Which type of wetland does not typically contain soil but has hydrophytes?

The correct choice is based on the distinctive characteristics of marine wetlands. Marine wetlands are primarily associated with coastal areas and are characterized by the presence of tidal influences and saline waters. In these environments, the substrate can often be sandy or rocky rather than composed of soil, which is typical of other types of wetlands.

Marine wetlands can support hydrophytes, which are plants adapted to growing in water or saturated soils, even though the typical organic soil layer found in other wetlands may not be present. This difference in substrate type is crucial in distinguishing marine wetlands from palustrine, riverine, or estuarine wetlands, which generally involve more substantial soil presence due to freshwater influences.

In contrast, palustrine wetlands usually have hydric soils and are often freshwater ecosystems that can include marshes and swamps. Riverine wetlands are typically associated with waterways and also feature hydric soils and a variety of vegetative types. Estuarine wetlands, which are located where freshwater from rivers meets saltwater from the sea, typically have a mixture of soil types influenced by both environments.

Thus, the unique absence of soil in marine wetlands, despite the presence of hydrophytes, makes them the correct choice for this question.