_l 

 < 



9 



LJ > 



< z: 



Q^ — 

 LJ Li_ 



^° 



Ld 

 DQ 



200 1 Effluent Bottom 

 150- 



100 



50 





 200 



150 



100 



50 



0- 



3 UNIT 

 OPERATION Eg^^g AFTER 



tffluent Surface 



Ik 



* * * 



1 6 7 

 AUG-FEB 



7 8 8 8 8 8 

 9 15 6 7 



FEB -AUG 



BEFORE 



* * 



* * * 



* * * 



7 8 8 8 8 

 9 15 6 



MAY- NOV 



7 8 8 8 8 

 9 1 6 7 



NOV- MAY 



Fig. 8. Mean numerical abundance of the shipworm, Teredo harischiy in exposure panels collected during 

 1979-1987 {* = abundance < 5). 



other cases, effect is more indirect; Limnoria, even 

 at high densities, does not occupy a substantial 

 area of the panel, but its feeding and excavating 

 activities alter panel surface characteristics and re- 

 duce shipworm recruitment (Fig. 1 1). 



Discussion 



Teredo navalis densities and percentage of 

 wood-loss in panels were higher, in the May-Nov 

 exposure period at WP and FI during 3-unit op- 

 eration, than the average values during 2-unit op- 

 eration. This pattern did not occur at at our 

 reference sites. The sampling site at BP was not 

 established until 1985, and most panels were lost 

 during Hurricane Gloria; the data from the re- 

 maining panels do not provide a temporal trend. 

 Values at GN, highest among sites during 2-unit 

 operation, were lower than WP in 1986-1987. 

 Because the increase at WP and FI represented 

 only a single exposure period during 3-unit oper- 

 ation, it carmot yet be determined whether these 



values are the result of natural variability in a 

 complex system, or the result of power plant op- 

 eration. Continued association of higher 

 shipworm densities and percentage wood-loss at 

 sampling stations with elevated water temperatures 

 would indicated a possible plant impact. 



Warm water could influence the local 

 woodborer community in several ways. Temper- 

 ature tolerance studies conducted from 1982-1985 

 (NUSCO 1987) corroborate findings of other re- 

 searchers, e.g., elevated water temperatures in- 

 crease shipworm growth rates (Board 1973), as 

 well as the fecundity and length of their breeding 

 season (Naylor 1965). Warm water could also 

 alter the competitive relationships between fouling 

 species (Nair and Sarawathy 1971; Sutherland and 

 Karison 1977), or the distribution of a 

 haplosporidian fungal parasite, implicated as a 

 source of shipworm mortality (Hillman et al. 

 1982). Naylor (1965) reported that heated 

 effluents could encourage breeding of non-native 

 species in areas which received warm water species. 



Exposure Panel Program 243 



