Aquatic habitats in relation to river flow in the Apalachicola River floodplain, Florida

Abstract

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Cyclic perturbation of lowland river channels and ecological response

“…Open-water communities, marshes, and wetland shrub communities were replacing bottom land hardwood swamps and croplands. Additional inferences regarding likely response of riverine systems in the southeastern USA can be drawn based on evidence regarding fish utilization of naturally occurring flooded forests (Baker et al, 1991;Killgore and Baker, 1996;Light et al, 1998) or river lakes and lentic backwaters (Baker et al, 1991). The majority of fish species occurring in rivers of this region use seasonally flooded areas, particularly forests, for feeding, spawning, nursery areas (Killgore and Baker, 1996), refugia from high velocities (Matheney and Rabeni, 1995) or other purposes.…”

“…For example, of the 91 species of freshwater fish recorded for the nontidal Apalachicola or lower Chipola Rivers, 73 are known to occur in river floodplains. Fifty-one of the 73 have been collected from the Apalachicola floodplain using limited sampling gears and approaches (Light et al, 1998). Streams in this region which periodically inundate their floodplains support fish assemblages distinct from those which do not because of channel incision (Shields et al, 1998).…”

Anthropogenic landforms and sediments from dredging and disposing sand along the Apalachicola River and its floodplain

“…Although no one has documented deepening other than downstream of the dam, parts of the river have widened during the interval between 1954 and 2004, based on comparing changes in tree-line width of the main channel at similar flow levels, the study area showed width increases from about 1-40% (Price et al, 2006). The botanical changes that the floodplain experiences, namely a drier forest composition (Light et al, 1998;Darst and Light, 2008;Stallins et al, 2010;Maxwell and Knapp, 2012;Smith et al, 2013), are thus not just due to reductions in water supply but aggravated by stage decreases for a given discharge by degradation and widening.…”

“…Many secondary channels become active at various flow levels. More than 300 sloughs connect to the main-stem river, with over 370 km (230 mi) of length (Light et al, 1998). The largest tributary to the Apalachicola itself (i.e., below the confluence of the Chattahoochee and Flint rivers) is the Chipola River, which drains a catchment of 3290 km 2 (1270 mi 2 ) in Florida (mostly) and Alabama, and connects with the main-stem Apalachicola about 67 and 45 km (41.5 and 28 RM) upstream of Apalachicola Bay.…”

“…Reduced flows and water levels have dried out the floodplain and sloughs, causing significant botanical changes, namely a drier forest composition and the loss of important swamp tree species such as Ogeechee tupelo (Light et al, 1998;Darst and Light, 2008;Stallins et al, 2010;Smith et al, 2013). The basin has threatened and endangered freshwater mussels that die during drought (Johnson et al, 2001;Gagnon et al, 2004;Peterson et al, 2011;Shea et al, 2013).…”