Aquatic Ecosystems and Energy Pyramids

Aquatic Habitats

An amoeba is a single-celled organism living in aquatic habitats, surviving by engulfing other single-celled organisms or organic material.
This section compares and contrasts marine and freshwater ecosystems and differentiates between terrestrial and aquatic energy pyramids.

Marine ecosystems are part of Earth's aquatic ecosystems, which include all ecosystems covered by water.
Marine ecosystems cover over 70% of Earth's surface.
Examples include:
- Salt marshes: Coastal areas with grasses, containing saltwater.
- Oceans
- Intertidal zones: Areas between terrestrial and marine ecosystems, covered by tides.
- Estuaries: Areas locked off from the ocean with a mixture of fresh and saltwater.
- Lagoons
- Coral reefs: Highly productive ecosystems with a large amount of coral.
- Deep sea and seafloor: The seafloor isn't very productive due to lack of light.
- Mangroves: Coastal forests, very productive ecosystems.
Deep sea ecosystems rely on energy from the surface or chemosynthetic organisms like tube worms near volcanic vents.
Estuaries have a mixture of salt and fresh water, making the water cloudy.
Coral reefs have high biodiversity.
Marine ecosystems house various animals, including birds (gulls, pelicans) and mammals (whales).
Many marine animals are endangered due to hunting, habitat loss, and pollution.
Marine ecosystems differ due to dissolved compounds, such as salt.
Salinity prevents freezing, which is crucial for aquatic life.
Adding salt to water lowers its freezing temperature; seawater freezes below 0°C (32°F).
Dissolved compounds allow for variation among species.

Marine ecosystems require abiotic factors like nutrients and light for producers.
Light penetrates only a small section near the surface, called the photic zone, where most productivity occurs.
Below about 35 feet, light is severely inhibited due to water filtering or scattering light.
The benthic zone on the ocean floor has limited light, making it a less productive ecosystem.
Tube worms use chemosynthesis, deriving energy from chemicals in volcanic vents, instead of photosynthesis.
Nutrients are poor in the open ocean and rich near the shores.
Organisms on the deep ocean floor survive by consuming dead bodies that fall from the surface.

Freshwater ecosystems contain little to no salt, although it's rare to have absolutely no salt in natural freshwater systems.
Most organisms, including humans, require some salt to survive, but too much salt can cause problems.
Examples of freshwater ecosystems include:
- Lakes
- Rivers
- Reservoirs
- Ponds
- Wetlands
A variety of organisms live in freshwater ecosystems, mostly different from marine ecosystems, though some species like salmon can transition between them.
Groups of organisms include vertebrates, amphibians, reptiles, mammals, protozoans, worms, mollusks, plants, algae, fungi, bacteria, viruses, and insects.
Plankton are the base of the food chain in freshwater ecosystems.

Lakes are bodies of freshwater on the mainland.
Ponds are small lakes where the water temperature is uniform.
Rivers and streams are moving bodies of water; rivers are larger than streams.
Canals are man-made moving bodies of water.
Wetlands are areas near bodies of water, covered by water during all or part of the year, but no more than six feet.
Reservoirs are man-made lakes used for hydroelectric power, flood control, and water supply.
Both marine and freshwater ecosystems are essential to the health of marine and terrestrial environments.
Coastal habitats generate one-third of all marine life forms.
Aquatic ecosystems are some of the most productive on the planet, with mangrove forests and coral reefs being especially productive.
They are defined by the amount of dissolved substances, especially salt.

Trophic Pyramid: Illustrates the flow of energy within a food chain.
- Depicts the flow of energy within a food chain.
- Energy is lost from one level to the next.
- Larger organisms consume more energy.

Shows the number of organisms in a population.
Aquatic pyramids are usually right-side up.
Example:
- Phytoplankton (primary producers) in large numbers.
- Fewer fish that feed on phytoplankton.
- Even fewer sharks that feed on fish.
Terrestrial pyramids can be inverted when one large tree feeds thousands of insects.

Represents the amount of energy contained in the total mass of organisms at each level.
Ocean biomass pyramid can be inverted because phytoplankton reproduce quickly, so their mass at any given time can be less than that of the consumers.

Shows direct energy transfer in an ecosystem.
Energy is lost from one level to the next (only about 10% is retained).
Eating producers (vegetarianism) is a more efficient use of energy.
It can never be inverted because of the fact that we lose energy every time we increase.

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\approx 10\%

The main difference between marine and freshwater ecosystems is the amount of dissolved substances, particularly salt.
Three types of trophic pyramids: pyramid of numbers, pyramid of biomass, and pyramid of energy.
A key difference between terrestrial and aquatic pyramids is that the pyramid of biomass can be inverted in some aquatic ecosystems but not in terrestrial ecosystems.