Animals in coastal wetlands: zonation, adaptations and energy flow

Key points Salt marshes contain abundant and diverse terrestrial and marine animals based on their high primary productivity; animals are classified by trophic functional group and size class; foraminifera are important in the marsh microecosystem and used for reconstructing past sea levels; vertical zonation is based on physical tolerances and biological competition from marine mudflats to terrestrial high marsh; in the tropics, mangrove forests support many large animals, while invertebrates inhabit their subaerial roots; coastal wetlands are highly productive ecosystems with the energy produced by plants and algae supporting large detritus-based food webs; marshes are often nitrogen-limited and are impacted by enrichment from sewage and agricultural runoff; secondary production is concentrated in detritivorous food webs rather than upper-level consumer webs; mangroves are the most carbon-rich forests on Earth. Animals that inhabit salt marshes As seen from Chapter 3, salt marshes and mangroves are extremely productive, which results in a large food web base that can support a high abundance and diversity of species dependent on the vegetation directly or indirectly for food or shelter. Recently, however, there has been a paradigm shift in understanding of the role that tall grasses such as Spartina alterniflora play in the feeding structure of a salt marsh (Mann, 2000). New stable isotope studies show that algae (diatoms and algal mats) are more important food sources to the deposit feeders than the decaying grass (Galván et al ., 2011), and picophytoplankton can play key trophic roles on intertidal flats (Paterson et al ., 2009). Regardless of differing views on salt marsh basal food webs, however, it is clear that salt marsh vegetation is an important driver of the faunal diversities and abundances in temperate regions. The physical environment of coastal wetlands supports a high faunal diversity because it is low-energy and contains many different lateral and vertical zones and microniches for both terrestrial and marine animals. The gradient between the terrestrial high marsh and marine mudflats not only influences plant zonation, but also the animal distributions. Animals must be adapted to a transient environment that changes with the tides and seasons, as well as anthropogenic changes such as habitat reduction and invasive species.

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