Mr. Rojas, a biology teacher, asks his class to evaluate two examples of changes to a pond ecosystem. The table summarizes the examples. Example 1 Example 2 Original pond community algae, cattails, a variety of fishes, ducks, raccoons algae, cattails, a variety of fishes, ducks, raccoons Change to the ecosystem increase in nitrogen and phosphorus content of the water, due to agricultural runoff decrease in the duck population, due to hunting by humans Result after one year an algal bloom that covers the surface of the pond, followed by a decrease in all animal populations Little or no effect; duck population returns to previous levels after one year Based on the results shown in the table, Mr. Rojas's class can evaluate which property of the pond ecosystem?