Marshes provide habitat for many types of plants and animals that have adapted to living in flooded conditions. The plants must be able to survive in wet mud with low oxygen levels. Many of these plants therefore have aerenchyma, channels within the stem that allow air to move from the leaves into the rooting zone. Marsh plants also tend to have rhizomes for underground storage and reproduction. Familiar examples include cattails, sedges, papyrus and sawgrass. Aquatic animals, from fish to salamanders, are generally able to live with a low amount of oxygen in the water. Some can obtain oxygen from the air instead, while others can live indefinitely in conditions of low oxygen. Marshes provide habitatfor many kinds of invertebrates, fish, amphibians, waterfowl and aquatic mammals. Marshes have extremely high levels of biological production, some of the highest in the world, and therefore are important in supporting fisheries. Marshes also improve water quality by acting as a sink to filter pollutants andsediment from the water that flows through them. Marshes (and other wetlands) are able to absorb water during periods of heavy rainfall and slowly release it into waterways and therefore reduce the magnitude of flooding. The pH in marshes tends to be neutral to alkaline, as opposed to bogs, where peat accumulates under more acid conditions.
A marshland habitat is a great ecosystem for grass snakes. You are very likely to find one in this habitat throughout the most of the UK. Adders may occasionally be found if the marshland is within a heath etc. Common lizards may inhabit the drier areas of the marsh. Marshes are great places for the common frog & toad. All 3 native newts can be found within a wetland espacially the smooth newt; the great crested and palmate newt may only be found here if it's near of in a place where they inhabit: the same goes for the pool frog.