D. Sedimentary Parameters 



Sedimentary parameters (e.g., mean grain size and silt/clay content) were obtained as part of the 

 monitoring studies and the quarterly values for each used as explanatory variables in the regression analyses. 



E. Climatic Extremes (Deviations) 



Additional variables were created to represent periods of extreme climatic conditions which have 

 occurred during the sampling period. High or low deviations were derived for each abiotic factor as the 

 difference between the quarterly mean or daily value and the ten year mean for that quarter. Deviations 

 based on quarterly means were intended to examine the effects of longer term extremes (i.e., an unusually 

 cold winter), while those based on daily values were intended to remove the effects of shorter-term 

 episodic events (i.e., storms). Daily deviations were averaged and summed (for cumulative effects) over 

 each sampling quarter. 



F. Seasonal Reproduction-Recruitment Component 



Many infaunal organisms in the Millstone area exhibit annual peaks in abundance, which often 

 reflect the seasonal nature of annual reproduction and recruitment cycles or periods of favorable climatic. 

 Spectral analyses of quarterly data showed that annual cycles in community abundance and numbers of 

 species were present. To account for this periodicity, harmonic terms having a period of 1 year were 

 included as explanatory variables in the regression models. 



In ail, .12 abiotic variables were available for the analyses (28 climatic variables, 2 sedimentary 

 charateristics and 2 seasonal harmonic components). 



Model Selection Procedure 



Lx)ng-term trends in the quarterly mean values were first detrended using a polynomial regression 

 equation. If no significant long-term trend was evident, residuals were created by subtracting the quarterly 

 mean from the six-year mean. A stepwise multiple regression on these residuals was then used to select 



