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.
Unconfined Aquifer Recharge Area Evaporation and transpiration Evaporation Precipitation Confined Recharge Area Runoff Flowing artesian well Recharge Unconfined Aquifer Stream Well requiring a pump Water table Infiltration Lake Infiltration Unconfined aquifer Less permeable material such as clay Confined aquifer Confining impermeable rock layer Fig. 14-3, p. 308
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
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.
Natural Capital Ecological Services of Rivers • Deliver nutrients to sea to help sustain coastal fisheries • Deposit silt that maintains deltas • Purify water • Renew and renourish wetlands • Provide habitats for wildlife Fig. 12-11, p. 267
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.
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
Definition • The temperature difference in deep lakes where there are warm summers and cold winters.
Lakes: Water-Filled Depressions • During summer and winter in deep temperate zone lakes the become stratified into temperature layers and will overturn. • This equalizes the temperature at all depths. • Oxygen is brought from the surface to the lake bottom and nutrients from the bottom are brought to the top.
Causes • During the summer, lakes become stratified into different temperature layers that resist mixing because summer sunlight warms surface waters, making them less dense.
Thermocline • The middle layer that acts as a barrier to the transfer of nutrients and dissolved oxygen.
Fall Turnover • As the temperatures begin to drop, the surface layer becomes more dense, and it sinks to the bottom. This mixing brings nutrients from the bottom up to the surface and sends oxygen to the bottom.
Spring Turnover • As top water warms and ice melts, it sinks through and below the cooler, less dense water, sending oxygen down and nutrients up.
Freshwater Inland Wetlands: Vital Sponges • Inland wetlands act like natural sponges that absorb and store excess water from storms and provide a variety of wildlife habitats. Figure 6-18
Freshwater Inland Wetlands: Vital Sponges • Filter and degrade pollutants. • Reduce flooding and erosion by absorbing slowly releasing overflows. • Help replenish stream flows during dry periods. • Help recharge ground aquifers. • Provide economic resources and recreation.
Marshes • An area of temporarily flooded, often silty land beside a river or lake.
Swamps • A lowland region permanently covered with water.
Hardwood Bottomland Forest • An area down by a river or stream where lots of hardwoods, like oaks, grow.
Prairie Potholes • These are depressions that hold water out on the prairie, especially up north in Canada. It is a very good duck habitat.
Peat Moss Bog • A wet area that over time fills in (the last stage of succession is peat moss). It can be very deep. In Ireland, they burn this for wood.
Importance of freshwater wetlands • They filter & purify water. • Habitat for many animals and plants.
Historical Aspects • Developers and farmers want Congress to revise the definition of wetlands. This would make 60-75% of all wetlands unavailable for protection. The Audubon Society estimates that wetlands provide water quality protection worth $1.6 billion per year, and they say if that wetlands are destroyed, the U.S. would spend $7.7 billion to $31 billion per year in additional flood-control costs.