Sediment oxidation capabilities of four submersed aquatic macrophytes

Abstract

Isoetids are submersed aquatic plants that thrive in soft water, oligotrophic bodies of water and possess small, stiff rosettes and extensive root systems. These roots absorb carbon dioxide and release oxygen, altering the biogeochemistry of sediment. Eriocaulon aquaticum and Lobelia dortmanna are representative isoetids. While Eleocharis acicularis and Utricularia resupinata do not strictly qualify as isoetids, they are commonly found anchored in or attached to sediment populated with isoetids. In a greenhouse experiment, the four macrophytes were planted in two contrasting sediment types to determine how the different species modify sediment redox potential, carbon dioxide concentration, and porewater pH. Eleocharis acicularis and U. resupinata oxidized both sediment types and acidified the porewater more than or equally as extensively as the isoetids ( p 5 0.05). Eleocharis acicularis was the only species that significantly reduced porewater carbon dioxide ( p 5 0.05). In the field study, sediment cores were collected over bare sediment and over each of the four species concurrently with redox and pH measurements. Sediment cores associated with all four aquatic plants had significantly higher redox potentials compared to bare sediment ( p 5 0.05). However, the redox values measured near E. acicularis and U. resupinata were generally lower than those taken near the isoetids. The field sediment oxidation data may be explained by the significantly lower biomass of U. resupinata and E. acicularis compared to the isoetids in the field study ( p 5 0.05). These results show that E. acicularis and U. resupinata are capable of isoetid-like sediment oxidation under greenhouse and field conditions.

Carbon dioxide and submersed macrophytes in lakes: linking functional ecology to community composition

“…We also included the morphologically similar Eleocharis acicularis and Myriophyllum tenellum , for which short stems rather than leaves protrude from relatively substantial belowground parts. Eleocharis acicularis has been shown to deplete CO 2 in sediment porewater (Freeman and Urban ), and the short‐statured Myriophyllum tenellum has dense concentrations of chloroplasts clustered around lacunae in its stems (D. F. Westlake, personal communication ), strongly suggesting uptake of CO 2 diffusing from the sediment. Other non‐isoetids may rely partially on CO 2 from sediment porewater, especially at low free CO 2 levels in the water column (Winkel and Borum ), but we do not believe that any additional species in our study rely primarily on sediment porewater CO 2 .…”