I 



Rock Weight 

 Exposure Panels Q_ EXPOSURE PANEL 



Rock Weight 



Fig. 12. Diagram of an exposure panel trawl-line used to sample the distribution ofshipworms in relation to 

 the effluent discharge point at the Millstone Nuclear Power Station (A. trawl-line of five lobster pots with the 

 locations of the 15 pine panels; B. pine panel showing the sections for subsampling). 



Results 



In the four exposure periods sampled to date, 

 2712 shipworms have been removed and identi- 

 fied, excluding data fi-om the 100 m panels in 

 May-Oct 1986. Virtually all were from the May- 

 Oct/Nov exposure period; four Teredo navalis 

 were found in panels collected in May 1 987 (Table 

 5). Most of the shipworms have been identified 

 as T. nmalis. Fourteen individuals (0.5%) were 

 T. bartschi, all from 100 m panels in Nov 1985. 



A trend of decreased Teredo navalis abundance 

 with increased distance from the quarry cuts has 

 been observed in the past two years (Table 5; 

 Fig. 13). Our data from 500 m (654 shipworms) 

 and 1000 m (525 shipworms) support conclusions 

 drawn last year (NUSCO 1987). Temperature 



data, collected at 100, 500, and 1000 m sites in 

 March 1988 (3-unit operation), are presented in 

 Figure 14. Preliminary data show that water tem- 

 peratures at the 100 m site varied with tidal stage; 

 on a flooding tide, ambient temperatures occurred 

 for 3-4 hours per tidal cycle, and elevated tem- 

 peratures (8 °C AT), occurred for the remaining 

 8-9 hours per cycle. A temperature gradient was 

 not seen between 500 and 1000 m, at least during 

 early spring. Temperatures at both sites were 

 similar to those at the intakes (i.e., ambient) and 

 showed the same 1 °C tidal fluctuation. 



Discussion 



Teredo bartschi have not been found in the 

 effluent mixing zone since Unit 3 began operation. 

 However, our samplirg gear at 100 m was removed 



Exposure Panel Program 



247 



