Question

how does a decline in submerged aquatic vegetation (sav) affect the energy available in the ecosystem?
energy in the ecosystem increases because more sunlight reaches the water.
energy in the ecosystem stays the same because consumers can eat other food sources.
energy in the ecosystem decreases because sav captures less sunlight.
energy in the ecosystem is recycled, so less sav has no effect on the energy flow.

Explanation:

Submerged aquatic vegetation (SAV) is a primary producer. Primary producers capture energy from sunlight through photosynthesis. If there is a decline in SAV, there are fewer producers to capture sunlight. Fewer producers mean less energy is captured and entered into the ecosystem.

Answer:

Energy in the ecosystem decreases because SAV captures less sunlight.