The physiological responses of Vallisneria natans to epiphytic algae with the increase of N and P concentrations in water bodies

Abstract

To reveal the mechanism of submerged plants decline in progressively eutrophicated freshwaters, physiological responses of Vallisneria natans to epiphytic algae were studied in simulation lab by measuring plant physiological indexes of chlorophyll content, malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity based on a 2 × 4 factorial design with two epiphytic conditions (with epiphytic algae and without) and four levels of N and P concentrations in water (N-P[mg.L(-1)]: 0.5, 0.05; 2.5, 0.25; 4.5, 0.45; 12.5, 1.25). Compared with control (non-presence of epiphytic algae), chlorophyll contents of V. natans were significantly decreased (p < 0.01) for the presence of epiphytic algae under any concentrations of N and P in water bodies. While the presence of epiphytic algae induced peroxidation of membrane lipids, MDA contents of V. natans had significantly increased (p < 0.05) by comparing with control. SOD activity significantly enhanced (p < 0.05) with the presence of epiphytic algae in the treatments of T2 and T3 in the whole culture process by comparing with control, sometimes reaching an extremely significant level (p < 0.01). However, in the treatments of T1 and T4, SOD activity had no obvious change with the presence of epiphytic algae (p < 0.05) by comparing with control. At the end of the experiment, the effects of epiphytic algae on chlorophyll content and SOD activity in the leaves of V. natans were increased at first and then decreased with the concentrations of N and P in water, and MDA content became higher with the increase of N and P. concentrations. Repeated measurement data testing showed that the effects of epiphytic algae on the chlorophyll content and MDA content and SOD activity were significant, respectively (p < 0.001), the effects of epiphytic algae were combining with effects of concentrations of N and P (p < 0.001), respectively, and their interaction (p < 0.001). Our observations confirmed that this prediction: the growth of epiphytic algae directly produced adverse effects on physiology of V. natans and epiphytic algal biomass were positively correlated with nutrient available in the water column.

Tolerance to Nitrogen ions enrichment in a Gulf of Mexico's freshwater submerged grass

“…in vitro) suggests that local ecotype Vallisneria americana at a juvenile age was tolerant to enrichments of NH 4 and NO 3 , including co-supply and within the meso-and eu-trophic range. The above supports the hypothesis that juvenile plants can tolerate very high ionized N concentration from any source of N[18,30,31], to the extent that under in vitro conditions, both variation phenotypic of V. americana and their total biomass showed similarities.In addition, the in vitro approximation allows to control factors of the exogenous environment that can cause confounding effects in the results, like osmotic stress or pH abrupt changes. Correspondingly, in a buffered medium the Arabidopsis species presented similar total biomass by different N ionic supplied sources (NH 4 vs. NO 3 ) related to the high adaptability of the non-aquatic plant[32].…”

“…Furthermore, N concentration variation, time exposure, and natural N ionic forms at different ratio are factors that have been related to trophic and environmental dynamics [2,4,5]. Moreover, similar effects of limited growth and productivity on submerged grasses have been observed in experiments of stress by N enrichment, with nitrate (NO 3 ), ammonium (NH 4 ) and both ions [2,6,7,8,9,10,11,12,13], compared with experiments of high salt concentration, temperature increases and low light intensity [4,14,15,16,17,18]. Additionally, the genotype-environment interactions and the concentration of all inorganic ions in the sediment and water, differ signi cantly from one experiment to another; making di cult to identify punctual stressors [19,20].…”

Determining the Optimal Biomass of Macrophytes during the Ecological Restoration Process of Eutrophic Shallow Lakes

“…They not only affect the composition and distribution of fish, plankton, and benthic animals in lakes, but can also eliminate waves and improve water quality [3][4][5]; they have an important impact on lake productivity and biogeochemical cycles [6]. In an aquatic ecosystem, macrophytes release allelochemicals into the water to inhibit phytoplankton growth [7][8][9]; directly absorb N and P from eutrophic water bodies for growth and reproduction [10][11][12]; remove nutrients from the water through the degradation and transformation of rhizosphere microorganisms [13][14][15]; and compete with phytoplankton for nutrients, light, and growth space, thus inhibiting phytoplankton growth [16][17][18]. The stable states in shallow lakes can be transformed from the turbid phytoplankton state to the clear macrophyte state [19][20][21], thus achieving water purification and water ecosystem restoration.…”

Community structure and assembly of denitrifying bacteria in epiphytic biofilms in a freshwater lake ecosystem

“…It implies the involvement of biotic and abiotic factors on the epiphytic denitrifying bacterial community. These factors, such as epiphytic biofi lm, algal secretion, and respiration, increased the pH in the ambience of epiphytic biofi lms, promoted the buildup of epiphytic microbial community and the heterotrophic microbial activity, and aff ected the ecological function of the microbial community (Kuehn et al, 2014;Song et al, 2015). Also, the low eff ect of aquatic environmental factors implies that the stochastic process may be the vital driving force to the construction of denitrifying microbial communities.…”