Answer: Option B) . a decrease in the amount of oxygen dissolved in
the pond
Explanation:
Anaerobic bacteria are able to survive in the absence of oxygen while aerobic bacteria survive only in the presence of abundant oxygen.
Hence, while reduced levels of dissolved oxygen in the pond decrease the amount of aerobic bacteria like Bacillus; anaerobic bacteria like Actinomyces flourish since they survive on organic substances like methane, cellulose instead.
