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III. Water, Water 

Summary

Students will measure water quality and its relevance to stream health 

by understanding water quality parameters. They will use standard 

water testing equipment to test and record precise measurements of 

water quality and learn about the indicators of a healthy waterway and 

the role oysters provide in a healthy Bay ecosystem.

Learning Objectives

Students will be able to:

• List 3 indicators of water quality and explain how 

information about these are obtained.

• Give an example of how water quality indicators affect living 

organisms.

• Give an example of how weather events might affect a

water quality indicator. 

K-12 Oysters in the Chesapeake Bay

Module I

Grade Level: 

Middle School 

Teaching Time: 3-4 class 

periods

Materials:

Student Data Sheets 1 

and 2

Water Test Kits (Dissolved 

oxygen, Salinity)

Data sheet

Probes (from Vernier, Hach, 

LaMotte)

Lead line

Secchi disk or turbidity tube

Pencils

Clipboards

Measuring tape

Thermometer

Anemometer (wind meter)

Compass

PFDs

Hand sanitizer

Bucket with rope

pH pen

Water test kits for dissolved 

oxygen, temperature, salinity, 

nitrates, pH, depth. Your 

school may already have water 

test kits but if not, you can 

purchase them from scientific 

companies or LaMotte, Hach, 

Hanna or local hardware stores
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Background Information 

Water quality is a measure of how suitable water is for a particular use based on certain 

physical, chemical, and biological characteristics. Scientists measure water temperatures, 

turbidity (clearness of the water), and other “indicators” to monitor the health of the 

Chesapeake Bay. Students will assess the water quality of a local stream or river, and compare 

their findings to published data of tributaries in the Chesapeake Bay. Ideally, water quality 

testing will continue throughout the school year, so the students can observe and try to explain 

trends in the data and begin to think about the consequences of human actions. 

These are typical water quality parameters that students may use for testing in their local area, 

the reasons for performing those tests, and the units of measurement used for documenting 

the results. 

Weather

Weather is a key factor in determining Chesapeake Bay water quality. Conditions like heavy 

rains or storms can impact water quality in various ways, such as causing a decrease in salinity 

and water temperature, or an increase in water depth and turbidity. Water quality 

measurements may differ greatly between a calm, sunny day and a stormy day. For this reason, 

it is important to document weather conditions when performing water quality tests.

Wind Speed/Direction

Wind speed and direction will be documented during the time of water quality testing. An 

anemometer (wind meter) will be used to measure wind speed in miles per hour (mph), and 

compasses will be provided for determining wind direction. Wind is important, because it plays 

a role in the amount of dissolved oxygen in water. As wind hits the water, it causes a mixing of 

water and air; air holding oxygen. Stronger winds will lead to more circulation of air into the 

water resulting in greater levels of dissolved oxygen (DO). 

Air Temperature

Air temperature largely has an effect on the temperature of water. During warmer summer 

months, sunlight and warm air temperatures can increase the temperature of surface waters. In 

the same way, surface water can become much colder during the winter due to the drop in air 

temperature. These temperature differences are important because cooler water holds more 

oxygen than warm water. This difference between warmer and cooler waters, depending on 

the season or other factors, can create a temperature barrier where warm waters will have low 

DO and the cooler waters will have high DO. This can be detrimental to organisms that may 

become trapped in the low DO layer, such as oysters that cannot move. 

Water Quality Parameters: 

Dissolved oxygen (DO) is a measurement of how much oxygen is in water, which will be 

measured in units of parts per million (ppm). PPM signifies how many parts of oxygen there are 

for every one million parts of water. Oxygen enters water either from the mixing of air and 
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water or photosynthesizing aquatic plants. DO is very important because aquatic animals such 

as crabs and oysters need oxygen to live just like humans. Oysters and most animals that live on 

oyster reefs need at least 2-3 ppm DO to survive, and larger fish need around 5 ppm. Dissolved 

oxygen levels are greatly influenced by several factors, including seasonal changes, excess 

nutrients, and turbidity. A large problem facing the Bay is the creation of “Dead zones” (areas of 

very low oxygen in which few organisms can survive) due to excess nutrients entering the water 

from urban and agricultural runoff. It is important to monitor DO to ensure that enough oxygen 

is present in the Bay for aquatic animals to survive.

Salinity is the total amount of salt dissolved in water. Students will measure salinity in parts per 

thousand (ppt). Freshwater salinity levels are 0ppt and oceans are at about 30ppt. In terms of 

salinity, the Bay has brackish water (a mix of fresh and salt water) between 1-30ppt. The Bay is 

brackish because fresh water runs into the Bay from its tributaries, and salt water enters the 

Bay from the Atlantic Ocean. Salinity is important because different organisms have varying 

tolerances to salinity which determine where they can live within the Bay. If salinity changes 

too much, or goes too far out of the normal range, it can be very harmful to the organisms 

living in that area, particularly to things like grasses or oysters that cannot migrate. Oysters are 

generally happier and produce more spat (young oysters) at higher levels of salinity, and can 

live in water with levels between 2-30ppt.

Water temperature is an important factor in water quality because it affects the ability of 

species to live in certain areas. Most species can only survive within a specific range of 

temperatures. Through development, humans can negatively impact the water temperature of 

the Bay. Water from industrial plants, roads, and parking lots that may run into the Bay tend to 

be warmer than rain, and can increase water temperature. Warm water cannot hold as much 

dissolved oxygen as cool water, so by increasing the temperature of the Bay, we are also 

decreasing the amount of oxygen available to Bay critters. 

The acidity of water, pH, is measured on a scale of 0(acidic)-14(basic). pH can have a large 

impact on Bay organisms, because every plant or animal has a specific pH range in which it can 

live. If pH changes too drastically, organisms can be harmed or die. Most organisms prefer a pH 

between 6-8 and can’t survive very well in acidic water. The Bay generally has a pH between 7-

9, which is neutral to slightly basic. 

Turbidity is the measure of how clear a water body is, and how well sunlight can penetrate the 

water. Water can become turbid (unclear or cloudy) when excessive amounts of sediments and 

nutrients enter it, usually through runoff. Turbidity not only inhibits plant growth, but degrades 

the environment for fish, crabs, and other aquatic animal species as well. Additionally, in areas 

with high turbidity, large amounts of sediment can completely cover and smother oyster reefs, 

killing the oysters. Turbidity also has an indirect effect on dissolved oxygen. Sunlight is required 

for plants to photosynthesize and produce oxygen, and if the Chesapeake Bay is cloudy, very 

limited amounts of sunlight can reach the bottom of the Bay where the plants grow. Fewer 

plants survive, and thus less oxygen is created. Turbidity in slow moving, deep waters can be 

measured using a device called a Secchi disk, a black and white, 20-cm diameter disk. The disk is 
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lowered into the water until it just disappears from sight. The depth at which the disk 

disappears is called the Secchi depth, and is recorded in meters.

Key Words

Dissolved Oxygen: Amount of oxygen in water; measured in units of parts per million (ppm).

-Importance: Aquatic animals need oxygen to survive (oysters at least 2ppm)

-Notes: Greatly affected by seasonal/weather changes, excess nutrients, and turbidity.

Impervious: Artificial surfaces (pavements, roads, sidewalks, parking lots) that do not allow 

water to filter through the soil. Runoff usually occurs faster on these surfaces. 

Oyster Reproduction: Oysters reproduce by releasing sperm and eggs into the water. Once 

sperm fertilizes the egg, the resulting larvae develop shells and these “spat” are ready to attach 

themselves to a solid substrate, preferably another oyster, a process called setting. 

pH: The acidity of water measured on a scale of 0(acidic)-14(basic)

-Importance: Every plant or animal has a specific pH range outside of which it cannot survive

-Notes: Most organisms prefer a pH between 6 and 8 and can’t survive very well in acidic water.

Porous: Surface material that has small holes through which water or air may pass.

Salinity: Total amount of salt dissolved in water; measured in parts per thousand (ppt)

-Importance: Organisms have varying tolerances to salinity; this determines where they can live

-Notes: The Bay has brackish water (a mix of fresh and saltwater) between 1-30ppt

Spawn: Mature oysters that release egg or sperm into the water to reproduce.

Turbidity: Measure of how clear a water body is and how well sunlight can penetrate water 

-Importance: Turbidity inhibits plant growth, degrades the environment for aquatic animals, 

and can cause a decrease in dissolved oxygen levels. Turbid (cloudy/unclear) water occurs by 

excessive inputs/runoff of sediment and nutrients 

Water Temperature: Most species can only survive within a specific range of temperatures.

Warm water cannot hold as much dissolved oxygen as cool water, so by increasing the 

temperature of the Bay, we are decreasing the amount of oxygen available to Bay critters. 

Water Depth: The depth of water can dictate the outcome of other water quality tests. 

Differences in dissolved oxygen, salinity, and pH measurements between surface and bottom 

waters may also occur.

Weather: A key factor in determining water quality. For instance, conditions like heavy rains or 

storms, can impact water quality in various ways such as causing a decrease in salinity, and 
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water temperature and an increase in water depth and turbidity. Water temperature 

differences are important because cooler water holds more oxygen than warm water. 

Wind Speed/ Direction: Wind plays a role in the amount of dissolved oxygen in water. As wind 

hits the water, it causes a mixing of water and air, which contains oxygen. Stronger winds will 

lead to more circulation of air into water resulting in greater levels of dissolved oxygen. 

Activity Procedure

Engagement

Pre-requisite knowledge: Students should have a clear understanding of the organizational 

patterns and relationships that are found in any ecosystem. (prey/predator, producers/

consumers/decomposers, niche/habitat/population/community, etc.) You will find a quick 

refresher of some of these concepts with this video 

https://www.youtube.com/watch?v=GlnFylwdYH4&ebc=ANyPxKobqSlxCwWh0dg3VDmhS2tkY

VP_HXUzhQGdYJmrqxP-v48OP8IR3_GqzNNkCYydAhaYp7F7NJI0kN7ouBCnRfP_jg8VlA

Discuss as a class, 

• What does biotic mean? (Living entities, such as animals, plants, bacteria, etc.)

• What does abiotic mean? (Non-living entities, such as water, sunlight, air, temperature, 

minerals, etc.)

Formative Assessment - Individually or in small groups, have the students develop a drawing of 

an estuarine ecosystem, and include biotic and abiotic factors. Have the students share their 

drawings with their peers. 

Exploration 

Demonstrate the use of the Secchi disk and other testing equipment along with all safety 

reminders. Divide students into small groups. Each group will use probes and test instruments 

to complete the data sheet for a part of the stream/river. NOTE: Every student who is near the 

water to perform a water quality test or collect a sample must wear a PFD (personal flotation 

device)

Students should observe and record weather conditions (general weather description, air 

temperature, wind speed, wind direction) on Student Data Sheet 1. Test the water sample for 

each of the 6 water quality parameters (dissolved oxygen, salinity, water temperature, 

turbidity, pH, water depth) using the appropriate equipment. Each student in the group will 

take at least one turn testing for a different parameter and recording the results of a test. 

Measure dissolved oxygen, salinity, pH and water temperature with instruments that you have 

available. These measurements will be taken from water in a bucket with a rope attached. One 

person from each group should measure turbidity and depth of the water at the edge. 
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After completing all individual tests and recording their results in Student Data Sheet 1, 

students should access the NOAA Chesapeake Bay Interpretive Buoy System. CBIBS is a 

collection of 10 interpretive buoys spread throughout the Chesapeake Bay that gather real-time 

data about water quality and weather conditions. The goal is to provide the most up-to-date 

information for environmental education, scientists, and outdoor enthusiasts. Go to 

(http://buoybay.noaa.gov/locations) and find a buoy near the site where your students 

collected their data. Students will record the data from the CBIBS website, and compare it to 

their data. They can also access via online or phone 1-877-286-9229. The information on Data 

Sheet 1 will be used in future activities. 

You can also use a series of 5 water quality lessons at 

http://oceanservice.noaa.gov/education/yos/lesson/Grades%205-

8/water_quality_teacher_guide.pdf (Monitoring Estuarine Water Quality)

Explanation 

Students have looked at water quality parameters and will investigate graphs taken from CBIBS 

data, and what they mean for the health of the Bay, by looking at seasonal patterns of the graphs 

and then determining the potential effect on Bay organisms. Have the students review the graphs 

in Student Data Sheet 2 and record their conclusions about the patterns of the graphs. Students 

will investigate:

• The relationships between air and water temperatures

• The relationships between water temperature and dissolved oxygen

• The relationships between turbidity and dissolved oxygen 

• The relationships between turbidity and amount of chlorophyll

Answers to Student Data Sheet 2 questions. 

1. 27.6

2. The air temperatures go up and down quicker than the water. 

3. It takes water longer to heat up or cool down. 

4. Summer cold fronts or thunderstorms. 

5. When the water temperature is high, the dissolved oxygen is low; when the water 

temperature is low, the dissolved oxygen is high. 

6. What kind of relationship would we say exists between temperature and dissolved 

oxygen? Inverse proportional – when one goes up, the other goes down.

7. Whether there are lots of plant life in the water which will add oxygen from 

photosynthesis, heavy rainfall, and mixing of the water with air. 

8. When the turbidity does up, the dissolved oxygen goes down. Inversely proportional

9. Heavy rains or even a hurricane.

10. All of these fish would survive. 

11. Cloudy water makes photosynthesis hard for plants.

12. It takes time for the effect of increased turbidity to affect the plant’s photosynthesis.
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13. Heavy rains

14. Turbidity, water temperature, dissolved oxygen and salinity. Oysters can decrease 

turbidity by filtering the water.

Extension 

Students will investigate the water quality factors of temperature, salinity, pH, dissolved oxygen, 

nitrates, and turbidity that affect oysters and the development of oyster reefs, and compare their 

requirements to the water quality in their local stream. Background information is provided on 

each factor. Students will look at the data from their stream to see if their water quality is

adequate for the growth and development of oysters and the maintenance of oyster reefs. They 

will complete Student Data Sheet 3. 

Answers to Student Data Sheet 3 questions: 

5. Decomposition of algae in the warm summer months can increase the acidity level (lowered pH)

6. Yes, the reading fluctuated between 7 and 8 and is within the range of 7.8 and 8.2 for oyster 

spawning. 

7. April to July

8. Growth of plants and algae in the spring and early summer. 

Evaluation 

Student data and conclusions in the Student Data Sheets 1 and 2 should be evaluated for

completeness and understanding of the characteristics of healthy waterways. 

With thanks to the Annapolis Maritime Museum
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Three Dimensional Learning How the Dimensions are 

Addressed.

Core Disciplinary 

Idea(s)

MS-LS2-A. Interdependent 

Relationships in Ecosystems Analyze 

and interpret data to provide evidence 

for the effects of resource availability on 

organisms and populations of organisms 

in an ecosystem 

Students will gather information 

about their local waterway and 

compare it with data obtained from 

buoys. 

Science/Engineering 

Practice(s)

Obtaining, evaluating, and 

communicating information in 6-8 

builds on K–5 experiences and 

progresses to using appropriate and 

sufficient evidence and scientific 

reasoning to defend and critique claims 

and explanations about the natural and 

designed world. 

Gather, read, and evaluate scientific 

and/or technical information from 

multiple authoritative sources, assessing 

the evidence and usefulness of each 

source. 

Construct an argument supported by 

empirical evidence that changes to 

physical or biological components of an 

ecosystem affect populations.

Students gather evidence about the 

physical characteristics of their local 

waterway. They start to gather 

evidence about what local factors 

might affect their waterway in 

preparation for following activities. 

Students compare their own data 

with information from NOAA and the 

Chesapeake Bay Foundation. Students 

develop a report providing evidence 

and a conclusion about the health of 

their stream or river, and indicate 

how the health may affect living 

organisms.

Cross-cutting 

Concepts

Patterns can be used to identify cause 

and affect relationships. 

Students will look for patterns in data 

between different bodies of water, 

time of day, weather events, and for

seasonal changes. 

Ties to Common 

Core

Grade 6: Ratios and Proportional 

Relationships. Represent and analyze 

quantitative relationships between 

dependent and independent variables. 

Students will use their own data and 

data from NOAA buoys to describe 

the relationships between water 

quality parameters, including 

proportional and inverse proportional 

relationships. 

Ties to MD 

Environmental 

Literacy Standards

Standard 3. Interaction of physical 

systems and the biosphere

Students will analyze and explain 

water quality parameters and the 

influence of these on organisms in 

an ecosystem. 
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Module References

Dissolved Oxygen

http://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar10d_disolvedox.html

http://www.serc.si.edu/for_media/pr.aspx?pr_id=68

Turbidity

http://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar10e_turbin

pH

http://www.umces.edu/hpl/locations/all/hpl/release/2010/jun/10/changing-chesapeake-bayacidity-impacting-oyster-shell-growth

http://www.chesapeakequarterly.net/V11N1/main4/

Pollution

http://oceanservice.noaa.gov/education/tutorial_pollution/011sediments.html

Oyster reefs – Ecosystem roles

http://chesapeakebay.noaa.gov/oysters/oyster-reefs

Water parameters and Estuaries 

http://estuaries.noaa.gov/ScienceData/Default.aspx?ID=543

Data and lesson plans

http://estuaries.noaa.gov/ScienceData/Default.aspx?ID=300

Water Quality and Oysters

http://www.oyster-restoration.org/wp-content/uploads/2012/07/CoenLuckRestMonitoring.pdf

http://www.bayjournal.com/article/ability_of_oysters_to_denitrify_bay_surprises_scientists

Maryland Environmental Literacy Standards

http://marylandpublicschools.org/programs/Documents/Environmental/MDEnvironmentalLitSt

andards.pdf

Additional Resources

http://estuaries.noaa.gov/ScienceData/Default.aspx?ID=289

http://www.mde.state.md.us/programs/water/tmdl/water%20quality%20standards/pages/pro

grams/waterprograms/tmdl/wqstandards/faqs.aspx

https://allianceforthebay.org/2011/10/volunteer-water-quality-monitoring-publications/

http://gcmd.gsfc.nasa.gov/KeywordSearch/Metadata.do?Portal=GCMD&MetadataType=0&Me

tadataView=Full&KeywordPath=&EntryId=%5BGCMD%5DCBP_WQDB