A large amount of untreated sewage entered the river. Many fish died. Untreated sewage contains organic matter and bacteria. Explain why many fish died. (5)

Sewage entering the water caused plants to die.Bacteria then decayed this dead organic plant matter (1) through digestion (1).These bacteria will carry out aerobic respiration, using oxygen (1).This therefore lowered the oxygen concentration in the water (1).Therefore this meant fish could no longer carry out sufficient aerobic respiration, reducing their energy production and therefore they died (1).


Answered by Joy C. Biology tutor

12278 Views

See similar Biology GCSE tutors

Related Biology GCSE answers

All answers ▸

What is the difference between a virus and a bacteria? What is an example of each?


What are the issues of monocropping in agriculture and how could inputting hedgerows improve this?


Use your knowledge of natural selection to suggest how the peacock's tail has evolved.


What is the structure and role of a chloroplast?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences