by the repression of phenol oxidase (Sinsabaugh et al., 1993; Carreiro et al., 2000). As

decomposition proceeds, nutrient availability becomes progressively less important and

lignin content controls litter decay rates (Taylor et al., 1989; Berg, 2000). As a

consequence of these complex interactions, the interpretation of individual enzyme

activities as simple responses to environmental substrate concentrations may not serve to

adequately predict the actual microbial community dynamics.

 A current strategy for predicting microbial degradation rates involves the use of a

resource allocation rationale and the MARCIE (Microbial Allocation of Resources

Among Community Indicator Enzymes) model for exposing linkages between individual

enzymes (Sinsabaugh and Moorhead, 1994; Sinsabaugh and Findlay, 1995; Sinsabaugh et

al., 1997, 2002). The model is based on the premise that enzyme mediated

decomposition of complex molecules are the rate-limiting step in C mineralization. It

relates bacterioplankton production or litterbag mass loss through a first order model that

includes C, N, and P allocation. It further indicates that the expression of enzymes is tied

to environmental nutrient availabilities and that the distribution of enzyme activities can

be interpreted as a resource allocation strategy (Sinsabaugh et al., 2002).

 Related to the MARCIE model, the Enzyme Index of Carbon Quality (EICQ) is a

relative index of the normalized activities of the hydrolytic enzymes to oxidative or lignin

degrading enzymes. EICQ has been shown to be correlated with microbial biomass

(r-0.71), productivity (r=.80) and negatively correlated with particulate organic carbon

(POC) turnover time (r=-0.99) (Sinsabaugh and Findlay, 1995). EICQ values and other

enzyme ratios reflect microbial community responses to the perceived abundance of

nutrients as well as lignin and thus respond to changes in substrate and environmental