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Why is less energy available to organisms at higher trophic levels in a marine food chain?

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Diagram showing ocean zonation by depth and region, with labeled layers: littoral, sublittoral, bathyal, abyssal, and hadal along the seafloor, and epipelagic, mesopelagic, bathypelagic, and abyssalpelagic in open water. The littoral zone is at the high-tide mark. Vertical scale marks photic and aphotic zones from surface to 10,000 meters. — Marine ecosystem Zonation of the ocean. Note that in the littoral zone the water is at the high-tide mark.

In a marine ecosystem, energy availability decreases at higher trophic levels primarily because a significant portion of energy is lost as heat during the transfer between levels.12

As organisms consume food, they expend a large amount of energy—often 80 to 90 percent—on essential metabolic processes, such as digestion and maintaining body functions. Consequently, only a small fraction of the energy consumed is converted into new biomass that can be passed on to the next level of the food chain.123

This ecological efficiency, which averages about 10 percent, dictates the structure of the trophic pyramid:
* Primary Producers: Phytoplankton and other autotrophs form the base, capturing solar energy or chemical energy to create organic substances.124
* Consumers: Herbivores (primary consumers) and subsequent carnivores (secondary and tertiary consumers) have progressively less energy available to them because they rely on the limited biomass produced by the level below them.123

Because of these energy losses, higher-level consumers, such as fish and marine mammals, have the least amount of energy available to support their populations.125