Aquatic Ecology
Life of the Wet Things
Marine vs. Fresh
• Marine = Salt water– Estuaries, Coastlines, Coral reefs,
Coastal marshes, Deep ocean
• Freshwater = Non-salty water– Lakes, Ponds, Stream, Rivers, Inland
wetlands
Major Types of Aquatic Life
• Plankton – Free floating
• Nekton – Strong swimming
• Benthos – Bottom dwelling
Advantages of Living in Water
• Natural buoyancy– Less energy spent on support
• Usually limited fluctuations of temperature
• Nutrients usually available
• Waste/toxins diluted
Limiting Factors of Life at Different Depths
• Three major zones– Surface
– Middle
– Bottom
Limiting Factors of Life at Different Depths
• Life limited by following factors at different depths– Temperature
– Sunlight
– DO
– Nutrients
Limiting Factors of Life at Different Depths
• Temperature drops as depth increases
Limiting Factors of Life at Different Depths
• Sunlight can only penetrate about 100ft (30m)– Euphotic Zone
Limiting Factors of Life at Different Depths
• DO– Varies by temperature and depth
– Comes mostly from atmosphere
– Can be added to by producers
– Depleted by consumers
Limiting Factors of Life at Different Depths
Limiting Factors of Life at Different Depths
• Nutrients– Affected by upwelling
– Phosphorus (phosphates) most limiting in freshwater
– Nitrogen (nitrates) most limiting in saltwater
Saltwater Life Zones
• Importance of oceans– 71% of planet– Heat sink– Major role in hydrologic cycle– Has a somewhat large influence in the
earth’s weather patterns• Ok, not so large, more like HUGE
– Gigantic reservoir for CO2
Saltwater Life Zones
• Two major life zones– Coastal Zone
• On top of the continental shelf• 10% of ocean/90% of ocean life• High primary and net productivity
– Open Ocean
Saltwater Life Zones
Saltwater Life Zones
Saltwater Life Zones
• Estuaries and Tidal Zones– Salt and freshwater mix
• Temperature and salinity vary– Runoff– Tidal flow
• Huge cleaning affect on environment
Saltwater Life Zones
• Coastal Wetlands– Covered by salt water most of the year
– Breeding grounds/habitat for wildlife
– Filters waste/toxin
– Buffers shores against damage
– Bays, Mud flats, Salt marshes
Saltwater Life Zones
• Rocky and Sandy Shores– Intertidal Zone
• Between low and high tide
– Rocky shores• Pounded by waves, but still lots of life
– Barrier beaches• Life must dig
Saltwater Life Zones
• Human impact on coastal zones– 2/3 of human life live within 100 miles of
a coast
– California has lost 91% of its original coastal wetlands
Saltwater Life Zones
• Coastal wetlands very vulnerable to pollution– Easy to trap pollutants
• Coral reefs decreasing due to human destruction
Saltwater Life Zones
• Open ocean– Three life zones based on penetration of
sunlight• Euphotic• Bathyal• Abyssal
Saltwater Life Zones
• Euphotic– Photosynthesis takes place
– Low nutrients
– High DO
Saltwater Life Zones
• Bathyal and abyssal zones– COLD– Low DO– High nutrients– Life includes
• Deposit feeders• Filter feeders
– Tragedy of Commons
Things to Remember While Googling
• Its abyssal, not abysmal.
Freshwater Life Zones
• Dissolved salt <1% by volume
• Two types– Standing
– Flowing
Freshwater Life Zones
• About 1% of earth’s surface, but 41% of known fish
Freshwater Life Zones
• Closely connected to their surrounding terrestrial biomes.– Why?
Freshwater Life Zones
• Dissolved salt <1% by volume
• Two types– Standing
– Flowing
Freshwater Life Zones
• About 1% of earth’s surface, but 41% of known fish
Freshwater Life Zones
• Closely connected to their surrounding terrestrial biomes.– Why?
Freshwater Lakes
• Lake Zones
Freshwater Lakes
• Littoral zone– Shallow– Near shore– Rooted plants stop growing outside the zone– Rich in nutrients– High in biological diversity
• Rooted plants, decomposers, and the usual suspects
Freshwater Lakes
• Limnetic zone– Like the euphotic zone
– Enough light for photosynthesis• Limits depth of limnetic zone
– Starting with plankton, simple food web
Freshwater Lakes
• Profundal zone– Deep, open water
– Too deep for photosynthesis
– Fish only
Freshwater Lakes
• Benthic zone– It’s the bottom.
– Mostly decomposers and detritus-feeders
Types of Freshwater Lakes
• Two types– Oligotrophic
– Eutrophic
Types of Freshwater Lakes
• Oligotrophic– Poorly nourished
Freshwater Lakes
Types of Freshwater Lakes
• Oligotrophic– Deep with steep
sides
– Crystal-clear blue or green water
Types of Freshwater Lakes
• Eutrophic– Well-nourished
Freshwater Lakes
Types of Freshwater Lakes
• Eutrophic– Lots of nutrients for producers
• Nitrates and phosphates
– Usually shallow and murky
– During summer, bottom may have low DO
Season Changes in Lakes
• Water is cool, especially when frozen– Makes water unique
– Also helps lakes survive wickedly cold winters• Wickedly meaning not like “Mr. Williamson,
it’s cold in here” or “It’s freezing outside in the F-quad”
Season Changes in Lakes
Season Changes in Lakes
• Lake layers– Epiliminon
– Thermocline
– Hypoliminon
Season Changes in Lakes
• Winter– Top layer freezes
• Insulates lower layers from “wicked” cold• DO ok in epiliminon, not so good in
hypoliminon
Season Changes in Lakes
Season Changes in Lakes
• Spring– Ice melts and warms, reaching max
density
– Sinks forcing nutrient rich water from bottom• Helped by winds
– Spring overturn
Season Changes in Lakes
Season Changes in Lakes
• Summer– VERY definite stratification
– Causes bottom to loose DO and nutrients
Season Changes in Lakes
Season Changes in Lakes
• Fall– Epiliminon cools and becomes more
dense
– Sinks, causing cooler, nutrient rich water to rise
– DO good everywhere
Freshwater Streams and Rivers
• Consists of runoff
• Watershed
Freshwater Streams and Rivers
• Three zones– Headwater or source zone
– Transition zone
– Flood plain zone
Freshwater Streams and Rivers
• Source zone– Cold water
– Fast moving
– Lots of DO
– Organisms well adapted to environment
Freshwater Streams and Rivers
Freshwater Streams and Rivers
Freshwater Streams and Rivers
• Transition zone– Deeper channels
– Slower water
– Warmer water
Freshwater Streams and Rivers
• Flood plain zone– Slow moving
– Murky
Freshwater Streams and Rivers
• Importance of inland wetlands– Food source and habitats
– Improved water quality
– Reduced flooding and erosion
– Replenish groundwater
Freshwater Streams and Rivers
• Human impact– Loss of wetlands due to
• Agriculture (80%)• Mining• Forestry• Oil/gas extraction• Urban development
Freshwater Streams and Rivers
• Mitigation banking– Replacing lost wetlands with equal area
of sime type• Doesn’t work well
Freshwater Streams and Rivers
• Best course of action– Prevention
Aquatic Life Zones
• Why are they important?
• How do humans impact them?
• How does species diversification relate?
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