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