APES
Name
Date
Period
Measuring Nitrates & Phosphates in Aquatic Ecosystems
Introduction / Purpose
Ecosystems can be studied by being broken down into two parts: the living, or biotic components and the nonliving or abiotic components. Examples of abiotic components include nutrients, sunlight, dissolved oxygen,
and temperature. As we have seen in class, living organisms have a range of tolerance to different abiotic
components. Because of this, the abiotic factors will determine the types of organisms that can live in any
given ecosystem. The purpose of this lab is to measure nitrates and phosphates in various aquatic ecosystems
and explore how varying levels of these two key nutrients might impact living organisms.
Background
In the spaces provided below, give a brief description of the nutrients listed. Include a definition of the
nutrient, its importance to aquatic ecosystems, and the expected “normal” range for the nutrient in aquatic
ecosystems.
Nutrient
Definition / Importance to Aquatic Ecosystems
“Normal” range in
aquatic ecosystems
(include units)
Nitrate
NO3
Phosphate
PO4
Experimental Design – Complete the experimental design organizer below.
Title/Purpose (Describe the experiment by using the format, “The effect of ___ on ___”)
Independent Variable (what you will be testing):
Levels (treatments) of
first I.V.
Number of Trials
(# of times each level of
I.V. is tested)
Dependent Variables (What you are measuring. Include all appropriate units):
Constants (List all conditions which are the same for each trial):
Hypothesis
Review the definitions for the different abiotic factors we will be measuring in this lab. Use the table below to
formulate a hypothesis about how each of these factors will vary in the different aquatic ecosystems. Rank
each of the water samples by assigning a number 1 through 6. For example, if you think the phosphate reading
of ocean water will be the greatest, you should assign it the number 6. If you think SF Bay water will be the
next highest in phosphates, give it the number 5.
Fill in the chart below so that all of the water samples have a ranking (1-6) for each of the abiotic factors.
Remember 6 is the highest ranking, 1 is the lowest. This is your hypothesis.
Phosphate
Nitrate
Ocean
SF Bay
Fish Tank
Pond
Rodeo Lagoon
Distilled Water
Materials / Procedure
• Ocean water
• SF Bay water
• Pond water
• Distilled water (control)
• Nitrate Test Kit
• Phosphate Test Kit
Work in groups of 4 as assigned by your teacher. You will be assigned one water type and will be required to
measure both nitrates and phosphates.
 Be certain to rinse your measuring instruments before and after each test to avoid contamination of
your samples
 Carefully follow the directions in the test kits to conduct your measurements.
 Keep all components of your test kit together
 Record your data in the chart below. Remember to include units.
SAFETYA. Avoid contact between reagent chemicals and skin, eyes, nose, and mouth.
B. Wear safety goggles or glasses when handling reagent chemicals.
C. Use the test tube caps or stoppers, not your fingers, to cover test tubes during shaking or mixing.
D. When dispensing a reagent from a plastic squeeze bottle, hold the bottle vertically, upside-down (not
at an angle) and gently squeeze it (if gentle squeeze does not suffice the dispensing cap, or plug might
be clogged.)
E. Wipe up any reagent chemical spills, liquid or powder, as soon as they occur. Rinse area with wet
sponge, then dry.
F. Thoroughly rinse test tubes before and after each test. Dry your hands and the out side of the test tube
(don’t go for the inside).
G. Tightly close all reagent containers immediate after use. Do not interchange caps from different
containers.
H. Avoid prolonged exposure of equipment and reagents to direct sunlight. Protect them from extremely
high temperatures, or freezing.
Data / Results
Record the results of your tests in the table below. Note, each group will be assigned one water type and will
be conducting one trial for both phosphate and nitrate. Be certain to include your results in the class data
table. INCLUDE UNITS.
DATA: The Effect of Water Type of Nutrient Level
Nutrient Level (mg/L = ppm)
Water Type
Ocean
SF Bay
Fish Tank
Pond
Rodeo Lagoon
Distilled Water
Phosphate
Phosphate
Phosphate
Nitrate
Nitrate
Nitrate
Trial 1
Trial 2
Average
Trial 1
Trial 2
Average
Graph: Construct a graph to illustrate the data in the table above.
Analysis Questions
1. Discuss the data you collected for phosphates. Which water type had the most phosphates? Why? Explain
in general why some aquatic ecosystems have more phosphates than others. Consider the phosphorus
cycle. Specifically, where might it be coming from?
2. Discuss the data you collected for nitrates. Which water type had the most nitrates? Why? Explain in
general why some aquatic ecosystems have more nitrates than others. Consider the nitrogen cycle.
Specifically, where might it be coming from?
3. What factors could cause these abiotic parameters to change on a monthly basis? Seasonal basis? Yearly
basis?
4. Summarize the results of this lab. How do your results compare with your hypothesis? What conclusions
can you make about the various abiotic properties of water?
5. Write a paragraph discussing how abiotic factors influence biotic factors in aquatic ecosystems. What is the
relationship between abiotic factors, range of tolerance and limiting factors? Review your text before
addressing this question. Answer on binder paper and attach to this sheet.
The Effect of Water Type on Nutrient Level- Class Data
Nutrient Level (mg/L = ppm)
Water Type
Ocean
SF Bay
Fish Tank
Pond
Rodeo Lagoon
Distilled
Water
Phosphate
Phosphate
Phosphate
Nitrate
Nitrate
Nitrate
Trial 1
Trial 2
Average
Trial 1
Trial 2
Average