Bellwork: 09/05/20121) Change 10 to 25% of the water within your

tank.

2) If you are not helping your group change water, you need to be finishing the fish morphology questions/activity from the past two days.

3) If you are done with the fish morphology, you need to be working on your exam review.

Analysis of Water Chemistry:Review

Outline

• Water Chemistry Background• Chemistry in Urban Streams

Temperature

• Most aquatic organisms are cold-blooded and have an ideal temperature range, specific to the organism:

• Diatoms - 15-25 degrees C

• Green algae - 25-35 degrees C

• Blue greens - 30-40 degrees C

• Salmonoids – 5.6 – 14.6 5 C (cold water fish)

• Coral reefs – 22 to 28 C

Temperature, continued

• Affects development of invertebrates, metabolism of organisms

• Affects dissolved oxygen• Warm water makes some substances more

toxic (cyanide, phenol, xylene, zinc) and, if combined with low DO, they become even more toxic

Dissolved Oxygen

• Oxygen that is dissolved in water• DO increases with cooler water and mixing of

water through riffles, storms, wind• Nutrient loading can lead to algal blooms which

result in decreased DO• 5 ppm DO is the minimum that will support large,

diverse fish populations. Ideal DO is 9 ppm. Below 3 ppm, all fish die.

pH

• pH measures the degree of acidity or alkalinity of the water (each number is a 10-fold difference)

• 0-6 = acid; 7 = neutral; 8-14 = base• Ideal for fish = 6.5 –8.6• Ideal for algae = 7.5 – 8.4• Acid waters make toxic chemicals (Al, Pb, Hg)

more toxic than normal, and alter trophic structure (few plants, algae)

Ammonia (NH3)• During the Nitrogen Cycle Ammonium,

NH4+ (relatively non-toxic) is converted to

ammonia NH3 (toxic at a basic pH).

1) NH4+ + 2O2 NO2

- + 2H2O

2) NO2- + O2 + 2H+ NO3

- + H2O

Biological Filtration

If the above biochemical reaction does not take place due to a lack of nitrifying bacteria ammonium will shift back and forth toammonia.

NH4+ NH3 + H+ When solution is

basic and warm

Ammonia (NH3), continued

• Ammonia is excreted by fish and invertebrates living within the tank.

• This ammonia serves as food for nitrifying bacteria.

• Without this beneficial bacteria the ammonia will very quickly kill life within the tank.

• Overcrowding will cause a dangerous level of ammonia.

• Ideal ammonia level is 0 to 0.05 ppm (mg/L)

Turbidity

• Measures the cloudiness of the water

• Turbidity caused by plankton, chemicals, silt, etc.

• Most common causes of excess turbidity are plankton and soil erosion (due to logging, mining, farming, construction)

Turbidity, continued• Excess Turbidity can be a problem:• Light can’t penetrate through the water –

photosynthesis may be reduced or even stop – algae can die

• Turbidity can clog gills of fish and shellfish –can be fatal

• Fish cannot see to find food, but can hide better from predators

• Turbidity levels should be as close to 0 NTUs (Nephelometric Turbidity Units)

Phosphorus (Reactive)

• Is necessary for plant and animal growth

• Natural source = phosphate-containing rocks

• Anthropogenic source = fertilizer and pesticide runoff from farming

• Can stimulate algal growth/bloom

• Seawater often only contains around 2 ppt Phosphate (active phosphorus)

Nitrates (NO3-)

• Formed by the process of nitrification (addition of O2 to NH3 by bacteria)

• Used by plants and algae• Is mildly toxic, fatal at high doses• Large amounts (leaking sewer pipes, fertilizer

runoff, etc.) can lead to algal blooms, which can alter community structure, trophic interactions and DO regimes)

Alkalinity

• A measure of the substances in water that can neutralize acid and resist changes in pH

• Natural source = rocks

• Ideal water for fish and aquatic organisms has a total alkalinity of 100-120 mg/L

• Groundwater has higher alkalinity than surface water

Hardness

• The amount of Calcium and Magnesium in the water (the two minerals mostly responsible)

• Natural source = rocks

• Limestone = hard water, granite = not hard water

Physical Effects of Urbanization Related to Water

Chemistry• Riparian (plant biome) Vegetation Removal

• Decreased Groundwater Recharge

• Heat Island Effect

• Increased Surface Runoff / Impervious Surfaces

• Leaky Storm-water / Sewage Pipes

• Point Source Pollution

Review Questions:

-Get with a partner, get out a sheet of paper and put both of your names on the paper.

1)Two identical water samples are stored at two different temperatures, one warm and the other cool. Which sample will have the highest amount of DO?

2)If the pH of a solution needs to be lowered what must you do?

3)To neutralize a strong acid, what must you add?