Complex sentence: In turn, as the population of drifting phytoplankton expands, the water becomes a suitable habitat for zooplankton, which are tiny drifting animals such as the larvae of fish and marine invertebrates.
Split into simpler sentences: In turn, as the population of drifting phytoplankton grows, the water becomes a suitable habitat for zooplankton. While phytoplankton are tiny drifting plants, zooplankton are tiny drifting animals, such as the larvae of fish and marine invertebrates.