1. Aquatic Ecology
Chapter 7

2. Types of aquatic life zones:
Saltwater or marine
Estuaries, coastlines, coral reefs, coastal marshes, mangrove swamps, and oceans
Freshwater
Lakes and ponds, streams and rivers, and inland wetlands

3. Major types of organisms
Phytoplankton – plant plankton
Free-floating microscopic cyanobacteria and algae
The producers and the basis of the food chain
Zooplankton – animal plankton
Nonphotosynthetic herbivores that feed on phytoplankton
Secondary consumers that feed on other zooplankton
Range from single-celled protozoa to large invertebrates such as jellyfish.

4. Nekton Benthos Decomposers Fish, turtles, and whales
Bottom-dwellers – barnacles & oysters that anchor to one spot
Worms – burrow into sand or mud
Lobsters and crabs – walk on the bottom
Some are filter-feeders
Decomposers
Bacteria that break down organic compounds

5. Key Characteristics of aquatic organisms
Less pronounced and fixed physical boundaries; therefore difficult to count and manage populations
More complex and longer food chains
More difficult to monitor and study because of their size and they are hidden from view.

6. Limiting Factors
Aquatic life zones are divided into three layers – surface, middle, and bottom
Factors are:
Temperature
Access to sunlight for photosynthesis
Dissolved oxygen (DO) content
Availability of nutrients such as carbon (CO2),
nitrogen (NO3), and phosphorus (PO4) for producers

7. Photosynthesis can take place only as deep as light can penetrate (euphotic zone)
Oxygen gets in from photosynthesis and diffusion for air and is removed by aerobic respiration (includes decomposition)
O2 can vary greatly in aquatic ecosystems
Most aquatic organisms cannot survive below 5 ppm of DO
DO and CO2 concentrations vary with depth

8. Why are oceans important?
Cover 71% of earth’s surface
Contain about 250,000 known species
Provide many ecological and economic services
Less that 5% has been explored and mapped

9. Coastal zone
Warm,nutrient-rich,shallow water that extends from the high tide mark to the margin of the continental shelf
makes up less than 10% of ocean but contains 90% of all marine species and is especially important to commercial fisheries.
Gets:
Sunlight and nutrients

10. Coastal Wetlands – covered by water all or part of the year
Estuaries – a partially enclosed area where seawater mixes with fresh water
An ecotone
Coastal Wetlands – covered by water all or part of the year
river mouths, inlets, bays, sounds, mangrove swamps, and salt marshes
Temperature and salinity vary widely
Tides, seasonal variation in water flow, unpredictable flows after heavy rains and floods
VERY PRODUCTIVE AREAS!

11. Intertidal zone – area of shoreline between high and low tides
Very stressful zone for organisms:
Wave stress
Immersed during high tides and dry during low tides
Changing levels of salinity
Organisms usually cling to something, dig or hide in shells.

12. Barrier Islands
Long, thin, low offshore islands of sedement that generally run parallel to shore
Help protect mainland
Constantly shift

13. Coral reefs
Form in clear, warm, coastal waters in tropics and subtropics
Have many types of organisms
Attached – corals, algae, and sponges
Fishes
Small organisms that bore into or attach themselves to coral
Easily damaged, grow slowly, can survive only in clear, shallow, warm water
Have been harmed by global warming
They face many threats from pollution and other human activities.

14. Open Sea Beyond the continental shelf
Euphotic zone: lighted upper area
Photosynthesis
Low nutrient levels
High DO
Bathyl zone: dimly lit middle zone
No photosynthesis
Abyssal zone: dark lower zone
Very cold
Little DO
Many nutrients

15. Some open sea organisms
Deposit feeders
Take mud into their bodies and extract nutrients from it
Filter feeders
Pass water through or over their bodies and extract nutrients from it
Average primary productivity & NPP are low.

16. Human Impact Losing coastal areas to development
Housing, marinas, golf courses
Filling in for agriculture
Much beach erosion due to development and rising sea levels
Dredging and heavy nets used in trawling is destroying bottom habitats
Coral reefs are being severely damaged

17. Freshwater life zones
Found where water with a dissolved salt concentration of less than 1% by volume either accumulates or flows through the surfaces of terrestrial biomes.
Standing water – lakes, ponds, inland wetlands
Flowing water – streams and rivers
Covers less than 1% of the earth’s surface but ecologically and economically important
Are very closely connected to terrestrial biomes due to nutrient run-off

18. Life zones
Ponds – shallow – light often penetrates to the bottom – usually have only one zone
Lakes – deeper – generally consist of four zones – defined by depth and distance from shore
Littoral zone – shallow water near shore where rooted plants grow
Limnetic zone – open sunlit water away from shore – as deep as sunlight penetrates
Profundal zone – deep open water that receives no sunlight – cool so although oxygen is low, some fish live here.
Benthic zone – bottom of lake – cool temperatures and low oxygen

19. © 2004 Brooks/Cole – Thomson Learning
Freshwater Systems
Ecological Services
Economic Services
• Climate moderation
• Nutrient cycling
• Waste treatment
and dilution
• Flood control
• Groundwater
recharge
• Habitats for aquatic
and terrestrial
species
• Genetic resources
and biodiversity
• Scientific
information
• Food
• Drinking water
• Irrigation water
• Hydroelectricity
• Transportation
corridors
• Recreation
• Employment

20. Eutrophication – the natural ageing of a lake
Classify lakes according to nutrient content and primary productivity
OLIGOTROPHIC LAKE – low nutrients
Geographically young
Deep
Blue in color
Colder
Low populations of phytoplankton
More desirable fish – bass and trout
Low NPP

21. EUTROPHIC LAKE – many nutrients
Old lake
Shallow
Green or brown in color (algae)
Warmer
Algal blooms are common
Less desirable types of fish – catfish, carp
High NPP

22. Figure 7-21 Page 158 Sunlight Oligotrophic lake Sunlight Narrow
littoral
zone
Little
shore
vegetation
Low concentration of
nutrients and plankton
Limnetic
zone
Sparse fish
population
Sleepily
sloping
shorelines
Profundal
zone
Sand, gravel,
rock bottom
Oligotrophic lake
Sunlight
Much
shore
vegetation
Wide
littoral
zone
High concentration of
nutrients and plankton
Dense fish
population
Limnetic
zone
Gently
sloping
shorelines
Figure 7-21 Page 158
Profundal
zone
Silt, sand,
clay bottom
Eutrophic lake

23. Cultural Eutrophication
Humans add nutrients from the atmosphere, urban, and agricultural areas accelerate eutrophication.

24. SEASONAL CHANGES IN LAKES
Occurs in temperate lake
Makes use of the property of water that it is less dense as a solid (0oC) then it is at a liquid (4oC);therefore ice floats on water.
This causes THERMAL STRATIFICATION of deep lakes

25. Summer Lakes have three distinct layers:
EPILIMNION – upper layer of warm water high levels of DO
THERMOCLINE – layer where the temperature changes with depth – usually 1oC/meter increase in depth – moderate oxygen – during summer acts as a barrier between epilimnion and hypolimnion
HYPOLIMNION – bottom layer of cold, dense water – low DO
To keep cool fish would be at the bottom but low DO there

26. Fall Overturn
Water begans to cool, becomes more dense and sinks to the bottom
The thermocline disappears
Water mixes – nutrients are carried to the top and oxygen to the bottom. Fish can be found at all depths

27. Winter Lake separates into layers again due to difference in density.
Warmest (4oC)water is at the bottom
Thermocline is reversed
Coldest water is at the top and freezes forming ice which insulates and protects the lake.

28. Spring overturn Water begins to warm up
Wind blows causing vertical currents
Lake overturns again bring nutrients to the top and oxygen to the bottom

30. Characteristics of Freshwater
Surface water forms when precipitation that does not sink into the ground or evaporate becomes run-off
Watershed – the land area that delivers run-off, sediment, and dissolved substances to a stream.
Streams join together to form rivers
Rivers flow downhill to the ocean

31. Inland wetlands – land covered with water all or part of the year located away from the ocean
Marshes – have a few trees
Swamps –dominated by trees and shrubs
Prairie potholes – depressions formed by glaciers
Floodplains – receive water during heavy rains or floods
Bogs and fens – waterlogged peaty areas

33. Human impact
60% of the world’s largest rivers are fragmented by dams – destroys wildlife and reduces water flow
Flood control levees and dikes – destroy habitats, disconnect rivers from floodplains,and eliminate wetlands
In U.S. 53% of the wetlands have been drained or filled to grow crops – this has increased flooding