Jump to main content

Harmful Algal Blooms in the Chesapeake Bay

52 reviews


Harmful algal blooms occur when algae, which form the base of the ocean food web, grow in massive numbers and produce toxic or harmful effects on people, fish, shellfish, marine mammals, and birds. In this project you will learn how to use archived data from continuous monitoring stations on the Chesapeake Bay to study how water quality measurements (dissolved oxygen (DO), salinity, temperature, pH, turbidity, and total chlorophyll) change before, during, and after harmful algal blooms.


Areas of Science
Time Required
Average (6-10 days)
Material Availability
Readily available
Very Low (under $20)
No issues

By Beth Jewell, Einstein Distinguished Fellow, Office of Education, NOAA

Edited by Andrew Olson, Ph.D., Science Buddies



The goal of this project is to use online data from continuous monitoring stations on the Chesapeake Bay to study water quality measurements before and after algal bloom events.


Have you read articles in the newspapers about dead fish found on a beach, or watched a TV news report informing the public of closed beaches due to water discoloration? These may be signs of harmful algal blooms (HABs). HABs occur when algae, which live in the sea and form the base of the food web, produce toxic or harmful effects on people, fish, shellfish, marine mammals, and birds. HABs have been reported in almost every U.S. coastal state. The frequency, extent, and severity of HAB events appear to be increasing. HABs are indicators of the health of ecosystems and are of national concern. Many coastal areas suffer from HAB events each year, threatening coastal ecosystems, local and regional economies, and endangering human health.

The Maryland Department of Natural Resources has a series of continuous monitoring stations that report water quality data for locations in and around the Chesapeake Bay. The stations measure: dissolved oxygen (DO), salinity, temperature, pH, turbidity, and total chlorophyll (details in table, below). You can view and print graphs of archived data from their website. The numerical data is also available for download. In this project, you will look for relationships between the water quality variables and learn how they are used to analyze HABs.

Description of Continuous Monitoring Data
Data Units Description
Dissolved Oxygen (DO) Concentration mg/l Since most aquatic organisms such as shellfish and other living resources require oxygen to survive, this is a very important measure of water quality. DO concentrations below 5 mg/l can stress organisms. DO concentrations of around 1 mg/l can result in fish kills.
DO Percent Saturation % normal maximum DO saturation percent shows the level of dissolved oxygen as a percentage of the normal maximum amount of DO that will dissolve in water. Colder water can hold more DO than warmer water. Super-saturation (over 100% DO saturation) can occur when there is a large algal bloom. During the daylight, when the algae are photosynthesizing, they can produce oxygen so rapidly that it is not able to escape into the atmosphere, thus leading to short-term saturation levels of greater than 100%.
Salinity ppt (parts per thousand) Salinity in the Bay and its tributaries comes from the ocean. Therefore, areas closer to the ocean have higher salinities. During periods of low precipitation and river flow, salinity increases as it intrudes further up the Bay and its tributaries, while during wetter periods, salinity decreases. Salinity cycles related to the tides may also be evident in these graphs as salinity increases during flood tides and decreases during ebb tides. Salinity levels are important to aquatic organisms, as some organisms are adapted to live only in brackish or salt water, while others require fresh water. If the salinity levels get too high, the health of freshwater fish as well as grasses in the river can be affected.
Water Temperature °F Water temperature is another variable affecting suitability of the waterway for aquatic organisms. If water temperatures are consistently higher or lower than average, organisms can be stressed and may even have to relocate to areas with a more suitable water temperature. Water temperature directly affects the solubility of oxygen (see DO Concentration, above). Water temperature is a product of warming from the sun and air temperature.
pH (Acidity) pH pH measures the acidity of the water. A neutral pH is 7. Lower numbers indicate higher acidity, while higher numbers indicate more alkaline conditions. pH can be affected by salinity (higher salinities tend to buffer pH in the 7-8 range) and algal blooms (large algal blooms can raise the pH over 8 in low-salinity waters).
Turbidity NTU Turbidity is a measure of water clarity. Events that stir up sediment or cause runoff such as storms will increase the turbidity of the water. Dense algae blooms will also lead to higher turbidities. Relatively clear water (low turbidity) is required for the growth and survival of Bay grasses.
Chlorophyll Concentration μg/l Chlorophyll concentration is a measure of the amount of algae in the water. Chlorophyll is the main chemical responsible for photosynthesis in plants, the process by which sunlight is converted into food energy. Values over 100 μg/l are considered to be a severe bloom. The chlorophyll concentrations we present are calculated from fluorescence values. At this time, blue-green algae such as Microcystis fluoresce outside the range of our probes. Therefore, blue-green algae blooms are not likely to show significant chlorophyll concentrations.
(Data descriptions in the table taken from MD DNR, 2006b.)

Terms and Concepts

To do this project, you should do research that enables you to understand the following terms and concepts:,



  • Data Sets
    • This website has both archived and current data from more than 30 continuous, remote monitoring stations in the Chesapeake Bay:
      Maryland Department of Natural Resources. (n.d.). Continuous Monitoring Data. Retrieved September 9, 2016.
  • Background Information

Materials and Equipment

To do this experiment you will need the following materials and equipment:

Experimental Procedure

This will guide you around the Maryland's Department of Natural Resources (MDNR) website, familiarizing yourself with the data and how to read it. Once you have a feel for things you can ask your own question, find information here or look at some of the other data sets that will help to answer questions along other coastlines.

Online Data: Navigating the Maryland DNR Chesapeake Bay Continuous Monitoring Website

  1. Explore the Maryland's Department of Natural Resources (MDNR) home website http://eyesonthebay.dnr.maryland.gov/ and their Continuous Monitoring Data website http://eyesonthebay.dnr.maryland.gov/contmon/ContMon.cfm. These pages have background information about why and how MDNR monitors water quality in the Chesapeake Bay. You may want to look around a bit before moving on to step 2.
  2. The Continuous Monitoring Data page contains a link to query for archived data. Click on that link. A selection box will open up. It allows you to set your query criteria.
  3. First, select the station from which you want to see data. Using the drop-down list, choose the "Patuxent River - Jug Bay" location.
  4. Select to receive data for Dissolved Oxygen (DO) and the Total Chlorophyll
  5. Select the time range you like to study. As an example, you could ask the data collected between 01/01/2005 and 12/31/2005.
  6. Select the resolution you like to obtain. As a start, choose the summery per month. This data is easy to graph, but might not have enough resolution to show correlations clearly
  7. Look at the data, and decide if this resolution in time is meaningful for the study you like to do. If you decide you need a finer time resolution, set up a new query and select to download the raw data.
  8. Create and print a graph of the dissolved oxygen over time. If you start from the raw data, you might need to manipulate the data first so you can get the time resolution you determined in step 7.
  9. Create and print a second graph of the dissolved total chlorophyll over time using the same resolution in time.
  10. Compare the total chlorophyll and dissolved oxygen graphs you printed from Patuxent River - Jug Bay for 2005. What similarities do you find between the two graphs? What differences do you notice? Why might chlorophyll and dissolved oxygen be indicators of algal blooms?
  11. Create and print out the graphs for each of the other data listed (DO Saturation, Salinity, Temperature, pH, and Turbidity). Comparing these graphs, see if you can generate one or more hypotheses about the relationships between the various types of water quality data and the total chlorophyll data. Making a matrix like the one below can help to organize your thoughts.

Matrix for Analyzing Relationships Between Water Quality Variables  
  DO Concentration DO Saturation Salinity Temperature pH Turbidity
Total Chlorophyll change (increase, decrease, no effect/unrelated)            
Hypothesis and Rationale            

A Harmful Algal Bloom Example

  1. Go online and see if you can find information of the Corsica River fish kill from 2006 that was linked to a Harmful Algal Bloom. Can you find supporting data for this fish kill by doing the Algal Bloom activity for the Corsica River for the year of the fish kill?
  2. In the Algal Bloom activity, you were asked to compare dissolved oxygen (DO) and total chlorophyll graphs looking for a relationship between the two. What was the relationship you discovered? Looking at the DO and total chlorophyll graphs for the Corsica River do you see this same relationship?
  3. What conclusions can you draw about the relationships between total chlorophyll and salinity, temperature, and turbidity?

Ideas for Projects

  1. Using data from several other stations, test your hypothesis about the relationship between dissolved oxygen and total chlorophyll. You will need to start back Algal Bloom activity and create the two graphs needed to make this correlation.
  2. Using data from several other stations, test your hypothesis about the relationship(s) between temperature, salinity, pH, turbidity, and total chlorophyll. You will need to collect the data and make the graphs needed to make this correlation.
  3. What impacts would a river or stream have on the water quality of an area? What impacts might you then see on the total chlorophyll?
icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Global Connections

The United Nations Sustainable Development Goals (UNSDGs) are a blueprint to achieve a better and more sustainable future for all.
This project explores topics key to Life Below Water: Conserve and sustainably use the oceans, seas and marine resources.


Here are some questions to get you thinking about possible variations of this project:

  • Are HABs increasing in frequency or severity?
  • What are the impacts of chlorophyll, temperature and salinity on HABs?
  • What are the impacts of winds, currents, bathymetry on HABs?
  • What are the impacts of HABs on shellfish?


If you like this project, you might enjoy exploring these related careers:

Career Profile
Do you enjoy going to the ocean? Do you like examining all of the marine creatures in tide pools? Do you read up on the different kinds of ocean mammals and fish for fun? If this is the case, then you may be the right fit for a career as a marine biologist. Marine biology is the study of ocean aquatic organisms, their behaviors, and their interactions with the environment. Because this field of study is an intersection of zoology, biology, and technology, marine biologists can apply their… Read more
Career Profile
Have you ever noticed that for people with asthma it can sometimes be especially hard to breathe in the middle of a busy city? One reason for this is the exhaust from vehicles. Cars, buses, and motorcycles add pollution to our air, which affects our health. But can pollution impact more than our health? Cutting down trees, or deforestation, can contribute to erosion, which carries off valuable topsoil. But can erosion alter more than the condition of the soil? How does an oil spill harm fish… Read more
Career Profile
Many aspects of peoples' daily lives can be summarized using data, from what is the most popular new video game to where people like to go for a summer vacation. Data scientists (sometimes called data analysts) are experts at organizing and analyzing large sets of data (often called "big data"). By doing this, data scientists make conclusions that help other people or companies. For example, data scientists could help a video game company make a more profitable video game based on players'… Read more
Career Profile
Have you ever climbed up high in a tree and then looked at your surroundings? You can learn a lot about your neighborhood by looking down on it. You can see who has a garden, who has a pool, who needs to water their plants, and how your neighbors live. Remote sensing scientists or technologists do a similar thing, except on a larger scale. These professionals apply the principles and methods of remote sensing (using sensors) to analyze data and solve regional, national, and global problems in… Read more

News Feed on This Topic

, ,

Cite This Page

General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Science Buddies Staff. "Harmful Algal Blooms in the Chesapeake Bay." Science Buddies, 20 Nov. 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/OceanSci_p001/ocean-sciences/algal-blooms. Accessed 4 Mar. 2024.

APA Style

Science Buddies Staff. (2020, November 20). Harmful Algal Blooms in the Chesapeake Bay. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/OceanSci_p001/ocean-sciences/algal-blooms

Last edit date: 2020-11-20
Free science fair projects.