Sources of nutrients to rooted submerged macrophytes growing in a nutrient‐rich stream

Abstract

1. The relative contribution of roots and leaves to nutrient uptake by submerged stream macrophytes was tested in experiments where plants were grown in an outdoor flow‐channel system. Water was supplied from a nutrient‐rich stream with inorganic nitrogen and phosphorus concentrations typical of Danish streams. 2. Four submerged macrophyte species were tested, Elodea canadensis, Callitriche cophocarpa, Ranunculus aquatilis and Potamogeton crispus, and all species were able to satisfy their demand for mineral nutrients by leaf nutrient uptake alone. This was evident from manipulative experiments showing that removal of the roots had no negative impact on the relative growth rate of the plants. Further, the organic N and P concentrations of the plant tissue was constant with time for the de‐rooted plants. 3. Enrichment of water and/or sediment had no effect on the relative growth rate of two species, E. canadensis and C. cophocarpa, indicating that in situ nutrient availability was sufficient to cover the needs for growth. Despite the lack of a response in growth rate, a reduced root/shoot biomass ratio was observed with nutrient enrichment of water and/or sediment, and an increased tissue‐P concentration in response to open‐water enrichment. 4. The open‐water nutrient concentrations of the stream in which the experiments were performed are in the upper part of the range found for Danish farmland streams (the majority of Danish streams). Still, however, the negligible effect of nutrient enrichment on the growth of submerged macrophytes observed suggests that mineral nutrient availability might play a minor role in controlling macrophyte growth in most Danish streams.

Effect of water quality and season on the population dynamics of Cabomba caroliniana in subtropical Queensland, Australia

“…Madsen and Cedergreen, 2002), there seems to be no consistent relationship between nutrient concentrations in the water column and growth parameters in the literature. Some studies find a lack of relationship between nutrient loading and macrophyte growth (Madsen and Cedergreen, 2002) while other report such a relationship (Wersal and Madsen, 2011;O'Hare et al, 2010). The reason for this might be that the available nutrients satisfy the nutrient requirements for maximum growth and therefore additional nutrients do not result in higher growth rates (Madsen and Cedergreen, 2002).…”

“…While macrophytes are commonly able to satisfy their nutrient requirements from the water column (e.g. Madsen and Cedergreen, 2002), there seems to be no consistent relationship between nutrient concentrations in the water column and growth parameters in the literature. Some studies find a lack of relationship between nutrient loading and macrophyte growth (Madsen and Cedergreen, 2002) while other report such a relationship (Wersal and Madsen, 2011;O'Hare et al, 2010).…”

Ecophysiological and anatomical responses ofVallisneria natansto nitrogen and phosphorus enrichment

“…Xie et al (2005) have suggested that the root morphology of V. natans varies considerably with the fertility of the sediment in which it grows. A marked effect of the nutrients in the water column on the growth of submerged macrophytes has been reported to be reduced root biomass (Rattray et al, 1991;Madsen and Cedergreen, 2002). Indeed, root morphology can be greatly affected by nutrient availability in the environment and by the nutrient status of the plant (Linkohr et al, 2002).…”

Improvement of water quality by sediment capping and re-vegetation with Vallisneria natans L.: A short-term investigation using an in situ enclosure experiment in Lake Erhai, China

“…In the present study, re-vegetation of V. natans improved the water quality slightly more than sediment capping alone. It is possible that the fertile sediments diminished the uptake of N and P nutrients from water by the plants (Squires and Lesack, 2003;Rooney et al, 2003) and the experimental period was not long enough for the recruitment of algal grazers (Estlander et al, 2009;Zhao et al, 2013), although submerged macrophytes were reported to improve the water quality through multiple mechanisms, such as taking up nutrients, stabilizing sediment, sheltering algae-filtering zooplanktons and competing with phytoplankton for light and nutrients (Scheffer et al, 1993;Madsen and Cedergreen, 2002).…”

“…They improve the water quality by ways of absorbing nutrients, stabilizing sediment, sheltering algae-filtering zooplanktons and competing with phytoplankton for light and nutrients (Scheffer et al, 1993;Qiu et al, 2001). Rooted submerged macrophytes absorb nutrients by both shoots and roots, but the relative importance of sediment versus overlying water as N and P sources for the plants varies among species and depends on nutrients concentrations in the water and sediment (Madsen and Cedergreen, 2002;Xie et al, 2005;Cao et al, 2011). The submerged macrophyte Vallisneria natans is a perennial species with a large amount of roots, that prefers mesotrophic to eutrophic water.…”