Recycling of Nutrients in an Enclosed Aquatic Community of Decomposing Macrophytes (Myriophyllum spicatum)

Abstract

A 0.5 m2 area of littoral zone in an eutrophic reservoir dominated by the aquatic vascular plant Myriophyllum spicatum L. was enclosed in order to study, in situ, the release of nitrogen (N) and phosphorus (P) compounds as the enclosed plant community decomposed. Decomposition is shown to be complete in about 50 d. Fixed N appeared mainly as NH3 at a maximum rate of 380 jig 1-1 d-l. P was mobilized mainly as PO-4 at a maximum rate of 34 [tg l-1 d-1 and also as soluble organic -P. Aquatic macrophytes accounted for only 3 to 4% of the regenerated N but for 40 to 44% of the regenerated P recycled by the enclosed system; blue-green algae and the mud surface accounted for the balance of the regenerated N and P. Total suspended bacterial biomass represented an average of 10% of the total organic N and P pool of the water column. The role of aquatic macrophytes, blue-green algae and mud surface is discussed in terms of the recycling of N and P.