The answer is a. correlational research.
In this scenario, you only do observation of one event and trying to find a link between them. This method is good for finding correlation, but not for causation.
Because you only observe the subject without intervention, it shouldn't be experimental research. What you observe is only one condition, so there is no control subject that get different condition.
Answer:
observation because you are using senses such as sight and smell to come to a logical conclusion about something.
As a result of the fertilizer being in an aquatic ecosystem ALGAE grows which can cause blockage from the sunlight which will also effect organisms in that aquatic system