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The Behavior of Nutrients in Tropical Aquatic Ecosystems
Published in Des W. Connell, Darryl W. Hawker, Pollution in Tropical Aquatic Systems, 1992
Major classes of aquatic organisms or organic material entering aquatic ecosystems have characteristic elemental ratios which are useful for scaling ecosystem nutrient fluxes and pool sizes (Table 2). The earliest and perhaps most widely used of these ratios, the “Redfield Ratio”256 broadly fits the composition of nutrient-replete marine phytoplankton.118 Similar ratios derived for other plant types growing in or contributing organic matter to aquatic ecosystems differ significantly from the composition of phytoplankton and bacteria.14,26,113,143 Bacteria have high N and P contents relative to vascular plants and macroalgae.85,120 Macrophytes are carbon-rich because of their structural polymers (e.g., cellulose, lignin). Atkinson and Smith14 calculated a mean C:N:P molar ratio of 550:30:1 for a broad range of marine macrophytes. A similar compilation has not been made for freshwater macrophytes, but composition ratios appear to be of similar order. Interestingly, fast-growing, noxious floating macrophytes such as Salvinia molesta and Eichhornia crassipes may exhibit low (10 to 20) N to P ratios more characteristic of microalgae. Fresh plant litter is usually depleted in both nitrogen and phosphorus relative to ratios in living leaves, but the relative N and P content can increase with time due to microbial colonization of the detritus268,315 or retention of humic material.258
The Marsh Underground
Published in Robert H. Kadlec, Treatment Marshes for Runoff and Polishing, 2019
Profiles in general reflect the nutrient ratios of the biomass from which they were formed. These have much more carbon than nitrogen, and much more nitrogen than phosphorus. The historical measure of these proportions is the Redfield ratio, first suggested for marine plankton, of C:N:P = 106:16:1. Some literature suggests that the marine proportions might apply to wetland soils (e.g., Kadlec and Knight, 1996; Reddy and Delaune, 2008), but those proportions do not hold for freshwater organisms (They et al., 2017). The ratios for organic wetland soils are much different. For instance, the newly accreted soils in Figure 4.9 have C:N:P = 353:24:1, while the underlying antecedent organic soils have C:N:P = 1190:88:1
Use of Wastewater to Improve the Economic Feasibility of Microalgae-Based Biofuels
Published in Leonel Pereira, Algal Biofuels, 2017
Ana L. Gonqalves, Sergio L. Pereira, Vitor J.P. Vilar, Jose C.M. Pires
The study of assimilation mechanisms is imperative for the development and optimization of systems that are based on the growth of microalgae. The ratio of nutrient uptake rates can follow the Redfield ratio. This empirical ratio establishes the molecular proportion of carbon, nitrogen and phosphorus that favours photosynthetic aquatic organisms and is defined by C:N:P = 106:16:1 (Redfield 1958). The comparison between this ratio and the one present in the medium enables the identification of limiting nutrients for microalgal growth.
Suitability of pre-digested dairy effluent for mixotrophic cultivation of the hydrogen-producing microalgae Tetraselmis subcordiformis
Published in Environmental Technology, 2022
Marcin Dębowski, Magda Dudek, Anna Nowicka, Piera Quattrocelli, Joanna Kazimierowicz, Marcin Zieliński
Microalgae-based processes are predominantly used for tertiary treatment of waste [28]. Microalgae release 1.50-1.92 kgO2/kg of the generated biomass through photosynthesis, with oxygenation capacity during degradation of organic pollutants ranging from 0.48–1.85 kgO2/m3·d [29]. The use of effluent directly reduces the costs of supplying water and nutrients necessary for the algae to grow efficiently [30,31]. Research so far has shown that high CO2 levels in wastewater promote microalgal growth, thus directly expediting degradation of pollutants [32]. In systems where algae are grown in salt water, inputting effluent can also balance the carbon, nitrogen, and phosphorus levels, achieving the optimal molecular ratio (C: N: P = 106:16:1) known as the Redfield ratio [33].
The N:P:Si stoichiometry as a predictor of ecosystem health: a watershed scale study with Ganga River, India
Published in International Journal of River Basin Management, 2019
Ekabal Siddiqui, Jitendra Pandey, Usha Pandey
The Redfield ratio of N:P:Si, which refers to the canonical ratio of 16:1:16, is essentially required for the sustained growth of phytoplankton. Also, changes in elemental stoichiometry influence aquatic ecosystem structure at sediment-water interface via altered biogeochemical processes and associated shift in benthic food webs (Glibert 2012). Driven by disproportionate input of N, P and Si, this ratio is rapidly changing in surface waters (Peñuelas et al2012, Pandey et al2014b, 2016b). A shift in N:P ratio towards <16:1 would change the phytoplankton community composition with greater share of P favoured taxa. Similarly, when N:Si ratio shift towards >1:1, the ecological condition will discourage silicified diatoms and, as a result, less silicified algal species will predominate. When the optimal N:Si ratio is not met and it is towards Si limitation then the non-diatom algal growth over compete the scene (Xu et al2008, Pandey et al2017). The N:P:Si ratio is, therefore, a sensitive indicator of aquatic health and food web. Thus, the overall concentration of these nutrients and their stoichiometric ratio, if used together, can be a more comprehensive predictor of eutrophy and will be the robust variables across broad landscapes as represented by the large rivers. The Ganga River, which receives large but disproportionate amount of nutrients through atmospheric deposition, surface runoff and urban-industrial effluent, is expected to have experienced a shift in N:P:Si stoichiometry (Pandey et al2016b). We hypothesized that the altered nutrient stoichiometry resulting from anthropogenic drivers leads to change the river health including trophic status and diatom abundance. This watershed scale study was an attempt to investigate the changes in trophic status and diatom abundance associated with altered N:P:Si stoichiometry in the Ganga River.