Macrophyte growth and sediment phosphorus and nitrogen in a Canadian prairie river

Abstract

1. The role of sediment phosphorus (P) and nitrogen (N) in regulating growth of rooted macrophytes in a Canadian prairie river was investigated by means of in situ observations and artificial stream fertilization experiments. 2. Biomass and percentage cover of rooted macrophytes in the South Saskatchewan River increased downstream of a municipal sewage treatment plant, with maximum abundance occurring between 25 and 100 km downstream of the outfall. Biomass in the river was related to sediment P but not N concentration, although sites of maximum biomass did not coincide with sites of maximum sediment P concentration. 3. Artificial stream experiments revealed that while biomass was unaffected by addition of N to the sediment, it was enhanced by the addition of P to sediments, and further enhanced with the addition of N and P together, indicating a primarily P‐limited system, with secondary N limitation when P is in excess. 4. Macrophyte biomass increased linearly with increasing sediment P concentration in the artificial streams, and tissue P concentration peaked at ≈ 400 μg g–1. Biomass did not respond to increasing sediment N concentration, and only a weak relationship was observed between tissue N and sediment N, with maximum tissue N corresponding to ≈ 140 μg g–1 sediment exchangeable N. 5. A lack of concurrence between the sediment P concentration producing maximum biomass and tissue P concentration in situ vs. under experimental conditions indicates that other environmental factors have an important role in regulating macrophyte growth in rivers. Thus, while nutrient control may be one element in a river macrophyte control programme, a holistic ecosystem approach should be adopted to account for the other factors that may affect the growth of rooted plants.

Changes in phosphorus content of two aquatic macrophytes according to water velocity, trophic status and time period in hardwater streams

“…For example, sediment phosphorus can be the main nutrient source for strong root system plants (Denny, 1972). Finally, ecological factors such as substratum (Clarke & Wharton, 2001), time period (Moutin et al, 1993;Maine et al, 1999;House & Denison, 2002) and water velocity (Royle & King, 1991;Carr & Chambers, 1998) can modify phosphorus availability and thus plant nutrition.…”

Vplivi obremenitev na združbe makrofitov in njihov pomen pri upravljanju z rečnimi ekosistemi / Impacts of stressors on macrophyte communities and their importance in river ecosystem management

“…Ukoreninjeni makrofiti imajo sposobnost privzema hranil iz vodnega stolpca in sedimenta (Chambers in sod. 1991, Carr 1998, Clarke & Wharton 2001. Po Carignan (1982), lahko v razmerah, ko so prisotne enake koncentracije fosforja v sedimentu in vodnem stolpcu pričakujemo, da bodo vodne rastline preko koreninskega sistema iz sedimenta pridobile le 27 % vsega fosforja.…”

“…Čeprav so za pojav (hiper) evtrofikacije potrebne povišane koncentracije hranil, je za doseganje maksimalnega rastnega potenciala makrofitov pomembno tudi, da so vsi ostali, za rast potrebni dejavniki v presežku (Carr 1998). Na rečnem odseku, ki je osenčen (v gozdu), rastni potencial pogosto ne bo dosežen zaradi pomanjkanja svetlobe, zato odsek ne bo kazal znakov (hiper) evtrofikacije.…”

Effects of different nutrient conditions on the growth of a submerged macrophyte, <i>Vallisneria natans</i>, in a mesocosm experiment

“…高浓度硝氮对植物胁迫也有报道 [29][30] . 以上研究表明在高营养环境里, 多种 [31][32][33][34][35][36][37] , 在高营养环境里, 水体和底泥均含有高浓度氮磷 时, 植物将会通过两种途径过量吸收氮磷 [14] , 导致沉水植物内在生理伤害, 表现出生长抑制现象. 可能 …”