Decomposers, such as bacteria and fungi, also break down plant and animal matter and recycle the nutrients. Excrement from birds, fish, and invertebrates further enhances marsh soils and waters with nitrogen rich compounds, which are taken up by algae and vascular plants. These materials are transported and mixed by streamflows, tidal circulation, and even the activities of burrowing clams and shrimp. As a result, the mudflats become rich in inorganic nutrients and organic foods. Salt marsh food webs are among the most complex in nature.
Coastal wetlands are home to a variety of animals.
Numerous fish species, including California killifish, bay goby, striped bass, topsmelt, and starry flounder are residents of wetlands and depend upon them for reproduction. Subtidal eelgrass beds shelter larval and juvenile fish, as well as many species of invertebrates. Salt marshes are home to insects such as the salt marsh water boatman, wandering skipper, and numerous species of beetles and flies, which graze on leave and seeds, help to pollinate the wetland flowers, and prey upon a variety of small animals. Clapper rails build platform nests in the low marsh, whereas Belding's savannah sparrows nest in and feed on the pickleweed of the higher marsh. Although relatively few bird species are year-round residents of coastal wetlands, many species temporarily inhabit salt marshes during their annual migrations.