and shades all others, comes to dominance

Kelps - Trophic Level Interactions

 

seaweeds --> urchins --> sea otters

 

Effects on one level has strong effects on other levels.

 

Alternative stable states:

Barrens - urchins dominate and rove for food, results in hard bottom covered with coralline algae

Kelp forest - urchins present but drift algae supplies their needs, urchins hide in crevices

 

Coral Reef Ecology

 

Definition: compacted and cemented assemblages of skeletons and sediment of sedentary organisms living in warm marine waters, where light intensity is high. Endoskeletal calcium carbonate. Framework of reef controls sedimentation.

Geological Importance: massive physical structures (1950 km Great Barrier Reef), islands and archipelagos, old and well-preserved fossil communities

Economic Importance: shoreline protection, harbors, fishing in developing world, tourism

 

Biological Importance: Hight diversity, many phyla, organisms with both very wide and sometimes very localized geographic distributions.

 

COASTAL REEFS VS. ATOLLS:

Coastal reefs represent a variety of reefs parallel to shore

Atolls - specific origin, sinking of sea mounts

 

Reef Limiting Factors:

1. Temperature - warm usually greater than 18C, usually > 23-25C (calcification)

2. Light - reefs grow in shallow water (zooxanthellae)

3. Turbidity - sedimentation - inhibits corals and reef growth (light, turbidity inhibits feeding)

5. Wave action - can topple corals, affects growth

RELATION TO PLEISTOCENE - periods of reef growth as sea level rises, period of exposure and erosion as sea level falls - formation of sink holes and other solution structures.

HERMATYPIC VS. AHERMATYPIC CORALS

HERMATYPIC: Reef framework building, have many zooxanthellae, hi calcification

AHERMATYPIC: not framework builders, low calcification

GROWTH FORMS:

BRANCHING VS. MASSIVE

Branching: grow in linear dimension fairly rapidly 10 cm per y

Massive: Produce lots of calcium carbonate but grow more slowly in linear dimensions, about 1 cm per y

Measures of coral growth:

1. Label with radioactive calcium

2. Spike driven into coral

3. Use of dyes

4. Natural growth bands

 CORAL REEFS - RECAP

 

LIMITING FACTORS - warm temperature, light, open marine salinity, low turbidity, good circulation

 

REEF TYPES - coastal reefs versus atolls

 

CORALS - phylum Cnidaria, order Scleractinia

 

hermatypic (reef-forming) vs. ahermatypic corals

 

growth forms: massive (ca. 1 cm y-1) versus branching (ca. 10 cm y-1)

 

zooxanthellae - symbiotic algae found in all hermatypic corals and other species

COMMUNITY STRUCTURE ON CORAL REEFS

 

(1) COMPETITION

Shading, overgrowth, interspecific digestion, sweeper tentacles, allelopathy

 

(2) PREDATION AND GRAZING

Importance of urchins in Caribbean (Diadema antillarum)

 

Crown of thorns starfish Acanthaster planci

 

(3) DISTURBANCE

 

(4) LARVAL RECRUITMENT

mass spawning, larval movements

 

(5) DISEASE

 

(6) GLOBAL CHANGE - TEMPERATURE

 


Diadema antillarum
Formerly dominant urchin
Caribbean

GRAZING EFFECTS -
*REMOVAL EXPERIMENTS
*GRAZING HALO AROUND PATCH REEFS
*ROLE OF GRAZING FISHES
(SURGEONFISHES - ACANTHURIDAE
PARROTFISHES - SCARIDAE)

DISEASE -
*SPREAD IN DIRECTION OF CURRENTS
*OVER 95% MORTALITY
*SLOW RECOVERY


CROWN OF THORNS STARFISH
Acanthaster planci

*OUTBREAKS IN 1960'S

*ALL OVER INDO-PACIFIC

BEHAVIOR:
1. HERDING
2. NOCTURNAL ¦ DIURNAL

EXPLANATIONS?

PESTICIDES
BLASTING OF HARBORS - LARVAE
COLLECTING OF PREDATOR -
GIANT TRITON Charonia tritonis
"NATURAL"

OUTBREAKS STILL OCCURRING

See What is Natural (Jan Sapp, 1999, Oxford University Press)