The Mississippi River stretches over 2,300 miles from its source in Minnesota to the Gulf of Mexico. It serves as a transportation artery and natural boundary for ten states, forming a vast, interconnected ecosystem. Its diverse habitats, from main channels to backwaters and floodplains, support a diverse array of plant and animal life.
Aquatic Life in the River’s Depths
Over 260 fish species inhabit the river, representing a quarter of North American fish, including popular sport fish and riverine species like blue sucker, shorthead redhorse, and bigmouth buffalo.
Ancient fish like paddlefish, lake sturgeon, and shovelnose sturgeon are present. Lake sturgeon, once common but declined due to overharvesting, can grow large. The endangered pallid sturgeon prefers swift currents and sandy substrates. Shovelnose sturgeon, a bottom feeder, typically inhabits deep waters, consuming aquatic insects.
The river hosts aquatic invertebrates like freshwater mussels and crayfish. The Upper Mississippi supports 39 mussel species, indicators of health. These bivalves filter water, removing organic matter; one mussel can filter up to 15 gallons daily. Many are long-lived, some surviving decades.
Crayfish are abundant, including the red swamp crayfish native to the southern Mississippi River drainage. These omnivores consume plants, animals, and organic debris, burrowing deep into the substrate to create “chimneys” of mud. They serve as a food source for many river inhabitants, linking different parts of the food web.
Reptiles and Amphibians of the River System
The river system hosts various semi-aquatic reptiles and amphibians. Common turtles include snapping turtles, softshell turtles, and various map turtles (13 species in the Upper Mississippi). Snapping turtles, with powerful jaws, prefer areas with abundant aquatic vegetation. Softshell turtles, like spiny and smooth softshell, reside in rivers and streams with sandy or muddy bottoms, often burying themselves to ambush prey.
The alligator snapping turtle, North America’s largest freshwater turtle, is found in the Mississippi and Illinois Rivers, often in deep, low-visibility waters. They can weigh over 100 pounds and have spiked shells. Water snakes, like the common water snake, are prevalent, basking on branches or swimming through quieter sections.
American alligators are present, particularly in the southern Mississippi River basin, mainly in Louisiana and Mississippi. These apex predators thrive in the marshy swamps and bayous connected to the river, with some areas having high concentrations. Alligators are less common in the northern states through which the river flows.
Amphibians like frogs and salamanders depend on the river’s wetlands, backwaters, and riparian zones for breeding and foraging. Moist environments along the river’s edge provide ideal conditions, as these species often move between aquatic and terrestrial habitats. Their presence contributes to the ecosystem, serving as both predators and prey.
Mammals and Birds of the River’s Edge
The river’s banks, floodplains, and airspace host mammals and birds. River otters, semi-aquatic weasels, thrive along the river. Their diet consists primarily of fish, amphibians, crayfish, and small mammals. Otter populations have rebounded due to improved water quality and conservation, making them a common sight along the river.
Beavers, ecosystem engineers, construct dams that create wetlands, diversifying aquatic habitats. These large rodents are well-adapted to river life, using their strong teeth to fell trees for their lodges and dams.
Muskrats, smaller semi-aquatic rodents, inhabit the river system, building dome-shaped houses from vegetation or burrowing into banks. They are primarily vegetarians, feeding on aquatic plants, but will also consume mussels, crayfish, and small fish.
Raccoons are common along the river, foraging for aquatic invertebrates, fish, and plants.
The Mississippi Flyway, a major migratory corridor for millions of birds, follows the river. Waterfowl like mallards, teals, northern pintails, wood ducks, and diving ducks use the river’s pools, backwaters, and floodplain forests for resting, feeding, and breeding. Wading birds, including herons and egrets, are often observed along shallow edges, hunting fish and amphibians.
Raptors, such as bald eagles, are strongly associated with the river; the upper river supports one of the largest nesting populations. They often perch in tall trees along the banks, preying on abundant fish. Seasonal migrations highlight the river’s importance as a stopover point, providing resources for their long journeys.
Adapting to a Dynamic Environment
The Mississippi River is dynamic; its animals adapt to fluctuating conditions. Variations occur along its length in flow rates, temperatures, and sediment. These characteristics influence which species thrive; cold-water fish might dominate upstream, while species tolerant of warmer, slower waters are found downstream.
The river system encompasses a mosaic of microhabitats, supporting distinct communities. These include the main channel with strong currents, calmer backwaters, oxbow lakes, and floodplains. This diversity allows species to coexist, each exploiting different ecological niches. Fish, for example, may use deeper channels for migration and shallower, vegetated areas for spawning and rearing young.
Animals cope with natural fluctuations like seasonal floods and droughts. During floods, many aquatic species expand into newly inundated areas, accessing food and breeding grounds. Mammals and birds may move to higher ground or find temporary refuge in elevated floodplain areas. Conversely, during low water, species might concentrate in remaining pools or deeper channels, increasing competition.
Many river inhabitants adapt behaviorally or physiologically to these changes. Some fish tolerate a wide range of water temperatures or oxygen levels, persisting through varying conditions. Mussels, anchored in the sediment, endure periods of low flow by burrowing deeper. The resilience of the river’s wildlife reflects their evolutionary history within this constantly changing natural system.