Between the sandy, shell covered beaches and swaying upland pine forests lies the Atlantic salt marshes – an ever-changing, flooded and drained zone. The ecosystems here are among the most productive on Earth. These coastal wetlands stretch the Atlantic coast from Canada to Florida. They are characterized by salt-tolerant plants, shallow, meandering tidal creeks and nutrient-rich — albeit a little stinky — mudflats that some call “pluff mud.” Despite often being overlooked as “just marsh,” Atlantic salt marshes teem with life, providing essential habitat, food sources and nursery grounds for countless species.
Life in the salt marsh isn’t easy. High salinity, fluctuating water levels and oxygen-poor soils create challenging conditions for life. Yet many incredible species have adapted beautifully to these extremes.
Salt Marshes’ Roots
Plants stabilize the marsh and provide food and habitat for numerous insects, birds, fish and mammals. Hardy grasses tend to dominate this landscape. Spartina, for example, anchors the marsh soil, slows erosion and creates microhabitats that shelter a wide range of species. Black needle rush, marsh elder, glasswort, seaside goldenrod and sea lavender thrive in saline conditions. Even some threatened plants, like the seabeach amaranth depend on adjacent marsh for its continued survival. Each species occupies a specific niche within the marsh, depending on its tolerance to salt and inundation. Beneath the surface, countless invertebrates work tirelessly to sustain the marsh ecosystem. Crabs — particularly fiddler crabs — burrow into the mud, aerating the soil and aiding in nutrient cycling. Snails, like the marsh periwinkle, climb grass stalks to feed and avoid predators.
Small but mighty creatures including some seafood restaurant items — mud shrimp, oysters, mussels, amphipods, and countless insects — form the foundation of the marsh food web and help break down waste from other, larger species.
One invertebrate you may not realize depends on salt marshes is the endangered monarch butterfly. While most of North America’s monarchs overwinter in Mexico, a small population spends their entire lives in the swamps and coastal salt marshes of the Southeast. Researchers found these monarchs summer inland in swamps, then overwinter in the salt marshes along this coast. These iconic butterflies survive off aquatic milkweed and native swallow-wort as a host plant for reproduction.
Supporting the Skies
Atlantic salt marshes are vital for bird life. They support resident species and provide critical stopover points for migratory birds. The threatened Eastern black rail, willet, seaside sparrow, Worthington’s marsh wren, American oystercatcher and saltmarsh sparrow are closely tied to these habitats. Wading birds like egrets and herons hunt in the shallow creeks, feasting on fish and crustaceans. In autumn, enormous flocks of migrating plovers and waterfowl, among others, descend on the marshes to refuel during their long journeys. Marsh hawks, also called harriers, are commonly seen flying low over the grasses while they seek out a meal. Without healthy salt marshes, many bird populations would struggle to survive.
Rock-a-Bye, Small Fry
For many fish species, salt marshes are indispensable nurseries. Juvenile Atlantic sturgeon, striped bass, redfish, Atlantic silversides and flounder find shelter and abundant food in the shallow, grassy waters. Complex root systems and tidal creeks provide ideal hiding spots from predators, enabling young fish to grow before moving into deeper waters. Even economically important species like blue crabs and shrimp rely on salt marshes during critical stages of their life cycles.
Swimming Through, Enjoying a Salt Marshy Snack
While less conspicuous, mammals like river otters, muskrats and raccoons are frequent visitors to Atlantic salt marshes. These animals forage for crabs, fish, and plant material, playing important roles in the marshes’ food web.
Reptiles, such as the declining diamondback terrapin, are closely associated with salt marsh ecosystems. They nest in sandy areas nearby and feed within the tidal creeks. It’s not uncommon to see a sea turtle taking a break from the “big water” to cruise through a calm marsh creek.
Florida manatees feed along salt marsh margins, particularly on saltmarsh cord grass during the warmest months of the year as they move north, out of Florida. Manatees use the salt marsh as seasonal travel corridors, resting in deeper, connected channels when necessary.
Preserving Marshes’ Intricate Cycles of Life
Despite their resilience, Atlantic salt marshes face serious threats. Coastal development, pollution, rising sea levels and climate change are degrading these vital habitats. Salt marsh loss not only impacts biodiversity but also reduces the marshes’ ability to buffer storm surges, sequester carbon and filter water.
The Atlantic salt marsh is far more than a swath of grasses by the sea. It is a vibrant, dynamic ecosystem bursting with life. From the tiniest invertebrates to charismatic birds and elusive mammals, these wetlands support an intricate web of life. We must protect and restore Atlantic salt marshes to ensure they continue to thrive for generations to come.
Author
Heather Clarkson
Katherine Sayler
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