The dominant second trophic level in a lake ecosystem is:
In a food chain of lake ecosystem the producers are phytoplanktons and the consumers which directly depend on phytoplanktons for food are called primary consumers. These primary consumers in a lake ecosystem are basically zooplanktons, although it may include some fishes that feed on the phytoplanktons. Therefore the dominant second trophic level in a lake ecosystem is zooplankton. Moreover zooplanktons do not occupy any other trophic levels as they only feed on the primary producers- phytoplanktons.