In the following question, a part of the sentence (a word or phrase) has been highlighted in bold. Four different ways of writing the word or phrase have been given in the options (1), (2), (3), and (4). Find the correct replacement of the given bold word or phrase. If the given word or phrase is grammatically correct, then select option (5).

The lake was really captivating because of thousands of ice bubbles shaped like pancakes caused by bacteria at the bottom of the lake eating organic matter and excreting methane.