reservoirs can be summarized: (1) reduc- 

 tion of silt and associated nutrient 

 inputs for some distances below dams, (2) 

 excessive bed and bank scour below dams 

 with accompanying modification or exter- 

 mination of benthic and epibenthic fauna, 

 (3) loss of bank-stabilizing vegetation by 

 frequent flow changes, (4) disruption of 

 normal fish breeding and feeding on the 

 floodplain, (5) elimination of sufficient 

 high v/ater for the annual flushing of 

 detritus from the floodplain, and (6) 

 encouragement of clearcutting, site con- 

 version to tree plantations and row crop 

 agriculture on formerly saturated flood- 

 plains. 



CHEMICAL COUPLING WITH THE WATER TABLE AND 

 ATMOSPHERE 



It is seldom acknowledged that Pied- 

 mont alluvial rivers crossing the Coastal 

 Plain may have numerous blackwater tribu- 

 taries, the DOM of which is subsequently 

 camouflaged by suspended inorganics. The 

 lower sections of alluvial rivers are, in 

 effect, chemically mixed rivers, in pro- 

 portion to the respective discharges that 

 each type stream contributes. Likewise, 

 there is lateral coupling with the under- 

 ground aquifer in limesink zones. At times 

 of high water, acid blackwater may enter 

 and corrode underground corridors; con- 

 versely, aquifer flow at times raises the 

 pH and the nitrate level of the river 

 (Kaufman and Dysart 1978). 



Wetlands, including bottomland hard- 

 woods, modify temperature and moisture 

 content of the lower atmosphere. They 

 ameliorate freeze conditions and provide 

 a more equithermal refuge for many animals 

 which could not otherwise exist at that 

 latitude. Wetlands modify lake and sea 

 breezes, the urban boundary layer, and 

 even the behavior of tropical cyclones. 

 In Florida, relatively minor changes in 

 land-water coverage and soil moisture 

 result in surprisingly large changes in 

 sea breezes, cumulus cloud formations, and 

 precipitation (Gannon et al. 1978). 



COUPLING VIA FAUNAL MOVEMENTS 



Rivers and their floodplains are 

 also coupled with marine systems through 



anadromous, catadromous and other marine 

 species. Blue crabs occur to RM (river 

 mile) 50 in the Altamaha. The southern 

 flounder ( Paralichthys lethostigma ) and 

 striped mullet ( Mugil cephalus ) migrate 

 and feed as far as 193 km (120 mi ) up the 

 Altamaha, while two common coastal fishes, 

 the hogchoker (Trinectes maculatus ) and 

 the needlefish ( Strongylura marina ), actu- 

 ally spawn in the mid-reaches of the river 

 (John Adams, Georgia Power Co., Environ- 

 mental Laboratory, Atlanta; personal com- 

 munication). Various shad species parti- 

 tion the river into spawning and nursery 

 sections (Adams and Street 1969; Adams 

 1970). American shad ( Alosa sapidissima ) 

 spawn in the Altamaha itself between RM 60 

 and 120, with primary nursery centers at 

 RM 21-30 and RM 100-110. Hickory shad (A. 

 miediocris ) spawn in floodplain oxbows, 

 sloughs, and tributaries between RM 20 and 

 137. Blueback herring (A. aestivalis ) 

 spawn on the floodplain floor between RM 5 

 and 137, with primary nurseries between RM 

 10 and 30. Examples of catadromous spe- 

 cies are American eel and mountain mullet 

 ( Aqonostomus monticola ), the latter in 

 gulf coast rivers. 



Striped bass formerly traveled up the 

 Savannah as far as Tallulah Gorge and 

 still ascend many Coastal Plain streams. 

 Two species of sturgeon (Atlantic and 

 shortnosed) ascend rivers entering the 

 Atlantic slope. Other animals such as 

 manatees use the Altamaha at least to the 

 limit of tidal range and go up the Suwan- 

 nee to Manatee Springs. The glochidian 

 larvae of many clams can travel up- and 

 downstream attached to fishes, often 

 providing a mechanism for repopulating 

 depleted areas. 



Terrestrial fauna may be coupled to 

 the uplands, as when deer who base their 

 home range on floodplains graze in up- 

 lands. Conversely, upland forms such as 

 the black racer and pine vole may use the 

 floodplain at drydown. The narrow green- 

 belts of bottomland hardwoods also provide 

 routes for migration and restocking. 



SUMMARY 



In summary, bottomland hardwood 

 swamps are integrally coupled to the sur- 

 rounding uplands, downstream estuarine 



107 



