Multi-level phenotypic plasticity and the persistence of seagrasses along environmental gradients in a subtropical lagoon

•We studied seagrass responses to water and sediment variability in a coastal lagoon.•Both studied species were found along the environmental gradients in the lagoon.•H. wrightii focused phenotypic responses at the meadow/shoot and biochemical level.•R. maritima focused phenotypic responses at the biochemical level.•The study provides baseline data for monitoring these seagrass meadows.