Grade level

High School

Materials

• Computer with Internet access
• Student Data Worksheets
• VES-V Software Tutorial (This Tutorial is the same as Activity I in this and each of the three modules.)
• Module Presentation Graphics - (Click to download)

Time

There are 7 activities in this module. Each activity will require 1-2 class periods (assuming 50-minute class periods) to complete.

Summary

This module uses the concepts of food webs and trophic levels to explore populations of marine species in ocean ecosystems. Students will explore simulated marine environments using a computer-based virtual reality (VR) data visualization tool called VES-V (The Virtual Ecosystem Scenario Viewer). VES-V displays marine environments as though one was SCUBA diving in those habitats. The numbers and types of fish and other aquatic creatures displayed in different locations in the VES-V simulations are based on actual abundances of marine creatures and how the abundances respond to a variety of conditions.

Students will explore a marine environment in VES-V. Each student will conduct research about one of the species found in that environment, determining what it eats and what preys upon it. Students will combine their data in a whole-class jigsaw activity to create a food web diagram for this marine environment.

Next, students will gather data about populations of predators and their prey in two specific ocean environments. The first case study, based in the Gulf of Maine, explores the relationship between herring and cod that feed on them. Students will collect cod and herring biomass data during “virtual dives” in VES-V. Students will determine the relationship between trophic level and biomass for herring and cod. The second case study is set in kelp forests in Monterey Bay. Students will again “dive” in VES-V to collect biomass data. The key species in the second case study are sardines, sea lions that eat sardines, and orcas that eat sea lions. Students will again collect biomass data for the species in VES-V, then compare biomass with trophic level to reinforce their understanding of the relationship between those two quantities.

Finally, students will explore an ecosystem in the Florida Keys to see how their knowledge of trophic levels and biomass can be used to help predict the supply of a commercially important fish. Students will use biomass data for mackerel, collected in VES-V, to predict the biomass of tuna which feed on mackerel. Students will then compare estimates of tuna biomass with actual data about tuna biomass to see whether the trophic level and biomass relationship is useful for making predictions. The lesson wraps up with a discussion of the future availability of fish, such as tuna, that people are fond of eating.

Background

Modern techniques and technologies make fishing so efficient that it is possible for humans to deplete populations of marine species. People must therefore monitor and manage populations of marine creatures to ensure that they are sustainable. This usually involves placing upper limits on the number of fish or other marine species allowed to be caught each year. Government agencies, such as NOAA Fisheries, strive to set catch limits that balance peoples’ desire for fish as a food source with the need to keep fish stocks above critical thresholds that ensure sustainable populations.

Fishery management experts need data about fish populations to assess the size and health of those populations, so they can set appropriately balanced catch limits. It is impossible to count all the fish in the sea, so fishery scientists use different methods to estimate populations of marine species. Sometimes it is very difficult to get an accurate count of a certain type of species. In some cases, one can infer general trends in a population of fish based on the population levels of a different fish that it preys upon if the second type of fish is easier to count than the first. Sometimes one can get a decent estimate of population size of a predatory fish by collecting data about its prey.

Learning Objectives

• Students will conduct research about a specific marine species, including what it eats and what preys upon it and communicate their findings to the class.
• Students will construct a food web diagram, as a whole-class “jigsaw” activity, by combining data about individual species that each student researched.
• Students will use a virtual reality software environment (VES-V) to visualize marine habitats and gather data about species in those habitats.
• Students will collect biomass data as well as analyze food webs and trophic levels.
• Students will use their knowledge of trophic levels to estimate the unknown biomass for one species based on the known biomass of another (predator or prey) species.
• Students will discuss the extent to which knowledge of food webs and trophic levels can help improve predictions about population levels of marine species that are difficult to directly observe.

Key Words - Vocabulary

• Biomass - the total mass of a group of organisms combined. The biomass is the sum of the masses of all the individuals in the group.
• Consumer - a species that eats other creatures, instead of producing its own food source internally.
• Food Chain - a simple diagram showing a sequence of species that feed on one another.
• Food Web - a complex diagram showing the organisms in an ecosystem and the relationships between them in terms of what-eats-what.
• Primary Consumer - a consumer that feeds on producers, such as sheep grazing on grass.
• Producer - a species that produces its own food internally, usually via photosynthesis. Producers don’t eat other species.
• Secondary Consumer - a consumer that feeds on primary consumers, such as a wolf that eats sheep.
• Tertiary Consumer - a consumer that feeds on secondary consumers. A shark that eats a fish that itself is a predator is an example of a tertiary consumer.
• Trophic Level (model validation) - a number that represents the place of a species in a food web based on what they eat. Producers are trophic level 1, primary consumers are trophic level 2, secondary consumers are level 3, and tertiary consumers are level 4.
• Trophic Pyramid (model validation) - a diagram that shows the species in an ecosystem based on trophic level, with the lowest trophic level at the bottom. The diagram is pyramid-shaped to indicate that most energy and biomass resides in the lowest trophic levels.

Procedure

Introduction: Introduce the Ocean Food Webs Module with a Big Question: “How do Individuals, communities or governments ensure that there is enough seafood for people to eat in the future?”

1. Ask students whether they eat any seafood. Since some students may not like or care about seafood, also ask them whether they work in a restaurant that serves seafood, or hope to get a job in food service. What might happen to the seafood they eat, or to jobs in those restaurants, if seafood prices rose because of limited supplies?
2. Discussion: Engage students in a discussion with the following suggested prompts:
   • Ask students what happens if we notice that some marine species becomes severely depleted? What might that mean for the health of the rest of the ecosystem?
   • How can we make sure that there are adequate supplies of seafood (or any other limited resource) for people to eat/use in the future?
   • How can we predict the population sizes for various kinds of marine species, or the amount of other potentially limited resources people consume, or use in the future?
   • If we are interested in a certain type of fish (such as tuna), and we notice large changes in the populations of other fish that tuna eat, does that tell us anything about the likely future tuna population?