Freshwater Organisms and Niches

AQUATIC ENVIRONMENTS Saltwater and freshwater aquatic life zones cover almost three-fourths of the earth’s surface Figure 6-2

Types of Biomes/Zones Freshwater Brackish Marine Rivers and streams Lakes and ponds Wetlands Marshes/Swamps Brackish Esturaries Mangroves Marine Intertidal Coral Reef Open Ocean

Freshwater Ecosystems

FRESHWATER LIFE ZONES Freshwater life zones include: Figure 6-14 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.

Ecological Services of Rivers 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 Figure 12.11 Natural capital: important ecological services provided by rivers. Currently, the services are given little or no monetary value when the costs and benefits of dam and reservoir projects are assessed. According to environmental economists, attaching even crudely estimated monetary values to these ecosystem services would help sustain them. QUESTIONS: Which two of these services do you think are the most important? Which two of these services do you think we are most likely to decline? 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.

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

Thermal Stratification- the temp Thermal Stratification- the temp. difference in deep lakes where there are warm summers and cold winters During the summer lakes become stratified into different temperature layers that resist mixing because summer sunlight warms surface waters, making them less dense

Lakes and Ponds Thermocline- the middle layer that acts as a barrier to the transfer of nutrients and dissolved oxygen

Lakes and Ponds Fall Turnover- Spring Turnover- As temp decrease, surface layers become more dense and sink to the bottom This brings nutrients up and oxygen down Spring Turnover- As top water warms and ice melts, water sinks through and below the cooler, less dense water, sending oxygen down and nutrients up

Causes During the summer, lakes become stratified into different temperature layers that resist mixing because summer sunlight warms surface waters, making them less dense.

Freshwater Wetlands

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.