Phytoneuston Ecology of a Temperate Marine Lagoon1

Comparison of neuston (upper 0.4 cm) and plankton (10 cm deep) water samples from a temperate marine lagoon and an adjacent, less sheltered bay indicates that: 1) the surface microlayer exhibits greater and more rapid environmental fluctuations than the subsurface water; 2) no abundant phytoneuston populations develop outside the lagoon; 3) in the main lagoon fairly abundant phytoneuston populations develop; 4) phytoneuston population are most developed in the shallow sheltered pond area of the lagoon, particularly in summer; 5) taxonomic diversity is generally lower and dominance greater in well‐developed phytoneuston populations than in underlying phytoplankton populations; 6) photosynthetic assimilation ratios are greater in phytoneuston than in phytoplankton populations.