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Harmful Algal Blooms in the Chesapeake Bay

Time Required Average (6-10 days)
Prerequisites None
Material Availability Readily available
Cost Very Low (under $20)
Safety No issues


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.


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.


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

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


Cite This Page

MLA Style

Science Buddies Staff. "Harmful Algal Blooms in the Chesapeake Bay" Science Buddies. Science Buddies, 11 Oct. 2014. Web. 27 Mar. 2015 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/OceanSci_p001.shtml?from=Blog>

APA Style

Science Buddies Staff. (2014, October 11). Harmful Algal Blooms in the Chesapeake Bay. Retrieved March 27, 2015 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/OceanSci_p001.shtml?from=Blog

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Last edit date: 2014-10-11


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:,

  • harmful algal bloom,
  • phytoplankton,
  • shellfish,
  • red tide,
  • brown tide,
  • shellfish,
  • Ciguatera,
  • Pfiesteria,
  • eutrophication.


  • Why can total chlorophyll be used as a measurement of the amount of phytoplankton in an area?
  • Is there a relationship between total chlorophyll and dissolved oxygen?
  • Are all algal blooms harmful? What makes one harmful and not another?


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Materials and Equipment

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

  • Computer with Internet access
  • Printer

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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. Go to Maryland's Department of Natural Resources (MDNR) Continuous Monitoring program website at http://mddnr.chesapeakebay.net/newmontech/contmon/index.cfm. This page has background information about why MDNR monitors water quality in the Chesapeake Bay. This page also has links to current and archived data. You may want to explore a bit before moving on to step 2.
  2. Near the top of the page, under "More Info," there is a link that will take you to "Archived Results." Click on that link. There is a brief description of the data that has been collected and why it is important.
  3. The data is archived according to year. Choose the "2005 All Stations" link.
  4. Here you can select the station from which you want to see data. Using the drop-down list, choose the "Patuxent River - Jug Bay" location, then click on the "Get Date Range" button. (For a map of the data station sites, go to: http://mddnr.chesapeakebay.net/eyesonthebay/index.cfm.)
  5. Click on the "See All 2005 Data for Patuxent River - Jug Bay" link.
  6. Scroll down to the 2005 Dissolved Oxygen (DO) Concentration graph. Print this graph.
  7. Under the DO graph are buttons that will link to other water quality data graphs for this same station and time period. Click on the Total Chlorophyll button and print out that graph.
  8. 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?
  9. 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 to Maryland's Department of Natural Resources (MDNR) monitoring stories and highlights website at http://mddnr.chesapeakebay.net/hab/news_100505.cfm. Click on the Corsica River Fish Kill link. Here you will find some background information about a fish kill that was linked to a Harmful Algal Bloom as well as data that will support this connection.
  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 at step 3 of the procedure and locate 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 start back at step 3 of the procedure and locate 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?

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

  • Are HAB's 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 HAB's on shellfish?

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