Final answer:
The water hyacinth most likely had a competitive effect on the native water plants for resources.
Step-by-step explanation:
The water hyacinth most likely had a competitive effect on the native water plants for resources. When water hyacinths cover the surface of the lake, they block sunlight from reaching the native plants, which can cause them to die off. Additionally, the water hyacinths can outcompete the native plants for nutrients and space, further reducing their ability to thrive.