This conservation asset was not assessed for vulnerability
Florida’s largest rivers are in the northern part of the state. Florida rivers, typically flow towards the nearest coast, with the exception of the St. Johns River which flows north to the Atlantic. The only major river that does not flow to the gulf or to the Atlantic is the Kissimmee River, which flows south and discharges to Lake Okeechobee. Florida's rivers and streams can be divided up into six main categories, including Alluvial, Blackwater, Spring-run, Seepage, Calcareous, and Tidally-influenced Rivers and Streams. Many rivers are a mixture of these types, transitioning along their path.
Alluvial rivers have large, well-defined drainage basins, carry high sediment loads and have large forested floodplains. These rivers typically flood each year, usually in the winter. All of Florida’s alluvial rivers are in the Panhandle, including the Apalachicola, Choctawhatchee, Escambia and Ochlockonee. Due to the high natural turbidity of these streams there is minimal vegetation which is mostly confined to channel edges or backwaters.
Typical blackwater rivers have dark, stained waters from decomposing plant materials. They typically drain pine flatwoods and cypress swamps. The flow rate is usually gentle in smaller streams to moderate in larger, but is altogether influenced by seasonal local rainfall. Blackwater streams differ from alluvial streams by having high, steep banks, and by lacking extensive floodplains and natural levees. This habitat is well distributed throughout Florida, except in the regions of north and central Florida dominated by Calcareous Streams, and in the Everglades/Big Cypress region of south Florida, where wetlands and coastal streams dominate the aquatic landscape.
Springs and spring-run rivers are present in the north and central regions of Florida where underlying limestone is close to the surface. Spring-run rivers often represent headwaters or low-order tributaries. The bottoms of spring runs are generally sand or exposed limestone along a central, stable channel. Calcareous Rivers occur only in the north and central regions of the state. These rivers typically have a high pH, high carbonate level, and sand bottom with some limestone exposed.
Most calcareous streams are clear and cool, although in areas where they flow through pinelands or scrub the streams will become stained by the tannins in the vegetation. Some are associated with sinks, where all or sections of the stream flow underground before resurfacing to flow overland. Submerged plants are frequently dense, and can include tape grass, wild rice, and giant cutgrass.
Tidally influenced rivers and streams includes the freshwater or brackish portions of a river or stream adjacent to an estuary or marine habitat in which the effects of tides cause the rise and fall of water levels. The effect of the tides at the upper limits of influence may lag several hours behind tides on the coast. Saltwater wedges are formed in many of these systems, enabling numerous species a mechanism to move up or down river. Water flow is bidirectional in coastal tidal rivers and streams; as the tide rises, water flows toward the head of the river and, as the tide retreats, the water flows toward the coastal outlet. These streams bridge the freshwater and marine realms, with aquatic communities ranging from tidal freshwater to tidal brackish; salinities can vary from freshwater to approximately that of seawater. This variation, along with temperature and water clarity, determines the flora and fauna of these streams. Typical plants may include cord grass or submerged aquatic vegetation such as seagrasses and algae.
This conservation asset includes Alluvial, Blackwater Streams, Spring-run, Seepage, Calcareous, and Tidally-influenced Rivers and Streams.
Increased precipitation and storm events will cause bank erosion, increased siltation, and run-off in rivers and streams. Sea level rise will result in the inland movement of seawater, shifting the tidal influence zone of streams and rivers upstream and permanently inundating downstream riparian/coastal habitats with brackish water.
Tidal and storm surges can degrade aquatic habitats through oxygen depletion, changes in salinity, and increased siltation and turbidity.
Decreased precipitation may cause extreme low water levels or even create fragmented/disconnected systems as some areas dry completely, resulting in isolated pools of water rather than a flowing connected system.
Increasing air temperature will cause warming water temperatures. This could be further exacerbated by reduced precipitation, with shallower water areas experiencing more warming.
Increased temperatures, as well as extreme events will enhance invasive species processes, from introduction through establishment and expansion.
More information about general climate impacts to habitats in Florida.
Species with narrow temperature tolerances will be impacted when water temperatures exceed their maximum threshold. Additionally, higher water temperatures can increase the stress on the fish, leading to declines in health and increases in vulnerability to parasites and disease.
Sea level rise will increase the salinity levels further up tidal rivers and streams, impacting those species with lower salinity tolerances and shifting community dynamics as more salt tolerant species move in.
Changes in the timing and rate of flow will affect species that are sensitive to microclimate variations associated with flow dynamics.
Some species, particularly fish will be impacted by fragmentation of the system (loss of connectivity) that may occur during extended dry periods and droughts.
Increased runoff and groundwater pollution as a result of increased precipitation and flooding would significantly alter the nutrient balance and have negative effects on the system and associated wildlife. Limpkins, found along Florida's rivers and streams feed primarily on apple snails, but will also eat insects, worms and mussels. Water quality degradation could significantly reduce the abundance and availability of these prey items for the limpkin and other species with similar diets.
More information about general climate impacts to species in Florida.