Final answer:
The level of study for an investigation into the effects of ocean currents, temperatures, and food availability on migratory patterns of aquatic mammals is Ecosystem ecology, as it involves studying multiple species and environmental factors together.
Step-by-step explanation:
The level of study for an investigation focused on how ocean currents, temperatures, and food availability affect the migratory patterns of multiple species of aquatic mammals over a few years is d) Ecosystem ecology. Ecosystem ecology examines the living species (biotic components) as well as the nonliving portions (abiotic components), such as air, water, and soil. It includes both the biological and the physical aspects of the environment.
When ecologists study an ecosystem, they look at how these biotic and abiotic factors influence each other and shape the environment. In the context of the question, ocean currents, temperatures, and food availability are abiotic factors, while the aquatic mammals represent biotic components. Their interaction and the examination of migratory patterns over time fall within the discipline of ecosystem ecology because it involves studying multiple species and environmental factors together.