these elevated model parameters is predicted to be increased decomposition at the

enriched habitats. However, increases in net primary production, resulting in greater C

flow, may exceed any increase in decomposition, resulting in a net accumulation of

organic matter (Davis, 1991).

 Ecell/En and Ecell/Ep values did not predict more favorable microbial conditions in

the open water habitat. Rather, this habitat was generally the most limiting in terms of N

and P on C mineralization. This may be a consequence of algal competition for N and P

resources due to the more prolific periphyton community in the open water habitats. This

contradiction in prediction between the N and P models with Ecell/Eox and EICQ may be

due to varying shifts in the type of microbial community responses to different

environmental changes. The nutrient gradient is most related to changes in N and P and

thus it would be expected that these nutrients would be the main driving force behind

microbial changes when habitat types remain constant. Conversely, changes in

vegetative types would be expected to influence the actual degradability of the C source

by the microbial community, due to varying shielding effects on nutrients by refractory

compounds within the plant structures. In fact, the mineralization of organic C was most

affected by C quality with total P concentration and the lignocellulose index (LCI)

accounting for 91% of the variability in aerobic C mineralization of plant litter along the

WCA-2A gradient (DeBusk and Reddy, 1998). Thus, different enzyme components

would be involved in regulating the productivity between these two types of changes.

These contrasts in enzyme components most related to productivity have been

documented with the BGL and PHO correlation with bacterial production in nutrient

enriched and unenriched mesocosms, respectively (Chr6st and Rai, 1993). This suggests