20-Apr-99 WFSC575 Chapt 9

Upwellings

SW Canada to SW California coasts

W coast of S. America

NW coast of Africa

SW coast of Africa

All Antarctic coasts

W coast Australia

Equatorial trade winds generates most upwelling. The Antarctic upwelling caused by currents from Pacific and Atlantic oceans; rapid ice melts and growth; polynayas and fresh and salt water pockets encourage nutrients.

Coastal systems

Ecosystem- Productivity: grams of Carbon/ Meter squared /year:

Coral reefs-2000/5000 gC/m2/yr

Rocky shores- upwelling: 1000 non-upwelling: 100-1000 gC/m2/yr

Salt marshes

Sea-grass- 300-1000 gC/m2/yr

Coastal phytoplankton- 50-250 gC/m2/yr

Mangroves

Sand/mudflats

Sugar cane field- 2000 gC/m2/yr

Benthic = Attached grows up from the bottom

 

Theories: why so many seaweeds? Paradox - Diversity remains high and the late stages to not take over

Littner functional form group:

Succession Series: Pioneer Early Stages Gradually to Mid to Late Successional Stages

Palatability: High, Gradual Decrease, to Mid, to Low

Forms- Sheets: Filaments: Coarse/fleshy: Thick/leathery: Jointed/calcified: Crusty calcified

Examples: Ulva: Cladophera: Gracilaria: Dictyota/Padina: Amphiroa: Poralitton

Growth Rate High: Gradual Decrease To Low

Equilibrium - develop many stable niches algae support each other mutualism; grazing pressure keeps any one type from being dominant

Non-equilibrium - disturbance theory

 

Seaweed life cycles:

Dispersal stage (spores) Plankton stage: Pressures: place to land & grow, fish grazing; drift. Solutions: produce many spores at 1 time; do not spend much time in water.

Recruitment stage: spores attach & grow microthallus. Pressures: finding a spot to grow, eaten by fish. Solution: can go into a dormant stage to wait for better conditions.

Vegetative growth stage: macrothallus. Pressures: wave disturbance; larger surface areas to collect nutrients; grazing.

Reproductive stage: back to dispersal stage

Environmental factors

Tides: determine how deep seaweed goes light penetration surf exposure

Substrate: determines where it grows sandy vs. rocky

Fertility: nutrient content Oxygen etc.

24 hr tide cycles:

Semidiurnal: 2 highs, 2 lows. Ex. Maine

Diurnal: 1high 1 low. Ex Florida

Mixed tides: 1 really low; 1 really high; 1 shallow low; 1 shallow high. Ex. West coast; creates more niches for tidal zonation: different alga grow in different air exposure.

Food chain: Coastal communities support food chain Seaweeds = benthic producers that trap most light energy not very digestible feed food chain through:

Dissolved organic matter (rot on bottom) bacteria which are eaten by protozoa

Detritus (rot on bottom) benthic - eaten by deposit feeders sea cucumbers

Detritus water column (spores floaties) eaten by: Suspension /filter feeders sponges bivalves (also eat protozoa)

Direct feeding by benthic herbivores: sea urchins snails fish (eaten by sea otters dolphins etc.)

Phytoplankton eaten by : zooplankton that are eaten by planktivorouse fish suspension feeders that are eaten by benthic predators (starfish shrimp snails) that are eaten by predatory fish birds, mammals.