APES Chapter 7 NotesAquatic Ecology: Biodiversity in Aquatic

Systems

Two Types of Aquatic ZonesMarine (saltwater) FreshwaterEstuariesCoastlinesCoral reefsCoastal marshesMangrove swampsOceans

Lakes and pondsStreams and rivers

Main types of organisms in aquatic life zones:Phytoplankton– plant plankton—microscopic

photosynthesis organisms.Zooplankton—animal plankton–

nonphotosynthetic primary and secondary consumers range from single-celled to large invertebrates.

Nekton—strong swimming consumers such as fish, turtle, and whales.

Benthos—bottom dwellersDecomposers—mostly bacteria

Characteristics of Aquatic Life ZonesLess pronounced and fixed physical

boundaries than terrestrial ecosystems.More complex and longer food chains and

food webs

More difficult to monitor due to their size and because they are largely hidden from view.

In addition to salinity levels, the most important abiotic factors in aquatic life zone are:

1. Sunlight for photosynthesis. Photosynthesis is confined mostly to the upper laver, or euphotic zone.

2. Temperature

3. Dissolved oxygen (DO)—most fist die when the dissolved oxygen levels fall below 5 ppm.Factors influencing DO levels include:

Temperature Number of producers (add oxygen) Number of consumers and aerobic decomposers

(remove O2)

4. Availability of nutrients

Special Aquatic Life Zones:Estuaries—An ecotone between the marine

environment and the land where large volumes of fresh water from land and salty ocean water mix.

Intertidal Zone—the area between high tide and low tide; changing moisture and salinity levels, numerous ecological niches.

Special Aquatic Life Zones:Coral reefs—form in clear, warm coastal

waters of the tropics and subtropics.Among the world’s oldest, most diverse, and

productive ecosystems.Home for about one-fourth of all marine

species.Often called the (Rainforest of the Sea)Vulnerable to damage because they:

Grow slowly Are disrupted easily Corals can live only in water temps. of 18-30 deg. C.

(64-86 F)

Freshwater ZonesStanding water—lakes and pondsFlowing water—streams and rivers

Freshwater LakesClassified according their nutrient levels.

Oligotrophic—young, deep lake with low nutrient levels and limited food.

Eutrophic—old, more shallow lake with high nutrient levels and complex feeding relationships.

Mesotrophic –fall between the two extremes.

Types of Lakes: Oligotrophic

Fig. 7-21 p. 158

Types of Lakes: Eutrophic

Fig. 7-21 p. 158

Cultural eutrophication—occurs when human activities speed the eutrophication processes.

Nutrients in runoff are carried into a lake causing a rapid increase in algae growth that then die and decay.

Aerobic bacteria causing the decay of the plants, remove large amounts of oxygen causing the death of many other species.

Cultural Eutrophication