Conveniently, there are roughly 6 main stages in the process of eutrophication, so if you can memorise each one, step by step, you are sure to scoring full marks!
1) Algae blooms block light
2) No photosynthesis, so plants die.
3) Saprobiotic decomposition occurs.
4) Microorganisms respire aerobically (use up oxygen)
5) Less oxygen for fish to respire, therefore they die
6) Increase in anaerobic microorganisms; release hydrogen sulphide/ nitrates/ toxic waste
7) Water becomes putrid
Please note: This answer has been written in note form to aid in your understanding and memorisation, but ALWAYS WRITE FULL SENTENCES IN EXAMS…examiners don’t like scrappy notes :)