Ozark Streams

Alley_Spring.jpg

Photo of the creek flowing away from Alley Spring
Many Ozark streams are fed by the cool, clear water of springs.
Julianna Schroeder

The Ozark Aquatic Faunal Region lies mostly south of the Missouri River. Its streams are typically clear, cool, and fast-flowing, with high gradients and chert bottoms.

Missouri has more than 110,000 miles of running water, which are the product of the land surrounding them. Their watersheds consist of uplands, floodplains, stream corridors, stream channels, and groundwater. Missouri biologists specializing in aquatic animals (aquatic fauna) have divided the state into four Aquatic Faunal Regions to describe where fish, crayfish, and other aquatic animals live.

Ozark Streams

In Missouri, the Ozark highlands occur mostly south of the Missouri River. To the east, they end where the Bootheel lowlands begin, and to the west, they transform gradually into the Prairie Faunal Region, showing a blend of characteristics along a line drawn roughly from Morgan through Jasper counties.

The streams in the Ozark region typically have steeper gradients than those in the north, and have coarse, rocky substrates.

Photo of the Jacks Fork River showing adjacent gravel wash and cliff
Ozark streams, like the Jacks Fork River, are typically clear, cool, and fast-flowing, with high gradients and chert bottoms.
Jim Rathert

Geologically, the Ozarks are an elevated plain of ancient bedrock, through which streams have carved deep channels, creating a complex system of rugged hills, rock outcrops and bluffs, and thin, stony soils. Much of the land is forested, and the primary agricultural use is pasture.

The limestone and dolomite karst geology in the Ozarks is famous for its caves and springs, and these influence the character of Ozark streams. Ozark streams typically occupy narrow, steep-sided valleys and often amount to a series of short pools connected by well-defined riffles. Ozark streams usually have coarse, rocky substrates and steeper gradients than those in our prairie regions. Chert gravel is often at the bottom of the stream bed. Ozark streams are typically clear and relatively cool, often because they are fed by springs.

The aquatic animals that live in these clear, cool, high-gradient, fast-flowing, chert-bottomed streams are particularly diverse, because the many separate stream systems are generally isolated from each other. Thus a fish, crayfish, or other aquatic species that lives in one stream may not occur at all in a separate stream only a few miles away — as the crow flies — because they cannot travel overland to reach that different stream system.

In addition to its famous streams and springs, the Ozark Aquatic Faunal Region also contains some large reservoirs created when certain rivers were dammed. The Lake of the Ozarks and Table Rock Lake are examples. These large lakes have their own habitat conditions quite different from Ozark streams, and their dams prevent aquatic animals from moving past them, particularly upstream.

Examples

The following major rivers and their systems of tributary streams are prime examples of the Ozark Aquatic Faunal Region.

  • The Osage and Gasconade rivers (which flow into the Missouri River)
  • The Meramec and St. Francis rivers (and others that flow into the Mississippi)
  • The James and North Fork rivers (which flow into the White River)
  • The Black River system (including the Eleven Point and Current rivers)
  • The Elk and Spring rivers (which flow into the Neosho River).

Typical Plants And Animals

The rather fast-flowing, clear, cool waters of Ozark streams, their substrates, and their water chemistry are home to many plants and animals not usually found elsewhere in the state. For example, of the two large groups of aquatic snails, it is the gilled snails (prosobranch snails) that predominate in Ozark streams, mostly because the fast-flowing, cool waters of Ozark streams hold more oxygen, making them better suited for snails that must extract oxygen from the water through gills.

Another example are the darters, a group of small fishes that are well represented and especially diverse in Ozark streams. Darters are adapted for life in swift-flowing sections of clear, rocky streams. To keep them from being swept downstream, the gas-filled swim bladder found in most fishes is absent or much reduced in darters, so when they are not swimming, they tend to sink to the bottom. They use their enlarged pectoral fins to hold them in place against rocks. Sculpins, another group of fish mainly present in Ozark streams, use their enlarged pectoral fins in much the same way.

Darters and many minnows in Ozark streams are often brilliantly colored, especially during breeding time. The colors function for mate attraction and assist in territorial displays. The clarity of Ozark streams permits such colors to be visible to other fish; murky water would preclude their usefulness.

Plants that predominate in Ozark streams are ones that are suited for high oxygen content, cool temperatures, relatively little silt, and fast flows. A typical example is water cress.

 

Distribution in Missouri
Mostly south of the Missouri River.

Management Practices

Because streams and rivers are so fundamentally linked to the watersheds that surround them, most of the threats to terrestrial habitat systems also threaten streams. If the watershed and habitat systems within them are fully functioning and intact, the stream is more likely to be healthy, as it is a reflection of that watershed. Of course, in-stream impacts, such as channel dredging, channelization, and damming, also have direct and severe impacts on aquatic systems.

Urbanization

Construction activities without effective erosion control can cause sedimentation in streams. In developed urban areas, impervious surfaces like roads, buildings, rooftops, etc. can have the opposite effect by not allowing enough sediment into streams, especially when the channels themselves are put through pipes, culverts or lined in concrete. This can cause excessive velocities that erode the stream channel and degrade stream habitat. Frequent urban water quality problems include increased stream temperatures from impervious surfaces, lack of riparian buffers; and pollutants from vehicles, yards, and municipal sewage overflows, etc.

Agriculture

Overgrazing can increase erosion and run-off into stream channels which can increase sedimentation that creates turbidity and fills interstitial spaces that are critical habitat to benthic organisms. Excess nitrification from manure that enters streams can cause algae blooms and decrease water quality. Certain row cropping practices can also be detrimental to streams by allowing exposed soil to erode off fields, causing stream sedimentation. Fertilizer and chemical run-off can also negatively affect water quality. Tiling practices change the delivery rate of water to streams by condensing water into underground tubes that are often piped directly to a stream, enter at high velocities, and can erode the stream channel. Cumulatively, throughout a watershed, these and other practices can have a dramatic effect on habitat, water quality, and biota in a stream system.

Connectivity Loss

Streams rely on their watershed connections that run horizontally into the riparian area and floodplains, longitudinally up and down channels, and vertically between the channel bed and the water table. Common causes of horizontal connectivity loss occur in floodplains and riparian areas when development or levees encroach on floodplains, side channels and oxbows are filled in or cut off, or riparian vegetation is removed or altered. Alterations of natural ecological flow regimes from industry, municipal or agricultural uses, or downstream of large dams, and many other causes can also cause this loss.

Longitudinal connectivity is critical for fulfilling migration requirements, genetic dispersal, and habitat utilization of many aquatic organisms. Longitudinal barriers are created by limiting the movement of organisms physically or behaviorally; dams, poorly designed road crossings (e.g., slab concrete crossing), and culverts are common examples. Large reservoirs and the cumulative effects of small ponds have altered hydrology, habitat, and aquatic species throughout the state as well.

Stream Habitat Destruction

In-channel activities, such as channelization, improper mining activities, channel reaming, filling, burying or excessive armoring, and others can cause localized and system-wide losses to stream habitat. Deforestation and the loss of an adequate riparian corridor throughout much of the state, ongoing since settlement, have altered stream hydrology and habitat and energy cycles. In addition, the loss and lack of wooded stream corridors deprives stream channels of large woody debris which maintains and creates various habitat types throughout the channel network and is a critical component of the food chain for invertebrate and vertebrate species.

Invasive Species

Beyond ecological concerns, aquatic invasive species have tremendous impact, on local, state, and federal economies, impacting aquatic industries like water treatment, commercial and sport fisheries, recreational boating, etc. Terrestrial invasives are no different, and combined, in the United States alone, these invasive species amount to hundreds of billions of dollars per year to manage.

Like terrestrial habitat systems, aquatic systems are extremely vulnerable to the effects of invasive species, especially due to the high connectivity of most aquatic systems. Connectivity can be both a benefit and a detriment to a system. Connectivity benefits native species by minimizing habitat fragmentation and allowing species and genetic diversity and distribution, but it also allows for the rapid population expansion and distribution of invasive species. Some of the most well-known aquatic invasive species in Missouri include zebra mussels (Dreissena polymorpha), quagga mussels (Dreissena bugensis), invasive carp including bighead and silver carp (Hypophthalmichthys nobilis and H. molitrix), hydrilla (Hydrilla verticillata), and didymo, or "rock snot" (Didymosphenia geminata).

These invasives are highly competitive with native species with impacts that can include direct competition for food, predation, displacement, smothering or shading, disease introduction, and potentially, interbreeding. Any one or combination of these factors can lead to upsetting the delicate balance of native aquatic ecosystems.