In a lake ecosystem, the primary consumers are _________ .

zooplankton

The correct answer is Option (1) – zooplankton

In a lake ecosystem, the primary consumers are typically zooplankton.

Primary consumers are organisms that directly consume producers, which in aquatic ecosystems are often phytoplankton (microscopic algae). Zooplankton, which include tiny animals such as small crustaceans, rotifers, and larval stages of larger organisms, feed on phytoplankton. Therefore, zooplankton serve as the primary consumers in lake ecosystems by consuming phytoplankton as their primary food source.