The relation between sediment nutrient content and macrophyte biomass and community structure along a water transparency gradient among lakes of the Mackenzie Delta

Abstract

Macrophyte abundance and distribution among lakes of the Mackenzie Delta were assessed where increasing distance from the river (chain set) and increasing frequency of flooding (sill set) corresponded with increasing water transparency. Overall, sediment organic matter (OM) and total nitrogen (TN) content increased with increasing biomass of macrophytes but was higher in the sill set than in the chain set. The amount of phosphorus (P) in sediments was similar among lakes, but pore-water P was appreciably higher in the chain set. Increasing sediment OM and water clarity corresponded with increasing biomass of macrophytes in the lakes. Community structure shifted from dominance by erect Potamogeton at low and intermediate transparency and moderate sediment OM content to low-growing Chara and Ceratophyllum at high transparency and high sediment OM. Similar transparency in the chain set supported greater biomass of macrophytes than in the sill set. A high rate of inorganic sedimentation (linked with frequent flooding) and organic sedimentation (linked with high transparency and plant biomass) may result in the most suitable substrate for the growth of macrophytes among lakes of the Mackenzie Delta. Submersed plant biomass was higher in the Mackenzie Delta lakes than in temperate lakes and comparable to that in the temperate and tropical floodplains, despite the high-latitude location.