composition, with an abundant Chara spp. mat composing the majority of the benthic

layer, has been shown to replace the Utricularia spp. and periphyton communities after

one year of P loading (Craft and Richardson, 1995). Elevated Ca levels in the benthic

and TP in the soil may be attributed to the CaCO3 and CaHP04 bands of the cell walls of

Chara spp. (Kiyosawa, 2001). The higher TP in the soil is supported by elevated

Ecell/Ep, suggesting a lower P limitation on C mineralization than the enriched site in

WCA-2A. Therefore, some of the enzyme activities reflected at this site may be

attributed to the metabolic and structural attributes of the resident algal community.

 Several reasons may account for the nutrient dynamics at the transitional sites.

Upstream porewater dynamics may be exerting pressures on the transitional site. The

increase in TP in the soil layer, which is greater than that at the enriched site, suggests

that P is possibly being released from the soil at sites closer to the inflow. This may be

due to the reduction of P loading from the canals in recent years to a concentration lower

than that of the soil. The deposition of P downstream appears to result in the expansion

of the P front and may continue until a relatively static equilibrium is reached. Secondly,

and more specifically to the WCA-2A transitional site, the elevated TP may be due to P

removal capabilities of the Chara spp. communities and eventual burial into the soil layer.

 The most consistent increase at the transitional sites in both the soil and benthic

layers was in relation to LEU. The decrease of average TN at the transitional sites in 6 of

8 cases supports these elevated activities. However, WCA-2A appears to be unique in

this regard. This is the only area, in both layers, to show an increase in Ecell/En at the

transitional site, indicating that N is less limiting to the microbial community as related to

C mineralization.