Aquatic Ecosystems - Biology 20

Flashcards covering physical and chemical factors affecting aquatic ecosystems, along with biological indicators of health.

What are zones in deeper bodies of water that lack light called?

Aphotic zones

In which type of water zone can photosynthetic organisms thrive?

Photic zones (shallow waters)

What is turbidity a measure of in water?

Clarity

What tool is used to measure turbidity?

A secchi disk

What benefit do aquatic plants provide in regions with light and soil?

They can root into the soil, obtain nutrients, and provide a greater diversity of habitats.

What is the soil region in the aphotic zone called?

Benthic zone

What are organisms that live in the benthic zone called?

Benthos

Which zone refers to where light reaches the soil (photic zone)?

Littoral zone

What is the term for open water in an aquatic ecosystem?

Limnetic zone

How does water motion, such as rapids and ripples, affect dissolved gases?

It increases the amount of dissolved gases.

At what temperature is water most dense?

4oC

What happens to bodies of water when different regions have varying temperatures and densities?

They become stratified (layered).

Why can life be supported underneath winter ice?

Water at 0oC (ice) is less dense than cooler water, so it floats.

What are some characteristics of cooler waters?

They contain more dissolved gases and are more nutrient-rich and productive.

Which region separates layers of differing temperatures in stratified bodies of water?

The thermocline

During summer, where do nutrients become locked in lakes?

In the hypolimnion (at the bottom of lakes)

What phenomenon occurs in the fall and spring that pushes nutrients up and around in a lake?

Mixis or turnover

What can N2 and P4 from fertilizers cause when they run off into aquatic ecosystems?

Eutrophication

What are the long-term effects of eutrophication on lakes?

Lakes become shallow, murky, anaerobic, and less diverse.

What do phosphate levels higher than 0.03 ppm contribute to?

Increased plant growth

What are some sources of nitrogen in water?

Human and animal waste, decomposing organic matter, and lawn and crop fertilizer run-off.

What is the optimal pH range for most aquatic organisms?

6.5 to 8.2

What is pH a measurement of?

The activity of hydrogen ions in a water sample.

What factors influence the pH of aquatic ecosystems?

Geologic surroundings, runoff, plant life, and pollutants such as sulfur compounds.

What is Dissolved Oxygen?

The amount of oxygen available to organisms for cellular respiration.

What is Biological Oxygen Demand (BOD)?

The amount of oxygen required by organisms.

When is Biological Oxygen Demand (BOD) higher?

When there is a lot of decomposing material, because decomposers use up oxygen fast.

What does the presence of coliform bacteria in water indicate?

A relatively large amount of feces in the water, indicative of larger water contamination problems.

Why are amphibians good biological indicators due to their gas exchange?

They complete gas exchange through their skin, making them very susceptible to changes in the chemical environment.

How do amphibians' life stages make them good biological indicators?

They have both aquatic and terrestrial forms, so if the quality of either declines, they will be affected.

Why is amphibians' external development a factor in their role as biological indicators?

Their eggs and larvae are exposed to contaminants in the water.