Final answer:
The study of manatee size in relation to biomass consumed and caloric intake falls under the field of organismal ecology, which examines physiological adaptations and behaviors that support the survival of individual organisms.
Step-by-step explanation:
The study of how manatee size (length and diameter) corresponds with biomass consumed and extrapolated caloric intake relates to organismal ecology. This field of ecology focuses on the physiological adaptations that enable individuals to live in specific habitats, as well as the behaviors related to feeding and energy consumption that support their survival and growth. The energy requirements and nutrient intake are crucial for understanding manatee health and viability within their habitats.