Regardless of other environmental factors that 

 might be influencing shipworm abundance, the 

 thermal incursions at 100 m provided an extended 

 settlement season for Teredo navalis. Enhanced 

 settlement and growth were demonstrated for 

 shipworms grown in a mixture of Effluent and 

 Jordan Cove water (NUSCO, unpublished data). 

 Imai et al. (1950) noted that boring activity of 

 larvae does not begin until water temperature 

 reaches 14 °C. This occurs in early June at am- 

 bient sites, but given an 8 °C AT, it could occur 

 in May at 100 m from the cuts. Therefore, in- 

 creased densities of T. navalis near MNPS dis- 

 charges would be expected, because seawater tem- 

 peratures would enhance settlement, grow^th and 

 survival. 



Summary 



1. The fouling community on exposure panels 

 has vshown no clear response to 3-unit oper- 

 ation. The assemblages continue to be di- 

 verse, and the abundance and distribution of 

 the component species remain patchy. 

 Throughout the study, there has been a neg- 

 ative correlation between fouling cover and 

 shipworm recruitment. 



2. There has been an increase in density of 

 shipworms. Teredo na\'alis, and an increase 

 in the amount of wood lost at the WP and 

 EI sites during the first May-Nov exposure 

 period of Unit 3 operation. At a reference 

 site, GN, shipworm density decreased. 



3. Higher densities of shipworms and increased 

 wood-loss have occurred in panels in the un- 

 diluted effluent (EB and ES) during 3-unit 

 operation, resulting from increased attack by 

 Teredo bartschi, a non-native shipworm. 

 These increases are attributed to the oppor- 

 tunistic life liistory of T. bartschi, but altered 

 water circulation patterns in the effluent 

 quarry may also expose the panels to more 

 larvae. 



4. Panels placed at 100, 500, and 1000 m from 

 the quarry cuts continued to show increased 



recruitment of T. navalis at panels closer to 

 the discharge. Teredo bartschi, which had 

 been found in 100 m panels during 2-unit 

 operation, was not sampled during initial 

 3-unit operation, because the May-Oct 100 

 m panels were dragged off-station by fisher- 

 men. 



Conclusions 



Since Unit 3 began operation, increased 

 shipworm abundance and increased wood-loss 

 were observed at sites in the MNPS effluent, and 

 during one exposure period, at White Point and 

 Fox Island, which were potentially exposed to 

 the 3-unit thermal plume. Further monitoring 

 will be required to determine whether these 

 changes are related to 3-unit operation, or are 

 expressions of natural variability. 



References Cited 



Board, P.A. 1973. The effects of temperature and 

 other factors on the tunnelling of Lyrodus 

 pedicellatus and Teredo navalis. Pages 797-805 

 iji Proc. 3rd Int. Congr. on Marine Corrosion 

 and Fouling, Natl. Bur. Std., Gaitherburg, 

 Maryland, U.S.A. 



Dale, H.M., and T. Gillespie. 1977. Diurnal fluc- 

 tuations of temperature near the bottom of 

 shallow water bodies as affected by solar radi- 

 ation, bottom color and water circulation. 

 Hydrobiologia 55:87-92. 



Dean, D., and C.B. Officer. 1977. Development 

 document in support of alternative effluent 

 limitations pursuant to section 316(a) of the 

 Federal Water Pollution Control Act for Maine 

 Yankee Nuclear Generating Station. Maine 

 Yankee Atomic Power Company, Wiscasset. 



de Wilde, P.A.W.J., and E.M. Berghuis. 1979. 

 Cyclic temperature fluctuations in a tidal mud- 

 flat. Pages 435-441 in E. Naylor and R.G. 

 HartnoU ed. Cyclic phenomena in marine plants 



250 



