CHAPTER 8 



HUMAN IMPACTS AND APPLIED ECOLOGY 



Since the days when Henry Flagler's 

 railway first exposed the lush subtropical 

 environment of south Florida to an influx 

 of people from outside the region, the 

 area has been subjected to great change at 

 the hands of man. Through the 1950's, 

 booming development precipitated the 

 destruction of many acres of submerged 

 lands as demands for industrial, residen- 

 tial, and recreational uses in this unique 

 part of the Nation increased. While sea- 

 grass beds generally have experienced less 

 direct damage than have the mangrove 

 shorelines, seagrasses have not been 

 totally spared the impact of development. 

 Environmental agencies receive permit 

 requests regularly, many of which would 

 directly or indirectly impact seagrass 

 beds. Because of the concern for these 

 biologically important habitats several 

 articles have been published which docu- 

 ment their importance and man's impact 

 (e.g. Thayer et al . 1975b; Zieman 1975b, 

 1975c, 1976; Phillips 1973; Ferguson 

 et al. 1980). 



8.1 DREDGING AND FILLING 



Probably the greatest amount of 

 destruction of seagrasses in south Flor- 

 ida has resulted from dredging practices. 

 Whether the objective is landfill for 

 causeway and waterfront property con- 

 struction, or deepening of waters for 

 channels and canals, dredging operations 

 typically involve the burial of portions 

 of an estuary with materials from nearby 

 locations. Such projects therefore can 

 involve the direct destruction of not 

 only the construction site, but also many 



acres of adjacent habitats. The impact of 

 dredging can be long-lasting since such 

 disturbance creates sediment conditions 

 unsuitable for seagrass recolonization for 

 a protracted period (Zieman 1975c). 



Of the Gulf Coast States, Florida 

 ranks third, behind Texas and Louisiana, 

 in amount of submeraed land that has been 

 filled by dredge spo'il (9,520 ha or 23,524 

 acres). In Texas and Louisiana, however, 

 most of the spoil created came from 

 dredged navigation channels, while in 

 Florida this accounts for less than 5? of 

 the State total. Not surprisingly, the 

 majority of filling of land in Florida, 

 about 7,500 ha (18,525 acres), has been to 

 create land for residential and industrial 

 development (Figure 26), In addition to 

 the direct effect of burial, secondary 

 effects from turbidity may have serious 

 consequences by restricting nearby produc- 

 tivity, choking filter feeders by exces- 

 sive suspended matter, and depleting oxy- 

 gen because of rapid utilization of sus- 

 pended organic matter. The dredged sedi- 

 ments are unconsolidated and readily sus- 

 pended. Thus a spoil bank can serve as a 

 source of excess suspended matter for a 

 protracted time after deposition. Zieman 

 '(1975b) noted that in the Caribbean 

 dredged areas were not recolonized by tur- 

 tle grass for many years after operations 

 ceased. Working in estuaries near Tampa 

 and Tarpon Springs, Godcharles (1971) 

 found no recovery of either turtle grass 

 or manatee grass in areas where commercial 

 hydraulic clam dredges had severed rhi- 

 zomes or uprooted the plants, although at 

 one station recolonization of shoal orass 

 was observed. 



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