Influence of aquatic macrophytes on phosphorus cycling in lakes

Abstract

Emergent macrophytes take up their phosphorus exclusively from the sediment. Submerged species obtain phosphorus both from the surrounding water and from the substrate, but under normal pore and lake water phosphorus concentrations, substrate uptake dominates. Release of phosphorus from actively growing macrophytes (both submerged and emergent) is minimal and epiphytes obtain phosphorus mainly from the water. Decaying macrophytes may act as an internal phosphorus source for the lake and add considerable quantities of phosphorus to the water. A large part of the released phosphorus is often retained by the sediments. In perennial macrophytes the amount of phosphorus released from decaying shoots is dependent on the degree of phosphorus conservation within the plant. Macrophyte stands may also be a permanent phosphorus sink due to burial of plant litter. Macrophytes affect the chemical environment (oxygen, pH), which in turn has effects on the phosphorus cycling in lakes. However, the impact of aquatic macrophytes on whole-lake phosphorus cycling is largely unknown. Controlled fullscale harvesting, herbicide or herbivory experiments are almost totally lacking. Emergent macrophytes respond positively to eutrophication, but fertilization experiments have shown that nitrogen rather than phosphorus may be the key element. Submerged macrophytes are adversely affected by a large increase in the external phosphorus input to a lake. This effect may be caused by epiphyte shading, phytoplankton shading or deposition of unfavourable sediments.

Efficiency of a constructed wetland for retention of sediment-associated phosphorus

“…Sub-catchments 2 and 3 contributed approximately 21% of the total P load to the wetland, but this input alone can not explain the high amount of P in the upper sediment layer of the shallow vegetated areas. Emergent macrophytes, such as T. latifolia, are able to supply their nutrient demand from the sediments alone, acting as P "pumps" transferring P from the sediment to the aboveground plant tissues (Granéli & Solander, 1988). Though the topsoil had been removed, it is likely that the mineral soil on which the wetland was constructed contained P available to plants as it was formerly agricultural land.…”

Flood pulse influence and anthropic impact on the chemical composition and energy content of Oryza glumaepatula in an Amazonian lake

“…This characteristic is even more pronounced in ecosystems with low nutrient concentrations, such as the clear and black water Amazonian ecosystems (Sioli, 1984;Setaro & Melack, 1984;Esteves et al, 1990). The participation of aquatic macrophytes in nutrient cycling has been verified by many authors (e.g., Granéli & Solander, 1988;Nogueira et al, 1996), who have demonstrated the role of this community in the absorption of nutrients from the sediment as well as their liberation in the water column.…”

Light-dependent uptake, translocation and foliar release of phosphorus by the intertidal seagrass Zostera noltii Hornem.

“…Perez-Llorens & Niell (1989) reported a foliar release in Z. no/Iii of 0.05/Lmol P·g-I·h -I (7.1 mg P-m -2·day-l) in an in situ experiment. Graneli & Solander (1988), in a review paper, supported the idea that the P released to the water from actively growing macrophytes is, in general, low, reporting rates of 0.01-0.03/Lmol P'g-l'h -I, which are in agreement with the values found in Z. no/Iii: 0.014 }lmol P'g-I'h -I in the dark (2% of the P taken up) and 0.025/Lmol P'g-l'h -1 in the light (4%).…”

“…noitii, as others submerged aquatic angiosperms, is capable of taking up P from the surrounding water by the leaves as well as by the root-rhizomes from the interstitial water of the sediment. Presumably, the sediment is the principal source of phosphate but the relative concentrations of phosphate in the water and sediment determine the main site for uptake (McRoy & Barsdate, 1970;Bristow & Whitecombe, 1971;Denny, 1972;McRoy et aL, 1972;Patriquin, 1972;DeMarte & Hartman, 1974;Gentner, 1977;McRoy & McMillan, 1977;Twilley et al, 1977;Best & Mantai, 1978;Carignan & Kalff, 1979;Welsh & Denny, 1979;Penhale & Thayer, 1980;Carignan, 1982;Gabrielson et aL, 1984;Brix & Lingby, 1985;Smith & Adams, 1986;Graneli & Solander, 1988;Moeller et al, 1988).…”