Decomposition of exotic versus native aquatic plant litter in a lake littoral zone: Stoichiometry and life form analyses

The decomposition rates and stoichiometric characteristics of many aquatic plants remain unclear, and our understanding of material flow and nutrient cycles within freshwater ecosystems is limited. In this study, an insitu experiment involving 23 aquatic plants (16 native and 7 exotic species) was carried out via the litter bag method for 63 days, during which time the mass loss and nutrient content (carbon (C), nitrogen (N), and phosphorus (P)) of plants were measured. Floating-leaved plants exhibited the highest decomposition rate (0.038 +/- 0.002 day(-1)), followed by submerged plants and free-floating plants (0.029 +/- 0.002 day(-1)), and emergent plants had the lowest decomposition rate (0.019 +/- 0.001 day(-1)). Mass loss by aquatic plants correlated with stoichiometric characteristics; the decomposition rate increased with an increasing P content and with a decreasing C content, C:N ratio, and C:P ratio. Notably, the decomposition rate of submerged exotic plants (0.044 +/- 0.002 day(-1)) significantly exceeded that of native plants (0.026 +/- 0.004 day(-1)), while the decomposition rate of emergent exotic plants was 55 +/- 4 % higher than that of native plants. The decomposition rates of floatingleaved and free-floating plants did not significantly differ between the native and exotic species. During decomposition, emergent plants displayed an increase in C content and a decrease in N content, contrary to patterns observed in other life forms. The P content decreased for submerged (128 +/- 7 %), emergent (90 +/- 5 %), floating-leaved (104 +/- 6 %), and free-floating plants (32 +/- 6 %). Exotic plants released more C and P but accumulated more N than did native plants. In conclusion, the decomposition of aquatic plants is closely linked to litter quality and influences nutrient cycling in freshwater ecosystems. Given these findings, the invasion of the littoral zone by submerged and emergent exotic plants deserves further attention.