After the students have shown connections between the different organisms (on both the inside and outside version of the activity) introduce one of the scenarios (For the inside version, you could give different groups a different scenario.):
A. A large commercial fishing company triples their annual catch of red cod in the area.
B. The land on the edge of the estuary is converted to intensive farming. There is a big increase in agricultural run-off and nutrients into the estuary. This increases the risk of phytoplankton blooms.
C. Due to increased carbon emissions, the ocean is becoming more acidic. Bryozoans and other shelled animals will no longer be able to make shells.
Ask the students to revise their food web to show what they think might happen to the food web based on the scenario.