Hudson River Ecology

How does the Hudson River ecosystem respond to different types of changes over time? Are these changes permanent, and how will the ecosystem respond? Our curriculum addresses these questions through modules which combine unique and engaging Hudson River data collected by the Cary Institute and other scientists, investigations, readings, and visualizations.

Introduction to Zebra Mussels

One 45 minute lesson

Students will know what lives in the Hudson River, and will be able to create a food web drawing to represent the organisms living in the river. They will also know that the Hudson River food web is changing in response to the zebra mussel invasion, and will be able to make predictions about how native organisms will be affected by this invasion.  




  1. Begin by asking a formative assessment question: What lives in the Hudson River? Ask students to sketch, individually or in pairs, a food web for the Hudson River.
  2. Once they draw their food webs, students can view and critique a partner’s food web. Discuss what students have created, and create a class-wide food web on the board.  One way to do this is to hand out post-it notes to each pair of students and ask them to write down, or draw, a representative organism and place it on the board.  You can then add in arrows to represent the flow of matter and energy.  Ask students to think about which parts of the created web may be missing organisms or missing links between organisms (students often do not include plankton, detritus, or bacteria). Students should save their webs in order to add to them later (Sample Food Web Diagram attached).



  1. Students will become more familiar with the base of the Hudson River food web by viewing demoslides, cultures, etc, of various plankton specimens using microscopes (or, students will watch videos of common plankton).  Students could make drawings of these organisms to add to the food web diagrams. 
  2. Based on these observations, ask students to add to the class Hudson River food web diagram. 
  3. Hand out the worksheet “Introduction to zebra mussels”. 
  4. Students will watch Part 1 of the AMNH Hudson River Ecology video which introduces the zebra mussels.  Before continuing on to the second video, ask students to make a claim about how the zebra mussels will impact the Hudson River food web on the worksheet provided (“Intro to zebra mussels”).
  5. Students will then watch Part 2 of the video series. This video introduces research that is being done to explore the effects of zebra mussel invasion. Students can answer questions about this research on the worksheet.
  6. A powerpoint is available to support this discussion – it includes an overview of common characteristics of invasives, costs of invasion, and a brief introduction to the zebra mussel life cycle. 



  1. Viewing the base of the food web, either with microscopes or with videos, allows students to build knowledge about this important part of the Hudson River.  Once students have added the organisms they observed to the class food web, ask students to add in the energy arrows. 
  2. Students often overlook or are not familiar with the importance of inputs from the terrestrial system (e.g. vegetation), along with the microorganisms that decompose them. This is an important part of most aquatic food webs, including that of the Hudson River. In the Hudson, inputs from the watershed account for 90% of the carbon that is available (phytoplankton provides about 2%, and rooted plants about 6%).  Leaves and organic matter that enter the river from the terrestrial environment are decomposed by bacteria. Bacteria, the “biofilm” it creates on the surface of dead organic material, and broken down bits of organic matter are all important food sources for microzooplankton (tiny aquatic invertebrates). In turn, zooplankton are an important source of food for fish. Students should add the terrestrial inputs to their food web diagrams. The following is a simplified version of the Hudson River Food web which appears in the AMNH Hudson River Ecology videos. Notice that the base of the food chain is made up of both aquatic and terrestrial energy sources.
  3. Phytoplankton is a blanket term for one-celled organisms, mostly protists, which have the ability to photosynthesize. While these primary producers are a food source (mostly for filter-feeding organisms) they also help oxygenate the water.
  4. Zebra mussels are small, filter feeding, aquatic mollusks that were introduced to the Hudson River in the early 1990s. While there are other species of filter feeding mollusks native to the Hudson River, the zebra mussels have had a more significant impact on the river since their introduction. Zebra mussels are small, cryptic and they are prolific reproducers. They can easily be spread by humans- attaching themselves to the hull of boats, being transported as larvae in bait buckets, etc. They attach themselves firmly to hard surfaces on the riverbed with a mass of thread-like strands called a byssus, which makes them hard to dislodge.
  5. Cary Institute researchers have been exploring conditions in the Hudson River Estuary before and after zebra mussel invasion. Zebra mussels were 1st recorded in the Hudson River in 1992, but scientists had been monitoring biotic and abiotic conditions in the river since 1986. Accordingly, they were able to make predictions about how the zebra mussels would affect the river, and look for evidence of change over time once it arrived.



  1. Students will research an aquatic organism for homework, and share information with classmates on Day Two. Students should be assigned their organisms so that at least two students research each organism, forming an “expert group”. A handout is provided with websites that students can use for research.  Students will then convene with their “expert group” on Day Two to share what they learned, and complete a graphing exercise. Students should use the attached worksheet (“Exploring a population”) as a guide for their research.
      Example Organisms
    1 Sphaeriidae (native, freshwater clams)
    2 Phytoplankton (e.g. Euglena, Volvox)
    3 Rotifers (microzooplankton)
    4 Alosa (open water fish)
    5 Cladocera (macrozooplankton)
    6 Centrarchidae (shallow water fish)
    7 Bacterial abundance (decomposers of detritus and organic material)
    8 Copepods (macrozooplankton)
    9 Copepod nauplii (larval macrozooplankton)
    10 Unionidae (freshwater pearly mussels)
  2. Students should come prepared to discuss what they learned with their expert groups tomorrow.*(More on Jigsaw Teaching Technique at
  3. Reading AMNH River Ecology Passages 1 and 2 prior to their second class day will give students background about the Hudson River food web, as well as information about zebra mussels (including the life history traits that researchers consider when making predictions about what effects it might have on the ecosystem). Students can answer the questions at the end of these passages, or they can be used as guidelines for review at the beginning of Lesson 2.
  4. Students can play a game teaching them about different types of invasive species, found here:



  1. Assess student understanding of the materials presented in the videos by having them share answers from their worksheet (“Intro to zebra mussels”).
  2. Students can share claims about the impacts of zebra mussels on the Hudson River ecosystem- can be discussed in class, submitted via their worksheet, or as an exit ticket, etc. 
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