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Lecture 25

BIO SCI 94 Lecture Notes - Lecture 25: Thermocline, Upwelling, TurbidityPremium

Biological Sciences
Course Code
Brad Hughes

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Types of Aquatic Biomes
Freshwater/Saltwater, three key factors- affect distribution/abundance of
Nutrient availability
Water depth
Water movement
Salinity- proportion of solutes dissolved in water
Solutes have positive charge(sodium,potassium), combines with negative
charge(chlorine, bromine)→ salt
Salinity- dramatic effect of osmosis, water balance in organism
Water Depth
Water depth- determine amount of light reaches organism in area
Water absorbs/scatters light; amount/type of wavelength available change as
water water depth/light intensity increases
Turbidity- cloudiness of water- important in light penetration
Light important to productivity- total amount of of carbon fixed by photosynthesis
per unit area per year
Water Flow
Rate of water movement/water depth- important factors shaping environment in
aquatic ecosystem
Water movement critical- presents physical challenge, sweeps organisms off feet
Nutrient Availability
Nutrients washed away in moving water→ Fall to bottom of still water→ short
supply in aquatic ecosystem
Nutrient level important- limit growth rates in photosynthetic organisms which
provide food for other species
Ocean upwelling/lake turnover → bring nutrients from bottom to water surface→
affect nutrient availability
Ocean Upwelling
Nutrient in sunlit surface waters- lost in form of dead organisms that rain down
into depths
Coastal regions- nutrients brought to surface by currents that cause
Surface water moves away from coast→ replaced by water from ocean bottom
Upwelling water nutrient rich
Lake Turnover
Glacially formed lakes experience spring/fall turnover every year
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