Results 1 - 10 of 62

Phosphorus versus nitrogen limitation in the marine environment

by S. V. Smith - Limnol. Oceanogr , 1984
"... Limnological and marine geochemical opinion favors phosphorus limitation of organic production in aquatic environments, while marine biological opinion favors nitrogen limitation. Clues in the literature and nutrient budgets for selected marine ecosystems suggest that phosphorus vs. nitrogen limitat ..."
Abstract - Cited by 52 (1 self) - Add to MetaCart
Limnological and marine geochemical opinion favors phosphorus limitation of organic production in aquatic environments, while marine biological opinion favors nitrogen limitation. Clues in the literature and nutrient budgets for selected marine ecosystems suggest that phosphorus vs. nitrogen limitation is a function of the relative rates of water exchange and internal biochemical processes acting to adjust the ratio of ecosystem N:P availability. A limiting factor to biological activity is that material available in an amount most closely approaching the critical minimum required to sustain that activity (Odum 197 1). This definition can be applied at any scale from cellular metabolism to global biogeochemical cycles. This paper deals with inorganic plant nutrients as limiting factors for the net production of new organic material in marine systems. Marine geochemists and biologists hold antithetical views about nutrient limitation in the ocean. The view held by most marine geochemists (e.g. Lerman et al. 1975; Meybeck 1982; Broecker and Peng 1982) can apparently be traced to the seminal paper by Redfield ( 1958). Redfield concluded that phosphorus availability limits net organic production in the sea. He pointed out that any nitrogen deficits can be met by the biological fixation of atmospheric nitrogen, hence nitrogenous compounds can accumulate until the available phosphorus is utilized.

Phytoplankton growth and stoichiometry under multiple nutrient limitation. Limnology and Oceanography 49: 1463–1470

by Christopher A. Klausmeier, Elena Litchman, Simon A. Levin , 2004
"... Phytoplankton growth and stoichiometry depend on the availability of multiple nutrients. We use a mathematical model of phytoplankton with flexible stoichiometry to explain patterns of phytoplankton composition in chemostat experiments and nutrient drawdown dynamics that are found in the field. Expo ..."
Abstract - Cited by 38 (3 self) - Add to MetaCart
Phytoplankton growth and stoichiometry depend on the availability of multiple nutrients. We use a mathematical model of phytoplankton with flexible stoichiometry to explain patterns of phytoplankton composition in chemostat experiments and nutrient drawdown dynamics that are found in the field. Exponential growth and equilibrium represent two distinct phases, each amenable to mathematical analysis. In a chemostat at a fixed dilution (growth) rate, phytoplankton stoichiometry matches the nutrient supply stoichiometry over a wide range at low growth rates and over a narrow range at high growth rates. In a chemostat with a fixed nutrient supply stoichiometry, phyto-plankton stoichiometry varies with dilution rate nonlinearly, between the supply stoichiometry at low dilution rates and a species-specific optimal ratio at high dilution rates. The flexible-stoichiometry model we study predicts low equilibrium concentrations of two nutrients over a wide range of supply ratios, contrary to the predictions of a traditional fixed-stoichiometry model. The model is in quantitative agreement with experimental data, except at extreme nutrient supply ratios, which require a negative feedback from quota to uptake to fit the data. Our analysis points to the importance of better understanding the regulation of uptake rates in determining phytoplankton stoi-chiometry and incorporating this knowledge into phytoplankton models. Phytoplankton require multiple nutrients for growth. Knowledge of how multiple nutrients interact to limit growth is essential to understanding the causes of variation in phy-toplankton stoichiometry (Rhee 1978; Goldman et al. 1979), the identity of the nutrient(s) limiting biomass and primary production (Smith 1982), and the effect of resource com-petition on community structure (Tilman 1982). Of particular interest are nitrogen (N) and phosphorus (P), two macro-nutrients that are commonly thought to limit phytoplankton

Control of lacustrine phytoplankton by nutrients: erosion of the phosphorus paradigm. International Review of Hydrobiology 93:446–465

by William M. Lewis, Wayne A. Wurtsbaugh , 2008
"... key words: algae, dissolved organic nutrients, eutrophication, lake ecosystems, lake management, nitrogen Control of lacustrine phytoplankton biomass by phosphorus is one of the oldest and most stable paradigms in modern limnology. Even so, evidence from bioassays conducted by multiple investigators ..."
Abstract - Cited by 25 (0 self) - Add to MetaCart
key words: algae, dissolved organic nutrients, eutrophication, lake ecosystems, lake management, nitrogen Control of lacustrine phytoplankton biomass by phosphorus is one of the oldest and most stable paradigms in modern limnology. Even so, evidence from bioassays conducted by multiple investigators at numerous sites over the last three decades shows that N is at least as likely as P to be limiting to phytoplankton growth. A number of important flaws in the evidence supporting the phosphorus para-digm have contributed to an unrealistic degree of focus on phosphorus as a controlling element. These include insufficient skeptism in interpretation of: 1) the phosphorus: chlorophyll correlation in lakes, 2) the results of whole-lake fertilization experiments, and 3) stoichiometric arguments based on total N:total P ratios for inland waters. A new paradigm based on parity between N and P control of phyto-plankton biomass in lakes seems more viable than the P paradigm. The new paradigm renews interest in the degree to which plankton communities are molded in composition by small differences in relative availability of N and P, the mechanisms that lead to a high frequency of N limitation in oligotrophic lakes, and the failure of aquatic N-fixers to compensate significantly for N deficiency under most condi-tions. A new N/P paradigm still must acknowledge that suppression of P loading often will be the most effective means of reducing phytoplankton biomass in eutrophic lakes, even if N is initially limiting. From error to error one discovers the entire truth SIGMUND FREUD 1.
(Show Context)

Responses of estuarine and coastal marine phytoplankton to nitrogen and phosphorus enrichment

by Val H. Smith - Limnol. Oceanogr , 2006
"... A cross-ecosystem comparison of data obtained from 92 coastal zone ecosystems worldwide revealed a strong positive response of marine phytoplankton biomass to nutrient enrichment that is highly consistent with the general patterns reported previously in the limnological literature for freshwater lak ..."
Abstract - Cited by 22 (1 self) - Add to MetaCart
A cross-ecosystem comparison of data obtained from 92 coastal zone ecosystems worldwide revealed a strong positive response of marine phytoplankton biomass to nutrient enrichment that is highly consistent with the general patterns reported previously in the limnological literature for freshwater lakes and reservoirs. Average concentrations of chlorophyll a in estuarine and coastal marine systems were strongly dependent on the mean concentrations of total nitrogen and total phosphorus in the water column. Moreover, as is true of freshwater ecosystems, the identity of the primary growth-limiting nutrient for marine phytoplankton appeared to be generally predictable from watercolumn total nitrogen: total phosphorus (TN: TP) ratios. This similarity in physiological response to nutrients likely derives from the shared evolutionary histories of marine and freshwater phytoplankton. Much of our current knowledge of eutrophication is derived from research on lake systems in North America and Europe, which led to the development of the predictive frameworks now used worldwide in freshwater management (Smith 1998). However, it is clear that, in many nutrientsensitive coastal marine waters, eutrophication can cause increased rates of primary productivity, changes in algal and vascular plant biomass, shifts in algal and vascular plant species composition, diebacks of sea grasses and corals, reduced populations of fish and shellfish, reductions in transparency, losses of acceptable aquatic habitats and biodiversity, and oxygen depletion in bottom waters (National Research Council 2000). Coastal marine environmental quality is thus an issue of major global concern (United Nations Environment

Misuse of inorganic N and soluble reactive P concentrations to indicate nutrient status of surface waters

by Walter K Dodds - Journal of the North American Benthological Society , 2003
"... PERSPECTIVES This section of the journal is for the expression of new ideas, points of view, and comments on topics of interest to benthologists. The editorial board invites new and original papers as well as comments on items already published in The utility of such measurements should be question ..."
Abstract - Cited by 16 (0 self) - Add to MetaCart
PERSPECTIVES This section of the journal is for the expression of new ideas, points of view, and comments on topics of interest to benthologists. The editorial board invites new and original papers as well as comments on items already published in The utility of such measurements should be questioned, particularly based on well-known problems associated with determination of the concentration of SRP, which is commonly assumed to represent PO 4 3Ϫ . Another potential problem with using inorganic nutrient pools to represent trophic state and nutrient availability ratios arises because concentration values are in units of mass per unit volume, and cannot be used with certainty to estimate supply (i.e., turnover rate of the nutrient pool, expressed either in mass per unit volume per unit time or simply as per unit time) to organisms without information on uptake and remineralization. Two data sets with lotic water-column nutrient values were explored, a large, continental-scale data set with analyses and collections done by many laboratories, and a more limited data set collected and analyzed by the same laboratory. In concert, the data sets indicated that at high total N (TN) (i.e., Ͼ5 mg/L) and total P (TP) (i.e., Ͼ2 mg/L) concentrations, Ͼ60% of the nutrient is usually made up of dissolved inorganic forms, but at low levels the ratio of dissolved inorganic to total nutrients is highly variable. Last, DIN:SRP is a weak surrogate for TN:TP and thus should be used with caution to indicate nutrient limitation. Key words: ammonium, dissolved reactive phosphorus, inorganic nutrients, nitrate, nutrient limitation, phosphate, water-quality monitoring. Nutrients such as N and P are required for organisms and can control ecosystem production. The most commonly limiting nutrients in fresh waters are N and P SRP and DIN are commonly measured and reported in water-quality data sets, presumably as a measure of trophic status (i.e., relative nutrient availability) or to indicate eutrophication problems. By extension, if DIN and SRP are indicative of trophic status (relative nutrient avail-

The relationship between chemically analyzed phosphorus fractions and bioavailable phosphorus

by Marie E. Bradford, Robert Henry Peters - Limnol. Oceanogr , 1987
"... To identify available phosphorus, phosphorus was measured by 2-week bioassay in water from 39 sites in Ontario and Quebec and regressed against total phosphorus and the phosphorus (P) in 11 analytically measured fractions (total soluble, total reactive, particulate, and soluble reactive P, both befo ..."
Abstract - Cited by 7 (0 self) - Add to MetaCart
To identify available phosphorus, phosphorus was measured by 2-week bioassay in water from 39 sites in Ontario and Quebec and regressed against total phosphorus and the phosphorus (P) in 11 analytically measured fractions (total soluble, total reactive, particulate, and soluble reactive P, both before and after autoclaving; and soluble reactive P after exposure to enzymes, to UV radiation, and to both). Covariance analysis showed that low-P (~30 pg TP liter-‘) lakes and rivers, P-rich lakes, and P-rich rivers required separate analysis. Total P was a consistently poor correlate of available P (? = 0.44-0.72). A best estimator for various subsets of the data was identified in terms of descriptive power (r2, F), normality, and analytical ease. At low concentrations of P, the fraction of choice is total reactive phosphorus, which explained 73 % of the total variation in bioassay P. Total soluble phosphorus was the most useful correlate of bioassay P in eutrophic lakes (r2 = 0.98) and rivers (r2 = 0.95). The applicability of these regressions to waters other than those sampled or as predictors of lake eutrophication remains to be cvaluatcd. Residual error in regressions of lake re-sponse against total phosphorus is high, and

Constraints on primary producer N:P stoichiometry along N:P supply ratio gradients

by Spencer R Hall , Val H Smith , David A Lytle , Mathew A Leibold - Ecology , 2005
"... Abstract. A current principle of ecological stoichiometry states that the nitrogen to phosphorus ratio (N:P) of primary producers should closely match that from environmental nutrient supplies. This hypothesis was tested using data from ponds in Michigan, USA, a freshwater mesocosm experiment, a sy ..."
Abstract - Cited by 7 (0 self) - Add to MetaCart
Abstract. A current principle of ecological stoichiometry states that the nitrogen to phosphorus ratio (N:P) of primary producers should closely match that from environmental nutrient supplies. This hypothesis was tested using data from ponds in Michigan, USA, a freshwater mesocosm experiment, a synthesis of studies from diverse systems (cultures, lakes, streams, and marine and terrestrial environments), and simple dynamic models of producer growth and nutrient content. Unlike prior laboratory studies, the N:P stoichiometry of phytoplankton in Michigan ponds clustered around and below the Redfield ratio (7.2:1 by mass), despite wide variation in N:P supply ratios (2:1-63:1 by mass) and the presence of grazers. In a mesocosm experiment, the N:P stoichiometry of phytoplankton cells again deviated from a nearly 1:1 relationship with N:P supply. Phytoplankton seston exhibited lower N:P content than expected at high N:P supply ratios, and often higher N:P content than anticipated at low N:P supply ratios, regardless of herbivore presence. Similar deviations consistently occur in the N:P stoichiometry of algae and plants in the other diverse systems. The models predicted that both high loss rates (sinking, grazing) and physiological limits to nutrient storage capacity could attenuate producer stoichiometry. In the future, research should evaluate how limits to elemental plasticity of producers can influence the role of stoichiometry in structuring communities and ecosystem processes.

P.: The physical and chemical limnology of 24 ponds and one lake from

by Dermot Antoniades , Marianne S V Douglas , John P Smol - Isachsen, Ellef Ringnes Island, Int. Rev. Hydrobiol
"... Abstract The limnology of freshwaters surrounding Isachsen, Ellef Ringnes Island, Nunavut was examined to determine the baseline physical and chemical limnological conditions present in the region. Sites were found to be circumneutral to slightly acidic, and were oligotrophic. Concentrations of mos ..."
Abstract - Cited by 2 (1 self) - Add to MetaCart
Abstract The limnology of freshwaters surrounding Isachsen, Ellef Ringnes Island, Nunavut was examined to determine the baseline physical and chemical limnological conditions present in the region. Sites were found to be circumneutral to slightly acidic, and were oligotrophic. Concentrations of most measured chemical variables were highly variable, with broad ranges that greatly exceeded those found in previous surveys conducted in the High Arctic. Ratios of nitrogen to phosphorus suggest that nitrogen may be the limiting nutrient for algal growth at the majority of sites. Principal Components Analysis (PCA) indicated that the major controls on water chemistry variability between sites were conductivity and related variables, and nutrients, explaining 36.5% and 26.5% of the variation in the dataset, respectively.
(Show Context)

2003. Invasibility of plankton food webs along a trophic state gradient

by Jay T. Lennon, Val H. Smith, Andrew R. Dzialowski - Oikos
"... food webs along a trophic state gradient. – Oikos 103: 191–203. Biological invasions are becoming more common, yet the majority of introduced exotic species fail to establish viable populations in new environments. Current ecological research suggests that invasion success may be determined by prope ..."
Abstract - Cited by 1 (1 self) - Add to MetaCart
food webs along a trophic state gradient. – Oikos 103: 191–203. Biological invasions are becoming more common, yet the majority of introduced exotic species fail to establish viable populations in new environments. Current ecological research suggests that invasion success may be determined by properties of the native ecosystem, such as the supply rate of limiting nutrients (i.e. trophic state). We examined how trophic state influences invasion success by introducing an exotic zooplankter, Daphnia lumholtzi into native plankton communities in a series of experimental mesocosms exposed to a strong nutrient gradient. We predicted that the attributes of nutrient-enriched communities would increase the likelihood of a successful invasion attempt by D. lumholtzi. Contrary to our original predictions, we found that D. lumholtzi was often absent from mesocosms that developed under high nutrient supply rates. Instead, the presence of D. lumholtzi was associated with systems that had low nutrients, low zooplankton biomass, and high zooplankton species diversity. Using generalized estimating equations (GEE) and multivariate species data, we found that the presence–absence of D. lumholtzi could be explained by variations in zooplankton community structure, which was itself strongly influ-enced by nutrient supply rate. We argue that the apparent invasion success of D. lumholtzi was inhibited by the dominance of another cladoceran species, Chydorus sphaericus. These results suggest that the interaction between trophic state and species identity influenced the invasion success of introduced D. lumholtzi.
(Show Context)

unknown title

by Universität Konstanz, Mathematisch-naturwissenschaftliche Sektion, Fachbereich Biologie, Onur Kerimoglu
"... Trophic interactions and abiotic forcing in the aquatic ecosystems: a modeling approach ..."
Abstract - Add to MetaCart
Trophic interactions and abiotic forcing in the aquatic ecosystems: a modeling approach
(Show Context)