Aquatic Ecology I
Dec 24, 2015
Aquatic Ecology I
Question of the Day
• Which of the following elements is most likely to limit primary production in freshwater lakes?
• oxygen• calcium• phosphorus• carbon• iron
Aquatic Ecology Notes
Chapter Overview Questions
• What are the basic types of aquatic life zones and what factors influence the kinds of life they contain?
• What are the major types of freshwater life zones, and how do human activities affect them?
Chapter Overview Questions
• What do we know about aquatic biodiversity, and what is its economic and ecological importance?
• How are human activities affecting aquatic biodiversity?
• How can we manage and sustain the world’s marine fisheries?
Chapter Overview Questions (cont’d)
• How can we protect, sustain, and restore wetlands?
• How can we protect, sustain, and restore lakes, rivers, and freshwater fisheries?
Chapter Overview Questions
• Why is water so important, how much freshwater is available to us, and how much of it are we using?
• What causes freshwater shortages, and what can be done about this problem?
• What are the advantages and disadvantages of withdrawing groundwater?
• What are the advantages and disadvantages of using dams and reservoirs to supply more water?
Chapter Overview Questions (cont’d)
• What are the advantages and disadvantages of transferring large amounts of water from one place to another?
• Can removing salt from seawater solve our water supply problems?
• How can we waste less water?• How can we use the earth’s water more
sustainably?• What causes flooding, and what can we do
about it?
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
• Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle.
• Only about 0.02% of the earth’s water supply is available to us as liquid freshwater.
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
• Comparison of population sizes and shares of the world’s freshwater among the continents.
Figure 14-2
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
• Some precipitation infiltrates the ground and is stored in soil and rock (groundwater).
• Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water.– The land from which the surface water drains
into a body of water is called its watershed or drainage basin.
Fig. 14-3, p. 308
Unconfined Aquifer Recharge Area
Precipitation Evaporation and transpiration Evaporation
Confined Recharge Area
Runoff
Flowing artesian well
Recharge Unconfined Aquifer
Stream Well requiring a pumpInfiltration Water
table LakeInfiltration
Unconfined aquifer
Confined aquiferConfining impermeable rock layer
Less permeable material such as clay
Groundwater plays a key role
• Groundwater = any precipitation that does not evaporate, flow into waterways, or get taken up by organisms
– Groundwater makes up one fifth of the Earth’s freshwater supply
• Aquifers = Porous sponge-like formations of rock, sand, or gravel that hold groundwater
• Zone of aeration = pore spaces are partially filled with water
• Zone of saturation = spaces are completely filled with water
• Water table = boundary between the two zones• Aquifer recharge zone = any area where water
infiltrates Earth’s surface and reaches aquifers
WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
• We currently use more than half of the world’s reliable runoff of surface water and could be using 70-90% by 2025.
• About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources.
• Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).
Salinity
• The saltiness.
What Kinds of Organisms Live in Aquatic Life Zones?
• Aquatic systems contain floating, drifting, swimming, bottom-dwelling, and decomposer organisms.– Plankton: important group of weakly
swimming, free-floating biota.• Phytoplankton (plant), Zooplankton (animal),
Ultraplankton (photosynthetic bacteria)– Necton: fish, turtles, whales.– Benthos: bottom dwellers (barnacles,
oysters).– Decomposers: breakdown organic
compounds (mostly bacteria).
Phytoplankton
• Description – small drifting plants• Niche – they are producers that
support most aquatic food chains• Example – cyanobacteria & many
types of algae
Zooplankton
• Description – herbivores that feed on phytoplankton or other zooplankton
• Niche – food stock for larger consumers
• Example – krill; small crustaceans
Nekton
• Description – larger, strong-swimming consumers
• Niche – top consumers in the aquatic ecosystem
• Example – fish, turtles, and whales
Benthos
• Description – bottom-dwelling creatures
• Niche – primary consumers, decomposers
• Example – barnacles, oysters, and lobsters
River Food Chains
Freshwater Ecosystems
FRESHWATER LIFE ZONES
• Freshwater life zones include:– Standing (lentic)
water such as lakes, ponds, and inland wetlands.
– Flowing (lotic) systems such as streams and rivers.
Figure 6-14
Flowing Water Ecosystems
Because of different environmental conditions in
each zone, a river is a system of different
ecosystems.
Fig. 12-11, p. 267
• Deliver nutrients to sea to help sustain coastal fisheries
• Deposit silt that maintains deltas
• Purify water
• Renew and renourish wetlands
• Provide habitats for wildlife
Natural Capital
Ecological Services of Rivers
Freshwater Streams and Rivers:
From the Mountains to the Oceans
• Water flowing from mountains to the sea creates different aquatic conditions and habitats.
Figure 6-17
Headwater Stream Characteristics
• A narrow zone of cold, clear water that rushes over waterfalls and rapids. Large amounts of oxygen are present. Fish are also present. Ex. trout.
Downstream Characteristics
• Slower-moving water, less oxygen, warmer temperatures, and lots of algae and cyanobacteria.
Changes is River Flow
Energy Source
• Gravity
Standing Water Ecosystems
Lakes, ponds, etc.
Life in Layers
• Life in most aquatic systems is found in surface, middle, and bottom layers.
• Temperature, access to sunlight for photosynthesis, dissolved oxygen content, nutrient availability changes with depth.– Euphotic zone (upper layer in deep
water habitats): sunlight can penetrate.
Lakes: Water-Filled Depressions
• Lakes are large natural bodies of standing freshwater formed from precipitation, runoff, and groundwater seepage consisting of:– Littoral zone (near shore, shallow, with rooted
plants).– Limnetic zone (open, offshore area, sunlit).– Profundal zone (deep, open water, too dark for
photosynthesis).– Benthic zone (bottom of lake, nourished by dead
matter).
Littoral Zone• A shallow area near the shore, to
the depth at which rooted plants stop growing. Ex. frogs, snails, insects, fish, cattails, and water lilies.
Limnetic Zone
• Open, sunlit water that extends to the depth penetrated by sunlight.
Profundal Zone
• Deep, open water where it is too dark for photosynthesis.
Lakes: Water-Filled Depressions
Figure 6-15
Zones in Lakes and Ponds
Question of the Day
• Which of the following is the zone of a pond or lake in which rooted emergent plants such as cattails and rushes are located?
• Benthic• Limnetic• Littoral• Profundal• Riparian