135 



4 

 "We do not have a complete understanding of the natural 

 dynamics of phytoplankton communities and controlling 

 mechanisms, nor of the linkages between anthropogenic additions 

 of nutrients and changes in phytoplankton community structure, 

 productivity, or other key response variables. Because of these 

 limitations, it is difficult at this time to quantify the exact risk of 

 potential adverse effects on the phytoplankton community due to 

 discharges from the nev^ outfall. However, based on the weight of 

 evidence provided above, it is reasonable to conclude that 

 discharges from the new outfall would not lead to large changes in 

 phytoplankton community structure and productivity on a baywide 

 scale. For example, even based on the worst-case scenario that 

 all of the current nitrogen loading from Boston Harbor is 

 representing a new source to the bay, the prevailing evidence 

 seems to suggest that discharges of nutrients from the new outfall 

 would not lead to dramatic baywide changes in primary 

 productivity. Increases in nutrient concentrations, the first 

 prerequisite link in the chain of impact events, for one thing, are 

 likely to be localized. Potential effects on the phytoplankton 

 community are likely to be localized as well. Such changes may 

 include stimulated biomass yield, carbon production rates, and 

 species grov^^h rates, based on results of experimental nutrient- 

 enrichment studies.' 



EPA in this statement and throughout the Assessment uses a "baywide scale" 

 standard, the effect of which is not only to diminish through dilution effects 

 expected nutrient loading but to simplify analysis of most probable impacts. 

 Thus, the Assessment concluded that baywide changes in primary productivity 

 and phytoplankton biomass are probably unlikely. However, it is generally 

 recognized that environmental and biotic patchiness are major determinants of 

 food web dynamics and regulation. Although the Assessment acknowledges 

 such "localized" consequences of the outfall delivery, it does not adequately 

 evaluate the resultant sub-regional patchiness and associated food. web 

 consequences. The baywide approach, i.e. average resultant changes, is 

 inadequate to the required analyses. Note also EPA's use of such equivocal 

 expressions as "seems to suggest' and "are likely to be' in the above quotation, 

 and representative of the Assessment generally. That is, ambivalent, 

 scientifically non-rigorous conclusions (= guesses) are a consequence of the 

 'weight-of-evidence" approach used, as well as reflect the lack of adequate 

 data to evaluate the issues of endangerment under consideration. 



The authors should also have known that the fvlERL experiments alluded 

 to (p. 4-27) in support of the conclusion that phytoplankton species composition 

 is not significantly altered at steady-state nitrogen concentrations is irrelevant. 

 The MERL mesocosms must include frequent vertical mixing to prevent sinking 

 of the phytoplankton. However, the majority of nuisance algal species are 

 inhibited by turbulence (data of Berdalet, Estrada, Maranda, Pokorny, White) 

 leading to death and/or a reduced grov^rth rate. Their blooms usually occur 

 during summer stratification, during which many exhibit diel vertical migrations. 



This inadequate unoerstanding of phytoplankton ecophysiology is 

 evident throughout the Assessment. The authors indicate their extensive use of 

 the Blumberg-Mellor model to generate results is based primarily on a winter- 



