Rocky Shore Ecosystems

Every organism depends on other organisms and their environment for survival. In the first lesson of this unit, students are introduced to different interactions within an ecosystem, exploring the phenomena of how different organisms are connected to one another. Students use evidence to create a rocky shore food web model, using the model to describe different relationships among the organisms.

• Ecosystems are communities of different species that depend on interacting with each other and their physical environment for survival.
• Scientists who study how organisms interact with one another see that there are patterns in the interactions that can be observed across different ecosystems.
• Organisms have different relationships with other living things within an ecosystem as they interact with one another for survival.
• Scientists who are interested in the health of an ecosystem need to understand how energy flows through the ecosystem. Scientists do this by studying the food webs within an ecosystem.
• Food webs are visuals that show the network of food chains in an ecosystem. Food chains show specific paths that energy travels as one organism eats another.
• A change to one species in a food web will impact the entire ecosystem.
• Ecologists study living things in their natural environment to know where organisms are found in ecosystems, their relationships with one another, and the interactions between energy and life.

• What are some of the living and nonliving parts of a rocky shore ecosystem?
• What is the cause-and-effect relationship between an organism’s ability to access resources and its chances of survival?
• How is a predatory interaction different from a mutually beneficial one?
• Why is it helpful for scientists to know about the different kinds of interactions within an ecosystem?
• Where does all the energy in food webs come from?
• Why is the first level of every food web made up of producers?
• What is the difference between primary, secondary, and tertiary consumers?
• How are decomposers different from either producers or consumers?
• How do food webs provide evidence that energy is transferred within an ecosystem?
• What can cause ecosystems to change?

Misconception: Arrows in a food web show which organisms eat other organisms.

Fact: Arrows show the flow of energy in a food web.

Misconception: Decomposers release energy that is cycled back to plants in a food web.

Fact: Decomposers return nutrients, not energy, back into the soil to be used by plants.

Misconception: Different species “get along” in an ecosystem.  

Fact: Species compete for resources and eat one another for energy and nutrients.

Decomposers : organisms that break down organic waste and feed on the nutrients

Ecology : the study of living things in their natural environment; includes where organisms are found in an ecosystem, the relationships between organisms, and interactions between energy and life

Ecosystem : a community of different species that depend on interacting with each other and their physical environment for survival

Environmental threat : anything that can cause harm to an ecosystem (e.g., pollution, deforestation, invasive species, overhunting, climate change)

Filter feeders : marine animals with organs that gather energy by straining nutrients and small organisms out of the water (e.g., mussels, barnacles, sponges)

Food web : a visual that shows the network of food chains in an ecosystem

Intertidal zone : the region of land that is covered and uncovered by water between high and low tides

Population : all of the members of the species within a particular area

Predator : an organism that eats other organisms for energy

Producers : organisms that capture energy directly from the sun to make their own food; trees, grasses, and some microbes do this with photosynthesis

Shore :the place where land and water meet

Mussel “Glue”

Blue mussels are a common sight on rocks on many coastlines. They remain in place even as waves crash into the shore over and over again. A shore is the place where land and water meet. Scientists and engineers are fascinated by how blue mussels can survive the force of the waves. They have studied them looking for clues about how they are able to stick so firmly to the rocks as the waves crash over them.

Scientists have learned that blue mussels make adhesives just as strong as human glue. They produce thin, bungee-like silky fibers called byssal threads. They anchor themselves to rocks with these threads. Byssal threads begin as a sticky mixture of proteins and other substances. The sticky, adhesive mixture hardens. It turns into strong and flexible threads that keep the mussels attached to rocks.

An Adaptation at Risk

This ability to produce byssal threads is an adaptation. It helps the mussels survive the harsh conditions of their environment. When the waves pound the rocks, the byssal threads help to anchor the blue mussels so they don’t get swept out to sea.

Recently, scientists have said they are concerned that climate change will make it harder for the blue mussel to attach firmly to rocks. A group of scientists announced in 2013 that the byssal threads become weaker when water temperatures are 7 degrees Celsius (15 Fahrenheit) warmer than typical summer temperatures.

A Connected Ecosystem

Scientists worry about what will happen to the rocky shore ecosystem if the blue mussels become less able to survive. An ecosystem is a community of different species that depend on interacting with each other and their physical environment for survival.

All ecosystems include living things. They also include oxygen and carbon dioxide from the atmosphere; water; and energy from the sun.

Blue mussels play several important roles in many rocky shore ecosystems. First, blue mussels are filter feeders. Filter feeders are marine animals with organs that gather energy by straining nutrients and small organisms out of the water. As they strain food out of the water, they also remove sediment, heavy metals, and toxins from the water. This process cleans the water.

Another role of blue mussels is to provide a habitat for other living things. This is because blue mussels often form large mussel beds, attaching to other mussels. Many different kinds of organisms live on or in between the mussels.

A third role of the blue mussel is as food for other living things. Remember that an important life function of all living things is getting energy from food. Blue mussels get food by filtering other organisms from the water. Blue mussels are also an important food source for many organisms in the rocky shore ecosystem, including sea stars, fish, birds, and humans.

In this lesson, students survey various organisms that can be found in phenomena of a rocky shore ecosystem and then develop a model to evaluate how the organisms rely on each other for survival. Students use the model to analyze the science phenomena ecosystems, the different relationships between producers, consumers, and decomposers in this ecosystem.