Answer:
oxygen
Explanation:
A limiting factor is any condition whose decrease, increase, absence or presence is able to limit/stop population growth. Examples of limiting factors include abiotic conditions (e.g., temperature, water, oxygen, CO2, etc) or biotic conditions (e.g., food, mate, etc). There are many aquatic species that require high levels of oxygen (e.g., fish), thus being it a limiting factor for these species.
