Answer:
Phytoplankton
Step-by-step explanation:
Formed by unicellular eukaryote microalgae, phytoplankton is defined as the portion of planktonic organisms capable of photosynthesis, constituting the basis of the food chain in aquatic ecosystems. For this reason, we can say that in an ocean ecosystem, phytoplankton production is necessary to start a food chain.
Phytoplankton are composed of individuals from different taxonomic groups that have some common characteristics: they all have individualized nucleus and complex organelles in their cytoplasm, as well as photosynthetic pigments (chlorophyll a, b, carotenoids). These organisms, predominantly autotrophic, can also ingest particles, being characterized in some cases as myxotrophic.