The correct answer is A. They control the major biogeochemical cycles that keep Earth’s biosphere in balance.
Explanation:
Ocean microbes include organisms such as bacteria, protists or archaea found in the ocean. These organisms are one of the most important factors for life in the ocean and on all the planet. This can be explained as microbes in the ocean clean toxins and wastes that might affect other living organisms, and serve as food for others. This is the case of plankton that is consumed by many fish in the ocean, and it is necessary for many multicellular organisms.
Besides this, microbes regulate multiple biogeochemical cycles that include regulating carbon levels, as well as other substances that are necessary for life such as nutrients, nitrogen or phosphorus. Thus, it is crucial to study ocean microbes because "They control the major biogeochemical cycles that keep Earth’s biosphere in balance".
