Lesson Plan

Piecing Together the Fjord Estuary Ecosystem Puzzle

A Park Ranger shows a plankton sample to a Junior Ranger.
NPS photo


By exploring the coast of Resurrection Bay, students will learn about the formation of a fjord, the relationships within an estuary ecosystem, and the importance of conserving the biodiversity within Kenai Fjords National Park.


Students will gain a better understanding of the local glaciology, geology, and ecology within a fjord estuary ecosystem. They will compare tests of water temperature and salinity between a brackish stream and the ocean in order to understand the importance of abiotic factors in supporting a diverse marine habitat. Hand held microscopes will be used to examine plankton and provide students with a better picture of the food chain base. Students will focus on detail by attempting to create scientifically accurately drawings of intertidal invertebrates, seaweeds, and plankton.


Fjords are glacially carved U-shaped valleys. Resurrection Bay was carved by a massive tidewater glacier during the late Wisconsin Glaciation (approx. 23,000 years ago). Local bathymetry shows that the ice that carved out Resurrection Bay stretched about 40 miles in to the Gulf of Alaska.

An estuary is where fresh and salt water mix together. Estuaries are transition zones between river ecosystems and ocean ecosystems, they are subject to marine influences, such as tides, waves, and the influx of saline water; and riverine influences- such as flows of fresh water and sediment. The mixing of saltwater and freshwater provides high levels of nutrients in both the water column and sediment, making estuaries one of the most bio diverse habitats in the world. Sea water generally has a salinity of 31-38 parts per thousand (PPT). And distilled fresh water should have a salinity of 0 PPT. Water in an estuary has more salinity (diluted salt) than fresh water, and can be referred to as brackishwater. In places where estuaries are formed by glacial melt-water mixing in to seawater, water temperatures tend to be cooler. The coldest water in the estuary can be found near the mouths of glacial streams. Often plumes of glacial silt settle out from melt-water streams when they reach larger bodies of water. 

Ecosystems are habitats in which abiotic and biotic elements interact with each other. A few of the abiotic elements of Resurrection Bay are water, air, wind, temperature, weather, wave action, and rocks. The abundance of marine mammals, fish, marine invertebrates, seabirds, and microscopic plankton make up the biotic elements of the ecosystem. 

Plankton are microscopic free floating plants (phytoplankton) and animals (zooplankton). Plankton are an extremely important support piece in the fjord estuary food web. Fish rely on great density and distribution of plankton to match that of their new larvae (plankton stage) which would otherwise starve because plankton cannot control where it swims. Natural and man-made factors can strongly affect zooplankton, which can in turn strongly affect larval survival, and therefore breeding success. 

Trophic levels are a way of identifying where species exist on the food chain. Plankton is generally divided in to three trophic groups: phytoplankton are considered primary produces, zooplankton-consumers and bacterioplankton-decomposers. 

There are global and local impacts that estuary ecosystems must face. Impacts of climate change on this environment can be seen in warming ocean temperatures impacting fragile life cycles, melting ice leading to loss of habitat for seals and certain sea birds. Other human caused impacts: pollution, marine debris-one of the largest killer of marine mammals (give students an idea of how difficult it can be for marine animals to escape from debris in water where there aren't objects to rub against with activity: put rubber band around thumb, behind hand and around pinkie finger and have them try to remove the rubber band without using anything but the hand it is on), overfishing and fishing key trophic species, involuntary and voluntary introduction of marine invasives.


  • Ranger introduces his/herself as a National Park Ranger. Explain walk logistics. Although this walk is not IN Kenai Fjords National Park, the Fjord of Resurrection bay was formed the same way that the Fjords in the Park were formed. This ecosystem is similar to those in the Park. Even though we are in town, there are enough clues in the natural landscape to help us 'Piece Together the Fjord Estuary Ecosystem Puzzle of Resurrection Bay'.
  • Lead group south on sidewalk to the bike path and make first stop to explain fjord formation and introduce the concept of estuaries. Look for clues that this is a fjord (U-shaped valleys) AND an estuary (fresh water mixing with salt water).
  • Make second stop at culvert easy access. Discuss puzzle pieces: salinity, brackish water and tides. Why are they significant pieces of the ecosystem? Where is the fresh water part of the estuary puzzle coming from? Encourage students to form hypothesis for salinity PPT and temperature of the brackish culvert water vs. the ocean water on the beach further along walk. Test water salinity using refractometer (see below). Have students take water temperature in culvert and record on map/note sheet.
  • Good beach access right past little pavilion on bike path. Third stop on beach to discuss glacially carved features- trim lines, rounded Mountain tops (with view of Mount Marathon runners peak)ancient nunataks like Mount Alice. Introduce map page and make notes on the number of U-shaped valleys that the students can count.
  • Further along beach stop near water to talk about the ecosystem part of the puzzle. What is an ecosystem? Discuss abiotic vs. biotic elements of an ecosystem. Importance of biodiversity. Trophic levels and the base of the food chain-plankton. The difference between zooplankton and phytoplankton. How have scientists learned about those differences? Discuss good observation techniques and scientific drawing. Conduct plankton tow (see below).
  • Discuss drawing to scale. Encourage students to pay attention to detail by attempting to sketch anatomically accurate (use ruler and scale up or down) drawings of abiotic or biotic ecosystem elements. Make notes on map page of observation sites.
  • Discuss possible threats to this environment and which trophic levels would be most susceptible- marine debris, climate change leading to warming ocean temperatures, melting ice, and rising sea levels.
  • Repeat salinity measurement and temperature of water at turn around spot on beach. Discuss original hypotheses and potential water differences within estuary ecosystem.
  • Conclude by bringing together entire Fjord Estuary Ecosystem puzzle. Without every piece we do not have a complete picture. The puzzle may still hold together if one part goes missing, but the more pieces that disappear, the more likely the entire puzzle will fall apart. Why is Resurrection Bay an important place to conserve and protect? Are we doing a good job of protecting 'the pieces' of Resurrection Bay? How about the fjords within Kenai Fjords National Park? How can these ecosystems be influenced by humans even if we aren't living in them? What changes can we make in our lives to help conserve marine environments like this one?
  • Lead group back to Information Center along bike path. Conduct final head count of students and chaperones. Collect Fjord backpacks and check for equipment. Leave students in the care of their teachers and chaperones and check for lost/found gear. 
Hand Held Refractometer for salinity analysis.
  • Before program: Use distilled water to adjust refractometer: Allow sample to remain on prism for 30 seconds. Remove black plastic cap from small screw behind prism. Adjust focus with long central grip. Use small screw driver to adjust calibration screw so that light/dark boundary coincides with the null (0 PPT) line.
  • During program: Show students how to open daylight plate, Place 3-4 drops of water on main prism using eye dropper. Close plate and press slightly so that water spreads out eliminating air bubbles and dry spaces. Take reading by looking through eye piece, focus using long central grip, read right hand side (PPT). Clean off prism and plate using blue cloth and store refractometer in case. Repeat process with ocean water further along walk.
Plankton Tow:
  • Pull plankton net through water along shore. It may take a few times to get a high plankton concentration.
  • Have students ready their petri dishes for plankton samples.
  • Use large eye dropper to take samples out of collection jar and place in student petri dishes.
  • Students can use magnifying glasses to observe plankton in their dishes. They should make notes on and/or draw at least one organism in their dish.
  • Place plankton net in plastic bag, rinse thoroughly upon completion of program.


  • Scientific drawings include measurements and scale.
  • Students have taken notes on both temperature and salinity of brackish water and seawater.

Park Connections

Other national parks could be incorporated by discussing thefjord estuary ecosystems of Glacier Bay National Park and differences in rates of melting for standalone glaciers vs. glaciers fed by an icefield. Many national parks throughout Alaska and the lower 48 boast glacially carved landscapes. Expand by comparing older and newer glacial landscapes (i.e. Yosemite to Kenai Fjords).



This lesson could be adapted to lower age groups by downsizing some of the vocabulary,also adapted to be a junior ranger badge/fjord patch program.


Additional Resources

Elias, Scott. Alaskan National Parks. Washington and London: Smithsonian Institution Press, 1995.

Field, Carmen and Conrad Field. Alaska's Seashore Creatures: A Guide to Selected Marine Invertebrates.Anchorage: Alaska. Alaska Northwest Books. 1999.

Kenai Fjords National Park Teachers Resource Manual. Forging Connections: An Educational Resource for Kenai Fjords National Park. Seward, Alaska.

Lindeberg, Mandy and Sandra Lindstrom. Field Guide to Seaweeds of Alaska. Fairbanks: Alaska. Alaska Sea Grant College Program, 2010.

National Geographic Environmental Literacy Teacher Guide. One Ocean: A guide for teaching the Ocean in Grades 3 to 8.National Geographic Education Beta website.

Wiley, Sally. Blue Ice in Motion: The Story of Alaska's Glaciers. Anchorage: Alaska Natural History Association, 1990. 


Tidewater glacier, bathymetry, fjord, estuary, tides, waves, sediment, nutrients, habitat, salinity, brackish water, ecosystem, abiotic, biotic, marine mammals, invertebrates, food web, density, distribution, intertidal zone, trophic levels, consumer, producer, decomposer, marine mammals, marine debris, overfishing, marine invasive species, pollution, conservation.