meroplankton

Meroplankton are organisms that spend only part of their life cycle in the plankton. In contrast, holoplankton remain planktonic throughout their entire life cycle. Meroplanktonic stages are typically larvae, juveniles, or reproductive stages that drift or swim in the water column before settling into a benthic, nektonic, or sessile adult form.

The meroplankton include the larvae of many marine invertebrates and some fish. Crustaceans such as barnacles, crabs, and lobsters often have planktonic nauplius and/or zoea stages. Molluscs such as gastropods (snails) and bivalves (clams and oysters) usually have free-living trochophore and/or veliger larval stages. Echinoderms such as sea stars and sea urchins produce larval forms like bipinnaria, pluteus, and brachiolaria. Fish eggs and larvae represent another major component of meroplankton in many ecosystems.

The duration of the planktonic phase varies from days to months and is influenced by temperature, food availability, and ocean currents. Meroplanktonic drift enables dispersal and connectivity between populations, influences community structure, and contributes to recruitment in adult populations. They are often highly exposed to predation and environmental variability.

In ecological research, meroplankton are studied through plankton sampling and larval identification, including morphological and molecular methods. Changes in meroplankton communities can reflect shifts in climate, nutrient supply, and habitat conditions.