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Sources of nutrients to rooted submerged macrophytes growing in a nutrient‐rich stream
Author(s) -
Madsen Tom Vindbæk,
Cedergreen Nina
Publication year - 2002
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1046/j.1365-2427.2002.00802.x
Subject(s) - macrophyte , nutrient , phosphorus , aquatic plant , biomass (ecology) , potamogeton crispus , biology , elodea canadensis , relative growth rate , agronomy , botany , environmental science , ecology , growth rate , chemistry , geometry , organic chemistry , mathematics
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.