LONG-TERM EFFECTS OF BEACH NOURISHMENT ON THE BENTHIC FAUNA 

 OF PANAMA CITY BEACH, FLORIDA 



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 J.K. Culter and S. Mahadevan 



1 . INTRODUCTION 



1. Background Information . 



Coastal erosion is a major problem on many U.S. coastlines including 

 the we;jt coast of Florida. The westernmost beaches of Bay County on the 

 Florida panhandle are considered critical areas of erosion (U.S. Army 

 Engineer Division, South Atlantic, 1971; Bruno, 1971). Before the initia- 

 tion of a nourishment program in 1976, the shoreline west of the entrance 

 to St. Andrew Bay suffered considerable erosion for a number of years, 

 causing many coastal structures to become vulnerable to storm damage. 

 On 23 September 1975 Hurricane Eloise caused additional erosion and de- 

 stroyed or undermined the foundations of numerous coastal structures 

 (Saloman, 1976). Extensive areas of the Panama City and neighboring 

 beaches were renourished in 1976 by hydraulically dredging offshore sands 

 to replace the eroded beaches; however, observations made during this 

 study inidicate that the bulk of the material deposited during the nourish- 

 ment program has since eroded to prenourishment levels . 



This study, which CERC contracted to the Mote Marine Laboratory, 

 evaluates the long-term nourishment effects on the benthic fauna and 

 surface sediments of the nearshore zone off Panama City Beach, Florida. 

 The results of the study (1979-80) are compared to those obtained in the 

 prenourishment study (1974-75) and in the study of short-term effects 

 (1976-77) of the same beach (Saloman, 1976; Saloman, Naughton, and Taylor, 

 in preparation, 1982) . 



Saloman 's prenourishment study (1974-75) describes the area as having 

 a diverse benthic macroinfauna with the number of species and faunal den- 

 sities fluctuating seasonally. Species of polychaetes and amphipods domi- 

 nated the fauna. The distribution of species was generally uniform along 

 the beach with the number of species increasing offshore. There was no 

 correlation of animal abundance to selected sedimentological parameters, 

 which showed little spatial variation. 



The short-term study of nourishment effects (Saloman, Naughton, and 

 Taylor, in preparation, 1982) concluded that an initial destruction of 

 the bottom community at the borrow pits was followed by rapid recovery 

 virtually complete after 1 year. Minor differences in sediment para- 

 meters could be detected at the borrow pits after 1 year, but no dis- 

 tinction could be made between the faunas in and outside the borrow pits. 

 The authors also concluded that normal seasonal variations of tempera- 

 ture and salinity could mediate changes in benthic diversity and abun- 

 dance possibly masking or preventing detection of nourishment effects. 



